Merge pull request 'Release: dev to main (Cities & Knights)' (#9) from dev into main

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_016eTor2tpxKb4dXbd8RqnvZ

CLAUDE.md

@@ -1,78 +1,61 @@
-> **Moved to Gitea.** CI now runs on Gitea Actions at
-> `git.wallacenet.ca/devadmin/ProLibertateGames`, publishing to Cloudflare Pages
-> (`plg.wallacenet.ca`) only. The sandbox notes below describe the earlier GitHub
-> setup (no CI run from session pushes, `workflow_dispatch` as the workaround);
-> re-verify them against Gitea before relying on them.
-
 # Working on this repo with Claude
 
-## Nothing a session does triggers CI. Dispatch it explicitly.
+CI runs on **Gitea Actions** at `git.wallacenet.ca/devadmin/ProLibertateGames`
+(workflows in `.github/workflows/`), publishing to Cloudflare Pages
+(`plg.wallacenet.ca`). The workflow below was measured on the dev machine
+(`~/ProLibertateGames`); it replaces the earlier GitHub-sandbox notes, which no
+longer apply.
 
-GitHub creates **no workflow run** for anything this sandbox does — pushing a
-branch, opening a pull request, or merging one. All of it goes through the same
-integration, and GitHub suppresses event-triggered runs from it. The pull
-request will say it was opened by the repo owner; that is only how the UI
-attributes it, and it does not change the suppression.
+## Build, test and lint locally
 
-This was measured, not assumed:
+Gradle works on the dev machine. Two environment variables are required: the
+default JDK is 25, which Gradle 8.14 cannot use, and the Android SDK lives in the
+home directory.
 
-| Action | Result |
-| --- | --- |
-| Human pushes a Claude-authored commit (`d165e5ef`, `469c900e`) | CI runs |
-| Session pushes `dev` / `main` (`43394b8`, `742add4`) | no run |
-| Session opens a PR against `dev` (#1) | no run |
-| Session calls `workflow_dispatch` | **runs** |
+```
+export JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64
+export ANDROID_HOME=$HOME/android-sdk      # platform 34, build-tools 34.0.0
+./gradlew testDebugUnitTest lintDebug assembleDebug
+```
 
-`workflow_dispatch` works because it creates a run directly instead of relying
-on an event. It is the only mechanism available from a session, so every build
-has to be asked for by hand.
+The Katan tests run in seconds; a clean build takes a few minutes. Run the full
+suite, lint and `assembleDebug` before pushing: they are what CI runs. There is
+no KVM, so no emulator; the engine and the UI logic are covered by unit tests
+(see `docs/UI-catan.md`).
 
-## Verify before merging, without publishing
+## Shipping: branch, PR, CI, merge
 
-`ci.yml` builds, tests and lints on any ref, but its staging and publishing
-steps are gated on `github.ref == 'refs/heads/dev'`. Dispatching it on a
-**feature branch** therefore gives the full check — build, unit tests, Android
-lint — and publishes nothing.
-
-So the working loop is:
-
-1. Commit and push the feature branch.
-2. Dispatch `ci.yml` on that branch. Wait for green. This is the real review
-   gate, and it is the only verification that exists (see below).
-3. Open the PR through the API and merge it there, so the change is reviewable
-   and the merge commit is honest about what happened. Neither step builds
-   anything.
-4. Dispatch the target branch's workflow to actually build and publish:
-   `ci.yml` on `dev`, `release.yml` on `main`.
-
-Skipping step 4 leaves a branch whose head was never built and no release.
+1. Branch from `dev`; before pushing, merge `origin/dev` in (it moves between
+   sessions).
+2. Plain `git push` has no credentials. Use the Gitea token as a one-off header:
+   `git -c "http.extraheader=Authorization: token $(cat ~/.config/gitea/token)" push -u origin <branch>`.
+3. Open the PR with `POST /api/v1/repos/devadmin/ProLibertateGames/pulls`
+   (same token, `Authorization: token ...`). CI (`ci.yml`) runs on the PR: build,
+   unit tests and Android lint; it publishes nothing. Poll
+   `/actions/runs` until it completes (about 7 minutes).
+4. Merge with `POST .../pulls/N/merge {"Do":"merge"}`. The push to `dev` runs
+   `ci.yml` again and publishes the build (about 9 minutes).
 
 ## Merging is a shipping action
 
 Both long-lived branches publish, so a merge is a release, not just an
 integration:
 
-- **`dev`** → `ci.yml` publishes a `v<series>.N-dev` **prerelease**, offered by the
-  in-app updater to anyone on the Dev channel.
-- **`main`** → `release.yml` publishes a **production** release, which the
-  updater installs for everyone on the Production channel.
+- **`dev`** publishes a `v<series>.N-dev` build to
+  `https://plg.wallacenet.ca/dev/latest.json`, offered by the in-app updater to
+  anyone on the Dev channel.
+- **`main`** runs `release.yml` and publishes a **production** release for
+  everyone on the Production channel. Confirm before merging to `main`.
+  `release.yml` runs `assembleDebug` only (no tests, no lint), so a `main`
+  release is only as verified as the `dev` build it replays.
 
-Confirm before shipping to `main`. Note that `release.yml` runs `assembleDebug`
-only — no tests, no lint — so a `main` release is only as verified as the `dev`
-build it replays.
+## Katan
 
-## Gradle does not run in the sandbox
-
-`./gradlew` cannot resolve the Android plugin here: the proxy blocks
-`dl.google.com` with a 403. No local build, no local test run, no local lint. A
-dispatched CI run is the only way to find out whether a change compiles.
-
-## A permanent fix, if you want one
-
-The suppression is a property of the sandbox's credential, so it cannot be
-fixed from inside a session. Giving the environment a personal access token to
-push with would make pushes and PRs behave normally for everyone. Until then,
-the dispatch step above is the workaround.
+The island game is catalogue id `catan`, shown as **Katan**. It has two rule
+sets chosen at setup: the base game (`docs/RULES-catan.md`) and Cities & Knights
+(`docs/RULES-catan-ck.md`, code in `game/catan/CatanCk*.kt`, state behind
+`CatanState.ck`, which is null in the base game). The screen is layered; see
+`docs/UI-catan.md` before changing it.
 
 ## Bash output is filtered before it reaches the model
 

README.md

@@ -373,7 +373,9 @@ game:
   the game is out of print and the rulebook could not be obtained, so the
   document says which parts are attested and which were derived
 - [Katan](docs/RULES-catan.md) — the island game (catalogue id `catan`); the
-  rules engine and AI are in place, the screen lands with its own task
+  rules engine, AI and screen are in place
+- [Katan: Cities & Knights](docs/RULES-catan-ck.md) — the expansion rule set, chosen on
+  the setup screen: commodities, knights, barbarians, city improvements and progress cards
 
 ## Layout
 
@@ -396,7 +398,7 @@ game/          rules engines and AI — pure Kotlin, no Android, unit-tested
   mastermind/  Mastermind codes, scoring, and a code breaker
   pirates/     Pirates and Bulgars — the cross board, the hunt, search
   tayu/        Ta Yü tile geometry, river rules, scoring, AI
-  catan/       Katan island geometry, production, trade, dev cards, heuristic AI
+  catan/       Katan island geometry, production, trade, dev cards, Cities & Knights, heuristic AI
 net/           wire protocol, LAN transport, lobby, match driver
 score/         scorekeeper sheet — pure Kotlin, unit-tested — and its store
 settings/      DataStore-backed preferences

app/src/main/java/org/prolibertate/games/game/Catalog.kt

@@ -360,7 +360,7 @@ object GameCatalog {
             minPlayers = 3,
             maxPlayers = 4,
             teamBased = false,
-            blurb = "Trade, build, and settle the island.",
+            blurb = "Trade, build, and settle the island, in the base game or Cities & Knights.",
             // Engine and screen exist but have not been verified on two real
             // devices yet. Dev builds can open it as a *Preview*; a production
             // build does not list it. Flip `available` on, and `devPreview`

app/src/main/java/org/prolibertate/games/game/catan/CatanAi.kt

@@ -20,10 +20,14 @@ import org.prolibertate.games.game.engine.GameAi
  */
 class CatanAi : GameAi<CatanState, CatanMove> {
 
+    /** Plays the Cities & Knights tables; this class keeps the base game. */
+    private val ck = CatanCkAi(this)
+
     override fun chooseMove(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
         require(legal.isNotEmpty() || state.phase == CatanPhase.PLAYING) {
             "No legal move for seat $seat"
         }
+        if (state.isCk) return ck.choose(state, seat, legal)
         return when (state.phase) {
             CatanPhase.SETUP_FIRST, CatanPhase.SETUP_SECOND ->
                 chooseSetup(state, seat, legal.filterIsInstance<SetupPlace>())
@@ -38,10 +42,12 @@ class CatanAi : GameAi<CatanState, CatanMove> {
 
             CatanPhase.TRADE_PENDING -> chooseResponse(state, seat, legal)
 
+            CatanPhase.TRADE_COUNTERS -> chooseCounter(state, legal)
+
             CatanPhase.PLAYING -> choosePlaying(state, seat, legal)
 
-            CatanPhase.GAME_OVER -> legal.firstOrNull()
-                ?: error("The game is over; nobody chooses a move")
+            CatanPhase.CHORE, CatanPhase.GAME_OVER -> legal.firstOrNull()
+                ?: error("Nothing to choose in phase ${state.phase}")
         }
     }
 
@@ -49,7 +55,7 @@ class CatanAi : GameAi<CatanState, CatanMove> {
     // Setup
     // -----------------------------------------------------------------------
 
-    private fun chooseSetup(state: CatanState, seat: Int, places: List<SetupPlace>): SetupPlace {
+    internal fun chooseSetup(state: CatanState, seat: Int, places: List<SetupPlace>): SetupPlace {
         require(places.isNotEmpty()) { "No legal settlement placement" }
         return places.maxByOrNull { place ->
             spotValue(state, place.vertex) +
@@ -260,23 +266,38 @@ class CatanAi : GameAi<CatanState, CatanMove> {
     }
 
     private fun chooseResponse(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
-        val accept = legal.filterIsInstance<AcceptTrade>().firstOrNull() ?: run {
-            return legal.first { it is DeclineTrade }
-        }
-        val offer = state.pendingTrade ?: return legal.first()
-        // Accept when what arrives is worth more than what leaves: a mild
-        // table, not a shark.
-        val incoming = offer.get.sumOf { want(it) }
-        val outgoing = offer.give.sumOf { want(it) }
+        val accept = legal.filterIsInstance<AcceptTrade>().firstOrNull()
+        val offer = state.pendingTrade
+        if (accept == null || offer == null) return legal.first { it is DeclineTrade }
+        // Accept when what arrives (the offerer's give) is worth more than what
+        // leaves (the offerer's get): a mild table, not a shark.
+        val incoming = offer.give.sumOf { want(it) }
+        val outgoing = offer.get.sumOf { want(it) }
         return if (incoming > outgoing) accept else legal.first { it is DeclineTrade }
     }
 
+    /**
+     * Picks the counter-offer that gains the most by the same valuation, or
+     * turns them all down. The AI never counters itself: it only answers.
+     */
+    private fun chooseCounter(state: CatanState, legal: List<CatanMove>): CatanMove {
+        val offer = state.pendingTrade ?: return legal.first()
+        val best = legal.filterIsInstance<AcceptCounter>()
+            .map { choice -> choice to offer.counters.first { it.by == choice.seat } }
+            .maxByOrNull { (_, c) -> c.give.sumOf { want(it) } - c.get.sumOf { want(it) } }
+        if (best != null) {
+            val (choice, c) = best
+            if (c.give.sumOf { want(it) } > c.get.sumOf { want(it) }) return choice
+        }
+        return legal.first { it is DismissCounters }
+    }
+
     // -----------------------------------------------------------------------
     // Valuations
     // -----------------------------------------------------------------------
 
     /** What a seat would think of building on [vertex]: production and ports. */
-    private fun spotValue(state: CatanState, vertex: Int): Double {
+    internal fun spotValue(state: CatanState, vertex: Int): Double {
         if (state.buildings[vertex] != null) return -1.0
         var value = 0.0
         val kinds = mutableSetOf<Resource>()
@@ -297,7 +318,7 @@ class CatanAi : GameAi<CatanState, CatanMove> {
      * What a road on this edge leads to: the best settlement spot it brings
      * within reach, discounted for being one step further out.
      */
-    private fun roadValue(state: CatanState, move: BuildRoad): Double {
+    internal fun roadValue(state: CatanState, move: BuildRoad): Double {
         var best = 0.0
         val (from, to) = CatanBoard.EDGE_VERTICES[move.edge]
         for (endpoint in listOf(from, to)) {
@@ -309,7 +330,7 @@ class CatanAi : GameAi<CatanState, CatanMove> {
     }
 
     /** How much the AI wants to hold one card of [resource]. */
-    private fun want(resource: Resource): Double = when (resource) {
+    internal fun want(resource: Resource): Double = when (resource) {
         Resource.ORE -> 1.20 // the city
         Resource.GRAIN -> 1.15 // the city and the dev cards
         Resource.LUMBER -> 1.0 // every road and settlement

app/src/main/java/org/prolibertate/games/game/catan/CatanCkAi.kt

@@ -0,0 +1,345 @@
+package org.prolibertate.games.game.catan
+
+/**
+ * The computer opponent for Cities & Knights, reached through [CatanAi].
+ *
+ * It plays the same cautious game as the base AI — settle well, raise cities —
+ * and adds the three things this rule set asks of a player: keep enough active
+ * knights standing when the barbarians land, spend commodities on improvements
+ * as soon as it can, and answer every chore the table raises with the card it
+ * values least. It reads only what a player at the table could see, plus its
+ * own hand.
+ *
+ * It is not a strong player. It never moves knights about (they stay where
+ * hired, and are activated when the barbarians draw near), never plays the
+ * progress cards whose value depends on a plan (Inventor, Alchemist, Diplomat,
+ * Deserter, Intrigue), and makes no domestic offers, though it answers them.
+ */
+internal class CatanCkAi(private val ai: CatanAi) {
+
+    fun choose(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove = when (state.phase) {
+        CatanPhase.SETUP_FIRST, CatanPhase.SETUP_SECOND ->
+            ai.chooseSetup(state, seat, legal.filterIsInstance<SetupPlace>())
+
+        CatanPhase.AWAIT_ROLL -> legal.first { it is RollDice }
+
+        CatanPhase.CHORE -> chooseChore(state, seat, legal)
+
+        CatanPhase.ROBBER -> chooseRobber(state, seat, legal.filterIsInstance<MoveRobber>())
+
+        CatanPhase.FREE_ROADS -> chooseFreeRoad(state, seat, legal)
+
+        CatanPhase.TRADE_PENDING -> chooseResponse(state, seat, legal)
+
+        CatanPhase.TRADE_COUNTERS -> chooseCounter(state, legal)
+
+        CatanPhase.PLAYING -> choosePlaying(state, seat, legal)
+
+        CatanPhase.DISCARDING, CatanPhase.GAME_OVER -> legal.firstOrNull()
+            ?: error("Nothing to choose in phase ${state.phase}")
+    }
+
+    // -----------------------------------------------------------------------
+    // Chores
+    // -----------------------------------------------------------------------
+
+    private fun chooseChore(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
+        val ck = state.ck!!
+        return when (val chore = ck.chores.first()) {
+            is DiscardChore -> {
+                val n = minOf(chore.count, CatanCk.goodsCount(state, seat))
+                DiscardGoods(CatanCk.goodsList(state, seat).sortedBy { worth(state, seat, it) }.take(n))
+            }
+
+            is GiveChore -> {
+                val pool = CatanCk.goodsList(state, seat)
+                    .filter { !chore.commoditiesOnly || it.isCommodity }
+                    .sortedBy { worth(state, seat, it) }
+                GiveGoods(pool.take(minOf(chore.count, pool.size)))
+            }
+
+            is PillageChore ->
+                legal.filterIsInstance<PillageCity>().minByOrNull { production(state, it.vertex) } ?: legal.first()
+
+            is PickDeckChore -> {
+                val picks = legal.filterIsInstance<PickDeck>()
+                picks.maxByOrNull { CatanCk.improvement(state, seat, it.track) } ?: legal.first()
+            }
+
+            is DropProgressChore ->
+                legal.filterIsInstance<DropProgress>().minByOrNull { drop ->
+                    ck.progressHands[seat].first { it.id == drop.card }.kind.let(::cardWorth)
+                } ?: legal.first()
+
+            is MetropolisChore ->
+                legal.filterIsInstance<PlaceMetropolis>().maxByOrNull { production(state, it.vertex) }
+                    ?: legal.first()
+
+            is AqueductChore ->
+                legal.filterIsInstance<TakeAqueduct>().maxByOrNull { ai.want(it.resource) } ?: legal.first()
+
+            is RelocateChore -> legal.first()
+
+            is RemoveKnightChore ->
+                legal.filterIsInstance<RemoveKnight>().minByOrNull {
+                    CatanCk.knightAt(state, it.vertex)?.level ?: 0
+                } ?: legal.first()
+
+            is PlaceKnightChore -> legal.first()
+
+            is SpyChore -> legal.first()
+
+            is SmithChore ->
+                legal.filterIsInstance<PromoteKnight>().firstOrNull() ?: legal.first { it is EndSmith }
+        }
+    }
+
+    // -----------------------------------------------------------------------
+    // The robber
+    // -----------------------------------------------------------------------
+
+    private fun chooseRobber(state: CatanState, seat: Int, moves: List<MoveRobber>): MoveRobber {
+        require(moves.isNotEmpty()) { "No legal robber move" }
+        val points = CatanRules.publicVictoryPoints(state)
+        return moves.maxByOrNull { move ->
+            val hex = CatanBoard.hexIndex.getValue(move.hex)
+            var score = 0.0
+            for (v in CatanBoard.HEX_CORNERS[hex]) {
+                val building = state.buildings[v] ?: continue
+                val worth = if (building.type == BuildingType.CITY) 2 else 1
+                val odds = CatanBoard.numberOdds(state.numbers[hex]) / 36.0
+                score += if (building.owner == seat) -worth * odds else worth * odds
+            }
+            if (move.victim != null) {
+                score += 0.15 * CatanCk.goodsCount(state, move.victim) + 0.3 * points[move.victim]
+            }
+            score
+        } ?: moves.first()
+    }
+
+    // -----------------------------------------------------------------------
+    // The main phase
+    // -----------------------------------------------------------------------
+
+    private fun choosePlaying(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
+        val ck = state.ck!!
+        val soon = ck.barbarians <= 3
+
+        // Chase the robber off a hex it is squatting on.
+        if (ck.attacked) {
+            val onMine = legal.filterIsInstance<ChaseRobber>().firstOrNull()
+            val robberHurtsMe = CatanBoard.HEX_CORNERS[state.robber].any { state.buildings[it]?.owner == seat }
+            if (onMine != null && robberHurtsMe) return onMine
+        }
+
+        // The cheap upgrade first, then the full-price one.
+        legal.filterIsInstance<PlayProgress>()
+            .filter { kindOf(state, seat, it) == ProgressType.MEDICINE }
+            .maxByOrNull { production(state, it.vertex!!) }
+            ?.let { return it }
+
+        legal.filterIsInstance<BuildCity>().maxByOrNull { production(state, it.vertex) }
+            ?.let { return it }
+
+        legal.filterIsInstance<BuildSettlement>().maxByOrNull { ai.spotValue(state, it.vertex) }
+            ?.let { return it }
+
+        // Improvements spend cards nothing else needs. Favour the track furthest along.
+        legal.filterIsInstance<BuyImprovement>()
+            .maxByOrNull { CatanCk.improvement(state, seat, it.track) * 10 + trackLean(it.track) }
+            ?.let { return it }
+
+        // Knights: stand ready by the time the barbarians land.
+        defence(state, seat, legal, soon)?.let { return it }
+
+        progress(state, seat, legal)?.let { return it }
+
+        legal.filterIsInstance<BuildWall>().firstOrNull()?.let {
+            if (CatanCk.goodsCount(state, seat) >= 7) return it
+        }
+
+        legal.filterIsInstance<BuildRoad>()
+            .filter { ai.roadValue(state, it) > 0.1 }
+            .maxByOrNull { ai.roadValue(state, it) }
+            ?.let { return it }
+
+        legal.filterIsInstance<GoodsBankTrade>()
+            .filter { completes(state, seat, it) }
+            .minByOrNull { CatanCk.bankRatio(state, seat, it.give) }
+            ?.let { return it }
+
+        return legal.lastOrNull { it is EndTurn } ?: legal.first()
+    }
+
+    /** Hire, promote and activate so the knights are standing when the barbarians land. */
+    private fun defence(state: CatanState, seat: Int, legal: List<CatanMove>, soon: Boolean): CatanMove? {
+        val mine = CatanCk.knightsOf(state, seat)
+        val grainLeft = state.resources[seat][Resource.GRAIN] ?: 0
+
+        if (soon) {
+            legal.filterIsInstance<ActivateKnight>().firstOrNull()?.let { return it }
+        }
+        val want = if (soon) 4 else 2
+        if (mine.size < want) {
+            legal.filterIsInstance<HireKnight>().maxByOrNull { ai.spotValue(state, it.vertex) }?.let { hire ->
+                // Keep a grain back for waking it, once the ship is close.
+                if (!soon || grainLeft >= 1) return hire
+            }
+        }
+        if (soon || mine.size >= 2) {
+            legal.filterIsInstance<PromoteKnight>().firstOrNull()?.let { return it }
+        }
+        if (soon) {
+            legal.filterIsInstance<ActivateKnight>().firstOrNull()?.let { return it }
+        }
+        return null
+    }
+
+    /** Progress cards worth playing without a plan. */
+    private fun progress(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove? {
+        val ck = state.ck!!
+        val soon = ck.barbarians <= 4
+        val plays = legal.filterIsInstance<PlayProgress>()
+        fun kindOf(play: PlayProgress) = ck.progressHands[seat].first { it.id == play.card }.kind
+        fun first(kind: ProgressType) = plays.firstOrNull { kindOf(it) == kind }
+
+        first(ProgressType.IRRIGATION)?.let { return it }
+        first(ProgressType.MINING)?.let { return it }
+        first(ProgressType.ENGINEER)?.let { return it }
+        first(ProgressType.SMITH)?.let { return it }
+        first(ProgressType.WEDDING)?.let { return it }
+        if (soon) first(ProgressType.WARLORD)?.let { return it }
+
+        plays.filter { kindOf(it) == ProgressType.MASTER_MERCHANT }
+            .maxByOrNull { play -> play.goods.orEmpty().sumOf { worth(state, seat, it) } }
+            ?.let { return it }
+
+        first(ProgressType.SPY)?.let { return it }
+        first(ProgressType.BISHOP)?.let { return it }
+
+        if (legal.filterIsInstance<BuildRoad>().size >= 2) first(ProgressType.ROAD_BUILDING)?.let { return it }
+
+        // Crane: only when it makes the difference to an improvement.
+        first(ProgressType.CRANE)?.let { crane ->
+            val helps = Track.entries.any { track ->
+                val level = CatanCk.improvement(state, seat, track)
+                val have = ck.commodities[seat][track.commodity] ?: 0
+                level < IMPROVEMENT_MAX && have == level // one short of the next level's price
+            }
+            if (helps) return crane
+        }
+
+        // Saboteur: when someone level or ahead is sitting on a pile.
+        first(ProgressType.SABOTEUR)?.let { saboteur ->
+            val vp = CatanRules.publicVictoryPoints(state)
+            val pile = (0 until state.playerCount).filter { it != seat && vp[it] >= vp[seat] }
+                .sumOf { CatanCk.goodsCount(state, it) / 2 }
+            if (pile >= 4) return saboteur
+        }
+
+        // Monopolies: only when the table is holding a pile of it.
+        plays.filter { kindOf(it) == ProgressType.RESOURCE_MONOPOLY || kindOf(it) == ProgressType.TRADE_MONOPOLY }
+            .maxByOrNull { held(state, seat, it.good!!) }
+            ?.let { best ->
+                val each = if (kindOf(best) == ProgressType.RESOURCE_MONOPOLY) 2 else 1
+                val take = (0 until state.playerCount).filter { it != seat }
+                    .sumOf { minOf(each, CatanCk.goodsOf(state, it)[best.good!!] ?: 0) }
+                if (take >= 3) return best
+            }
+
+        // The merchant, on the best hex beside a building of ours.
+        plays.filter { kindOf(it) == ProgressType.MERCHANT }
+            .maxByOrNull { play ->
+                val hex = play.hexA!!
+                CatanBoard.numberOdds(state.numbers[hex]).toDouble()
+            }?.let { return it }
+
+        // A commercial harbour turns spare resources into commodities.
+        plays.filter { kindOf(it) == ProgressType.COMMERCIAL_HARBOR }
+            .maxByOrNull { held(state, seat, it.good!!) }
+            ?.let { if (held(state, seat, it.good!!) >= 2) return it }
+
+        return null
+    }
+
+    private fun kindOf(state: CatanState, seat: Int, play: PlayProgress): ProgressType =
+        state.ck!!.progressHands[seat].first { it.id == play.card }.kind
+
+    /** What a building on [vertex] would draw, by the odds of its hexes and what the seat wants. */
+    private fun production(state: CatanState, vertex: Int): Double =
+        CatanBoard.VERTEX_HEXES[vertex].sumOf { h ->
+            val want = state.terrains[h].produces?.let { ai.want(it) } ?: 0.0
+            want * CatanBoard.numberOdds(state.numbers[h]) / 36.0
+        }
+
+    private fun held(state: CatanState, seat: Int, good: Good): Int = CatanCk.goodsOf(state, seat)[good] ?: 0
+
+    /** Whether the trade leaves a hand that can pay for a city, a settlement or an improvement. */
+    private fun completes(state: CatanState, seat: Int, trade: GoodsBankTrade): Boolean {
+        val hand = CatanCk.goodsOf(state, seat).toMutableMap()
+        hand[trade.give] = (hand[trade.give] ?: 0) - CatanCk.bankRatio(state, seat, trade.give)
+        hand[trade.get] = (hand[trade.get] ?: 0) + 1
+        fun covers(cost: Map<Resource, Int>) = cost.all { (r, n) -> (hand[Good.of(r)] ?: 0) >= n }
+        if (covers(CatanRules.CITY_COST) || covers(CatanRules.SETTLEMENT_COST)) return true
+        return Track.entries.any { track ->
+            val level = CatanCk.improvement(state, seat, track)
+            level < IMPROVEMENT_MAX &&
+                (hand[Good.of(track.commodity)] ?: 0) >= level + 1 &&
+                (state.ck!!.commodities[seat][track.commodity] ?: 0) < level + 1
+        }
+    }
+
+    private fun chooseFreeRoad(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove =
+        legal.filterIsInstance<BuildRoad>()
+            .filter { ai.roadValue(state, it) > 0.05 }
+            .maxByOrNull { ai.roadValue(state, it) }
+            ?: legal.firstOrNull { it is EndFreeRoads }
+            ?: legal.first()
+
+    private fun chooseResponse(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
+        val decline = legal.first { it is DeclineTrade }
+        val accept = legal.firstOrNull { it is AcceptTrade } ?: return decline
+        val offer = state.ck?.goodsOffer
+        if (offer != null) {
+            val incoming = offer.give.sumOf { worth(state, seat, it) }
+            val outgoing = offer.get.sumOf { worth(state, seat, it) }
+            return if (incoming > outgoing) accept else decline
+        }
+        val plain = state.pendingTrade ?: return decline
+        val incoming = plain.give.sumOf { ai.want(it) }
+        val outgoing = plain.get.sumOf { ai.want(it) }
+        return if (incoming > outgoing) accept else decline
+    }
+
+    /** Counters to a human's... the AI never makes an offer, so this only guards the phase: take none. */
+    private fun chooseCounter(state: CatanState, legal: List<CatanMove>): CatanMove =
+        legal.firstOrNull { it is DismissCounters } ?: legal.first()
+
+    // -----------------------------------------------------------------------
+    // Valuations
+    // -----------------------------------------------------------------------
+
+    /** What a card is worth to this seat: resources as the base AI sees them, commodities by what they buy. */
+    private fun worth(state: CatanState, seat: Int, good: Good): Double =
+        good.resource?.let { ai.want(it) } ?: when (good) {
+            Good.PAPER -> 0.95
+            Good.COIN -> 0.9
+            else -> 0.85
+        }
+
+    /** Which track to lean toward when two are level: politics for the knights, then science. */
+    private fun trackLean(track: Track): Int = when (track) {
+        Track.POLITICS -> 2
+        Track.SCIENCE -> 1
+        Track.TRADE -> 0
+    }
+
+    private fun cardWorth(kind: ProgressType): Double = when (kind) {
+        ProgressType.INVENTOR, ProgressType.ALCHEMIST, ProgressType.DIPLOMAT,
+        ProgressType.DESERTER, ProgressType.INTRIGUE, ProgressType.MERCHANT_FLEET,
+        -> 0.0
+
+        ProgressType.MERCHANT, ProgressType.COMMERCIAL_HARBOR, ProgressType.CRANE -> 0.5
+        else -> 1.0
+    }
+}

app/src/main/java/org/prolibertate/games/game/catan/CatanCkModel.kt

@@ -0,0 +1,486 @@
+package org.prolibertate.games.game.catan
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+/*
+ * The data of the Cities & Knights rule set. The rules themselves live in
+ * [CatanCk]; docs/RULES-catan-ck.md describes them and the choices made.
+ *
+ * Everything here is reached through [CatanState.ck], which is null for the
+ * base game, so a base game never sees any of it.
+ */
+
+/** Steps the barbarian ship must make before it lands. */
+const val BARBARIAN_STEPS = 7
+
+/** Commodity cards of each type the bank starts with (resources have 19). */
+const val BANK_PER_COMMODITY = 12
+
+/** Knights of each strength one player owns. */
+const val KNIGHTS_PER_LEVEL = 2
+
+/** City walls one player owns. */
+const val MAX_WALLS = 3
+
+/** Levels of city improvement in each track. */
+const val IMPROVEMENT_MAX = 5
+
+/** Progress cards a player may keep in hand. */
+const val PROGRESS_HAND_MAX = 4
+
+/** Cards a player may hold through a seven, before walls. */
+const val BASE_HAND_LIMIT = 7
+
+/** Longest Road is worth two points here; there is no Largest Army. */
+const val CK_LONGEST_ROAD_VP = 2
+
+/** Improvement level that unlocks the track's special power. */
+const val IMPROVEMENT_POWER_LEVEL = 3
+
+/** Level at which a track can claim its metropolis, and the level that can steal one. */
+const val METROPOLIS_LEVEL = 4
+
+/**
+ * What the three cities-of-industry give in place of a second resource:
+ * forest gives paper, pasture cloth and mountains coin.
+ */
+@Serializable
+enum class Commodity { CLOTH, COIN, PAPER }
+
+/**
+ * Any card a player can hold in hand and trade: a resource or a commodity.
+ * Progress cards are not goods.
+ */
+@Serializable
+enum class Good {
+    LUMBER, BRICK, WOOL, GRAIN, ORE, CLOTH, COIN, PAPER;
+
+    val resource: Resource?
+        get() = when (this) {
+            LUMBER -> Resource.LUMBER
+            BRICK -> Resource.BRICK
+            WOOL -> Resource.WOOL
+            GRAIN -> Resource.GRAIN
+            ORE -> Resource.ORE
+            else -> null
+        }
+
+    val commodity: Commodity?
+        get() = when (this) {
+            CLOTH -> Commodity.CLOTH
+            COIN -> Commodity.COIN
+            PAPER -> Commodity.PAPER
+            else -> null
+        }
+
+    val isCommodity: Boolean get() = commodity != null
+
+    companion object {
+        fun of(resource: Resource): Good = when (resource) {
+            Resource.LUMBER -> LUMBER
+            Resource.BRICK -> BRICK
+            Resource.WOOL -> WOOL
+            Resource.GRAIN -> GRAIN
+            Resource.ORE -> ORE
+        }
+
+        fun of(commodity: Commodity): Good = when (commodity) {
+            Commodity.CLOTH -> CLOTH
+            Commodity.COIN -> COIN
+            Commodity.PAPER -> PAPER
+        }
+
+        val RESOURCES: List<Good> = Resource.entries.map { of(it) }
+        val COMMODITIES: List<Good> = Commodity.entries.map { of(it) }
+    }
+}
+
+/**
+ * The three tracks of city improvement. Each is bought with one commodity, has
+ * a colour of progress-card deck and a power that unlocks at level three.
+ */
+@Serializable
+enum class Track(val commodity: Commodity) {
+    /** Yellow, bought with cloth: trade commodities two for one. */
+    TRADE(Commodity.CLOTH),
+
+    /** Blue, bought with coin: knights may become mighty. */
+    POLITICS(Commodity.COIN),
+
+    /** Green, bought with paper: the aqueduct. */
+    SCIENCE(Commodity.PAPER),
+}
+
+/**
+ * One face of the event die: a ship, or a city gate of a track's colour.
+ * Three faces are ships.
+ */
+@Serializable
+enum class EventFace { SHIP, TRADE, POLITICS, SCIENCE }
+
+/** The progress cards: [copies] of each in the deck of its [track]. */
+@Serializable
+enum class ProgressType(val track: Track, val copies: Int, val scoresAtOnce: Boolean = false) {
+    // Science (green)
+    ALCHEMIST(Track.SCIENCE, 2),
+    CRANE(Track.SCIENCE, 2),
+    ENGINEER(Track.SCIENCE, 1),
+    INVENTOR(Track.SCIENCE, 2),
+    IRRIGATION(Track.SCIENCE, 2),
+    MEDICINE(Track.SCIENCE, 2),
+    MINING(Track.SCIENCE, 2),
+    PRINTER(Track.SCIENCE, 1, scoresAtOnce = true),
+    ROAD_BUILDING(Track.SCIENCE, 2),
+    SMITH(Track.SCIENCE, 2),
+
+    // Politics (blue)
+    BISHOP(Track.POLITICS, 2),
+    CONSTITUTION(Track.POLITICS, 1, scoresAtOnce = true),
+    DESERTER(Track.POLITICS, 2),
+    DIPLOMAT(Track.POLITICS, 2),
+    INTRIGUE(Track.POLITICS, 2),
+    SABOTEUR(Track.POLITICS, 2),
+    SPY(Track.POLITICS, 3),
+    WARLORD(Track.POLITICS, 2),
+    WEDDING(Track.POLITICS, 2),
+
+    // Trade (yellow)
+    COMMERCIAL_HARBOR(Track.TRADE, 2),
+    MASTER_MERCHANT(Track.TRADE, 2),
+    MERCHANT(Track.TRADE, 6),
+    MERCHANT_FLEET(Track.TRADE, 2),
+    RESOURCE_MONOPOLY(Track.TRADE, 4),
+    TRADE_MONOPOLY(Track.TRADE, 2),
+}
+
+/** One progress card; [id] is stable for the life of the game. */
+@Serializable
+data class ProgressCard(val id: Int, val kind: ProgressType)
+
+/**
+ * A knight on the board. [level] is its strength: 1 basic, 2 strong, 3 mighty.
+ *
+ * [activatedTurn] and [promotedTurn] record the turn number each happened on:
+ * a knight cannot act on the turn it was activated, and cannot be promoted twice
+ * in one turn.
+ */
+@Serializable
+data class Knight(
+    val vertex: Int,
+    val owner: Int,
+    val level: Int,
+    val active: Boolean = false,
+    val activatedTurn: Int = 0,
+    val promotedTurn: Int = 0,
+)
+
+/** A metropolis stands on one city: [vertex] of seat [seat]. */
+@Serializable
+data class MetropolisAt(val seat: Int, val vertex: Int)
+
+/** The merchant sits on a hex, controlled by [seat] (who holds its point). */
+@Serializable
+data class MerchantAt(val seat: Int, val hex: Int)
+
+/** A counter-proposal to a [GoodsOffer]: seat [by] would [give] these if the offerer handed over [get]. */
+@Serializable
+data class GoodsCounter(val by: Int, val give: List<Good>, val get: List<Good>)
+
+/**
+ * A domestic trade offer in goods, which may include commodities. It is the
+ * base game's [TradeOffer] in cards of any kind, and works the same way: [to] is
+ * the one seat it is addressed to or null for the whole table, [asking] is the
+ * seat that may answer now, and [counters] collect for the offerer to choose from.
+ */
+@Serializable
+data class GoodsOffer(
+    val by: Int,
+    val to: Int?,
+    val give: List<Good>,
+    val get: List<Good>,
+    val asking: Int = to ?: -1,
+    val counters: List<GoodsCounter> = emptyList(),
+)
+
+/** Where play goes when the queue of [Chore]s runs out. */
+@Serializable
+enum class Back { PLAYING, AWAIT_ROLL, AFTER_EVENT, AFTER_DISCARDS, AFTER_PRODUCTION }
+
+/**
+ * Something one seat must decide before the game can go on. A chore is queued
+ * when a roll, an attack or a card needs an answer from somebody (possibly not
+ * the player whose turn it is); the first in [CkState.chores] is the one being
+ * asked.
+ */
+@Serializable
+sealed interface Chore {
+    val seat: Int
+}
+
+/** Give [count] cards to the bank, of the seat's choosing (a seven, a saboteur). */
+@Serializable
+@SerialName("c_discard")
+data class DiscardChore(override val seat: Int, val count: Int) : Chore
+
+/**
+ * Hand [count] cards of the seat's choosing to seat [to] (a wedding, a
+ * commercial harbour). [commoditiesOnly] restricts them to commodities, and
+ * [reward] is the resource [to] gives back for each.
+ */
+@Serializable
+@SerialName("c_give")
+data class GiveChore(
+    override val seat: Int,
+    val count: Int,
+    val to: Int,
+    val commoditiesOnly: Boolean = false,
+    val reward: Good? = null,
+) : Chore
+
+/** The barbarians won and this seat lost the contest: pick a city to fall. */
+@Serializable
+@SerialName("c_pillage")
+data class PillageChore(override val seat: Int) : Chore
+
+/** Choose a colour of progress deck to draw from. */
+@Serializable
+@SerialName("c_pickDeck")
+data class PickDeckChore(override val seat: Int) : Chore
+
+/** More progress cards than the hand holds: give one back. */
+@Serializable
+@SerialName("c_dropProgress")
+data class DropProgressChore(override val seat: Int) : Chore
+
+/** Choose the city that will bear the [track] metropolis. */
+@Serializable
+@SerialName("c_metropolis")
+data class MetropolisChore(override val seat: Int, val track: Track) : Chore
+
+/** The aqueduct pays out: take any one resource. */
+@Serializable
+@SerialName("c_aqueduct")
+data class AqueductChore(override val seat: Int) : Chore
+
+/** A knight was driven from its place; move it, or lose it. [knight] stood on [Knight.vertex]. */
+@Serializable
+@SerialName("c_relocate")
+data class RelocateChore(override val seat: Int, val knight: Knight) : Chore
+
+/** A deserter was played against this seat: remove one of your knights. */
+@Serializable
+@SerialName("c_removeKnight")
+data class RemoveKnightChore(override val seat: Int, val by: Int) : Chore
+
+/** Place a knight of [level] on the board for free, active or not as given. */
+@Serializable
+@SerialName("c_placeKnight")
+data class PlaceKnightChore(override val seat: Int, val level: Int, val active: Boolean) : Chore
+
+/** Choose one of [target]'s progress cards to take. */
+@Serializable
+@SerialName("c_spy")
+data class SpyChore(override val seat: Int, val target: Int) : Chore
+
+/** Promote up to [left] more knights for free. */
+@Serializable
+@SerialName("c_smith")
+data class SmithChore(override val seat: Int, val left: Int) : Chore
+
+/**
+ * Everything Cities & Knights adds to the table.
+ *
+ * Counts that are public ([progressCounts], the knights, the improvement
+ * levels) are stored directly; the decks and the other seats' progress hands are
+ * here in full because the host owns the truth, and [CatanRules.viewFor] keeps
+ * them off the wire.
+ */
+@Serializable
+data class CkState(
+    /** Commodity cards per seat. */
+    val commodities: List<Map<Commodity, Int>>,
+    /** Improvement level (0..5) per seat and track. */
+    val improvements: List<Map<Track, Int>>,
+    /** The metropolis of each track that has one. */
+    val metropolises: Map<Track, MetropolisAt> = emptyMap(),
+    val knights: List<Knight> = emptyList(),
+    /** Vertices whose city has a wall. */
+    val walls: List<Int> = emptyList(),
+    /** Steps left before the barbarians land, [BARBARIAN_STEPS] at the start. */
+    val barbarians: Int = BARBARIAN_STEPS,
+    /** Whether the barbarians have landed once: until then the robber sleeps. */
+    val attacked: Boolean = false,
+    val eventDie: EventFace? = null,
+    /** Progress decks, top first. Order is hidden. */
+    val decks: Map<Track, List<ProgressCard>>,
+    val progressHands: List<List<ProgressCard>>,
+    /** Public mirror of the progress-hand sizes. */
+    val progressCounts: List<Int>,
+    /** Victory points from Constitution and Printer, played face up at once. */
+    val progressVp: List<Int>,
+    /** Defender of Catan cards won, one point each. */
+    val defenderVp: List<Int>,
+    val merchant: MerchantAt? = null,
+    /** A crane was played this turn and its discount is unspent. */
+    val crane: Boolean = false,
+    /** A merchant fleet was played this turn for this good. */
+    val fleet: Good? = null,
+    /** Dice named by an alchemist, used by the next roll. */
+    val alchemist: List<Int>? = null,
+    /** The robber is being moved by a bishop, which robs everyone nearby. */
+    val bishop: Boolean = false,
+    val chores: List<Chore> = emptyList(),
+    val back: Back = Back.PLAYING,
+    val goodsOffer: GoodsOffer? = null,
+    /** Seats that have already drawn a defender or winners' card this attack, for the log only. */
+    val lastAttack: String? = null,
+)
+
+// ---------------------------------------------------------------------------
+// Moves
+// ---------------------------------------------------------------------------
+
+/** Buy the next level of improvement in [track]. */
+@Serializable
+@SerialName("buyImprovement")
+data class BuyImprovement(val track: Track) : CatanMove
+
+/** Hire a basic knight onto [vertex], an empty crossing at the end of one of your roads. */
+@Serializable
+@SerialName("hireKnight")
+data class HireKnight(val vertex: Int) : CatanMove
+
+/** Pay a grain to activate the knight on [vertex]. */
+@Serializable
+@SerialName("activateKnight")
+data class ActivateKnight(val vertex: Int) : CatanMove
+
+/** Promote the knight on [vertex] one level (paid, or free under a Smith). */
+@Serializable
+@SerialName("promoteKnight")
+data class PromoteKnight(val vertex: Int) : CatanMove
+
+/** Move the active knight on [from] along your roads to [to], driving off a weaker knight there. */
+@Serializable
+@SerialName("moveKnight")
+data class MoveKnight(val from: Int, val to: Int) : CatanMove
+
+/** The active knight on [vertex] chases the robber; the robber move follows. */
+@Serializable
+@SerialName("chaseRobber")
+data class ChaseRobber(val vertex: Int) : CatanMove
+
+/** Raise a wall around the city on [vertex]. */
+@Serializable
+@SerialName("buildWall")
+data class BuildWall(val vertex: Int) : CatanMove
+
+/**
+ * Play a progress card. Which of the optional arguments are used depends on
+ * the card (see [CatanCk]); the engine's legal list names every combination it
+ * accepts, so a client only ever chooses among them.
+ */
+@Serializable
+@SerialName("progress")
+data class PlayProgress(
+    val card: Int,
+    val target: Int? = null,
+    val vertex: Int? = null,
+    val edge: Int? = null,
+    val hexA: Int? = null,
+    val hexB: Int? = null,
+    val good: Good? = null,
+    val dice: List<Int>? = null,
+    val goods: List<Good>? = null,
+) : CatanMove
+
+/**
+ * Trade [give] to the bank for [get], at the best ratio this seat has for the
+ * card it gives. Replaces [MaritimeTrade] in Cities & Knights, where
+ * commodities trade too.
+ */
+@Serializable
+@SerialName("goodsBank")
+data class GoodsBankTrade(val give: Good, val get: Good) : CatanMove
+
+/**
+ * Offer a trade in goods to seat [to], or to the whole table when [to] is null.
+ * Free-form like [OfferTrade], so it is checked structurally and is not in the
+ * enumerated move list.
+ */
+@Serializable
+@SerialName("offerGoods")
+data class OfferGoods(val to: Int?, val give: List<Good>, val get: List<Good>) : CatanMove
+
+/**
+ * Answer the goods offer on the table with different terms. Structural, like
+ * [OfferGoods]; the answers to the counters are the shared [AcceptCounter] and
+ * [DismissCounters].
+ */
+@Serializable
+@SerialName("counterGoods")
+data class CounterGoods(val give: List<Good>, val get: List<Good>) : CatanMove
+
+/**
+ * Give up exactly the cards named, to a [DiscardChore]. Structural, not
+ * enumerated; the legal list carries one example so a seat is never without a move.
+ */
+@Serializable
+@SerialName("discardGoods")
+data class DiscardGoods(val cards: List<Good>) : CatanMove
+
+/** Hand over the cards named to a [GiveChore]. Structural, like [DiscardGoods]. */
+@Serializable
+@SerialName("giveGoods")
+data class GiveGoods(val cards: List<Good>) : CatanMove
+
+/** Let the city on [vertex] fall to the barbarians. */
+@Serializable
+@SerialName("pillageCity")
+data class PillageCity(val vertex: Int) : CatanMove
+
+/** Draw from the deck of this track's colour. */
+@Serializable
+@SerialName("pickDeck")
+data class PickDeck(val track: Track) : CatanMove
+
+/** Give up one progress card from a hand that is over the limit. */
+@Serializable
+@SerialName("dropProgress")
+data class DropProgress(val card: Int) : CatanMove
+
+/** Put the metropolis on the city at [vertex]. */
+@Serializable
+@SerialName("placeMetropolis")
+data class PlaceMetropolis(val vertex: Int) : CatanMove
+
+/** Take one [resource] from the bank for an aqueduct. */
+@Serializable
+@SerialName("aqueduct")
+data class TakeAqueduct(val resource: Resource) : CatanMove
+
+/** Move the knight that was driven off to [to]. */
+@Serializable
+@SerialName("relocateKnight")
+data class RelocateKnight(val to: Int) : CatanMove
+
+/** Take the knight on [vertex] off the board, for a deserter. */
+@Serializable
+@SerialName("removeKnight")
+data class RemoveKnight(val vertex: Int) : CatanMove
+
+/** Place the free knight from a deserter on [vertex]. */
+@Serializable
+@SerialName("placeKnight")
+data class PlaceKnight(val vertex: Int) : CatanMove
+
+/** Take the spied progress card with this id. */
+@Serializable
+@SerialName("spyTake")
+data class SpyTake(val card: Int) : CatanMove
+
+/** Stop promoting knights under a Smith. */
+@Serializable
+@SerialName("endSmith")
+data object EndSmith : CatanMove

app/src/main/java/org/prolibertate/games/game/catan/CatanModel.kt

@@ -12,6 +12,11 @@ const val LONGEST_ROAD_MIN = 5
 /** Knights required to take Largest Army. */
 const val LARGEST_ARMY_MIN = 3
 
+/** Pieces each player has: a player who has laid them all cannot build another. */
+const val MAX_ROADS = 15
+const val MAX_SETTLEMENTS = 5
+const val MAX_CITIES = 4
+
 /** Resource cards of each type the bank starts with. */
 const val BANK_PER_RESOURCE = 19
 
@@ -69,17 +74,34 @@ enum class DevCardType { KNIGHT, ROAD_BUILDING, MONOPOLY, YEAR_OF_PLENTY, VICTOR
 data class DevCard(val id: Int, val type: DevCardType, val boughtTurn: Int = 0)
 
 /**
- * A domestic trade offer on the table. [by] is the offering seat and [to]
- * the only seat that may respond — v1 has no counter-offers and no open
- * auctions, so an offer is always addressed to one player.
+ * A counter-proposal to a [TradeOffer]: seat [by] would [give] these cards to
+ * the offerer if the offerer would hand over [get].
  */
 @Serializable
-data class TradeOffer(val by: Int, val to: Int, val give: List<Resource>, val get: List<Resource>)
+data class TradeCounter(val by: Int, val give: List<Resource>, val get: List<Resource>)
+
+/**
+ * A domestic trade offer on the table. [by] is the offering seat. [to] is the
+ * one seat it is addressed to, or null for an open offer to the whole table.
+ * Seats are asked one at a time, in seat order after the offerer; [asking] is
+ * the seat that may answer now. Each may accept (the trade happens at once),
+ * decline, or counter; counters are kept in [counters] and, if nobody accepts,
+ * the offerer chooses among them in [CatanPhase.TRADE_COUNTERS].
+ */
+@Serializable
+data class TradeOffer(
+    val by: Int,
+    val to: Int?,
+    val give: List<Resource>,
+    val get: List<Resource>,
+    val asking: Int = to ?: -1,
+    val counters: List<TradeCounter> = emptyList(),
+)
 
 /**
  * Where the game stands. The phases that involve more than the player
  * whose turn it is carry their own bookkeeping: [discardSeat] during
- * [CatanPhase.DISCARDING], [pendingTrade] during [CatanPhase.TRADE_PENDING].
+ * [CatanPhase.DISCARDING], [pendingTrade] during [CatanPhase.TRADE_PENDING] and [CatanPhase.TRADE_COUNTERS].
  */
 @Serializable
 enum class CatanPhase {
@@ -104,16 +126,37 @@ enum class CatanPhase {
     /** A played Road Building card: up to two roads remain to be placed. */
     FREE_ROADS,
 
-    /** The offered seat must accept or decline. */
+    /** The [TradeOffer.asking] seat must accept, decline or counter. */
     TRADE_PENDING,
 
+    /** Nobody accepted but some seats countered: the offerer picks one or none. */
+    TRADE_COUNTERS,
+
     GAME_OVER,
+
+    /**
+     * Cities & Knights only: the first seat in [CkState.chores] has something
+     * to decide (a discard, a city to give up, a card to draw…) and the game
+     * waits on it. Play resumes where [CkState.back] says.
+     */
+    CHORE,
+}
+
+/** Which rules a table plays. The expansion is a whole rule set, not a toggle. */
+@Serializable
+enum class CatanRuleSet {
+    /** The base game: development cards, Largest Army, a robber from the start. */
+    BASE,
+
+    /** Cities & Knights: commodities, knights, barbarians, city improvements. */
+    CITIES_AND_KNIGHTS,
 }
 
 @Serializable
 data class CatanOptions(
     val playerCount: Int = 3,
     val pointsToWin: Int = 10,
+    val ruleSet: CatanRuleSet = CatanRuleSet.BASE,
 ) {
     init {
         require(playerCount in 3..4) { "The island seats three or four players" }
@@ -185,9 +228,14 @@ data class CatanState(
     val rngStep: Int,
     val winner: Int?,
     val log: List<String>,
+    /** Everything Cities & Knights adds; null in the base game. */
+    val ck: CkState? = null,
 ) {
     val playerCount: Int get() = options.playerCount
 
+    /** Whether this table plays Cities & Knights. */
+    val isCk: Boolean get() = ck != null
+
     /** Total resource cards held by [seat]. */
     fun resourceCount(seat: Int): Int = resources[seat].values.sum()
 
@@ -222,7 +270,11 @@ data class SetupPlace(val vertex: Int, val edge: Int) : CatanMove
  */
 @Serializable
 @SerialName("roll")
-data class RollDice(val forced: List<Int>? = null) : CatanMove
+data class RollDice(
+    val forced: List<Int>? = null,
+    /** Test-only, like [forced]: the event die of a Cities & Knights roll. */
+    val event: EventFace? = null,
+) : CatanMove
 
 /** Discard exactly these cards. */
 @Serializable
@@ -273,7 +325,8 @@ data class PlayMonopoly(val card: Int, val resource: Resource) : CatanMove
 data class PlayYearOfPlenty(val card: Int, val take: List<Resource>) : CatanMove
 
 /**
- * Offer a domestic trade to [to]: [give] of ours for [get] of theirs.
+ * Offer a domestic trade to [to] (null: everyone, asked in turn): [give] of
+ * ours for [get] of theirs.
  *
  * Like a forced dice roll this is a free-form intent rather than an
  * enumerated move — the space of two card multisets is combinatorial — so
@@ -282,7 +335,7 @@ data class PlayYearOfPlenty(val card: Int, val take: List<Resource>) : CatanMove
  */
 @Serializable
 @SerialName("offer")
-data class OfferTrade(val to: Int, val give: List<Resource>, val get: List<Resource>) : CatanMove
+data class OfferTrade(val to: Int?, val give: List<Resource>, val get: List<Resource>) : CatanMove
 
 @Serializable
 @SerialName("accept")
@@ -292,6 +345,25 @@ data object AcceptTrade : CatanMove
 @SerialName("decline")
 data object DeclineTrade : CatanMove
 
+/**
+ * Answer the offer on the table with different terms: we would [give] these
+ * cards if the offerer handed over [get]. Free-form like [OfferTrade], so
+ * validated by [CatanRules.isLegalMove] rather than listed.
+ */
+@Serializable
+@SerialName("counter")
+data class CounterTrade(val give: List<Resource>, val get: List<Resource>) : CatanMove
+
+/** The offerer takes the counter-proposal made by [seat]. */
+@Serializable
+@SerialName("acceptCounter")
+data class AcceptCounter(val seat: Int) : CatanMove
+
+/** The offerer takes none of the counter-proposals. */
+@Serializable
+@SerialName("dismissCounters")
+data object DismissCounters : CatanMove
+
 /** Bank trade: [give] at the best ratio this seat can trade at for [get]. */
 @Serializable
 @SerialName("bank")

app/src/main/java/org/prolibertate/games/game/catan/CatanRules.kt

@@ -57,9 +57,16 @@ object CatanRules : GameRules<CatanState, CatanMove> {
         val board = CatanBoard.generate(config.seed)
         // A different random stream than the island, so the same seed still
         // produces both a fixed island and a fixed deck.
-        val devDeck = DEV_DECK
-            .mapIndexed { id, type -> DevCard(id, type) }
-            .shuffled(Random(config.seed + 1))
+        val ck = options.ruleSet == CatanRuleSet.CITIES_AND_KNIGHTS
+        // Cities & Knights has no development cards: knights and progress
+        // cards take their place.
+        val devDeck = if (ck) {
+            emptyList()
+        } else {
+            DEV_DECK
+                .mapIndexed { id, type -> DevCard(id, type) }
+                .shuffled(Random(config.seed + 1))
+        }
 
         return CatanState(
             options = options,
@@ -91,8 +98,10 @@ object CatanRules : GameRules<CatanState, CatanMove> {
             rngStep = 0,
             winner = null,
             log = listOf(
-                "Catan — ${options.playerCount} players, first to ${options.pointsToWin} victory points.",
+                "Catan${if (ck) " — Cities & Knights" else ""} — ${options.playerCount} players, " +
+                    "first to ${options.pointsToWin} victory points.",
             ),
+            ck = if (ck) CatanCk.initial(options, config.seed) else null,
         )
     }
 
@@ -101,7 +110,10 @@ object CatanRules : GameRules<CatanState, CatanMove> {
         CatanPhase.SETUP_FIRST -> state.setupIndex
         CatanPhase.SETUP_SECOND -> 2 * state.playerCount - 1 - state.setupIndex
         CatanPhase.DISCARDING -> state.discardSeat
-        CatanPhase.TRADE_PENDING -> state.pendingTrade?.to
+        CatanPhase.TRADE_PENDING -> state.pendingTrade?.asking?.takeIf { it >= 0 }
+            ?: state.ck?.goodsOffer?.asking?.takeIf { it >= 0 }
+        CatanPhase.TRADE_COUNTERS -> state.turn
+        CatanPhase.CHORE -> state.ck?.chores?.firstOrNull()?.seat
         CatanPhase.AWAIT_ROLL, CatanPhase.ROBBER,
         CatanPhase.PLAYING, CatanPhase.FREE_ROADS,
         -> state.turn
@@ -130,12 +142,19 @@ object CatanRules : GameRules<CatanState, CatanMove> {
 
             is OfferTrade -> offerLegal(state, seat, move)
 
-            else -> move in legalMoves(state, seat)
+            is CounterTrade -> counterLegal(state, seat, move)
+
+            else -> if (state.isCk) {
+                CatanCk.structurallyLegal(state, seat, move) ?: (move in legalMoves(state, seat))
+            } else {
+                move in legalMoves(state, seat)
+            }
         }
     }
 
     override fun legalMoves(state: CatanState, seat: Int): List<CatanMove> {
         if (currentSeat(state) != seat) return emptyList()
+        if (state.isCk) return CatanCk.legalMoves(state, seat)
         return when (state.phase) {
             CatanPhase.SETUP_FIRST, CatanPhase.SETUP_SECOND -> setupMoves(state)
 
@@ -152,11 +171,13 @@ object CatanRules : GameRules<CatanState, CatanMove> {
 
             CatanPhase.TRADE_PENDING -> tradeResponses(state, seat)
 
-            CatanPhase.GAME_OVER -> emptyList()
+            CatanPhase.TRADE_COUNTERS -> counterChoices(state)
+
+            CatanPhase.CHORE, CatanPhase.GAME_OVER -> emptyList()
         }
     }
 
-    private fun setupMoves(state: CatanState): List<SetupPlace> {
+    internal fun setupMoves(state: CatanState): List<SetupPlace> {
         val moves = mutableListOf<SetupPlace>()
         for (v in 0 until CatanBoard.VERTEX_COUNT) {
             if (!vertexOpenForSettlement(state, v)) continue
@@ -272,11 +293,18 @@ object CatanRules : GameRules<CatanState, CatanMove> {
         return takes
     }
 
-    /** Road placements that connect to [seat]'s network, cost aside. */
-    private fun roadMoves(state: CatanState, seat: Int): List<BuildRoad> =
-        (0 until CatanBoard.EDGE_COUNT)
-            .filter { state.roads[it] == NO_PLAYER && roadConnects(state, seat, it) }
-            .map { BuildRoad(it) }
+    /**
+     * Road placements that connect to [seat]'s network, cost aside. A player
+     * with all fifteen roads laid has none.
+     */
+    internal fun roadMoves(state: CatanState, seat: Int): List<BuildRoad> =
+        if (state.roads.count { it == seat } >= MAX_ROADS) {
+            emptyList()
+        } else {
+            (0 until CatanBoard.EDGE_COUNT)
+                .filter { state.roads[it] == NO_PLAYER && roadConnects(state, seat, it) }
+                .map { BuildRoad(it) }
+        }
 
     /**
      * Settlement placements: an open vertex at least two edges from every
@@ -284,18 +312,33 @@ object CatanRules : GameRules<CatanState, CatanMove> {
      * connection requirement does not apply — that is why setup uses its
      * own move.)
      */
-    private fun settlementVertices(state: CatanState, seat: Int): List<Int> =
-        (0 until CatanBoard.VERTEX_COUNT).filter { v ->
-            vertexOpenForSettlement(state, v) &&
-                CatanBoard.VERTEX_EDGES[v].any { state.roads[it] == seat }
+    internal fun settlementVertices(state: CatanState, seat: Int): List<Int> =
+        if (piecesOf(state, seat, BuildingType.SETTLEMENT) >= MAX_SETTLEMENTS) {
+            emptyList()
+        } else {
+            (0 until CatanBoard.VERTEX_COUNT).filter { v ->
+                vertexOpenForSettlement(state, v) &&
+                    CatanBoard.VERTEX_EDGES[v].any { state.roads[it] == seat }
+            }
         }
 
-    private fun cityVertices(state: CatanState, seat: Int): List<Int> =
-        (0 until CatanBoard.VERTEX_COUNT).filter { v ->
-            state.buildings[v] == CatanBuilding(BuildingType.SETTLEMENT, seat)
+    internal fun cityVertices(state: CatanState, seat: Int): List<Int> =
+        if (piecesOf(state, seat, BuildingType.CITY) >= MAX_CITIES) {
+            emptyList()
+        } else {
+            (0 until CatanBoard.VERTEX_COUNT).filter { v ->
+                state.buildings[v] == CatanBuilding(BuildingType.SETTLEMENT, seat)
+            }
         }
 
-    private fun tradeResponses(state: CatanState, seat: Int): List<CatanMove> {
+    private fun hasKnight(state: CatanState, vertex: Int): Boolean =
+        state.ck?.knights?.any { it.vertex == vertex } == true
+
+    /** How many settlements or cities [seat] currently has standing. */
+    private fun piecesOf(state: CatanState, seat: Int, type: BuildingType): Int =
+        state.buildings.count { it?.owner == seat && it.type == type }
+
+    internal fun tradeResponses(state: CatanState, seat: Int): List<CatanMove> {
         val offer = state.pendingTrade ?: return emptyList()
         val responses = mutableListOf<CatanMove>()
         if (state.holdsAll(seat, offer.get) && state.holdsAll(offer.by, offer.give)) {
@@ -305,23 +348,61 @@ object CatanRules : GameRules<CatanState, CatanMove> {
         return responses
     }
 
+    /** What the offerer may do with the counters: take one that is still affordable, or none. */
+    internal fun counterChoices(state: CatanState): List<CatanMove> {
+        val offer = state.pendingTrade ?: return emptyList()
+        val moves = mutableListOf<CatanMove>()
+        for (counter in offer.counters) {
+            if (state.holdsAll(counter.by, counter.give) && state.holdsAll(offer.by, counter.get)) {
+                moves += AcceptCounter(counter.by)
+            }
+        }
+        moves += DismissCounters
+        return moves
+    }
+
+    private fun counterLegal(state: CatanState, seat: Int, move: CounterTrade): Boolean {
+        val offer = state.pendingTrade ?: return false
+        if (state.phase != CatanPhase.TRADE_PENDING || offer.asking != seat) return false
+        if (move.give.isEmpty() || move.get.isEmpty()) return false
+        if (countOf(move.give) == countOf(move.get)) return false
+        // Taking the offer as made is Accept, not a counter.
+        if (countOf(move.give) == countOf(offer.get) && countOf(move.get) == countOf(offer.give)) return false
+        return state.holdsAll(seat, move.give) && state.holdsAll(offer.by, move.get)
+    }
+
     /** An empty vertex with no building on it or one edge away. */
-    private fun vertexOpenForSettlement(state: CatanState, v: Int): Boolean =
-        state.buildings[v] == null &&
+    internal fun vertexOpenForSettlement(state: CatanState, v: Int): Boolean =
+        state.buildings[v] == null && !hasKnight(state, v) &&
             CatanBoard.VERTEX_NEIGHBORS[v].all { state.buildings[it] == null }
 
-    /** A road on [edge] would join [seat]'s network of roads and buildings. */
+    /**
+     * A road on [edge] would join [seat]'s network of roads and buildings.
+     *
+     * It must start from a crossing the network actually reaches. An opponent's
+     * settlement or city on a crossing breaks the network there: roads on either
+     * side of it do not join, so a road cannot be laid *past* it, even with one
+     * of your own roads ending at the same crossing.
+     */
     private fun roadConnects(state: CatanState, seat: Int, edge: Int): Boolean {
         val (a, b) = CatanBoard.EDGE_VERTICES[edge]
-        return CatanBoard.VERTEX_EDGES[a].any { state.roads[it] == seat } ||
-            CatanBoard.VERTEX_EDGES[b].any { state.roads[it] == seat } ||
-            state.buildings[a]?.owner == seat ||
-            state.buildings[b]?.owner == seat
+        return networkReaches(state, seat, a) || networkReaches(state, seat, b)
+    }
+
+    /** Whether [seat]'s roads and buildings reach [vertex] so a road may start there. */
+    private fun networkReaches(state: CatanState, seat: Int, vertex: Int): Boolean {
+        val building = state.buildings[vertex]
+        // A knight is a wall to everyone but its owner, like a building.
+        val knight = state.ck?.knights?.firstOrNull { it.vertex == vertex }
+        if (knight != null && knight.owner != seat) return false
+        // Your own building is always a way in; anyone else's is a wall.
+        if (building != null) return building.owner == seat
+        return CatanBoard.VERTEX_EDGES[vertex].any { state.roads[it] == seat }
     }
 
     private fun offerLegal(state: CatanState, seat: Int, move: OfferTrade): Boolean {
         if (state.phase != CatanPhase.PLAYING || state.turn != seat) return false
-        if (move.to !in 0 until state.playerCount || move.to == seat) return false
+        if (move.to != null && (move.to !in 0 until state.playerCount || move.to == seat)) return false
         if (move.give.isEmpty() || move.get.isEmpty()) return false
         // Like-for-like is not a trade; the published game rejects it too.
         if (countOf(move.give) == countOf(move.get)) return false
@@ -353,21 +434,28 @@ object CatanRules : GameRules<CatanState, CatanMove> {
             is OfferTrade -> applyOfferTrade(state, seat, move)
             AcceptTrade -> applyAcceptTrade(state, seat)
             DeclineTrade -> applyDeclineTrade(state, seat)
+            is CounterTrade -> applyCounterTrade(state, seat, move)
+            is AcceptCounter -> applyAcceptCounter(state, move)
+            DismissCounters -> applyDismissCounters(state)
             is MaritimeTrade -> applyMaritimeTrade(state, seat, move)
             EndTurn -> applyEndTurn(state, seat)
             EndFreeRoads -> applyEndFreeRoads(state, seat)
-        }
+            else -> CatanCk.apply(state, seat, move)
+        }.let { if (it.isCk) CatanCk.settle(it) else it }
     }
 
     private fun applySetup(state: CatanState, seat: Int, move: SetupPlace): CatanState {
         val n = state.playerCount
         val second = state.phase == CatanPhase.SETUP_SECOND
+        // In Cities & Knights the second placement is a city.
+        val first = if (state.isCk && second) BuildingType.CITY else BuildingType.SETTLEMENT
         var s = state.copy(
             buildings = state.buildings.toMutableList().also {
-                it[move.vertex] = CatanBuilding(BuildingType.SETTLEMENT, seat)
+                it[move.vertex] = CatanBuilding(first, seat)
             },
             roads = state.roads.toMutableList().also { it[move.edge] = seat },
-            log = state.log + "Seat $seat settles at ${move.vertex} and lays a road on ${move.edge}.",
+            log = state.log + ("Seat $seat ${if (first == BuildingType.CITY) "raises a city" else "settles"} " +
+                "at ${move.vertex} and lays a road on ${move.edge}."),
         )
 
         if (second) {
@@ -401,6 +489,7 @@ object CatanRules : GameRules<CatanState, CatanMove> {
     }
 
     private fun applyRoll(state: CatanState, seat: Int, move: RollDice): CatanState {
+        if (state.isCk) return CatanCk.applyRoll(state, seat, move)
         val dice = move.forced ?: derivedDice(state)
         val total = dice[0] + dice[1]
         val s = state.copy(lastDice = dice, rngStep = state.rngStep + 1)
@@ -475,6 +564,7 @@ object CatanRules : GameRules<CatanState, CatanMove> {
         ((after + 1) until state.playerCount).firstOrNull { state.resourceCount(it) > 7 }
 
     private fun applyRobber(state: CatanState, seat: Int, move: MoveRobber): CatanState {
+        if (state.isCk) return CatanCk.applyRobber(state, seat, move)
         val hex = CatanBoard.hexIndex[move.hex]
             ?: throw IllegalArgumentException("No hex at ${move.hex}")
         var s = state.copy(robber = hex, rngStep = state.rngStep + 1)
@@ -491,8 +581,8 @@ object CatanRules : GameRules<CatanState, CatanMove> {
         }
         return s.copy(
             phase = CatanPhase.PLAYING,
-            log = s.log + "Seat $seat moves the robber to the ${terrainName(state.terrains[hex])}" +
-                " (${move.hex.q},${move.hex.r})$stolen.",
+            log = s.log + ("Seat $seat moves the robber to the ${terrainName(state.terrains[hex])}" +
+                " (${move.hex.q},${move.hex.r})$stolen."),
         )
     }
 
@@ -504,7 +594,7 @@ object CatanRules : GameRules<CatanState, CatanMove> {
         if (free) {
             val left = s.pendingFreeRoads - 1
             s = s.copy(pendingFreeRoads = left)
-            if (left == 0) s = s.copy(phase = CatanPhase.PLAYING)
+            if (left == 0) s = s.copy(phase = phaseAfterRoads(s))
         }
         return checkWin(s.copy(log = s.log + "Seat $seat builds a road on ${move.edge}."))
     }
@@ -529,7 +619,10 @@ object CatanRules : GameRules<CatanState, CatanMove> {
             },
         )
         s = payCost(s, seat, CITY_COST)
-        return checkWin(s.copy(log = s.log + "Seat $seat raises a city at ${move.vertex}."))
+        s = s.copy(log = s.log + "Seat $seat raises a city at ${move.vertex}.")
+        // A city can be what a waiting metropolis needed.
+        if (s.isCk) s = CatanCk.afterCityBuilt(s, seat)
+        return checkWin(s)
     }
 
     private fun applyBuyDevCard(state: CatanState, seat: Int): CatanState {
@@ -602,33 +695,117 @@ object CatanRules : GameRules<CatanState, CatanMove> {
         )
     }
 
-    private fun applyOfferTrade(state: CatanState, seat: Int, move: OfferTrade): CatanState =
-        state.copy(
-            phase = CatanPhase.TRADE_PENDING,
-            pendingTrade = TradeOffer(by = seat, to = move.to, give = move.give, get = move.get),
+    private fun applyOfferTrade(state: CatanState, seat: Int, move: OfferTrade): CatanState {
+        val audience = if (move.to == null) "the table" else "seat ${move.to}"
+        val offered = state.copy(
             log = state.log + "Seat $seat offers ${describe(countOf(move.give))} for " +
-                "${describe(countOf(move.get))} to seat ${move.to}.",
+                "${describe(countOf(move.get))} to $audience.",
         )
+        val offer = TradeOffer(by = seat, to = move.to, give = move.give, get = move.get)
+        val first = nextAsker(offered, offer, seat)
+            ?: return offered.copy(log = offered.log + "Nobody has any cards to trade.")
+        return offered.copy(
+            phase = CatanPhase.TRADE_PENDING,
+            pendingTrade = offer.copy(asking = first),
+        )
+    }
 
-    private fun applyAcceptTrade(state: CatanState, seat: Int): CatanState {
-        val offer = state.pendingTrade!!
-        var resources = withCards(state.resources, offer.to, offer.get, -1)
-        resources = withCards(resources, offer.by, offer.give, -1)
-        resources = withCards(resources, offer.by, offer.get, 1)
-        resources = withCards(resources, offer.to, offer.give, 1)
+    /**
+     * The next seat to ask after [after], or null when the round is over. An
+     * addressed offer asks only its addressee; an open one walks the table in
+     * seat order, skipping seats with no cards (they could neither pay nor counter).
+     */
+    private fun nextAsker(state: CatanState, offer: TradeOffer, after: Int): Int? {
+        if (offer.to != null) return if (after == offer.by) offer.to else null
+        var s = (after + 1) % state.playerCount
+        while (s != offer.by) {
+            if (state.resourceCount(s) > 0) return s
+            s = (s + 1) % state.playerCount
+        }
+        return null
+    }
+
+    /** Moves the offer on to the next seat, or closes the round when everyone has answered. */
+    private fun advanceTrade(state: CatanState, offer: TradeOffer, after: Int, said: String): CatanState {
+        val next = nextAsker(state, offer, after)
+        val log = state.log + said
+        if (next != null) {
+            return state.copy(pendingTrade = offer.copy(asking = next), log = log)
+        }
+        if (offer.counters.isNotEmpty()) {
+            return state.copy(
+                phase = CatanPhase.TRADE_COUNTERS,
+                pendingTrade = offer.copy(asking = -1),
+                log = log,
+            )
+        }
         return state.copy(
             phase = CatanPhase.PLAYING,
             pendingTrade = null,
-            resources = resources,
+            log = log + "Nobody takes the offer.",
+        )
+    }
+
+    /** Seat [a] hands [aGives] to seat [b] and gets [bGives] back. */
+    private fun swapCards(
+        resources: List<Map<Resource, Int>>,
+        a: Int,
+        aGives: List<Resource>,
+        b: Int,
+        bGives: List<Resource>,
+    ): List<Map<Resource, Int>> {
+        var r = withCards(resources, a, aGives, -1)
+        r = withCards(r, b, bGives, -1)
+        r = withCards(r, b, aGives, 1)
+        return withCards(r, a, bGives, 1)
+    }
+
+    private fun applyAcceptTrade(state: CatanState, seat: Int): CatanState {
+        if (state.ck?.goodsOffer != null) return CatanCk.answerOffer(state, seat, accept = true)
+        val offer = state.pendingTrade!!
+        return state.copy(
+            phase = CatanPhase.PLAYING,
+            pendingTrade = null,
+            resources = swapCards(state.resources, offer.by, offer.give, seat, offer.get),
             log = state.log + "Seat $seat accepts — the cards cross the table.",
         )
     }
 
     private fun applyDeclineTrade(state: CatanState, seat: Int): CatanState =
-        state.copy(
+        if (state.ck?.goodsOffer != null) {
+            CatanCk.answerOffer(state, seat, accept = false)
+        } else {
+            advanceTrade(state, state.pendingTrade!!, seat, "Seat $seat declines the offer.")
+        }
+
+    private fun applyCounterTrade(state: CatanState, seat: Int, move: CounterTrade): CatanState {
+        val offer = state.pendingTrade!!
+        val counter = TradeCounter(by = seat, give = move.give, get = move.get)
+        return advanceTrade(
+            state,
+            offer.copy(counters = offer.counters + counter),
+            seat,
+            "Seat $seat counters: ${describe(countOf(move.give))} for ${describe(countOf(move.get))}.",
+        )
+    }
+
+    private fun applyAcceptCounter(state: CatanState, move: AcceptCounter): CatanState {
+        if (state.ck?.goodsOffer != null) return CatanCk.acceptCounter(state, move)
+        val offer = state.pendingTrade!!
+        val counter = offer.counters.first { it.by == move.seat }
+        return state.copy(
             phase = CatanPhase.PLAYING,
             pendingTrade = null,
-            log = state.log + "Seat $seat declines the offer.",
+            resources = swapCards(state.resources, offer.by, counter.get, counter.by, counter.give),
+            log = state.log + "Seat ${offer.by} takes seat ${counter.by}'s counter — the cards cross the table.",
+        )
+    }
+
+    private fun applyDismissCounters(state: CatanState): CatanState =
+        if (state.ck?.goodsOffer != null) CatanCk.dismissCounters(state) else state.copy(
+            phase = CatanPhase.PLAYING,
+            pendingTrade = null,
+            log = state.log + "Seat ${state.turn} turns the counter-offers down.",
         )
 
     private fun applyMaritimeTrade(state: CatanState, seat: Int, move: MaritimeTrade): CatanState {
@@ -637,8 +814,8 @@ object CatanRules : GameRules<CatanState, CatanMove> {
         val s = state.copy(resources = withCards(paid, seat, listOf(move.get), 1))
         val via = if (ratio == 4) "the bank" else "a $ratio:1 harbour"
         return s.copy(
-            log = s.log + "Seat $seat trades $ratio ${move.give.name.lowercase()} for a " +
-                "${move.get.name.lowercase()} via $via.",
+            log = s.log + ("Seat $seat trades $ratio ${move.give.name.lowercase()} for a " +
+                "${move.get.name.lowercase()} via $via."),
         )
     }
 
@@ -648,7 +825,7 @@ object CatanRules : GameRules<CatanState, CatanMove> {
         if (settled.phase == CatanPhase.GAME_OVER) return settled
 
         val next = (state.turn + 1) % state.playerCount
-        val s = state.copy(
+        val s = (if (state.isCk) CatanCk.endTurn(state) else state).copy(
             turn = next,
             turnNumber = state.turnNumber + 1,
             phase = CatanPhase.AWAIT_ROLL,
@@ -661,9 +838,13 @@ object CatanRules : GameRules<CatanState, CatanMove> {
         return checkWin(s)
     }
 
+    /** Where play goes after free roads: a card played before the roll returns to the roll. */
+    private fun phaseAfterRoads(state: CatanState): CatanPhase =
+        if (state.ck?.back == Back.AWAIT_ROLL) CatanPhase.AWAIT_ROLL else CatanPhase.PLAYING
+
     private fun applyEndFreeRoads(state: CatanState, seat: Int): CatanState =
         state.copy(
-            phase = CatanPhase.PLAYING,
+            phase = phaseAfterRoads(state),
             pendingFreeRoads = 0,
             log = state.log + "Seat $seat forfeits the remaining free road.",
         )
@@ -679,6 +860,7 @@ object CatanRules : GameRules<CatanState, CatanMove> {
      * view or the host's copy.
      */
     fun publicVictoryPoints(state: CatanState): List<Int> {
+        if (state.isCk) return CatanCk.publicVictoryPoints(state)
         val points = IntArray(state.playerCount)
         state.buildings.forEach { building ->
             if (building != null) {
@@ -694,7 +876,7 @@ object CatanRules : GameRules<CatanState, CatanMove> {
         publicVictoryPoints(state)[seat] +
             state.devHands[seat].count { it.type == DevCardType.VICTORY_POINT }
 
-    private fun checkWin(state: CatanState): CatanState {
+    internal fun checkWin(state: CatanState): CatanState {
         if (state.phase == CatanPhase.GAME_OVER) return state
         val seat = state.turn
         val points = victoryPoints(state, seat)
@@ -715,7 +897,7 @@ object CatanRules : GameRules<CatanState, CatanMove> {
      * road falls below five segments the award reopens to the longest road
      * of five or more, lowest seat first on a tie.
      */
-    private fun refreshLongestRoad(state: CatanState): CatanState {
+    internal fun refreshLongestRoad(state: CatanState): CatanState {
         val lengths = (0 until state.playerCount).map { longestRoadFor(state, it) }
         val holder = state.longestRoadOwner
         val best = lengths
@@ -751,6 +933,7 @@ object CatanRules : GameRules<CatanState, CatanMove> {
             val building = state.buildings[v]
             if (building != null && building.owner != seat) blocked[v] = true
         }
+        state.ck?.knights?.forEach { if (it.owner != seat) blocked[it.vertex] = true }
         for (start in 0 until CatanBoard.VERTEX_COUNT) {
             if (CatanBoard.VERTEX_EDGES[start].none { state.roads[it] == seat }) continue
             val visited = BooleanArray(CatanBoard.VERTEX_COUNT)
@@ -812,7 +995,7 @@ object CatanRules : GameRules<CatanState, CatanMove> {
     fun bankSupply(state: CatanState, resource: Resource): Int =
         BANK_PER_RESOURCE - state.resources.sumOf { it[resource] ?: 0 }
 
-    private fun affordable(state: CatanState, seat: Int, cost: Map<Resource, Int>): Boolean =
+    internal fun affordable(state: CatanState, seat: Int, cost: Map<Resource, Int>): Boolean =
         cost.all { (resource, need) -> (state.resources[seat][resource] ?: 0) >= need }
 
     private fun payCost(state: CatanState, seat: Int, cost: Map<Resource, Int>): CatanState =
@@ -863,6 +1046,16 @@ object CatanRules : GameRules<CatanState, CatanMove> {
         return best
     }
 
+    /** 3 if [seat] has a settlement on a generic harbour, else the bank's 4. */
+    fun genericPortRatio(state: CatanState, seat: Int): Int {
+        for (port in state.ports) {
+            if (port.resource != null) continue
+            val (a, b) = CatanBoard.EDGE_VERTICES[port.edge]
+            if (state.buildings[a]?.owner == seat || state.buildings[b]?.owner == seat) return port.ratio
+        }
+        return 4
+    }
+
     // -----------------------------------------------------------------------
     // Results, redaction and wire format
     // -----------------------------------------------------------------------
@@ -877,12 +1070,15 @@ object CatanRules : GameRules<CatanState, CatanMove> {
         else -> "Seat $winner wins"
     }
 
-    override fun viewFor(state: CatanState, seat: Int): CatanState = state.copy(
-        // Hidden information stays with the holder and the host.
-        devDeck = emptyList(),
-        devHands = state.devHands.mapIndexed { index, hand ->
-            if (index == seat) hand else emptyList()
-        },
+    override fun viewFor(state: CatanState, seat: Int): CatanState = CatanCk.viewFor(
+        state.copy(
+            // Hidden information stays with the holder and the host.
+            devDeck = emptyList(),
+            devHands = state.devHands.mapIndexed { index, hand ->
+                if (index == seat) hand else emptyList()
+            },
+        ),
+        seat,
     )
 
     override fun encodeState(state: CatanState): String = json.encodeToString(state)

app/src/main/java/org/prolibertate/games/ui/GameSetupScreen.kt

@@ -58,6 +58,7 @@ import org.prolibertate.games.game.pirates.PiratesLevel
 import org.prolibertate.games.game.pirates.PiratesOptions
 import org.prolibertate.games.game.president.PresidentOptions
 import org.prolibertate.games.game.catan.CatanOptions
+import org.prolibertate.games.game.catan.CatanRuleSet
 import org.prolibertate.games.game.sequence.SequenceOptions
 import org.prolibertate.games.game.tayu.TayuLevel
 import org.prolibertate.games.game.tayu.TayuOptions
@@ -334,9 +335,55 @@ fun teamForSeat(gameId: String, seat: Int, seatCount: Int): Int = when (gameId)
     else -> seat
 }
 
+/** The targets the setup screen offers for a Katan rule set. */
+internal fun catanPointsChoices(ruleSet: CatanRuleSet): List<Int> = when (ruleSet) {
+    // Five is a short game for trying things out; ten is the published target.
+    CatanRuleSet.BASE -> listOf(5, 8, 10, 12)
+    // Cities & Knights is played to thirteen, which is also why it runs longer.
+    CatanRuleSet.CITIES_AND_KNIGHTS -> listOf(8, 10, 13, 15)
+}
+
+/** The published target for a rule set. */
+internal fun catanDefaultPoints(ruleSet: CatanRuleSet): Int = when (ruleSet) {
+    CatanRuleSet.BASE -> 10
+    CatanRuleSet.CITIES_AND_KNIGHTS -> 13
+}
+
+/**
+ * [options] switched to [ruleSet]. The target moves to the new rule set's own
+ * default unless the one already chosen is on its menu too.
+ */
+internal fun catanSwitchRules(options: CatanOptions, ruleSet: CatanRuleSet): CatanOptions =
+    options.copy(
+        ruleSet = ruleSet,
+        pointsToWin = options.pointsToWin.takeIf { it in catanPointsChoices(ruleSet) && it != catanDefaultPoints(options.ruleSet) }
+            ?: catanDefaultPoints(ruleSet),
+    )
+
+private fun catanRuleSetName(ruleSet: CatanRuleSet): String = when (ruleSet) {
+    CatanRuleSet.BASE -> "Base game"
+    CatanRuleSet.CITIES_AND_KNIGHTS -> "Cities & Knights"
+}
+
+private fun catanRuleSetBlurb(ruleSet: CatanRuleSet): String = when (ruleSet) {
+    CatanRuleSet.BASE ->
+        "Settle the island, trade, and play development cards. Longest Road and Largest Army score."
+    CatanRuleSet.CITIES_AND_KNIGHTS ->
+        "Cities make commodities, knights hold off the barbarians, and improvements earn progress " +
+            "cards and metropolises. No development cards; the robber sleeps until the first attack."
+}
+
 @Composable
 private fun CatanOptionsEditor(options: CatanOptions, onChange: (CatanOptions) -> Unit) {
     Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+        ChipRow(
+            label = "Rules",
+            values = CatanRuleSet.entries,
+            selected = options.ruleSet,
+            display = ::catanRuleSetName,
+            onSelect = { onChange(catanSwitchRules(options, it)) },
+        )
+        Text(catanRuleSetBlurb(options.ruleSet), style = MaterialTheme.typography.bodySmall)
         ChipRow(
             label = "Players",
             values = listOf(3, 4),
@@ -346,8 +393,7 @@ private fun CatanOptionsEditor(options: CatanOptions, onChange: (CatanOptions) -
         )
         ChipRow(
             label = "Game to",
-            // Five is a short game for trying things out; ten is the published target.
-            values = listOf(5, 8, 10, 12),
+            values = catanPointsChoices(options.ruleSet),
             selected = options.pointsToWin,
             display = { "$it points" },
             onSelect = { onChange(options.copy(pointsToWin = it)) },

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanBoardView.kt

@@ -11,8 +11,10 @@ import androidx.compose.runtime.rememberUpdatedState
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.geometry.Size
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.Path
+import androidx.compose.ui.graphics.PathEffect
 import androidx.compose.ui.graphics.StrokeCap
 import androidx.compose.ui.graphics.drawscope.DrawScope
 import androidx.compose.ui.graphics.drawscope.Stroke
@@ -30,6 +32,7 @@ import org.prolibertate.games.game.catan.BuildingType
 import org.prolibertate.games.game.catan.CatanBoard
 import org.prolibertate.games.game.catan.CatanState
 import org.prolibertate.games.game.catan.NO_PLAYER
+import org.prolibertate.games.game.catan.Resource
 
 /**
  * The island, drawn and tappable.
@@ -54,6 +57,10 @@ fun CatanBoardView(
     onHexTap: (Int) -> Unit,
     modifier: Modifier = Modifier,
     style: CatanStyle = LocalCatanStyle.current,
+    /** Hexes to light up as having produced on the latest roll. */
+    rolledHexes: Set<Int> = emptySet(),
+    /** Cities & Knights: the knight whose menu is open or that is about to move. */
+    selectedKnight: Int? = null,
 ) {
     val measurer = rememberTextMeasurer()
     var size by remember { mutableStateOf(IntSize.Zero) }
@@ -82,8 +89,8 @@ fun CatanBoardView(
                     val at = Pt(tap.x, tap.y)
                     val reach = board.radius * style.tapReach
                     when {
-                        targets.vertices.isNotEmpty() ->
-                            board.nearestVertex(at, reach, targets.vertices)?.let { vertexTap(it) }
+                        targets.tappableVertices.isNotEmpty() ->
+                            board.nearestVertex(at, reach, targets.tappableVertices)?.let { vertexTap(it) }
 
                         targets.edges.isNotEmpty() ->
                             board.nearestEdge(at, reach, targets.edges)?.let { edgeTap(it) }
@@ -99,11 +106,17 @@ fun CatanBoardView(
         drawRect(color = style.sea)
         drawPorts(state, board, style, measurer)
         drawHexes(state, board, style, measurer)
+        drawRolled(rolledHexes, board, style)
         drawRobber(state, board, style)
+        drawMerchant(state, board, style, measurer)
         drawRoads(state, board, style)
         drawEdgeTargets(targets, board, style)
         drawBuildings(state, board, style)
-        drawVertexTargets(targets, selectedVertex, board, style)
+        drawWalls(state, board, style)
+        drawMetropolises(state, board, style)
+        drawKnights(state, board, style)
+        drawKnightTargets(targets, board, style)
+        drawVertexTargets(targets, selectedVertex ?: selectedKnight, board, style)
         drawHexTargets(targets, board, style)
     }
 }
@@ -130,6 +143,17 @@ private fun DrawScope.drawHexes(
     }
 }
 
+/** A bright wash and rim on each hex that paid out, drawn over the terrain and under the pieces. */
+private fun DrawScope.drawRolled(hexes: Set<Int>, board: BoardLayout, style: CatanStyle) {
+    for (hex in hexes) {
+        val centre = board.hexCenter(hex)
+        val path = polygon(board.hexCorners(hex).map { insetToward(it, centre, style.hexInset + 0.04f) })
+        drawPath(path, color = style.rolled.copy(alpha = 0.28f))
+        drawPath(path, color = style.pieceOutline, style = Stroke(width = board.radius * 0.13f))
+        drawPath(path, color = style.rolled, style = Stroke(width = board.radius * 0.075f))
+    }
+}
+
 private fun DrawScope.drawToken(
     number: Int,
     at: Pt,
@@ -169,6 +193,10 @@ private fun DrawScope.drawToken(
 }
 
 private fun DrawScope.drawRobber(state: CatanState, board: BoardLayout, style: CatanStyle) {
+    // In Cities & Knights the robber sleeps, drawn faintly, until the barbarians first land.
+    val asleep = state.ck?.attacked == false
+    val tint = if (asleep) style.robber.copy(alpha = 0.3f) else style.robber
+    val rim = Color.White.copy(alpha = if (asleep) 0.25f else 0.7f)
     val hex = board.hexCenter(state.robber)
     // Beside the number token rather than on it, so the number stays readable.
     val x = hex.x + board.radius * 0.5f
@@ -181,11 +209,11 @@ private fun DrawScope.drawRobber(state: CatanState, board: BoardLayout, style: C
         lineTo(x + s * 0.55f, y + s * 0.9f)
         close()
     }
-    drawPath(pawn, color = style.robber)
-    drawCircle(color = style.robber, radius = s * 0.38f, center = Offset(x, y - s * 0.42f))
-    drawPath(pawn, color = Color.White.copy(alpha = 0.7f), style = Stroke(width = s * 0.07f))
+    drawPath(pawn, color = tint)
+    drawCircle(color = tint, radius = s * 0.38f, center = Offset(x, y - s * 0.42f))
+    drawPath(pawn, color = rim, style = Stroke(width = s * 0.07f))
     drawCircle(
-        color = Color.White.copy(alpha = 0.7f),
+        color = rim,
         radius = s * 0.38f,
         center = Offset(x, y - s * 0.42f),
         style = Stroke(width = s * 0.07f),
@@ -206,7 +234,7 @@ private fun DrawScope.drawPorts(
         val anchor = board.portAnchor(port.edge)
         val (a, b) = board.edgeEnds(port.edge)
         val tint = port.resource?.let { style.resource.getValue(it) } ?: style.portInk
-        // Two short piers from the marker to the vertices that can use the harbour.
+        // Two piers from the marker to the vertices that can use the harbour.
         for (end in listOf(a, b)) {
             drawLine(
                 color = style.portMarker.copy(alpha = 0.9f),
@@ -224,10 +252,26 @@ private fun DrawScope.drawPorts(
             center = anchor.offset(),
             style = Stroke(width = board.radius * 0.07f),
         )
+        // What the harbour trades: a picture of the resource, or "?" for any.
+        val iconAt = Pt(anchor.x, anchor.y - radius * 0.27f)
+        val iconSize = radius * 0.5f
+        val resource = port.resource
+        if (resource != null) {
+            drawResourceIcon(resource, iconAt, iconSize, tint, style.pieceOutline)
+        } else {
+            drawCentered(
+                measurer = measurer,
+                text = "?",
+                at = iconAt,
+                fontPx = board.radius * style.portText * 1.5f,
+                color = style.portInk,
+                weight = FontWeight.ExtraBold,
+            )
+        }
         drawCentered(
             measurer = measurer,
             text = "${port.ratio}:1",
-            at = anchor,
+            at = Pt(anchor.x, anchor.y + radius * 0.5f),
             fontPx = board.radius * style.portText,
             color = style.portInk,
             weight = FontWeight.Bold,
@@ -235,6 +279,81 @@ private fun DrawScope.drawPorts(
     }
 }
 
+/**
+ * A small pictogram of [resource] centred on [at], about 2·[s] across: a tree,
+ * bricks, a sheep, an ear of wheat or a rock. Drawn with paths so there are no
+ * image assets to ship or scale.
+ */
+private fun DrawScope.drawResourceIcon(resource: Resource, at: Pt, s: Float, fill: Color, line: Color) {
+    val outline = Stroke(width = s * 0.12f)
+    when (resource) {
+        Resource.LUMBER -> {
+            val crown = Path().apply {
+                moveTo(at.x, at.y - s)
+                lineTo(at.x + s * 0.8f, at.y + s * 0.3f)
+                lineTo(at.x - s * 0.8f, at.y + s * 0.3f)
+                close()
+            }
+            drawRect(color = line, topLeft = Offset(at.x - s * 0.14f, at.y + s * 0.3f), size = Size(s * 0.28f, s * 0.6f))
+            drawPath(crown, color = fill)
+            drawPath(crown, color = line, style = outline)
+        }
+
+        Resource.BRICK -> {
+            val w = s * 0.9f
+            val h = s * 0.42f
+            for ((row, shift) in listOf(0f to 0f, 1f to w * 0.5f)) {
+                val top = at.y - h + row * h
+                val left = at.x - w + shift - w * 0.25f
+                for (col in 0..1) {
+                    val x = left + col * w
+                    drawRect(color = fill, topLeft = Offset(x, top), size = Size(w, h))
+                    drawRect(color = line, topLeft = Offset(x, top), size = Size(w, h), style = outline)
+                }
+            }
+        }
+
+        Resource.WOOL -> {
+            for ((dx, dy) in listOf(-0.45f to 0f, 0.1f to -0.25f, 0.5f to 0.05f, 0f to 0.2f)) {
+                drawCircle(color = fill, radius = s * 0.42f, center = Offset(at.x + dx * s, at.y + dy * s))
+            }
+            drawCircle(color = line, radius = s * 0.24f, center = Offset(at.x - s * 0.85f, at.y + s * 0.15f))
+            drawRect(color = line, topLeft = Offset(at.x - s * 0.5f, at.y + s * 0.5f), size = Size(s * 0.14f, s * 0.45f))
+            drawRect(color = line, topLeft = Offset(at.x + s * 0.3f, at.y + s * 0.5f), size = Size(s * 0.14f, s * 0.45f))
+        }
+
+        Resource.GRAIN -> {
+            drawLine(color = line, start = Offset(at.x, at.y + s), end = Offset(at.x, at.y - s * 0.7f), strokeWidth = s * 0.14f)
+            for (i in 0..2) {
+                val y = at.y - s * 0.7f + i * s * 0.5f
+                for (side in listOf(-1f, 1f)) {
+                    val kernel = Path().apply {
+                        moveTo(at.x, y + s * 0.3f)
+                        lineTo(at.x + side * s * 0.6f, y - s * 0.05f)
+                        lineTo(at.x + side * s * 0.15f, y - s * 0.2f)
+                        close()
+                    }
+                    drawPath(kernel, color = fill)
+                    drawPath(kernel, color = line, style = Stroke(width = s * 0.08f))
+                }
+            }
+        }
+
+        Resource.ORE -> {
+            val peak = Path().apply {
+                moveTo(at.x - s, at.y + s * 0.8f)
+                lineTo(at.x - s * 0.3f, at.y - s * 0.6f)
+                lineTo(at.x + s * 0.1f, at.y + s * 0.05f)
+                lineTo(at.x + s * 0.45f, at.y - s * 0.3f)
+                lineTo(at.x + s, at.y + s * 0.8f)
+                close()
+            }
+            drawPath(peak, color = fill)
+            drawPath(peak, color = line, style = outline)
+        }
+    }
+}
+
 // ---------------------------------------------------------------------------
 // Pieces
 // ---------------------------------------------------------------------------
@@ -302,6 +421,131 @@ private fun cityPath(at: Pt, s: Float): Path = Path().apply {
     close()
 }
 
+// ---------------------------------------------------------------------------
+// Cities & Knights pieces
+// ---------------------------------------------------------------------------
+
+/** A dashed wall round each walled city, crenellated by the dashes. */
+private fun DrawScope.drawWalls(state: CatanState, board: BoardLayout, style: CatanStyle) {
+    val walls = state.ck?.walls ?: return
+    for (vertex in walls) {
+        val at = board.vertex(vertex).offset()
+        val radius = board.radius * style.citySize * 1.25f
+        val dash = PathEffect.dashPathEffect(floatArrayOf(radius * 0.38f, radius * 0.22f))
+        drawCircle(
+            color = style.pieceOutline,
+            radius = radius,
+            center = at,
+            style = Stroke(width = board.radius * 0.13f, pathEffect = dash),
+        )
+        drawCircle(
+            color = style.wall,
+            radius = radius,
+            center = at,
+            style = Stroke(width = board.radius * 0.09f, pathEffect = dash),
+        )
+    }
+}
+
+/** A pennant in the track's colour flying over a city that carries its metropolis. */
+private fun DrawScope.drawMetropolises(state: CatanState, board: BoardLayout, style: CatanStyle) {
+    val metropolises = state.ck?.metropolises ?: return
+    for ((track, at) in metropolises) {
+        val base = board.vertex(at.vertex)
+        val unit = board.radius * style.citySize
+        val poleTop = Pt(base.x + unit * 0.9f, base.y - unit * 2.0f)
+        val poleBottom = Pt(base.x + unit * 0.9f, base.y - unit * 0.4f)
+        drawLine(
+            color = style.pieceOutline,
+            start = poleBottom.offset(),
+            end = poleTop.offset(),
+            strokeWidth = board.radius * 0.05f,
+        )
+        val flag = Path().apply {
+            moveTo(poleTop.x, poleTop.y)
+            lineTo(poleTop.x + unit * 1.1f, poleTop.y + unit * 0.35f)
+            lineTo(poleTop.x, poleTop.y + unit * 0.7f)
+            close()
+        }
+        drawPath(flag, color = style.track.getValue(track))
+        drawPath(flag, color = style.pieceOutline, style = Stroke(width = board.radius * 0.035f))
+    }
+}
+
+/**
+ * Each knight is a shield in its owner's colour, marked with one, two or three
+ * dots for its strength. A sleeping knight is drawn faded; an awake one has a
+ * bright rim.
+ */
+private fun DrawScope.drawKnights(state: CatanState, board: BoardLayout, style: CatanStyle) {
+    val knights = state.ck?.knights ?: return
+    for (knight in knights) {
+        val at = board.vertex(knight.vertex)
+        val s = board.radius * style.knightSize
+        val seat = style.seats[knight.owner % style.seats.size]
+        val path = shieldPath(at, s)
+        if (knight.active) {
+            drawPath(path, color = style.knightReady, style = Stroke(width = s * 0.55f))
+        }
+        drawPath(path, color = if (knight.active) seat else seat.copy(alpha = 0.55f))
+        drawPath(path, color = style.pieceOutline, style = Stroke(width = s * 0.16f))
+        val pip = s * 0.14f
+        val gap = pip * 2.8f
+        val startX = at.x - gap * (knight.level - 1) / 2f
+        for (i in 0 until knight.level) {
+            drawCircle(
+                color = style.pieceOutline,
+                radius = pip,
+                center = Offset(startX + i * gap, at.y - s * 0.05f),
+            )
+        }
+    }
+}
+
+private fun shieldPath(at: Pt, s: Float): Path = Path().apply {
+    moveTo(at.x - s * 0.8f, at.y - s)
+    lineTo(at.x + s * 0.8f, at.y - s)
+    lineTo(at.x + s * 0.8f, at.y + s * 0.1f)
+    quadraticBezierTo(at.x + s * 0.8f, at.y + s * 0.9f, at.x, at.y + s * 1.25f)
+    quadraticBezierTo(at.x - s * 0.8f, at.y + s * 0.9f, at.x - s * 0.8f, at.y + s * 0.1f)
+    close()
+}
+
+/** A ring round each of the player's knights that can do something now. */
+private fun DrawScope.drawKnightTargets(targets: BoardTargets, board: BoardLayout, style: CatanStyle) {
+    for (vertex in targets.knights) {
+        drawCircle(
+            color = style.target,
+            radius = board.radius * style.knightSize * 1.9f,
+            center = board.vertex(vertex).offset(),
+            style = Stroke(width = board.radius * 0.07f),
+        )
+    }
+}
+
+/** The merchant: a coin in its controller's colour, beside the hex it sits on. */
+private fun DrawScope.drawMerchant(
+    state: CatanState,
+    board: BoardLayout,
+    style: CatanStyle,
+    measurer: TextMeasurer,
+) {
+    val merchant = state.ck?.merchant ?: return
+    val hex = board.hexCenter(merchant.hex)
+    val at = Pt(hex.x - board.radius * 0.5f, hex.y + board.radius * 0.3f)
+    val r = board.radius * 0.2f
+    drawCircle(color = style.seats[merchant.seat % style.seats.size], radius = r, center = at.offset())
+    drawCircle(color = style.pieceOutline, radius = r, center = at.offset(), style = Stroke(width = r * 0.3f))
+    drawCentered(
+        measurer = measurer,
+        text = "M",
+        at = at,
+        fontPx = r * 1.3f,
+        color = style.pieceOutline,
+        weight = FontWeight.ExtraBold,
+    )
+}
+
 // ---------------------------------------------------------------------------
 // Tap targets
 // ---------------------------------------------------------------------------

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanCkDialogs.kt

@@ -0,0 +1,813 @@
+package org.prolibertate.games.ui.game.catan
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.ExperimentalLayoutApi
+import androidx.compose.foundation.layout.FlowRow
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.heightIn
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.Button
+import androidx.compose.material3.FilledTonalButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedButton
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import org.prolibertate.games.game.catan.AcceptCounter
+import org.prolibertate.games.game.catan.ActivateKnight
+import org.prolibertate.games.game.catan.BuyImprovement
+import org.prolibertate.games.game.catan.CatanCk
+import org.prolibertate.games.game.catan.CatanMove
+import org.prolibertate.games.game.catan.CatanState
+import org.prolibertate.games.game.catan.ChaseRobber
+import org.prolibertate.games.game.catan.CounterGoods
+import org.prolibertate.games.game.catan.DropProgress
+import org.prolibertate.games.game.catan.GoodsBankTrade
+import org.prolibertate.games.game.catan.Good
+import org.prolibertate.games.game.catan.GoodsCounter
+import org.prolibertate.games.game.catan.GoodsOffer
+import org.prolibertate.games.game.catan.IMPROVEMENT_MAX
+import org.prolibertate.games.game.catan.MoveKnight
+import org.prolibertate.games.game.catan.OfferGoods
+import org.prolibertate.games.game.catan.PickDeck
+import org.prolibertate.games.game.catan.PlayProgress
+import org.prolibertate.games.game.catan.ProgressCard
+import org.prolibertate.games.game.catan.ProgressType
+import org.prolibertate.games.game.catan.PromoteKnight
+import org.prolibertate.games.game.catan.SpyTake
+import org.prolibertate.games.game.catan.TakeAqueduct
+import org.prolibertate.games.game.catan.Track
+
+/*
+ * The Cities & Knights dialogs. Like the base game's, each is a stateless
+ * composable apart from the choice it is helping the player make, and what is
+ * allowed is always asked of the engine's legal list through CatanInteraction.
+ */
+
+// ---------------------------------------------------------------------------
+// Shared pieces
+// ---------------------------------------------------------------------------
+
+/** A card tile with a minus and a plus, for choosing how many of a good. */
+@Composable
+private fun GoodCounter(good: Good, count: Int, max: Int, onChange: (Int) -> Unit) {
+    Column(horizontalAlignment = Alignment.CenterHorizontally, verticalArrangement = Arrangement.spacedBy(4.dp)) {
+        GoodTile(good, count, enabled = max > 0 || count > 0)
+        Row(horizontalArrangement = Arrangement.spacedBy(4.dp)) {
+            OutlinedButton(
+                onClick = { onChange(count - 1) },
+                enabled = count > 0,
+                contentPadding = PaddingValues(0.dp),
+                modifier = Modifier.width(34.dp).height(32.dp),
+            ) { Text("−") }
+            OutlinedButton(
+                onClick = { onChange(count + 1) },
+                enabled = count < max,
+                contentPadding = PaddingValues(0.dp),
+                modifier = Modifier.width(34.dp).height(32.dp),
+            ) { Text("+") }
+        }
+    }
+}
+
+private fun Map<Good, Int>.asGoods(): List<Good> = Good.entries.flatMap { g -> List(this[g] ?: 0) { g } }
+
+/** A row of the three track colours, used for decks and improvements. */
+@Composable
+private fun TrackChip(track: Track, style: CatanStyle = LocalCatanStyle.current) {
+    Box(
+        modifier = Modifier
+            .size(14.dp)
+            .clip(RoundedCornerShape(3.dp))
+            .background(style.track.getValue(track)),
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Choosing cards to give up
+// ---------------------------------------------------------------------------
+
+/**
+ * Pick exactly [quota] cards out of [held] — to discard on a seven or a saboteur,
+ * or to hand over for a wedding or a commercial harbour. Not dismissable: the
+ * game is waiting on it. [allowed] is the engine's structural check, so the
+ * confirm button only lights when the move would be accepted.
+ */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanGoodsPickDialog(
+    title: String,
+    intro: String,
+    held: Map<Good, Int>,
+    quota: Int,
+    confirmLabel: String,
+    selectable: (Good) -> Boolean,
+    allowed: (List<Good>) -> Boolean,
+    onConfirm: (List<Good>) -> Unit,
+) {
+    var picked by remember { mutableStateOf(emptyMap<Good, Int>()) }
+    val selection = picked.asGoods()
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text(title) },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(12.dp)) {
+                Text("$intro (${selection.size} of $quota chosen).")
+                FlowRow(
+                    horizontalArrangement = Arrangement.spacedBy(8.dp),
+                    verticalArrangement = Arrangement.spacedBy(8.dp),
+                ) {
+                    Good.entries.forEach { good ->
+                        val have = held[good] ?: 0
+                        if (have > 0 && selectable(good)) {
+                            GoodCounter(
+                                good = good,
+                                count = picked[good] ?: 0,
+                                max = if (selection.size < quota) have else (picked[good] ?: 0),
+                                onChange = { n -> picked = picked + (good to n.coerceIn(0, have)) },
+                            )
+                        }
+                    }
+                }
+            }
+        },
+        confirmButton = {
+            Button(onClick = { onConfirm(selection) }, enabled = allowed(selection)) { Text(confirmLabel) }
+        },
+    )
+}
+
+// ---------------------------------------------------------------------------
+// City improvements
+// ---------------------------------------------------------------------------
+
+/** The three improvement tracks: where the player stands, what the next level costs, and what it earns. */
+@Composable
+fun CatanImproveDialog(
+    state: CatanState,
+    seat: Int,
+    legal: List<CatanMove>,
+    onBuy: (BuyImprovement) -> Unit,
+    onCancel: () -> Unit,
+) {
+    val ck = state.ck ?: return
+    val buyable = CatanInteraction.improvable(legal)
+    AlertDialog(
+        onDismissRequest = onCancel,
+        title = { Text(CatanText.IMPROVE) },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 460.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(14.dp),
+            ) {
+                Track.entries.forEach { track ->
+                    val level = CatanCk.improvement(state, seat, track)
+                    val have = ck.commodities[seat][track.commodity] ?: 0
+                    Column(verticalArrangement = Arrangement.spacedBy(4.dp)) {
+                        Row(verticalAlignment = Alignment.CenterVertically, horizontalArrangement = Arrangement.spacedBy(6.dp)) {
+                            TrackChip(track)
+                            Text(CatanText.track(track), fontWeight = FontWeight.Bold)
+                            Text("level $level of $IMPROVEMENT_MAX", style = MaterialTheme.typography.labelMedium)
+                        }
+                        Text(CatanText.trackPower(track), style = MaterialTheme.typography.bodySmall)
+                        if (level >= IMPROVEMENT_MAX) {
+                            Text("Fully built.", style = MaterialTheme.typography.bodySmall)
+                        } else {
+                            val cost = CatanCk.improvementCost(state, seat, track)
+                            Button(onClick = { onBuy(BuyImprovement(track)) }, enabled = track in buyable) {
+                                Text(
+                                    "${CatanCk.improvementName(track, level + 1)}: $cost " +
+                                        "${CatanText.good(Good.of(track.commodity))} (you hold $have)",
+                                )
+                            }
+                            if (level + 1 == org.prolibertate.games.game.catan.METROPOLIS_LEVEL ||
+                                level + 1 == IMPROVEMENT_MAX
+                            ) {
+                                Text(
+                                    if (level + 1 == IMPROVEMENT_MAX) {
+                                        "Level five takes a metropolis from a seat still on four."
+                                    } else {
+                                        "Level four earns the first metropolis in this track: two more points."
+                                    },
+                                    style = MaterialTheme.typography.labelSmall,
+                                )
+                            }
+                        }
+                    }
+                }
+            }
+        },
+        confirmButton = {},
+        dismissButton = { TextButton(onClick = onCancel) { Text("Close") } },
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Progress cards
+// ---------------------------------------------------------------------------
+
+/**
+ * The player's progress cards. A card with nothing to decide plays at once; one
+ * that names a seat, a card or dice asks for it in a second step; one that
+ * needs a tap on the board closes the dialog and arms the board (see [ArmedCard]).
+ */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanProgressDialog(
+    hand: List<ProgressInHand>,
+    seats: CatanSeats,
+    onPlay: (CatanMove) -> Unit,
+    onArm: (ArmedCard) -> Unit,
+    onCancel: () -> Unit,
+) {
+    var chosen by remember { mutableStateOf<ProgressInHand?>(null) }
+    var target by remember { mutableStateOf<Int?>(null) }
+    var yellow by remember { mutableStateOf(1) }
+    var red by remember { mutableStateOf(1) }
+    val entry = chosen
+
+    AlertDialog(
+        onDismissRequest = onCancel,
+        title = { Text(entry?.let { CatanText.progress(it.card.kind) } ?: "Progress cards") },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 440.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(10.dp),
+            ) {
+                if (entry == null) {
+                    if (hand.isEmpty()) Text("You hold no progress cards.")
+                    hand.forEach { card ->
+                        ProgressRow(card) { picked ->
+                            val kind = picked.card.kind
+                            when {
+                                kind in CatanInteraction.BOARD_CARDS -> onArm(ArmedCard(kind, picked.plays))
+                                picked.plays.size == 1 && picked.plays[0].isBare() -> onPlay(picked.plays[0])
+                                else -> {
+                                    chosen = picked
+                                    target = null
+                                }
+                            }
+                        }
+                    }
+                } else {
+                    Text(CatanText.progressHelp(entry.card.kind), style = MaterialTheme.typography.bodySmall)
+                    val kind = entry.card.kind
+                    val plays = entry.plays
+                    when {
+                        kind == ProgressType.ALCHEMIST -> {
+                            Text("Production die (yellow)", fontWeight = FontWeight.Bold)
+                            DiePicker(yellow) { yellow = it }
+                            Text("Progress die (red)", fontWeight = FontWeight.Bold)
+                            DiePicker(red) { red = it }
+                        }
+
+                        kind == ProgressType.DESERTER || kind == ProgressType.SPY -> {
+                            Text("Choose a player:", fontWeight = FontWeight.Bold)
+                            plays.mapNotNull { it.target }.distinct().forEach { seat ->
+                                OutlinedButton(
+                                    onClick = { plays.firstOrNull { it.target == seat }?.let(onPlay) },
+                                    modifier = Modifier.fillMaxWidth(),
+                                ) { Text(seats.label(seat)) }
+                            }
+                        }
+
+                        kind == ProgressType.MASTER_MERCHANT -> {
+                            Text("Choose a player with more points:", fontWeight = FontWeight.Bold)
+                            Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                                plays.mapNotNull { it.target }.distinct().forEach { seat ->
+                                    if (target == seat) {
+                                        FilledTonalButton(onClick = { target = seat }) { Text(seats.label(seat)) }
+                                    } else {
+                                        OutlinedButton(onClick = { target = seat }) { Text(seats.label(seat)) }
+                                    }
+                                }
+                            }
+                            val seat = target
+                            if (seat != null) {
+                                Text("Take:", fontWeight = FontWeight.Bold)
+                                plays.filter { it.target == seat }.forEach { play ->
+                                    OutlinedButton(
+                                        onClick = { onPlay(play) },
+                                        modifier = Modifier.fillMaxWidth(),
+                                    ) { Text(CatanText.goods(play.goods.orEmpty())) }
+                                }
+                            }
+                        }
+
+                        else -> {
+                            val label = when (kind) {
+                                ProgressType.COMMERCIAL_HARBOR -> "Offer which resource?"
+                                ProgressType.MERCHANT_FLEET -> "Trade which card two for one?"
+                                ProgressType.RESOURCE_MONOPOLY -> "Name a resource:"
+                                else -> "Name a commodity:"
+                            }
+                            Text(label, fontWeight = FontWeight.Bold)
+                            FlowRow(
+                                horizontalArrangement = Arrangement.spacedBy(8.dp),
+                                verticalArrangement = Arrangement.spacedBy(8.dp),
+                            ) {
+                                plays.mapNotNull { it.good }.distinct().forEach { good ->
+                                    GoodTile(
+                                        good = good,
+                                        count = 0,
+                                        onClick = { plays.firstOrNull { it.good == good }?.let(onPlay) },
+                                    )
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        },
+        confirmButton = {
+            if (entry != null && entry.card.kind == ProgressType.ALCHEMIST) {
+                val play = entry.plays.firstOrNull { it.dice == listOf(yellow, red) }
+                Button(onClick = { play?.let(onPlay) }, enabled = play != null) { Text("Play") }
+            }
+        },
+        dismissButton = {
+            TextButton(
+                onClick = {
+                    if (entry == null) {
+                        onCancel()
+                    } else {
+                        chosen = null
+                        target = null
+                    }
+                },
+            ) { Text(if (entry == null) CatanText.CANCEL else "Back") }
+        },
+    )
+}
+
+private fun PlayProgress.isBare(): Boolean =
+    target == null && vertex == null && edge == null && hexA == null && hexB == null &&
+        good == null && dice == null && goods == null
+
+@Composable
+private fun DiePicker(selected: Int, onPick: (Int) -> Unit) {
+    Row(horizontalArrangement = Arrangement.spacedBy(6.dp)) {
+        (1..6).forEach { n ->
+            if (n == selected) {
+                FilledTonalButton(
+                    onClick = { onPick(n) },
+                    contentPadding = PaddingValues(0.dp),
+                    modifier = Modifier.size(40.dp),
+                ) { Text("$n") }
+            } else {
+                OutlinedButton(
+                    onClick = { onPick(n) },
+                    contentPadding = PaddingValues(0.dp),
+                    modifier = Modifier.size(40.dp),
+                ) { Text("$n") }
+            }
+        }
+    }
+}
+
+@Composable
+private fun ProgressRow(entry: ProgressInHand, onChoose: (ProgressInHand) -> Unit) {
+    val kind = entry.card.kind
+    Row(
+        modifier = Modifier.fillMaxWidth(),
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(8.dp),
+    ) {
+        TrackChip(kind.track)
+        Column(modifier = Modifier.weight(1f)) {
+            Text(CatanText.progress(kind), fontWeight = FontWeight.Bold)
+            Text(CatanText.progressHelp(kind), style = MaterialTheme.typography.bodySmall)
+        }
+        if (entry.playable) {
+            Button(onClick = { onChoose(entry) }) { Text("Play") }
+        } else {
+            Text("Not now", style = MaterialTheme.typography.labelSmall)
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Knights
+// ---------------------------------------------------------------------------
+
+/** What the knight on one crossing can do: wake, promote, move, chase the robber. */
+@Composable
+fun CatanKnightDialog(
+    state: CatanState,
+    vertex: Int,
+    actions: List<CatanMove>,
+    onDo: (CatanMove) -> Unit,
+    onMove: (Int) -> Unit,
+    onCancel: () -> Unit,
+) {
+    val knight = state.ck?.knights?.firstOrNull { it.vertex == vertex }
+    AlertDialog(
+        onDismissRequest = onCancel,
+        title = { Text(knight?.let { CatanText.knightName(it.level) } ?: "Knight") },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                if (knight != null) {
+                    val mood = when {
+                        !knight.active -> "Asleep. Waking it costs ${CatanText.ACTIVATE_COST}."
+                        knight.activatedTurn == state.turnNumber -> "Awake, but it woke this turn and cannot act yet."
+                        else -> "Awake and ready. It counts against the barbarians."
+                    }
+                    Text(mood, style = MaterialTheme.typography.bodySmall)
+                }
+                actions.forEach { move ->
+                    when (move) {
+                        is ActivateKnight ->
+                            Button(onClick = { onDo(move) }, modifier = Modifier.fillMaxWidth()) {
+                                Text("Wake (${CatanText.ACTIVATE_COST})")
+                            }
+
+                        is PromoteKnight ->
+                            Button(onClick = { onDo(move) }, modifier = Modifier.fillMaxWidth()) {
+                                Text("Promote (${CatanText.KNIGHT_COST})")
+                            }
+
+                        is MoveKnight ->
+                            OutlinedButton(onClick = { onMove(move.from) }, modifier = Modifier.fillMaxWidth()) {
+                                Text("Move along your roads")
+                            }
+
+                        is ChaseRobber ->
+                            OutlinedButton(onClick = { onDo(move) }, modifier = Modifier.fillMaxWidth()) {
+                                Text("Chase away the robber")
+                            }
+
+                        else -> Unit
+                    }
+                }
+                if (actions.isEmpty()) Text("Nothing to do with it right now.")
+            }
+        },
+        confirmButton = {},
+        dismissButton = { TextButton(onClick = onCancel) { Text("Close") } },
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Chores that are answered in a dialog
+// ---------------------------------------------------------------------------
+
+/** Choose a colour of progress deck to draw from. */
+@Composable
+fun CatanPickDeckDialog(legal: List<CatanMove>, onPick: (PickDeck) -> Unit) {
+    val open = legal.filterIsInstance<PickDeck>()
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text("Draw a progress card") },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                Text("Catan held. You tied for the strongest defence, so choose any deck.")
+                open.forEach { pick ->
+                    Button(onClick = { onPick(pick) }, modifier = Modifier.fillMaxWidth()) {
+                        TrackChip(pick.track)
+                        Text("  ${CatanText.track(pick.track)}")
+                    }
+                }
+            }
+        },
+        confirmButton = {},
+    )
+}
+
+/** The hand is over its limit: give one progress card back. */
+@Composable
+fun CatanDropProgressDialog(hand: List<ProgressCard>, onDrop: (DropProgress) -> Unit) {
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text("Too many progress cards") },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 380.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                Text("You may keep four. Choose one to give back.")
+                hand.forEach { card ->
+                    OutlinedButton(onClick = { onDrop(DropProgress(card.id)) }, modifier = Modifier.fillMaxWidth()) {
+                        TrackChip(card.kind.track)
+                        Text("  ${CatanText.progress(card.kind)}")
+                    }
+                }
+            }
+        },
+        confirmButton = {},
+    )
+}
+
+/** The aqueduct pays: take any one resource. */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanAqueductDialog(legal: List<CatanMove>, onTake: (TakeAqueduct) -> Unit) {
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text("Aqueduct") },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(12.dp)) {
+                Text("The dice paid you nothing. Take any resource.")
+                FlowRow(
+                    horizontalArrangement = Arrangement.spacedBy(8.dp),
+                    verticalArrangement = Arrangement.spacedBy(8.dp),
+                ) {
+                    legal.filterIsInstance<TakeAqueduct>().forEach { take ->
+                        ResourceTile(resource = take.resource, count = 1, onClick = { onTake(take) })
+                    }
+                }
+            }
+        },
+        confirmButton = {},
+    )
+}
+
+/** A spy: these are the progress cards the other player holds; take one. */
+@Composable
+fun CatanSpyDialog(cards: List<ProgressCard>, legal: List<CatanMove>, onTake: (SpyTake) -> Unit) {
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text("Spy") },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 380.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                Text("Choose a card to take.")
+                cards.forEach { card ->
+                    val take = SpyTake(card.id)
+                    OutlinedButton(
+                        onClick = { onTake(take) },
+                        enabled = take in legal,
+                        modifier = Modifier.fillMaxWidth(),
+                    ) {
+                        TrackChip(card.kind.track)
+                        Text("  ${CatanText.progress(card.kind)}")
+                    }
+                }
+            }
+        },
+        confirmButton = {},
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Trading in goods
+// ---------------------------------------------------------------------------
+
+private enum class GoodsTab { BANK, PLAYER }
+
+/**
+ * Trade with the bank at the best ratio each card has, or offer cards —
+ * commodities included — to one other player.
+ */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanGoodsTradeDialog(
+    state: CatanState,
+    seat: Int,
+    seats: CatanSeats,
+    legal: List<CatanMove>,
+    onBank: (GoodsBankTrade) -> Unit,
+    onOffer: (OfferGoods) -> Unit,
+    onCancel: () -> Unit,
+) {
+    var tab by remember { mutableStateOf(GoodsTab.BANK) }
+    var bankGive by remember { mutableStateOf<Good?>(null) }
+    var everyone by remember { mutableStateOf(true) }
+    var partner by remember { mutableStateOf<Int?>(null) }
+    var give by remember { mutableStateOf(emptyMap<Good, Int>()) }
+    var get by remember { mutableStateOf(emptyMap<Good, Int>()) }
+    val held = CatanCk.goodsOf(state, seat)
+
+    AlertDialog(
+        onDismissRequest = onCancel,
+        title = { Text(CatanText.TRADE) },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 460.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(12.dp),
+            ) {
+                Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                    GoodsTabButton(CatanText.TRADE_WITH_BANK, tab == GoodsTab.BANK) { tab = GoodsTab.BANK }
+                    GoodsTabButton(CatanText.TRADE_WITH_PLAYER, tab == GoodsTab.PLAYER) { tab = GoodsTab.PLAYER }
+                }
+                if (tab == GoodsTab.BANK) {
+                    val trades = CatanInteraction.goodsBankTrades(legal)
+                    if (trades.isEmpty()) {
+                        Text("You do not hold enough of any one card to trade with the bank.")
+                    } else {
+                        Text("Give:", fontWeight = FontWeight.Bold)
+                        FlowRow(
+                            horizontalArrangement = Arrangement.spacedBy(8.dp),
+                            verticalArrangement = Arrangement.spacedBy(8.dp),
+                        ) {
+                            trades.keys.forEach { good ->
+                                val ratio = CatanCk.bankRatio(state, seat, good)
+                                Column(horizontalAlignment = Alignment.CenterHorizontally) {
+                                    GoodTile(good, ratio, selected = bankGive == good, onClick = { bankGive = good })
+                                    Text("$ratio : 1", style = MaterialTheme.typography.labelSmall)
+                                }
+                            }
+                        }
+                        val chosen = bankGive
+                        if (chosen != null && chosen in trades) {
+                            Text("Get one:", fontWeight = FontWeight.Bold)
+                            FlowRow(
+                                horizontalArrangement = Arrangement.spacedBy(8.dp),
+                                verticalArrangement = Arrangement.spacedBy(8.dp),
+                            ) {
+                                trades.getValue(chosen).forEach { good ->
+                                    GoodTile(good, 1, onClick = { onBank(GoodsBankTrade(chosen, good)) })
+                                }
+                            }
+                        }
+                    }
+                } else {
+                    Text("Offer to:", fontWeight = FontWeight.Bold)
+                    FlowRow(
+                        horizontalArrangement = Arrangement.spacedBy(8.dp),
+                        verticalArrangement = Arrangement.spacedBy(8.dp),
+                    ) {
+                        GoodsTabButton(CatanText.EVERYONE, everyone) {
+                            everyone = true
+                            partner = null
+                        }
+                        (0 until state.playerCount).filter { it != seat }.forEach { other ->
+                            GoodsTabButton(seats.label(other), !everyone && partner == other) {
+                                everyone = false
+                                partner = other
+                            }
+                        }
+                    }
+                    Text(CatanText.YOU_GIVE, fontWeight = FontWeight.Bold)
+                    GoodCounters(give, { held[it] ?: 0 }) { give = it }
+                    Text(CatanText.YOU_GET, fontWeight = FontWeight.Bold)
+                    GoodCounters(get, { 9 }) { get = it }
+                }
+            }
+        },
+        confirmButton = {
+            if (tab == GoodsTab.PLAYER) {
+                val to = if (everyone) null else partner
+                val giveCards = give.asGoods()
+                val getCards = get.asGoods()
+                val allowed = (everyone || partner != null) &&
+                    CatanInteraction.goodsOfferAllowed(state, seat, to, giveCards, getCards)
+                Button(
+                    onClick = { onOffer(OfferGoods(to, giveCards, getCards)) },
+                    enabled = allowed,
+                ) { Text(CatanText.SEND_OFFER) }
+            }
+        },
+        dismissButton = { TextButton(onClick = onCancel) { Text(CatanText.CANCEL) } },
+    )
+}
+
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+private fun GoodCounters(counts: Map<Good, Int>, limit: (Good) -> Int, onChange: (Map<Good, Int>) -> Unit) {
+    FlowRow(
+        horizontalArrangement = Arrangement.spacedBy(8.dp),
+        verticalArrangement = Arrangement.spacedBy(8.dp),
+    ) {
+        Good.entries.forEach { good ->
+            GoodCounter(
+                good = good,
+                count = counts[good] ?: 0,
+                max = limit(good),
+                onChange = { n -> onChange(counts + (good to n.coerceIn(0, limit(good)))) },
+            )
+        }
+    }
+}
+
+@Composable
+private fun GoodsTabButton(label: String, selected: Boolean, onClick: () -> Unit) {
+    if (selected) {
+        FilledTonalButton(onClick = onClick) { Text(label) }
+    } else {
+        OutlinedButton(onClick = onClick) { Text(label) }
+    }
+}
+
+/**
+ * A goods offer has reached the local player: accept it, decline it, or answer
+ * with different terms. The counter's two sides start as the offer turned around.
+ */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanGoodsTradeResponseDialog(
+    state: CatanState,
+    seat: Int,
+    offer: GoodsOffer,
+    seats: CatanSeats,
+    canAccept: Boolean,
+    onAccept: () -> Unit,
+    onDecline: () -> Unit,
+    onCounter: (CounterGoods) -> Unit,
+) {
+    var countering by remember(offer) { mutableStateOf(false) }
+    var give by remember(offer) { mutableStateOf(offer.get.groupingBy { it }.eachCount()) }
+    var get by remember(offer) { mutableStateOf(offer.give.groupingBy { it }.eachCount()) }
+
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text(if (countering) "Counter-offer" else "Trade offer") },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 460.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                Text(
+                    "${seats.label(offer.by)} offers ${CatanText.goods(offer.give)} to " +
+                        "${if (offer.to == null) "the table" else "you"} for ${CatanText.goods(offer.get)}",
+                )
+                if (countering) {
+                    Text(CatanText.YOU_GIVE, fontWeight = FontWeight.Bold)
+                    GoodCounters(give, { CatanCk.goodsOf(state, seat)[it] ?: 0 }) { give = it }
+                    Text(CatanText.YOU_GET, fontWeight = FontWeight.Bold)
+                    GoodCounters(get, { CatanCk.goodsOf(state, offer.by)[it] ?: 0 }) { get = it }
+                } else if (!canAccept) {
+                    Text(
+                        "You cannot accept this: one side no longer holds the cards.",
+                        style = MaterialTheme.typography.bodySmall,
+                    )
+                }
+            }
+        },
+        confirmButton = {
+            if (countering) {
+                val move = CounterGoods(give.asGoods(), get.asGoods())
+                Button(
+                    onClick = { onCounter(move) },
+                    enabled = CatanInteraction.goodsCounterAllowed(state, seat, move.give, move.get),
+                ) { Text(CatanText.SEND_COUNTER) }
+            } else {
+                Button(onClick = onAccept, enabled = canAccept) { Text(CatanText.ACCEPT) }
+            }
+        },
+        dismissButton = {
+            Row(horizontalArrangement = Arrangement.spacedBy(4.dp)) {
+                if (countering) {
+                    TextButton(onClick = { countering = false }) { Text(CatanText.CANCEL) }
+                } else {
+                    TextButton(onClick = { countering = true }) { Text(CatanText.COUNTER) }
+                }
+                TextButton(onClick = onDecline) { Text(CatanText.DECLINE) }
+            }
+        },
+    )
+}
+
+/** The offerer's choice once nobody accepted a goods offer: take a counter-offer, or none. */
+@Composable
+fun CatanGoodsCounterChoiceDialog(
+    counters: List<GoodsCounter>,
+    seats: CatanSeats,
+    onTake: (AcceptCounter) -> Unit,
+    onNoDeal: () -> Unit,
+) {
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text("Counter-offers") },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 460.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                if (counters.isEmpty()) Text("None of the counter-offers can be met any more.")
+                counters.forEach { counter ->
+                    Column(verticalArrangement = Arrangement.spacedBy(4.dp)) {
+                        Text(
+                            "${seats.label(counter.by)} would give ${CatanText.goods(counter.give)} " +
+                                "for ${CatanText.goods(counter.get)}",
+                        )
+                        Button(onClick = { onTake(AcceptCounter(counter.by)) }) { Text(CatanText.ACCEPT) }
+                    }
+                }
+            }
+        },
+        confirmButton = { TextButton(onClick = onNoDeal) { Text(CatanText.NO_DEAL) } },
+    )
+}

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanDialogs.kt

@@ -35,6 +35,9 @@ import org.prolibertate.games.game.catan.DevCardType
 import org.prolibertate.games.game.catan.Discard
 import org.prolibertate.games.game.catan.MaritimeTrade
 import org.prolibertate.games.game.catan.OfferTrade
+import org.prolibertate.games.game.catan.TradeCounter
+import org.prolibertate.games.game.catan.CounterTrade
+import org.prolibertate.games.game.catan.AcceptCounter
 import org.prolibertate.games.game.catan.PlayKnight
 import org.prolibertate.games.game.catan.PlayRoadBuilding
 import org.prolibertate.games.game.catan.Resource
@@ -312,6 +315,7 @@ fun CatanTradeDialog(
 ) {
     var tab by remember { mutableStateOf(TradeTab.BANK) }
     var bankGive by remember { mutableStateOf<Resource?>(null) }
+    var everyone by remember { mutableStateOf(true) }
     var partner by remember { mutableStateOf<Int?>(null) }
     var give by remember { mutableStateOf(emptyMap<Resource, Int>()) }
     var get by remember { mutableStateOf(emptyMap<Resource, Int>()) }
@@ -371,9 +375,16 @@ fun CatanTradeDialog(
                     }
                 } else {
                     Text("Offer to:", fontWeight = FontWeight.Bold)
-                    Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                    FlowRow(
+                        horizontalArrangement = Arrangement.spacedBy(8.dp),
+                        verticalArrangement = Arrangement.spacedBy(8.dp),
+                    ) {
+                        TabButton(CatanText.EVERYONE, everyone) { everyone = true; partner = null }
                         (0 until state.playerCount).filter { it != seat }.forEach { other ->
-                            TabButton(seats.label(other), partner == other) { partner = other }
+                            TabButton(seats.label(other), !everyone && partner == other) {
+                                everyone = false
+                                partner = other
+                            }
                         }
                     }
                     Text(CatanText.YOU_GIVE, fontWeight = FontWeight.Bold)
@@ -389,13 +400,13 @@ fun CatanTradeDialog(
         },
         confirmButton = {
             if (tab == TradeTab.PLAYER) {
-                val to = partner
+                val to = if (everyone) null else partner
                 val giveCards = give.asCards()
                 val getCards = get.asCards()
-                val allowed = to != null &&
+                val allowed = (everyone || partner != null) &&
                     CatanInteraction.offerAllowed(state, seat, to, giveCards, getCards)
                 Button(
-                    onClick = { if (to != null) onOffer(OfferTrade(to, giveCards, getCards)) },
+                    onClick = { onOffer(OfferTrade(to, giveCards, getCards)) },
                     enabled = allowed,
                 ) { Text(CatanText.SEND_OFFER) }
             }
@@ -435,29 +446,57 @@ private fun TabButton(label: String, selected: Boolean, onClick: () -> Unit) {
     }
 }
 
-/** Another player has offered the local player a trade. */
+/**
+ * Another player has put an offer to the local player (alone, or as one of the
+ * table). Accept, decline, or — via a second step — answer with different terms.
+ */
+@OptIn(ExperimentalLayoutApi::class)
 @Composable
 fun CatanTradeResponseDialog(
+    state: CatanState,
+    seat: Int,
     offer: TradeOffer,
     seats: CatanSeats,
     canAccept: Boolean,
     onAccept: () -> Unit,
     onDecline: () -> Unit,
+    onCounter: (CounterTrade) -> Unit,
 ) {
+    var countering by remember(offer) { mutableStateOf(false) }
+    // What we would give the offerer, and what we would ask of them.
+    var give by remember(offer) { mutableStateOf(offer.get.groupingBy { it }.eachCount()) }
+    var get by remember(offer) { mutableStateOf(offer.give.groupingBy { it }.eachCount()) }
+
     AlertDialog(
         onDismissRequest = {},
-        title = { Text("Trade offer") },
+        title = { Text(if (countering) "Counter-offer" else "Trade offer") },
         text = {
-            Column(verticalArrangement = Arrangement.spacedBy(6.dp)) {
+            Column(
+                modifier = Modifier.heightIn(max = 460.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
                 Text(
                     CatanText.tradeSummary(
                         by = seats.label(offer.by),
-                        to = "you",
+                        to = if (offer.to == null) "the table" else "you",
                         give = offer.give,
                         get = offer.get,
                     ),
                 )
-                if (!canAccept) {
+                if (countering) {
+                    Text(CatanText.YOU_GIVE, fontWeight = FontWeight.Bold)
+                    CounterRow(
+                        counts = give,
+                        limit = { state.resources[seat][it] ?: 0 },
+                        onChange = { give = it },
+                    )
+                    Text(CatanText.YOU_GET, fontWeight = FontWeight.Bold)
+                    CounterRow(
+                        counts = get,
+                        limit = { state.resources[offer.by][it] ?: 0 },
+                        onChange = { get = it },
+                    )
+                } else if (!canAccept) {
                     Text(
                         "You cannot accept this: one side no longer holds the cards.",
                         style = MaterialTheme.typography.bodySmall,
@@ -465,8 +504,58 @@ fun CatanTradeResponseDialog(
                 }
             }
         },
-        confirmButton = { Button(onClick = onAccept, enabled = canAccept) { Text(CatanText.ACCEPT) } },
-        dismissButton = { TextButton(onClick = onDecline) { Text(CatanText.DECLINE) } },
+        confirmButton = {
+            if (countering) {
+                val move = CounterTrade(give.asCards(), get.asCards())
+                Button(
+                    onClick = { onCounter(move) },
+                    enabled = CatanInteraction.counterAllowed(state, seat, move.give, move.get),
+                ) { Text(CatanText.SEND_COUNTER) }
+            } else {
+                Button(onClick = onAccept, enabled = canAccept) { Text(CatanText.ACCEPT) }
+            }
+        },
+        dismissButton = {
+            Row(horizontalArrangement = Arrangement.spacedBy(4.dp)) {
+                if (countering) {
+                    TextButton(onClick = { countering = false }) { Text(CatanText.CANCEL) }
+                } else {
+                    TextButton(onClick = { countering = true }) { Text(CatanText.COUNTER) }
+                }
+                TextButton(onClick = onDecline) { Text(CatanText.DECLINE) }
+            }
+        },
+    )
+}
+
+/** The offerer's choice once nobody accepted: take a counter-offer, or none. */
+@Composable
+fun CatanCounterChoiceDialog(
+    counters: List<TradeCounter>,
+    seats: CatanSeats,
+    onTake: (AcceptCounter) -> Unit,
+    onNoDeal: () -> Unit,
+) {
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text("Counter-offers") },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 460.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                if (counters.isEmpty()) {
+                    Text("None of the counter-offers can be met any more.")
+                }
+                counters.forEach { counter ->
+                    Column(verticalArrangement = Arrangement.spacedBy(4.dp)) {
+                        Text(CatanText.counterSummary(seats.label(counter.by), counter.give, counter.get))
+                        Button(onClick = { onTake(AcceptCounter(counter.by)) }) { Text(CatanText.ACCEPT) }
+                    }
+                }
+            }
+        },
+        confirmButton = { TextButton(onClick = onNoDeal) { Text(CatanText.NO_DEAL) } },
     )
 }
 

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanGeometry.kt

@@ -102,7 +102,7 @@ object CatanGeometry {
     private const val LATTICE_Y_UNITS = 16
 
     /** Empty space round the island, in hex radii, for the sea and the harbours. */
-    const val MARGIN = 1.15f
+    const val MARGIN = 1.75f
 
     private val boardWidthInRadii = LATTICE_X_UNITS * SQRT3 / 2f + 2 * MARGIN
     private val boardHeightInRadii = LATTICE_Y_UNITS / 2f + 2 * MARGIN
@@ -119,5 +119,5 @@ object CatanGeometry {
 
 private const val SQRT3 = 1.7320508f
 
-/** How far past the coast a harbour marker sits, in hex radii. */
-private const val PORT_OFFSET = 0.62f
+/** How far past the coast a harbour marker sits, in hex radii. Far enough that its piers are clearly visible. */
+internal const val PORT_OFFSET = 1.0f

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanInteraction.kt

@@ -1,43 +1,101 @@
 package org.prolibertate.games.ui.game.catan
 
+import org.prolibertate.games.game.catan.AcceptCounter
 import org.prolibertate.games.game.catan.AcceptTrade
+import org.prolibertate.games.game.catan.ActivateKnight
 import org.prolibertate.games.game.catan.BuildCity
 import org.prolibertate.games.game.catan.BuildRoad
 import org.prolibertate.games.game.catan.BuildSettlement
+import org.prolibertate.games.game.catan.BuildWall
 import org.prolibertate.games.game.catan.BuyDevCard
+import org.prolibertate.games.game.catan.BuyImprovement
 import org.prolibertate.games.game.catan.CatanBoard
 import org.prolibertate.games.game.catan.CatanMove
 import org.prolibertate.games.game.catan.CatanPhase
 import org.prolibertate.games.game.catan.CatanRules
 import org.prolibertate.games.game.catan.CatanState
+import org.prolibertate.games.game.catan.ChaseRobber
+import org.prolibertate.games.game.catan.Chore
+import org.prolibertate.games.game.catan.CounterTrade
 import org.prolibertate.games.game.catan.DeclineTrade
 import org.prolibertate.games.game.catan.DevCard
 import org.prolibertate.games.game.catan.DevCardType
 import org.prolibertate.games.game.catan.Discard
 import org.prolibertate.games.game.catan.EndFreeRoads
+import org.prolibertate.games.game.catan.EndSmith
 import org.prolibertate.games.game.catan.EndTurn
+import org.prolibertate.games.game.catan.CounterGoods
+import org.prolibertate.games.game.catan.GoodsBankTrade
+import org.prolibertate.games.game.catan.GoodsCounter
+import org.prolibertate.games.game.catan.Good
 import org.prolibertate.games.game.catan.HexCoord
+import org.prolibertate.games.game.catan.HireKnight
 import org.prolibertate.games.game.catan.MaritimeTrade
+import org.prolibertate.games.game.catan.MoveKnight
 import org.prolibertate.games.game.catan.MoveRobber
+import org.prolibertate.games.game.catan.OfferGoods
 import org.prolibertate.games.game.catan.OfferTrade
+import org.prolibertate.games.game.catan.PillageCity
+import org.prolibertate.games.game.catan.PlaceKnight
+import org.prolibertate.games.game.catan.PlaceMetropolis
+import org.prolibertate.games.game.catan.TradeCounter
 import org.prolibertate.games.game.catan.PlayKnight
 import org.prolibertate.games.game.catan.PlayMonopoly
+import org.prolibertate.games.game.catan.PlayProgress
 import org.prolibertate.games.game.catan.PlayRoadBuilding
 import org.prolibertate.games.game.catan.PlayYearOfPlenty
+import org.prolibertate.games.game.catan.ProgressCard
+import org.prolibertate.games.game.catan.ProgressType
+import org.prolibertate.games.game.catan.PromoteKnight
+import org.prolibertate.games.game.catan.RelocateKnight
+import org.prolibertate.games.game.catan.RemoveKnight
 import org.prolibertate.games.game.catan.Resource
 import org.prolibertate.games.game.catan.RollDice
 import org.prolibertate.games.game.catan.SetupPlace
+import org.prolibertate.games.game.catan.Track
 
-/** What a player can ask to build by tapping the board. */
-enum class BuildKind { ROAD, SETTLEMENT, CITY }
+/**
+ * What a player can ask to build by tapping the board. Wall and Knight exist
+ * only in Cities & Knights; the base game's build menu lists the first three.
+ */
+enum class BuildKind {
+    ROAD, SETTLEMENT, CITY, WALL, KNIGHT;
 
-/** The parts of the board the player may tap right now. Everything else is inert. */
+    companion object {
+        val BASE: List<BuildKind> = listOf(ROAD, SETTLEMENT, CITY)
+    }
+}
+
+/**
+ * The parts of the board the player may tap right now. Everything else is inert.
+ * [knights] are crossings holding one of the player's own knights that can do
+ * something this turn: tapping one opens its menu.
+ */
 data class BoardTargets(
     val vertices: Set<Int> = emptySet(),
     val edges: Set<Int> = emptySet(),
     val hexes: Set<Int> = emptySet(),
+    val knights: Set<Int> = emptySet(),
+    /** The player's other knights: tappable for their menu, but with nothing to do, so not ringed. */
+    val idleKnights: Set<Int> = emptySet(),
 ) {
-    val isEmpty: Boolean get() = vertices.isEmpty() && edges.isEmpty() && hexes.isEmpty()
+    val isEmpty: Boolean
+        get() = vertices.isEmpty() && edges.isEmpty() && hexes.isEmpty() && knights.isEmpty() && idleKnights.isEmpty()
+
+    /** Every crossing a tap can land on. */
+    val tappableVertices: Set<Int> get() = vertices + knights + idleKnights
+}
+
+/**
+ * A progress card that is waiting for a tap on the board: [plays] are every play
+ * of it the engine accepts, and the player's tap picks one. [firstHex] is the
+ * first of the two hexes an Inventor swaps, once tapped.
+ */
+data class ArmedCard(val kind: ProgressType, val plays: List<PlayProgress>, val firstHex: Int? = null)
+
+/** One progress card in the local player's hand, and the plays the engine allows for it. */
+data class ProgressInHand(val card: ProgressCard, val plays: List<PlayProgress>) {
+    val playable: Boolean get() = plays.isNotEmpty()
 }
 
 /** What a tap on the board amounts to. */
@@ -53,6 +111,12 @@ sealed interface TapOutcome {
 
     /** The robber's hex has more than one possible victim: ask which. */
     data class PickRobberVictim(val hex: HexCoord, val victims: List<Int>) : TapOutcome
+
+    /** One of the player's own knights was tapped: open its menu. */
+    data class PickKnight(val vertex: Int) : TapOutcome
+
+    /** An Inventor's first hex was tapped; the second completes the swap. */
+    data class PickFirstHex(val hex: Int) : TapOutcome
 }
 
 /**
@@ -85,6 +149,10 @@ object CatanInteraction {
         legal: List<CatanMove>,
         building: BuildKind?,
         setupVertex: Int?,
+        movingKnight: Int? = null,
+        armed: ArmedCard? = null,
+        /** The local seat, so its sleeping knights can be tapped for their menu too. */
+        localSeat: Int? = null,
     ): BoardTargets {
         val setup = legal.filterIsInstance<SetupPlace>()
         if (setup.isNotEmpty()) {
@@ -100,9 +168,21 @@ object CatanInteraction {
             return BoardTargets(hexes = robber.mapNotNull { CatanBoard.hexIndex[it.hex] }.toSet())
         }
 
+        // Cities & Knights: answers to a queued chore are taps on the board.
+        val chore = choreVertices(legal)
+        if (chore.isNotEmpty()) return BoardTargets(vertices = chore)
+
         val roads = legal.filterIsInstance<BuildRoad>().map { it.edge }.toSet()
         if (state.phase == CatanPhase.FREE_ROADS) return BoardTargets(edges = roads)
 
+        if (armed != null) return armedTargets(armed)
+
+        if (movingKnight != null) {
+            return BoardTargets(
+                vertices = legal.filterIsInstance<MoveKnight>().filter { it.from == movingKnight }.map { it.to }.toSet(),
+            )
+        }
+
         return when (building) {
             BuildKind.ROAD -> BoardTargets(edges = roads)
             BuildKind.SETTLEMENT ->
@@ -111,15 +191,169 @@ object CatanInteraction {
             BuildKind.CITY ->
                 BoardTargets(vertices = legal.filterIsInstance<BuildCity>().map { it.vertex }.toSet())
 
-            null -> BoardTargets()
+            BuildKind.WALL ->
+                BoardTargets(vertices = legal.filterIsInstance<BuildWall>().map { it.vertex }.toSet())
+
+            BuildKind.KNIGHT ->
+                BoardTargets(vertices = legal.filterIsInstance<HireKnight>().map { it.vertex }.toSet())
+
+            null -> {
+                val ready = knightsWithActions(legal)
+                val mine = if (localSeat != null && legal.isNotEmpty()) {
+                    state.ck?.knights?.filter { it.owner == localSeat }?.map { it.vertex }?.toSet().orEmpty()
+                } else {
+                    emptySet()
+                }
+                BoardTargets(knights = ready, idleKnights = mine - ready)
+            }
         }
     }
 
+    /** The crossings a queued chore is asking the player to tap, from the legal list. */
+    private fun choreVertices(legal: List<CatanMove>): Set<Int> = buildSet {
+        legal.forEach { move ->
+            when (move) {
+                is PillageCity -> add(move.vertex)
+                is PlaceMetropolis -> add(move.vertex)
+                is RelocateKnight -> add(move.to)
+                is RemoveKnight -> add(move.vertex)
+                is PlaceKnight -> add(move.vertex)
+                else -> Unit
+            }
+        }
+        // A Smith's promotions are knights to tap, while the chore is open.
+        if (legal.any { it is EndSmith }) {
+            legal.filterIsInstance<PromoteKnight>().forEach { add(it.vertex) }
+        }
+    }
+
+    private fun choreMove(legal: List<CatanMove>, vertex: Int): CatanMove? = legal.firstOrNull { move ->
+        when (move) {
+            is PillageCity -> move.vertex == vertex
+            is PlaceMetropolis -> move.vertex == vertex
+            is RelocateKnight -> move.to == vertex
+            is RemoveKnight -> move.vertex == vertex
+            is PlaceKnight -> move.vertex == vertex
+            is PromoteKnight -> legal.any { it is EndSmith } && move.vertex == vertex
+            else -> false
+        }
+    }
+
+    // --- Cities & Knights: knights ---------------------------------------------
+
+    /** Crossings of the player's knights that have an action available. */
+    fun knightsWithActions(legal: List<CatanMove>): Set<Int> = buildSet {
+        legal.forEach { move ->
+            when (move) {
+                is ActivateKnight -> add(move.vertex)
+                is MoveKnight -> add(move.from)
+                is ChaseRobber -> add(move.vertex)
+                is PromoteKnight -> if (legal.none { it is EndSmith }) add(move.vertex)
+                else -> Unit
+            }
+        }
+    }
+
+    /** What the knight on [vertex] can do right now, in the order its menu lists them. */
+    fun knightActions(legal: List<CatanMove>, vertex: Int): List<CatanMove> =
+        legal.filter { move ->
+            when (move) {
+                is ActivateKnight -> move.vertex == vertex
+                is PromoteKnight -> move.vertex == vertex && legal.none { it is EndSmith }
+                is ChaseRobber -> move.vertex == vertex
+                else -> false
+            }
+        } + listOfNotNull(legal.firstOrNull { it is MoveKnight && it.from == vertex })
+
+    fun canEndSmith(legal: List<CatanMove>): Boolean = legal.any { it is EndSmith }
+
+    // --- Cities & Knights: progress cards --------------------------------------
+
+    /** [seat]'s progress cards, each with the plays the engine currently allows. */
+    fun progressHand(state: CatanState, seat: Int, legal: List<CatanMove>): List<ProgressInHand> =
+        state.ck?.progressHands?.getOrNull(seat).orEmpty().map { card ->
+            ProgressInHand(card, legal.filterIsInstance<PlayProgress>().filter { it.card == card.id })
+        }.sortedWith(compareBy({ it.card.kind.track.ordinal }, { it.card.kind.ordinal }, { it.card.id }))
+
+    /** The cards that are played by tapping the board, not by choosing in a dialog. */
+    val BOARD_CARDS: Set<ProgressType> = setOf(
+        ProgressType.ENGINEER, ProgressType.MEDICINE, ProgressType.MERCHANT,
+        ProgressType.DIPLOMAT, ProgressType.INTRIGUE, ProgressType.INVENTOR,
+    )
+
+    private fun armedTargets(armed: ArmedCard): BoardTargets = when (armed.kind) {
+        ProgressType.ENGINEER, ProgressType.MEDICINE, ProgressType.INTRIGUE ->
+            BoardTargets(vertices = armed.plays.mapNotNull { it.vertex }.toSet())
+
+        ProgressType.DIPLOMAT -> BoardTargets(edges = armed.plays.mapNotNull { it.edge }.toSet())
+
+        ProgressType.MERCHANT -> BoardTargets(hexes = armed.plays.mapNotNull { it.hexA }.toSet())
+
+        ProgressType.INVENTOR -> {
+            val first = armed.firstHex
+            val all = armed.plays.flatMap { listOfNotNull(it.hexA, it.hexB) }.toSet()
+            if (first == null) {
+                BoardTargets(hexes = all)
+            } else {
+                BoardTargets(
+                    hexes = armed.plays
+                        .filter { it.hexA == first || it.hexB == first }
+                        .flatMap { listOfNotNull(it.hexA, it.hexB) }
+                        .filter { it != first }
+                        .toSet(),
+                )
+            }
+        }
+
+        else -> BoardTargets()
+    }
+
+    /** The improvement tracks the player can buy a level of right now. */
+    fun improvable(legal: List<CatanMove>): Set<Track> =
+        legal.filterIsInstance<BuyImprovement>().map { it.track }.toSet()
+
+    // --- Cities & Knights: goods ----------------------------------------------
+
+    /** Bank trades on offer in Cities & Knights: what can be given, and for what. */
+    fun goodsBankTrades(legal: List<CatanMove>): Map<Good, List<Good>> =
+        legal.filterIsInstance<GoodsBankTrade>()
+            .groupBy({ it.give }, { it.get })
+            .mapValues { (_, gets) -> gets.sortedBy { it.ordinal } }
+            .toSortedMap(compareBy<Good> { it.ordinal })
+
+    fun goodsOfferAllowed(
+        state: CatanState,
+        seat: Int,
+        to: Int?,
+        give: List<Good>,
+        get: List<Good>,
+    ): Boolean = give.isNotEmpty() && get.isNotEmpty() &&
+        CatanRules.isLegalMove(state, seat, OfferGoods(to, give, get))
+
+    /** Whether [seat] may answer the goods offer on the table with [give] for [get]. */
+    fun goodsCounterAllowed(state: CatanState, seat: Int, give: List<Good>, get: List<Good>): Boolean =
+        give.isNotEmpty() && get.isNotEmpty() &&
+            CatanRules.isLegalMove(state, seat, CounterGoods(give, get))
+
+    /** The goods counter-offers the offerer may take right now, in the order they came in. */
+    fun goodsCounterChoices(state: CatanState, legal: List<CatanMove>): List<GoodsCounter> {
+        val takeable = legal.filterIsInstance<AcceptCounter>().map { it.seat }.toSet()
+        return state.ck?.goodsOffer?.counters.orEmpty().filter { it.by in takeable }
+    }
+
+    /** The chore at the front of the queue, if the table is waiting on one. */
+    fun chore(state: CatanState): Chore? =
+        if (state.phase == CatanPhase.CHORE) state.ck?.chores?.firstOrNull() else null
+
     fun onVertexTap(
         vertex: Int,
         legal: List<CatanMove>,
         building: BuildKind?,
         setupVertex: Int?,
+        movingKnight: Int? = null,
+        armed: ArmedCard? = null,
+        /** The local player's knights, which can be tapped for their menu even with nothing to do. */
+        ownKnights: Set<Int> = emptySet(),
     ): TapOutcome {
         val setup = legal.filterIsInstance<SetupPlace>()
         if (setup.isNotEmpty()) {
@@ -131,10 +365,27 @@ object CatanInteraction {
                 TapOutcome.Ignored
             }
         }
+        choreMove(legal, vertex)?.let { return TapOutcome.Submit(it) }
+
+        if (armed != null) {
+            val play = armed.plays.firstOrNull { it.vertex == vertex } ?: return TapOutcome.Ignored
+            return if (play in legal) TapOutcome.Submit(play) else TapOutcome.Ignored
+        }
+        if (movingKnight != null) {
+            val move = MoveKnight(movingKnight, vertex)
+            return if (move in legal) TapOutcome.Submit(move) else TapOutcome.Ignored
+        }
+
         val move: CatanMove = when (building) {
             BuildKind.SETTLEMENT -> BuildSettlement(vertex)
             BuildKind.CITY -> BuildCity(vertex)
-            else -> return TapOutcome.Ignored
+            BuildKind.WALL -> BuildWall(vertex)
+            BuildKind.KNIGHT -> HireKnight(vertex)
+            else -> return if (building == null && (vertex in knightsWithActions(legal) || vertex in ownKnights)) {
+                TapOutcome.PickKnight(vertex)
+            } else {
+                TapOutcome.Ignored
+            }
         }
         return if (move in legal) TapOutcome.Submit(move) else TapOutcome.Ignored
     }
@@ -144,12 +395,17 @@ object CatanInteraction {
         legal: List<CatanMove>,
         building: BuildKind?,
         setupVertex: Int?,
+        armed: ArmedCard? = null,
     ): TapOutcome {
         if (legal.any { it is SetupPlace }) {
             if (setupVertex == null) return TapOutcome.Ignored
             val move = SetupPlace(setupVertex, edge)
             return if (move in legal) TapOutcome.Submit(move) else TapOutcome.Ignored
         }
+        if (armed != null) {
+            val play = armed.plays.firstOrNull { it.edge == edge } ?: return TapOutcome.Ignored
+            return if (play in legal) TapOutcome.Submit(play) else TapOutcome.Ignored
+        }
         // Free roads need no build mode; a paid road does.
         val canBuild = building == BuildKind.ROAD || legal.any { it is EndFreeRoads }
         if (!canBuild) return TapOutcome.Ignored
@@ -157,7 +413,8 @@ object CatanInteraction {
         return if (move in legal) TapOutcome.Submit(move) else TapOutcome.Ignored
     }
 
-    fun onHexTap(hex: Int, legal: List<CatanMove>): TapOutcome {
+    fun onHexTap(hex: Int, legal: List<CatanMove>, armed: ArmedCard? = null): TapOutcome {
+        if (armed != null) return onArmedHexTap(hex, legal, armed)
         val coord = CatanBoard.HEXES.getOrNull(hex) ?: return TapOutcome.Ignored
         val moves = legal.filterIsInstance<MoveRobber>().filter { it.hex == coord }
         return when {
@@ -167,10 +424,45 @@ object CatanInteraction {
         }
     }
 
+    private fun onArmedHexTap(hex: Int, legal: List<CatanMove>, armed: ArmedCard): TapOutcome {
+        if (armed.kind == ProgressType.INVENTOR) {
+            val first = armed.firstHex ?: return if (hex in armedTargets(armed).hexes) {
+                TapOutcome.PickFirstHex(hex)
+            } else {
+                TapOutcome.Ignored
+            }
+            val play = armed.plays.firstOrNull {
+                (it.hexA == first && it.hexB == hex) || (it.hexA == hex && it.hexB == first)
+            } ?: return TapOutcome.Ignored
+            return if (play in legal) TapOutcome.Submit(play) else TapOutcome.Ignored
+        }
+        val play = armed.plays.firstOrNull { it.hexA == hex } ?: return TapOutcome.Ignored
+        return if (play in legal) TapOutcome.Submit(play) else TapOutcome.Ignored
+    }
+
     // --- Action bar ------------------------------------------------------------
 
     fun canRoll(legal: List<CatanMove>): Boolean = legal.any { it is RollDice }
 
+    /**
+     * The hexes that paid out for this turn's roll, so the board can light them.
+     * Empty until the turn's roll has happened (the dice left over from the last
+     * turn are not this turn's), on a seven, and for the hex the robber sits on.
+     */
+    fun rolledHexes(state: CatanState): Set<Int> {
+        if (state.lastDice.size != 2) return emptySet()
+        if (state.phase == CatanPhase.AWAIT_ROLL || state.phase == CatanPhase.SETUP_FIRST ||
+            state.phase == CatanPhase.SETUP_SECOND
+        ) {
+            return emptySet()
+        }
+        val total = state.lastDice.sum()
+        if (total == 7) return emptySet()
+        return (0 until CatanBoard.HEX_COUNT)
+            .filter { state.numbers[it] == total && it != state.robber }
+            .toSet()
+    }
+
     fun canEndTurn(legal: List<CatanMove>): Boolean = legal.any { it is EndTurn }
 
     fun canEndFreeRoads(legal: List<CatanMove>): Boolean = legal.any { it is EndFreeRoads }
@@ -181,6 +473,8 @@ object CatanInteraction {
         if (legal.any { it is BuildRoad }) add(BuildKind.ROAD)
         if (legal.any { it is BuildSettlement }) add(BuildKind.SETTLEMENT)
         if (legal.any { it is BuildCity }) add(BuildKind.CITY)
+        if (legal.any { it is BuildWall }) add(BuildKind.WALL)
+        if (legal.any { it is HireKnight }) add(BuildKind.KNIGHT)
     }
 
     fun tradeResponses(legal: List<CatanMove>): Pair<Boolean, Boolean> =
@@ -265,9 +559,20 @@ object CatanInteraction {
     fun offerAllowed(
         state: CatanState,
         seat: Int,
-        to: Int,
+        to: Int?,
         give: List<Resource>,
         get: List<Resource>,
     ): Boolean = give.isNotEmpty() && get.isNotEmpty() &&
         CatanRules.isLegalMove(state, seat, OfferTrade(to, give, get))
+
+    /** Whether [seat] may answer the offer on the table with [give] for [get]. */
+    fun counterAllowed(state: CatanState, seat: Int, give: List<Resource>, get: List<Resource>): Boolean =
+        give.isNotEmpty() && get.isNotEmpty() &&
+            CatanRules.isLegalMove(state, seat, CounterTrade(give, get))
+
+    /** The counter-offers the offerer may take right now, in the order they came in. */
+    fun counterChoices(state: CatanState, legal: List<CatanMove>): List<TradeCounter> {
+        val takeable = legal.filterIsInstance<AcceptCounter>().map { it.seat }.toSet()
+        return state.pendingTrade?.counters.orEmpty().filter { it.by in takeable }
+    }
 }

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanPanels.kt

@@ -11,6 +11,7 @@ import androidx.compose.foundation.layout.FlowRow
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.defaultMinSize
 import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.rememberScrollState
@@ -18,23 +19,36 @@ import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.foundation.verticalScroll
 import androidx.compose.material3.Button
+import androidx.compose.material3.DropdownMenu
+import androidx.compose.material3.DropdownMenuItem
 import androidx.compose.material3.FilledTonalButton
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.TextStyle
 import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
+import org.prolibertate.games.game.catan.BuildingType
+import org.prolibertate.games.game.catan.CatanCk
 import org.prolibertate.games.game.catan.CatanPhase
 import org.prolibertate.games.game.catan.CatanRules
 import org.prolibertate.games.game.catan.CatanState
+import org.prolibertate.games.game.catan.EventFace
+import org.prolibertate.games.game.catan.Good
 import org.prolibertate.games.game.catan.Resource
+import org.prolibertate.games.game.catan.Track
 
 /*
  * Stateless building blocks for the Katan screen.
@@ -93,7 +107,52 @@ fun ResourceTile(
     }
 }
 
-/** The local player's cards: one tile per resource, in a row that wraps. */
+/**
+ * One card type — a resource or a commodity — as a coloured tile with its count.
+ * Cities & Knights hands, discards and trades use this so commodities look the
+ * same everywhere.
+ */
+@Composable
+fun GoodTile(
+    good: Good,
+    count: Int,
+    modifier: Modifier = Modifier,
+    selected: Boolean = false,
+    enabled: Boolean = true,
+    style: CatanStyle = LocalCatanStyle.current,
+    onClick: (() -> Unit)? = null,
+) {
+    val resource = good.resource
+    if (resource != null) {
+        ResourceTile(resource, count, modifier, selected, enabled, style, onClick)
+        return
+    }
+    val commodity = good.commodity!!
+    val shape = RoundedCornerShape(10.dp)
+    val ink = style.commodityInk.getValue(commodity)
+    Column(
+        modifier = modifier
+            .defaultMinSize(minWidth = 56.dp)
+            .clip(shape)
+            .background(style.commodity.getValue(commodity).copy(alpha = if (enabled) 1f else 0.4f))
+            .border(
+                width = if (selected) 3.dp else 1.dp,
+                color = if (selected) Color.White else Color(0x33000000),
+                shape = shape,
+            )
+            .then(if (onClick != null && enabled) Modifier.clickable { onClick() } else Modifier)
+            .padding(horizontal = 6.dp, vertical = 6.dp),
+        horizontalAlignment = Alignment.CenterHorizontally,
+    ) {
+        Text(text = count.toString(), color = ink, fontWeight = FontWeight.Bold, fontSize = 20.sp)
+        Text(text = CatanText.good(good), color = ink, fontSize = 11.sp, maxLines = 1)
+    }
+}
+
+/**
+ * The local player's cards: one tile per resource, and in Cities & Knights one
+ * per commodity as well, in a row that wraps.
+ */
 @OptIn(ExperimentalLayoutApi::class)
 @Composable
 fun CatanHand(
@@ -106,8 +165,13 @@ fun CatanHand(
         horizontalArrangement = Arrangement.spacedBy(6.dp),
         verticalArrangement = Arrangement.spacedBy(6.dp),
     ) {
-        Resource.entries.forEach { resource ->
-            ResourceTile(resource, state.resources[seat][resource] ?: 0)
+        if (state.isCk) {
+            val held = CatanCk.goodsOf(state, seat)
+            Good.entries.forEach { good -> GoodTile(good, held[good] ?: 0) }
+        } else {
+            Resource.entries.forEach { resource ->
+                ResourceTile(resource, state.resources[seat][resource] ?: 0)
+            }
         }
     }
 }
@@ -118,11 +182,18 @@ fun CatanHand(
 
 /**
  * One player's public standing: colour, name, points, how many cards they hold
- * (not which), development cards, knights and their longest road.
+ * (not which), and — in the roomier layout — development cards, knights and
+ * their longest road.
+ *
+ * **Fixed height.** Every line is always present (blank when there is nothing to
+ * say) and never wraps, so the card is the same height whatever the game is
+ * doing. The board is given whatever room is left, so anything that made this
+ * card taller or shorter would rescale the island under the player's thumb.
  *
  * [points] is passed in rather than computed here because the local player's
  * own count includes hidden victory-point cards and everyone else's does not;
- * the screen decides which.
+ * the screen decides which. [compact] is the narrow portrait strip (four cards
+ * across a phone); the default has room for the detail lines.
  */
 @Composable
 fun CatanPlayerCard(
@@ -132,6 +203,7 @@ fun CatanPlayerCard(
     points: Int,
     modifier: Modifier = Modifier,
     style: CatanStyle = LocalCatanStyle.current,
+    compact: Boolean = false,
 ) {
     val onTurn = state.turn == seat && state.phase != CatanPhase.GAME_OVER
     val shape = RoundedCornerShape(12.dp)
@@ -155,60 +227,125 @@ fun CatanPlayerCard(
                     .background(style.seats[seat % style.seats.size])
                     .border(1.dp, style.pieceOutline, CircleShape),
             )
-            Text(
-                text = seats.label(seat),
-                fontWeight = FontWeight.Bold,
-                maxLines = 1,
-                style = MaterialTheme.typography.labelLarge,
+            CardLine(seats.label(seat), MaterialTheme.typography.labelLarge, FontWeight.Bold)
+        }
+        CardLine("$points VP", MaterialTheme.typography.titleMedium, FontWeight.Bold)
+        val ck = state.ck
+        if (ck != null) {
+            val cards = CatanCk.goodsCount(state, seat)
+            val strength = CatanCk.strength(state, seat)
+            if (compact) {
+                CardLine("$cards cards · ⚔$strength", MaterialTheme.typography.bodySmall)
+            } else {
+                CardLine("$cards cards · ${ck.progressCounts[seat]} progress", MaterialTheme.typography.bodySmall)
+                CardLine(
+                    "⚔ ${CatanCk.knightsOf(state, seat).size} · str $strength · " +
+                        "Road ${CatanRules.longestRoadFor(state, seat)}",
+                    MaterialTheme.typography.bodySmall,
+                )
+            }
+            // Trade, politics, science: the three improvement levels.
+            CardLine(
+                Track.entries.joinToString(" ") { "${it.name.first()}${CatanCk.improvement(state, seat, it)}" },
+                MaterialTheme.typography.bodySmall,
+                color = Color.Unspecified,
             )
-        }
-        Text(
-            text = "$points VP",
-            style = MaterialTheme.typography.titleMedium,
-            fontWeight = FontWeight.Bold,
-        )
-        Text(
-            text = "${state.resourceCount(seat)} cards · ${state.devHandCounts[seat]} dev",
-            style = MaterialTheme.typography.bodySmall,
-        )
-        Text(
-            text = "Knights ${state.knightsPlayed[seat]} · Road ${CatanRules.longestRoadFor(state, seat)}",
-            style = MaterialTheme.typography.bodySmall,
-        )
-        val awards = buildList {
-            if (state.longestRoadOwner == seat) add("Longest road")
-            if (state.largestArmyOwner == seat) add("Largest army")
-        }
-        if (awards.isNotEmpty()) {
-            Text(
-                text = awards.joinToString(" · "),
+            val ckAwards = buildList {
+                if (state.longestRoadOwner == seat) add(if (compact) "Road" else "Longest road")
+                ck.metropolises.forEach { (track, at) ->
+                    if (at.seat == seat) add(if (compact) track.name.first().toString() else "${CatanText.track(track)} metropolis")
+                }
+                if (ck.merchant?.seat == seat) add("Merchant")
+            }
+            CardLine(
+                text = ckAwards.joinToString(" · ").ifEmpty { BLANK },
                 style = MaterialTheme.typography.labelSmall,
+                weight = FontWeight.Bold,
                 color = MaterialTheme.colorScheme.primary,
-                fontWeight = FontWeight.Bold,
+            )
+            return@Column
+        }
+        if (compact) {
+            CardLine("${state.resourceCount(seat)} cards", MaterialTheme.typography.bodySmall)
+        } else {
+            CardLine(
+                "${state.resourceCount(seat)} cards · ${state.devHandCounts[seat]} dev",
+                MaterialTheme.typography.bodySmall,
+            )
+            CardLine(
+                "Knights ${state.knightsPlayed[seat]} · Road ${CatanRules.longestRoadFor(state, seat)}",
+                MaterialTheme.typography.bodySmall,
             )
         }
+        val awards = buildList {
+            if (state.longestRoadOwner == seat) add(if (compact) "Road" else "Longest road")
+            if (state.largestArmyOwner == seat) add(if (compact) "Army" else "Largest army")
+        }
+        // Always drawn, so the card does not grow when somebody takes an award.
+        CardLine(
+            text = awards.joinToString(" · ").ifEmpty { BLANK },
+            style = MaterialTheme.typography.labelSmall,
+            weight = FontWeight.Bold,
+            color = MaterialTheme.colorScheme.primary,
+        )
     }
 }
 
+/** A non-breaking space: a line of text with nothing in it, still one line tall. */
+private const val BLANK = "\u00A0"
+
+/** One line of a player card: never wraps, so the card's height cannot change. */
+@Composable
+private fun CardLine(
+    text: String,
+    style: TextStyle,
+    weight: FontWeight? = null,
+    color: Color = Color.Unspecified,
+) {
+    Text(
+        text = text,
+        style = style,
+        fontWeight = weight,
+        color = color,
+        maxLines = 1,
+        overflow = TextOverflow.Ellipsis,
+    )
+}
+
 // ---------------------------------------------------------------------------
 // Dice
 // ---------------------------------------------------------------------------
 
-/** The two dice as last rolled, with their total. Blank until the first roll. */
+/**
+ * The two dice as last rolled, with their total. Blank until the first roll. In
+ * Cities & Knights the dice are yellow and red (the red one decides progress
+ * cards) and a third, the event die, shows a ship or a coloured city gate.
+ */
 @Composable
-fun CatanDice(dice: List<Int>, modifier: Modifier = Modifier) {
+fun CatanDice(
+    dice: List<Int>,
+    modifier: Modifier = Modifier,
+    ck: Boolean = false,
+    event: EventFace? = null,
+    style: CatanStyle = LocalCatanStyle.current,
+) {
     Row(
         modifier = modifier,
         verticalAlignment = Alignment.CenterVertically,
         horizontalArrangement = Arrangement.spacedBy(6.dp),
     ) {
         val shown = if (dice.size == 2) dice else listOf(null, null)
-        shown.forEach { value ->
+        shown.forEachIndexed { index, value ->
+            val face = when {
+                !ck -> Color.White
+                index == 0 -> Color(0xFFFFF176)
+                else -> Color(0xFFEF9A9A)
+            }
             Box(
                 modifier = Modifier
                     .size(36.dp)
                     .clip(RoundedCornerShape(8.dp))
-                    .background(Color.White)
+                    .background(face)
                     .border(1.dp, Color(0x55000000), RoundedCornerShape(8.dp)),
                 contentAlignment = Alignment.Center,
             ) {
@@ -221,16 +358,82 @@ fun CatanDice(dice: List<Int>, modifier: Modifier = Modifier) {
                 )
             }
         }
-        if (dice.size == 2) {
-            Text(
-                text = "= ${dice.sum()}",
-                style = MaterialTheme.typography.titleMedium,
-                fontWeight = FontWeight.Bold,
-            )
+        if (ck) {
+            val gate = when (event) {
+                EventFace.TRADE -> style.track.getValue(Track.TRADE)
+                EventFace.POLITICS -> style.track.getValue(Track.POLITICS)
+                EventFace.SCIENCE -> style.track.getValue(Track.SCIENCE)
+                EventFace.SHIP -> style.barbarian
+                null -> Color(0x33000000)
+            }
+            Box(
+                modifier = Modifier
+                    .size(width = 52.dp, height = 36.dp)
+                    .clip(RoundedCornerShape(8.dp))
+                    .background(gate)
+                    .border(1.dp, Color(0x55000000), RoundedCornerShape(8.dp)),
+                contentAlignment = Alignment.Center,
+            ) {
+                Text(
+                    text = if (event == EventFace.SHIP) "⛵ Ship" else CatanText.event(event),
+                    color = if (event == EventFace.TRADE) Color(0xFF1C1B1F) else Color.White,
+                    fontWeight = FontWeight.Bold,
+                    fontSize = 11.sp,
+                    maxLines = 1,
+                )
+            }
         }
+        // Always drawn ("= –" before the first roll) so the row never changes width.
+        Text(
+            text = if (dice.size == 2) "= ${dice.sum()}" else "= –",
+            style = MaterialTheme.typography.titleMedium,
+            fontWeight = FontWeight.Bold,
+        )
     }
 }
 
+/**
+ * Cities & Knights: how close the barbarians are, and how the cities on the
+ * island compare with the knights standing ready. **Fixed height**, like every
+ * other strip around the board.
+ */
+@Composable
+fun CatanBarbarians(state: CatanState, modifier: Modifier = Modifier, style: CatanStyle = LocalCatanStyle.current) {
+    val ck = state.ck ?: return
+    val cities = state.buildings.count { it?.type == BuildingType.CITY }
+    val defence = (0 until state.playerCount).sumOf { CatanCk.strength(state, it) }
+    Row(
+        modifier = modifier.fillMaxWidth().height(24.dp),
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(6.dp),
+    ) {
+        Text("⛵", fontSize = 14.sp)
+        Row(horizontalArrangement = Arrangement.spacedBy(2.dp), modifier = Modifier.weight(1f)) {
+            // The ship starts seven steps out and lands when the last box fills.
+            val sailed = BARBARIAN_STEPS_DISPLAY - ck.barbarians
+            for (i in 0 until BARBARIAN_STEPS_DISPLAY) {
+                Box(
+                    modifier = Modifier
+                        .weight(1f)
+                        .height(10.dp)
+                        .clip(RoundedCornerShape(3.dp))
+                        .background(if (i < sailed) style.barbarian else Color(0x33000000)),
+                )
+            }
+        }
+        val verdict = if (defence >= cities) "holds" else "falls"
+        Text(
+            text = "${CatanText.barbarianSteps(ck.barbarians)} · knights $defence v. $cities cities ($verdict)",
+            style = MaterialTheme.typography.labelSmall,
+            maxLines = 1,
+            overflow = TextOverflow.Ellipsis,
+        )
+    }
+}
+
+/** Steps shown on the barbarian strip: the engine's seven. */
+private const val BARBARIAN_STEPS_DISPLAY = org.prolibertate.games.game.catan.BARBARIAN_STEPS
+
 // ---------------------------------------------------------------------------
 // Actions
 // ---------------------------------------------------------------------------
@@ -238,7 +441,6 @@ fun CatanDice(dice: List<Int>, modifier: Modifier = Modifier) {
 /** What the action bar offers right now. Built by the screen from [CatanInteraction]. */
 data class CatanActions(
     val canRoll: Boolean = false,
-    val showTurnActions: Boolean = false,
     val canBuild: Set<BuildKind> = emptySet(),
     val building: BuildKind? = null,
     val canBuyCard: Boolean = false,
@@ -248,9 +450,26 @@ data class CatanActions(
     val canEndFreeRoads: Boolean = false,
     /** A setup settlement is chosen and a different one may still be picked. */
     val canRepickSetup: Boolean = false,
+    /** Which kinds the Build menu lists: three in the base game, five in Cities & Knights. */
+    val buildKinds: List<BuildKind> = BuildKind.BASE,
+    /** Cities & Knights: the table plays the expansion, so the bar shows its buttons instead. */
+    val ck: Boolean = false,
+    val canImprove: Boolean = false,
+    val canPlayProgress: Boolean = false,
+    val progressCount: Int = 0,
+    val canEndSmith: Boolean = false,
 )
 
-/** The buttons for whatever the player can do now. Pure display: every press is a lambda. */
+/**
+ * The buttons for whatever the player can do now. Pure display: every press is a lambda.
+ *
+ * **The bar never changes size.** The top row holds the one "primary" action
+ * (roll, end turn, done with roads, cancel) and keeps its height when it is
+ * empty; the second row is always all six buttons, greyed out when they do not
+ * apply. Buttons appearing and disappearing used to resize this area and, with
+ * it, the board above — so nothing here may be conditionally *present*, only
+ * conditionally *enabled*.
+ */
 @OptIn(ExperimentalLayoutApi::class)
 @Composable
 fun CatanActionBar(
@@ -264,34 +483,62 @@ fun CatanActionBar(
     onEndFreeRoads: () -> Unit,
     onRepickSetup: () -> Unit,
     modifier: Modifier = Modifier,
+    /** Small screens: fold Road / Settlement / City into one "Build" button with a menu. */
+    compact: Boolean = false,
+    onImprove: () -> Unit = {},
+    onProgress: () -> Unit = {},
+    onEndSmith: () -> Unit = {},
 ) {
-    FlowRow(
-        modifier = modifier.fillMaxWidth(),
-        horizontalArrangement = Arrangement.spacedBy(8.dp),
-        verticalArrangement = Arrangement.spacedBy(8.dp),
-    ) {
-        if (actions.canRoll) Button(onClick = onRoll) { Text(CatanText.ROLL) }
-
-        if (actions.canRepickSetup) {
-            OutlinedButton(onClick = onRepickSetup) { Text(CatanText.CANCEL) }
+    Column(modifier = modifier.fillMaxWidth(), verticalArrangement = Arrangement.spacedBy(8.dp)) {
+        Row(
+            modifier = Modifier.fillMaxWidth().height(PRIMARY_ROW_HEIGHT),
+            verticalAlignment = Alignment.CenterVertically,
+            horizontalArrangement = Arrangement.spacedBy(8.dp),
+        ) {
+            if (actions.canRoll) Button(onClick = onRoll) { Text(CatanText.ROLL) }
+            if (actions.canRepickSetup) OutlinedButton(onClick = onRepickSetup) { Text(CatanText.CANCEL) }
+            if (actions.canEndFreeRoads) Button(onClick = onEndFreeRoads) { Text(CatanText.STOP_ROADS) }
+            if (actions.canEndSmith) Button(onClick = onEndSmith) { Text(CatanText.STOP_SMITH) }
+            if (actions.canEndTurn) Button(onClick = onEndTurn) { Text(CatanText.END_TURN) }
         }
 
-        if (actions.showTurnActions) {
-            BuildButton(BuildKind.ROAD, CatanText.ROAD, CatanText.ROAD_COST, actions, onBuild)
-            BuildButton(BuildKind.SETTLEMENT, CatanText.SETTLEMENT, CatanText.SETTLEMENT_COST, actions, onBuild)
-            BuildButton(BuildKind.CITY, CatanText.CITY, CatanText.CITY_COST, actions, onBuild)
-            OutlinedButton(onClick = onBuyCard, enabled = actions.canBuyCard) {
-                LabelWithCost(CatanText.BUY_CARD, CatanText.DEV_COST)
+        FlowRow(
+            modifier = Modifier.fillMaxWidth(),
+            horizontalArrangement = Arrangement.spacedBy(8.dp),
+            verticalArrangement = Arrangement.spacedBy(8.dp),
+        ) {
+            if (compact || actions.ck) {
+                BuildMenuButton(actions, onBuild)
+            } else {
+                BuildButton(BuildKind.ROAD, CatanText.ROAD, CatanText.ROAD_COST, actions, onBuild)
+                BuildButton(BuildKind.SETTLEMENT, CatanText.SETTLEMENT, CatanText.SETTLEMENT_COST, actions, onBuild)
+                BuildButton(BuildKind.CITY, CatanText.CITY, CatanText.CITY_COST, actions, onBuild)
+            }
+            if (actions.ck) {
+                OutlinedButton(onClick = onImprove, enabled = actions.canImprove) {
+                    LabelWithCost(CatanText.IMPROVE, CatanText.NO_COST)
+                }
+                OutlinedButton(onClick = onProgress, enabled = actions.canPlayProgress) {
+                    LabelWithCost(CatanText.CARDS_BUTTON, "${actions.progressCount} held")
+                }
+            } else {
+                OutlinedButton(onClick = onBuyCard, enabled = actions.canBuyCard) {
+                    LabelWithCost(CatanText.BUY_CARD, CatanText.DEV_COST)
+                }
+                OutlinedButton(onClick = onPlayCard, enabled = actions.canPlayCard) {
+                    LabelWithCost(CatanText.PLAY_CARD, CatanText.NO_COST)
+                }
+            }
+            OutlinedButton(onClick = onTrade, enabled = actions.canTrade) {
+                LabelWithCost(CatanText.TRADE, CatanText.NO_COST)
             }
-            OutlinedButton(onClick = onPlayCard, enabled = actions.canPlayCard) { Text(CatanText.PLAY_CARD) }
-            OutlinedButton(onClick = onTrade, enabled = actions.canTrade) { Text(CatanText.TRADE) }
         }
-
-        if (actions.canEndFreeRoads) Button(onClick = onEndFreeRoads) { Text(CatanText.STOP_ROADS) }
-        if (actions.canEndTurn) Button(onClick = onEndTurn) { Text(CatanText.END_TURN) }
     }
 }
 
+/** Room for one button, held whether or not there is one to show. */
+private val PRIMARY_ROW_HEIGHT = 48.dp
+
 @Composable
 private fun BuildButton(
     kind: BuildKind,
@@ -310,6 +557,56 @@ private fun BuildButton(
     }
 }
 
+/**
+ * The small-screen stand-in for the three build buttons: one "Build" button
+ * whose menu lists Road, Settlement and City with their costs. While a build
+ * mode is armed the button shows which, and choosing that entry again cancels it.
+ */
+@Composable
+private fun BuildMenuButton(actions: CatanActions, onBuild: (BuildKind?) -> Unit) {
+    var open by remember { mutableStateOf(false) }
+    val armed = actions.building
+    val anyEnabled = actions.canBuild.isNotEmpty() || armed != null
+    val label: @Composable () -> Unit = {
+        LabelWithCost(CatanText.BUILD, armed?.let { buildLabel(it) } ?: CatanText.NO_COST)
+    }
+    Box {
+        if (armed != null) {
+            FilledTonalButton(onClick = { open = true }, enabled = anyEnabled) { label() }
+        } else {
+            OutlinedButton(onClick = { open = true }, enabled = anyEnabled) { label() }
+        }
+        DropdownMenu(expanded = open, onDismissRequest = { open = false }) {
+            for (kind in actions.buildKinds) {
+                DropdownMenuItem(
+                    text = { LabelWithCost(buildLabel(kind), buildCost(kind)) },
+                    enabled = kind in actions.canBuild,
+                    onClick = {
+                        open = false
+                        onBuild(if (armed == kind) null else kind)
+                    },
+                )
+            }
+        }
+    }
+}
+
+private fun buildLabel(kind: BuildKind): String = when (kind) {
+    BuildKind.ROAD -> CatanText.ROAD
+    BuildKind.SETTLEMENT -> CatanText.SETTLEMENT
+    BuildKind.CITY -> CatanText.CITY
+    BuildKind.WALL -> CatanText.WALL
+    BuildKind.KNIGHT -> CatanText.KNIGHT
+}
+
+private fun buildCost(kind: BuildKind): String = when (kind) {
+    BuildKind.ROAD -> CatanText.ROAD_COST
+    BuildKind.SETTLEMENT -> CatanText.SETTLEMENT_COST
+    BuildKind.CITY -> CatanText.CITY_COST
+    BuildKind.WALL -> CatanText.WALL_COST
+    BuildKind.KNIGHT -> CatanText.KNIGHT_COST
+}
+
 @Composable
 private fun LabelWithCost(label: String, cost: String) {
     Column(horizontalAlignment = Alignment.CenterHorizontally) {

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanPreviews.kt

@@ -112,14 +112,13 @@ private fun PanelsPreview() {
     Column(Modifier.padding(8.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
         Row(Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.spacedBy(6.dp)) {
             (0 until state.playerCount).forEach { seat ->
-                CatanPlayerCard(state, seat, seats, points[seat], Modifier.weight(1f))
+                CatanPlayerCard(state, seat, seats, points[seat], Modifier.weight(1f), compact = true)
             }
         }
         CatanHand(state, seat = 0)
         CatanDice(state.lastDice)
         CatanActionBar(
             actions = CatanActions(
-                showTurnActions = true,
                 canBuild = setOf(BuildKind.ROAD, BuildKind.CITY),
                 building = BuildKind.ROAD,
                 canBuyCard = true,

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanScreen.kt

@@ -24,19 +24,34 @@ import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
 import org.prolibertate.games.game.catan.AcceptTrade
+import org.prolibertate.games.game.catan.AqueductChore
 import org.prolibertate.games.game.catan.BuyDevCard
+import org.prolibertate.games.game.catan.CatanCk
 import org.prolibertate.games.game.catan.CatanMove
 import org.prolibertate.games.game.catan.CatanPhase
 import org.prolibertate.games.game.catan.CatanRules
 import org.prolibertate.games.game.catan.CatanState
 import org.prolibertate.games.game.catan.DeclineTrade
+import org.prolibertate.games.game.catan.DiscardChore
+import org.prolibertate.games.game.catan.DiscardGoods
+import org.prolibertate.games.game.catan.DropProgress
+import org.prolibertate.games.game.catan.DropProgressChore
+import org.prolibertate.games.game.catan.DismissCounters
 import org.prolibertate.games.game.catan.EndFreeRoads
+import org.prolibertate.games.game.catan.EndSmith
 import org.prolibertate.games.game.catan.EndTurn
+import org.prolibertate.games.game.catan.GiveChore
+import org.prolibertate.games.game.catan.GiveGoods
+import org.prolibertate.games.game.catan.MoveKnight
 import org.prolibertate.games.game.catan.MoveRobber
+import org.prolibertate.games.game.catan.PickDeckChore
 import org.prolibertate.games.game.catan.RollDice
 import org.prolibertate.games.game.catan.SetupPlace
+import org.prolibertate.games.game.catan.SpyChore
 import org.prolibertate.games.net.MatchController
 import org.prolibertate.games.ui.ScreenScaffold
 
@@ -82,6 +97,13 @@ fun CatanScreen(
     var showTrade by remember { mutableStateOf(false) }
     var confirmingEnd by remember { mutableStateOf(false) }
     var resultDismissed by remember { mutableStateOf(false) }
+    // Cities & Knights: the knight whose menu is open, the one about to move,
+    // a progress card waiting for a tap on the board, and the two list dialogs.
+    var knightMenu by remember { mutableStateOf<Int?>(null) }
+    var movingKnight by remember { mutableStateOf<Int?>(null) }
+    var armed by remember { mutableStateOf<ArmedCard?>(null) }
+    var showImprove by remember { mutableStateOf(false) }
+    var showProgress by remember { mutableStateOf(false) }
 
     val dark = isSystemInDarkTheme()
     val style = remember(dark) { catanStyle(dark) }
@@ -95,10 +117,17 @@ fun CatanScreen(
         if (setupVertex != null && legal.none { it is SetupPlace && it.vertex == setupVertex }) {
             setupVertex = null
         }
+        if (movingKnight != null && legal.none { it is MoveKnight && it.from == movingKnight }) movingKnight = null
+        armed?.let { card -> if (card.plays.none { it in legal }) armed = null }
         if (legal.isEmpty()) {
             showCards = false
             showTrade = false
             victimChoice = null
+            showImprove = false
+            showProgress = false
+            knightMenu = null
+            movingKnight = null
+            armed = null
         }
     }
 
@@ -109,6 +138,11 @@ fun CatanScreen(
         victimChoice = null
         showCards = false
         showTrade = false
+        showImprove = false
+        showProgress = false
+        knightMenu = null
+        movingKnight = null
+        armed = null
     }
 
     val endGameAction: @Composable () -> Unit = {
@@ -125,12 +159,19 @@ fun CatanScreen(
         return
     }
 
-    val targets = CatanInteraction.targets(current, legal, building, setupVertex)
+    val targets = CatanInteraction.targets(current, legal, building, setupVertex, movingKnight, armed, localSeat)
+    val ownKnights = current.ck?.knights?.filter { it.owner == localSeat }?.map { it.vertex }?.toSet().orEmpty()
     val devHand = CatanInteraction.devHand(current, localSeat, legal)
+    val progressHand = CatanInteraction.progressHand(current, localSeat, legal)
     val playing = current.phase == CatanPhase.PLAYING && legal.isNotEmpty()
     val actions = CatanActions(
+        buildKinds = if (current.isCk) BuildKind.entries else BuildKind.BASE,
+        ck = current.isCk,
+        canImprove = CatanInteraction.improvable(legal).isNotEmpty(),
+        canPlayProgress = progressHand.any { it.playable },
+        progressCount = progressHand.size,
+        canEndSmith = CatanInteraction.canEndSmith(legal),
         canRoll = CatanInteraction.canRoll(legal),
-        showTurnActions = playing,
         canBuild = CatanInteraction.canBuild(legal),
         building = building,
         canBuyCard = CatanInteraction.canBuyDevCard(legal),
@@ -140,7 +181,15 @@ fun CatanScreen(
         canEndFreeRoads = CatanInteraction.canEndFreeRoads(legal),
         canRepickSetup = setupVertex != null,
     )
-    val prompt = CatanText.prompt(current, seats, setupVertexChosen = setupVertex != null, building = building)
+    val rolledHexes = CatanInteraction.rolledHexes(current)
+    val prompt = CatanText.prompt(
+        current,
+        seats,
+        setupVertexChosen = setupVertex != null,
+        building = building,
+        movingKnight = movingKnight != null,
+        armed = armed?.kind,
+    )
 
     val handle: (TapOutcome) -> Unit = { outcome ->
         when (outcome) {
@@ -148,6 +197,8 @@ fun CatanScreen(
             is TapOutcome.Submit -> submit(outcome.move)
             is TapOutcome.PickSetupVertex -> setupVertex = outcome.vertex
             is TapOutcome.PickRobberVictim -> victimChoice = outcome
+            is TapOutcome.PickKnight -> knightMenu = outcome.vertex
+            is TapOutcome.PickFirstHex -> armed = armed?.copy(firstHex = outcome.hex)
         }
     }
 
@@ -160,17 +211,28 @@ fun CatanScreen(
         ScreenScaffold(title = CatanText.TITLE, onBack = onExit, actions = endGameAction) { modifier ->
             BoxWithConstraints(modifier = modifier) {
                 val wide = maxWidth > maxHeight * 1.1f
+                // Phones (either way up) get the one-button build menu.
+                val compactBuild = !wide || maxWidth < 600.dp
 
                 val board: @Composable (Modifier) -> Unit = { boardModifier ->
                     CatanBoardView(
                         state = current,
                         targets = targets,
                         selectedVertex = setupVertex,
-                        onVertexTap = { handle(CatanInteraction.onVertexTap(it, legal, building, setupVertex)) },
-                        onEdgeTap = { handle(CatanInteraction.onEdgeTap(it, legal, building, setupVertex)) },
-                        onHexTap = { handle(CatanInteraction.onHexTap(it, legal)) },
+                        onVertexTap = {
+                            handle(
+                                CatanInteraction.onVertexTap(
+                                    it, legal, building, setupVertex, movingKnight, armed,
+                                    ownKnights = if (legal.isNotEmpty()) ownKnights else emptySet(),
+                                ),
+                            )
+                        },
+                        onEdgeTap = { handle(CatanInteraction.onEdgeTap(it, legal, building, setupVertex, armed)) },
+                        onHexTap = { handle(CatanInteraction.onHexTap(it, legal, armed)) },
                         modifier = boardModifier,
                         style = style,
+                        rolledHexes = rolledHexes,
+                        selectedKnight = movingKnight ?: knightMenu,
                     )
                 }
                 val players: @Composable (Boolean) -> Unit = { grid ->
@@ -194,6 +256,10 @@ fun CatanScreen(
                                 legal.firstOrNull { m -> m is EndFreeRoads }?.let(submit)
                             },
                             onRepickSetup = { setupVertex = null },
+                            compact = compactBuild,
+                            onImprove = { showImprove = true },
+                            onProgress = { showProgress = true },
+                            onEndSmith = { legal.firstOrNull { m -> m is EndSmith }?.let(submit) },
                         )
                     }
                 }
@@ -208,6 +274,7 @@ fun CatanScreen(
                             verticalArrangement = Arrangement.spacedBy(8.dp),
                         ) {
                             players(true)
+                            if (current.isCk) CatanBarbarians(current, style = style)
                             promptRow()
                             handAndActions()
                             CatanLog(current, Modifier.fillMaxWidth().height(120.dp))
@@ -216,6 +283,7 @@ fun CatanScreen(
                 } else {
                     Column(Modifier.fillMaxSize(), verticalArrangement = Arrangement.spacedBy(8.dp)) {
                         players(false)
+                        if (current.isCk) CatanBarbarians(current, style = style)
                         promptRow()
                         Box(Modifier.weight(1f).fillMaxWidth(), contentAlignment = Alignment.Center) {
                             board(Modifier)
@@ -237,6 +305,21 @@ fun CatanScreen(
                 showCards = showCards,
                 showTrade = showTrade,
                 devHand = devHand,
+                knightMenu = knightMenu,
+                showImprove = showImprove,
+                showProgress = showProgress,
+                progressHand = progressHand,
+                onMoveKnight = { from ->
+                    knightMenu = null
+                    movingKnight = from
+                },
+                onArmCard = { card ->
+                    showProgress = false
+                    armed = card
+                },
+                onCancelKnight = { knightMenu = null },
+                onCancelImprove = { showImprove = false },
+                onCancelProgress = { showProgress = false },
                 onExit = onExit,
                 onSubmit = submit,
                 onStay = controller::dismissAbandoned,
@@ -275,6 +358,7 @@ private fun PlayerCards(
                         points = pointsOf(seat),
                         modifier = Modifier.weight(1f),
                         style = style,
+                        compact = !twoPerRow,
                     )
                 }
                 // Keep an odd last row's card the same width as the others.
@@ -284,6 +368,14 @@ private fun PlayerCards(
     }
 }
 
+/**
+ * The one line telling the player what is going on, and the dice.
+ *
+ * **Fixed height.** The text always occupies exactly two lines (padded when it is
+ * shorter, clipped when it is longer) and a refused move replaces the prompt
+ * rather than adding to it, so this row is the same height whatever is said and
+ * the board below it never moves.
+ */
 @Composable
 private fun PromptRow(prompt: String, notice: String?, state: CatanState) {
     Row(
@@ -291,17 +383,16 @@ private fun PromptRow(prompt: String, notice: String?, state: CatanState) {
         verticalAlignment = Alignment.CenterVertically,
         horizontalArrangement = Arrangement.spacedBy(8.dp),
     ) {
-        Column(modifier = Modifier.weight(1f)) {
-            Text(prompt, style = MaterialTheme.typography.bodyMedium)
-            if (notice != null) {
-                Text(
-                    notice,
-                    style = MaterialTheme.typography.bodySmall,
-                    color = MaterialTheme.colorScheme.error,
-                )
-            }
-        }
-        CatanDice(state.lastDice)
+        Text(
+            text = notice ?: prompt,
+            style = MaterialTheme.typography.bodyMedium,
+            color = if (notice != null) MaterialTheme.colorScheme.error else Color.Unspecified,
+            minLines = 2,
+            maxLines = 2,
+            overflow = TextOverflow.Ellipsis,
+            modifier = Modifier.weight(1f),
+        )
+        CatanDice(state.lastDice, ck = state.isCk, event = state.ck?.eventDie)
     }
 }
 
@@ -323,6 +414,15 @@ private fun CatanDialogHost(
     showCards: Boolean,
     showTrade: Boolean,
     devHand: List<DevCardInHand>,
+    knightMenu: Int?,
+    showImprove: Boolean,
+    showProgress: Boolean,
+    progressHand: List<ProgressInHand>,
+    onMoveKnight: (Int) -> Unit,
+    onArmCard: (ArmedCard) -> Unit,
+    onCancelKnight: () -> Unit,
+    onCancelImprove: () -> Unit,
+    onCancelProgress: () -> Unit,
     onExit: () -> Unit,
     onSubmit: (CatanMove) -> Unit,
     onStay: () -> Unit,
@@ -333,6 +433,7 @@ private fun CatanDialogHost(
     onCancelTrade: () -> Unit,
 ) {
     val offer = state.pendingTrade
+    val goodsOffer = state.ck?.goodsOffer
     when {
         abandoned != null -> CatanAbandonedDialog(abandoned, onExit, onStay)
 
@@ -349,13 +450,47 @@ private fun CatanDialogHost(
                 onSubmit = onSubmit,
             )
 
-        state.phase == CatanPhase.TRADE_PENDING && offer != null && offer.to == localSeat ->
+        state.phase == CatanPhase.CHORE && CatanRules.currentSeat(state) == localSeat ->
+            ChoreDialog(state, localSeat, legal, onSubmit)
+
+        state.phase == CatanPhase.TRADE_PENDING && goodsOffer != null && goodsOffer.asking == localSeat ->
+            CatanGoodsTradeResponseDialog(
+                state = state,
+                seat = localSeat,
+                offer = goodsOffer,
+                seats = seats,
+                canAccept = CatanInteraction.tradeResponses(legal).first,
+                onAccept = { onSubmit(AcceptTrade) },
+                onDecline = { onSubmit(DeclineTrade) },
+                onCounter = onSubmit,
+            )
+
+        state.phase == CatanPhase.TRADE_COUNTERS && goodsOffer != null && state.turn == localSeat && legal.isNotEmpty() ->
+            CatanGoodsCounterChoiceDialog(
+                counters = CatanInteraction.goodsCounterChoices(state, legal),
+                seats = seats,
+                onTake = onSubmit,
+                onNoDeal = { onSubmit(DismissCounters) },
+            )
+
+        state.phase == CatanPhase.TRADE_PENDING && offer != null && offer.asking == localSeat ->
             CatanTradeResponseDialog(
+                state = state,
+                seat = localSeat,
                 offer = offer,
                 seats = seats,
                 canAccept = CatanInteraction.tradeResponses(legal).first,
                 onAccept = { onSubmit(AcceptTrade) },
                 onDecline = { onSubmit(DeclineTrade) },
+                onCounter = onSubmit,
+            )
+
+        state.phase == CatanPhase.TRADE_COUNTERS && state.turn == localSeat && legal.isNotEmpty() ->
+            CatanCounterChoiceDialog(
+                counters = CatanInteraction.counterChoices(state, legal),
+                seats = seats,
+                onTake = onSubmit,
+                onNoDeal = { onSubmit(DismissCounters) },
             )
 
         victimChoice != null ->
@@ -366,8 +501,47 @@ private fun CatanDialogHost(
                 onCancel = onCancelVictim,
             )
 
+        knightMenu != null ->
+            CatanKnightDialog(
+                state = state,
+                vertex = knightMenu,
+                actions = CatanInteraction.knightActions(legal, knightMenu),
+                onDo = onSubmit,
+                onMove = onMoveKnight,
+                onCancel = onCancelKnight,
+            )
+
+        showImprove ->
+            CatanImproveDialog(
+                state = state,
+                seat = localSeat,
+                legal = legal,
+                onBuy = onSubmit,
+                onCancel = onCancelImprove,
+            )
+
+        showProgress ->
+            CatanProgressDialog(
+                hand = progressHand,
+                seats = seats,
+                onPlay = onSubmit,
+                onArm = onArmCard,
+                onCancel = onCancelProgress,
+            )
+
         showCards -> CatanPlayCardDialog(devHand, onPlay = onSubmit, onCancel = onCancelCards)
 
+        showTrade && state.isCk ->
+            CatanGoodsTradeDialog(
+                state = state,
+                seat = localSeat,
+                seats = seats,
+                legal = legal,
+                onBank = onSubmit,
+                onOffer = onSubmit,
+                onCancel = onCancelTrade,
+            )
+
         showTrade ->
             CatanTradeDialog(
                 state = state,
@@ -380,3 +554,61 @@ private fun CatanDialogHost(
             )
     }
 }
+
+/**
+ * The dialog for the chore at the front of the queue, when it is the local
+ * player's. Chores that are answered by tapping the board (a city to lose, a
+ * metropolis site, a knight to place) have no dialog: the prompt line tells the
+ * player what to tap.
+ */
+@Composable
+private fun ChoreDialog(
+    state: CatanState,
+    localSeat: Int,
+    legal: List<CatanMove>,
+    onSubmit: (CatanMove) -> Unit,
+) {
+    val ck = state.ck ?: return
+    val check: (List<org.prolibertate.games.game.catan.Good>, (List<org.prolibertate.games.game.catan.Good>) -> CatanMove) -> Boolean =
+        { cards, make -> CatanRules.isLegalMove(state, localSeat, make(cards)) }
+    when (val chore = ck.chores.firstOrNull()) {
+        is DiscardChore -> {
+            val quota = minOf(chore.count, CatanCk.goodsCount(state, localSeat))
+            CatanGoodsPickDialog(
+                title = "Discard $quota cards",
+                intro = "Choose $quota cards to give up",
+                held = CatanCk.goodsOf(state, localSeat),
+                quota = quota,
+                confirmLabel = "Discard",
+                selectable = { true },
+                allowed = { check(it, ::DiscardGoods) },
+                onConfirm = { onSubmit(DiscardGoods(it)) },
+            )
+        }
+
+        is GiveChore -> {
+            val pool = CatanCk.goodsOf(state, localSeat).filterKeys { !chore.commoditiesOnly || it.isCommodity }
+            val quota = minOf(chore.count, pool.values.sum())
+            CatanGoodsPickDialog(
+                title = "Hand over $quota ${if (quota == 1) "card" else "cards"}",
+                intro = if (chore.commoditiesOnly) "Choose a commodity to give" else "Choose which cards to give",
+                held = pool,
+                quota = quota,
+                confirmLabel = "Give",
+                selectable = { !chore.commoditiesOnly || it.isCommodity },
+                allowed = { check(it, ::GiveGoods) },
+                onConfirm = { onSubmit(GiveGoods(it)) },
+            )
+        }
+
+        is PickDeckChore -> CatanPickDeckDialog(legal) { onSubmit(it) }
+
+        is DropProgressChore -> CatanDropProgressDialog(ck.progressHands[localSeat]) { onSubmit(it) }
+
+        is AqueductChore -> CatanAqueductDialog(legal) { onSubmit(it) }
+
+        is SpyChore -> CatanSpyDialog(ck.progressHands[chore.target], legal) { onSubmit(it) }
+
+        else -> Unit
+    }
+}

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanStyle.kt

@@ -3,8 +3,10 @@ package org.prolibertate.games.ui.game.catan
 import androidx.compose.runtime.Immutable
 import androidx.compose.runtime.staticCompositionLocalOf
 import androidx.compose.ui.graphics.Color
+import org.prolibertate.games.game.catan.Commodity
 import org.prolibertate.games.game.catan.Resource
 import org.prolibertate.games.game.catan.Terrain
+import org.prolibertate.games.game.catan.Track
 
 /**
  * Every visual decision for the Katan screen, in one place.
@@ -36,6 +38,8 @@ data class CatanStyle(
     val tokenHotInk: Color,
     /** The robber's pawn. */
     val robber: Color,
+    /** Outline and wash on hexes that produced for the latest dice roll. */
+    val rolled: Color,
     /** Harbour marker disc and its ink. */
     val portMarker: Color,
     val portInk: Color,
@@ -44,6 +48,19 @@ data class CatanStyle(
     val resource: Map<Resource, Color>,
     val resourceInk: Color,
 
+    // --- Cities & Knights ---------------------------------------------------
+    /** Commodity cards: cloth, coin and paper. */
+    val commodity: Map<Commodity, Color> = LightCommodities,
+    /** Ink on a commodity tile (paper is pale, so it is not white). */
+    val commodityInk: Map<Commodity, Color> = LightCommodityInk,
+    /** The colour of each improvement track, its city gate, its deck and its metropolis. */
+    val track: Map<Track, Color> = LightTracks,
+    /** Wall round a city, and the barbarian strip. */
+    val wall: Color = Color(0xFF5D4037),
+    val barbarian: Color = Color(0xFFB71C1C),
+    /** The halo round a knight that is awake. White, so it is not mistaken for the yellow tap ring. */
+    val knightReady: Color = Color(0xFFFFFFFF),
+
     // --- Players ------------------------------------------------------------
     /** One colour per seat, in seat order. Roads, settlements, cities, player strip. */
     val seats: List<Color>,
@@ -64,12 +81,31 @@ data class CatanStyle(
     val citySize: Float = 0.42f,
     val tokenRadius: Float = 0.36f,
     val robberSize: Float = 0.34f,
-    val portRadius: Float = 0.34f,
+    val portRadius: Float = 0.46f,
     val targetRadius: Float = 0.20f,
     /** How close a tap must land to a vertex / edge / hex centre to count. */
     val tapReach: Float = 0.55f,
     val tokenText: Float = 0.34f,
-    val portText: Float = 0.26f,
+    val portText: Float = 0.27f,
+    val knightSize: Float = 0.30f,
+)
+
+private val LightCommodities = mapOf(
+    Commodity.CLOTH to Color(0xFF7E57C2),
+    Commodity.COIN to Color(0xFFF9A825),
+    Commodity.PAPER to Color(0xFFECEFF1),
+)
+
+private val LightCommodityInk = mapOf(
+    Commodity.CLOTH to Color(0xFFFFFFFF),
+    Commodity.COIN to Color(0xFF3E2723),
+    Commodity.PAPER to Color(0xFF263238),
+)
+
+private val LightTracks = mapOf(
+    Track.TRADE to Color(0xFFF2C300),
+    Track.POLITICS to Color(0xFF1E6FD9),
+    Track.SCIENCE to Color(0xFF2E9E4F),
 )
 
 /** The light palette, which is also the reference for the dark one. */
@@ -88,6 +124,7 @@ private val LightStyle = CatanStyle(
     tokenInk = Color(0xFF2B2B2B),
     tokenHotInk = Color(0xFFC62828),
     robber = Color(0xFF263238),
+    rolled = Color(0xFFFFFFFF),
     portMarker = Color(0xFFFFF8E1),
     portInk = Color(0xFF2B2B2B),
     resource = mapOf(

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanText.kt

@@ -1,12 +1,29 @@
 package org.prolibertate.games.ui.game.catan
 
+import org.prolibertate.games.game.catan.AqueductChore
+import org.prolibertate.games.game.catan.CatanCk
 import org.prolibertate.games.game.catan.CatanPhase
 import org.prolibertate.games.game.catan.CatanRules
 import org.prolibertate.games.game.catan.CatanState
 import org.prolibertate.games.game.catan.DevCardType
+import org.prolibertate.games.game.catan.DiscardChore
+import org.prolibertate.games.game.catan.DropProgressChore
+import org.prolibertate.games.game.catan.EventFace
+import org.prolibertate.games.game.catan.GiveChore
+import org.prolibertate.games.game.catan.Good
+import org.prolibertate.games.game.catan.MetropolisChore
+import org.prolibertate.games.game.catan.PickDeckChore
+import org.prolibertate.games.game.catan.PillageChore
+import org.prolibertate.games.game.catan.PlaceKnightChore
 import org.prolibertate.games.game.catan.Port
+import org.prolibertate.games.game.catan.ProgressType
+import org.prolibertate.games.game.catan.RelocateChore
+import org.prolibertate.games.game.catan.RemoveKnightChore
 import org.prolibertate.games.game.catan.Resource
+import org.prolibertate.games.game.catan.SmithChore
+import org.prolibertate.games.game.catan.SpyChore
 import org.prolibertate.games.game.catan.Terrain
+import org.prolibertate.games.game.catan.Track
 
 /**
  * Who is who at the table, for wording. [names] may be empty or short — a
@@ -103,6 +120,16 @@ object CatanText {
     const val CONFIRM = "Confirm"
     const val STOP_ROADS = "Done with roads"
     const val BUILD = "Build"
+    const val COUNTER = "Counter…"
+    const val SEND_COUNTER = "Send counter"
+    const val EVERYONE = "Everyone"
+    const val NO_DEAL = "No deal"
+
+    /**
+     * The empty second line of a button that has no cost, so every button in the
+     * action bar is the same height. A non-breaking space: blank, but a line.
+     */
+    const val NO_COST = "\u00A0"
     const val YOUR_HAND = "Your hand"
     const val CARDS = "cards"
     const val ACCEPT = "Accept"
@@ -130,7 +157,12 @@ object CatanText {
         seats: CatanSeats,
         setupVertexChosen: Boolean,
         building: BuildKind?,
+        /** Cities & Knights: a knight has been picked to move, and its destination is awaited. */
+        movingKnight: Boolean = false,
+        /** Cities & Knights: a progress card is waiting for a tap on the board. */
+        armed: ProgressType? = null,
     ): String {
+        if (state.isCk) return ckPrompt(state, seats, setupVertexChosen, building, movingKnight, armed)
         val me = seats.me
         val onClock = CatanRules.currentSeat(state)
         val mine = onClock == me
@@ -184,15 +216,29 @@ object CatanText {
                     "$turn is placing free roads…"
                 }
 
+            CatanPhase.CHORE -> "Waiting for ${seats.label(onClock ?: state.turn)}…"
+
             CatanPhase.TRADE_PENDING -> {
                 val offer = state.pendingTrade
                 when {
                     offer == null -> "Waiting for a reply…"
-                    offer.to == me -> "${seats.label(offer.by)} offers you a trade."
-                    offer.by == me -> "Waiting for ${seats.label(offer.to)} to answer your offer…"
-                    else -> "${seats.label(offer.by)} has offered ${seats.label(offer.to)} a trade."
+                    offer.asking == me -> if (offer.to == null) {
+                        "${seats.label(offer.by)} offers the table a trade. Accept, decline or counter."
+                    } else {
+                        "${seats.label(offer.by)} offers you a trade. Accept, decline or counter."
+                    }
+
+                    offer.by == me -> "Waiting for ${seats.label(offer.asking)} to answer your offer…"
+                    else -> "${seats.label(offer.by)}'s offer is with ${seats.label(offer.asking)}."
                 }
             }
+
+            CatanPhase.TRADE_COUNTERS ->
+                if (mine) {
+                    "Nobody accepted, but there are counter-offers. Take one or turn them down."
+                } else {
+                    "$turn is weighing counter-offers…"
+                }
         }
     }
 
@@ -206,8 +252,224 @@ object CatanText {
     fun tradeSummary(by: String, to: String, give: List<Resource>, get: List<Resource>): String =
         "$by offers ${cards(give)} to $to for ${cards(get)}"
 
+    /** One counter-offer as the offerer sees it: what that seat gives and wants. */
+    fun counterSummary(by: String, give: List<Resource>, get: List<Resource>): String =
+        "$by gives ${cards(give)} for your ${cards(get)}"
+
     fun winnerHeadline(state: CatanState, seats: CatanSeats): String {
         val winner = state.winner ?: return "Game over"
         return if (winner == seats.me) "You won!" else "${seats.label(winner)} won"
     }
+
+    // --- Cities & Knights ----------------------------------------------------
+
+    fun good(good: Good): String = when (good) {
+        Good.LUMBER -> "Lumber"
+        Good.BRICK -> "Brick"
+        Good.WOOL -> "Wool"
+        Good.GRAIN -> "Grain"
+        Good.ORE -> "Ore"
+        Good.CLOTH -> "Cloth"
+        Good.COIN -> "Coin"
+        Good.PAPER -> "Paper"
+    }
+
+    /** "2 Lumber + 1 Cloth" for a flat list of goods. */
+    fun goods(cards: List<Good>): String =
+        cards.groupingBy { it }.eachCount().entries
+            .sortedBy { it.key.ordinal }
+            .joinToString(" + ") { (g, n) -> "$n ${good(g)}" }
+            .ifEmpty { "nothing" }
+
+    fun track(track: Track): String = when (track) {
+        Track.TRADE -> "Trade"
+        Track.POLITICS -> "Politics"
+        Track.SCIENCE -> "Science"
+    }
+
+    /** What the third level of a track gives, for the improvement dialog. */
+    fun trackPower(track: Track): String = when (track) {
+        Track.TRADE -> "From level 3, trade commodities with the bank two for one."
+        Track.POLITICS -> "From level 3, knights can be promoted to mighty."
+        Track.SCIENCE -> "From level 3, when the dice pay you nothing, take any resource."
+    }
+
+    fun knightName(level: Int): String = when (level) {
+        1 -> "Basic knight"
+        2 -> "Strong knight"
+        else -> "Mighty knight"
+    }
+
+    fun event(face: EventFace?): String = when (face) {
+        null -> "–"
+        EventFace.SHIP -> "Ship"
+        EventFace.TRADE -> "Trade"
+        EventFace.POLITICS -> "Politics"
+        EventFace.SCIENCE -> "Science"
+    }
+
+    fun progress(kind: ProgressType): String = CatanCk.progressName(kind)
+
+    fun progressHelp(kind: ProgressType): String = when (kind) {
+        ProgressType.ALCHEMIST -> "Before rolling, choose what the two number dice show."
+        ProgressType.CRANE -> "Your next city improvement costs one commodity less."
+        ProgressType.ENGINEER -> "Raise a wall round one of your cities for free."
+        ProgressType.INVENTOR -> "Swap two number tokens (not 2, 6, 8 or 12)."
+        ProgressType.IRRIGATION -> "Take 2 grain for each fields hex beside your settlements and cities."
+        ProgressType.MEDICINE -> "Upgrade a settlement to a city for 2 ore and 1 grain."
+        ProgressType.MINING -> "Take 2 ore for each mountains hex beside your settlements and cities."
+        ProgressType.PRINTER -> "One victory point."
+        ProgressType.ROAD_BUILDING -> "Build two roads for free."
+        ProgressType.SMITH -> "Promote up to two of your knights one level for free."
+        ProgressType.BISHOP -> "Move the robber and take a card from every player beside its new hex."
+        ProgressType.CONSTITUTION -> "One victory point."
+        ProgressType.DESERTER -> "Another player removes a knight; you place a free one of the same strength."
+        ProgressType.DIPLOMAT -> "Remove an open road. If it was yours, build it again anywhere for free."
+        ProgressType.INTRIGUE -> "Drive an opponent's knight off a crossing beside one of your roads."
+        ProgressType.SABOTEUR -> "Every player with as many points as you or more discards half their cards."
+        ProgressType.SPY -> "Look at another player's progress cards and take one."
+        ProgressType.WARLORD -> "Wake all your knights without paying grain."
+        ProgressType.WEDDING -> "Every player with more points gives you 2 cards."
+        ProgressType.COMMERCIAL_HARBOR -> "Offer a resource to each player; each swaps it for a commodity."
+        ProgressType.MASTER_MERCHANT -> "Take 2 cards from a player with more points."
+        ProgressType.MERCHANT -> "Put the merchant beside your settlement: trade that resource 2:1 and score a point."
+        ProgressType.MERCHANT_FLEET -> "This turn, trade one chosen card type with the bank two for one."
+        ProgressType.RESOURCE_MONOPOLY -> "Name a resource. Every other player gives you 2 of it."
+        ProgressType.TRADE_MONOPOLY -> "Name a commodity. Every other player gives you 1 of it."
+    }
+
+    const val IMPROVE = "Improve"
+    const val KNIGHTS = "Knights"
+    const val CARDS_BUTTON = "Progress"
+    const val WALL = "Wall"
+    const val KNIGHT = "Knight"
+    const val STOP_SMITH = "Done promoting"
+
+    val KNIGHT_COST: String get() = cost(CatanCk.KNIGHT_COST)
+    val ACTIVATE_COST: String get() = cost(CatanCk.ACTIVATE_COST)
+    val WALL_COST: String get() = cost(CatanCk.WALL_COST)
+
+    private fun ckPrompt(
+        state: CatanState,
+        seats: CatanSeats,
+        setupVertexChosen: Boolean,
+        building: BuildKind?,
+        movingKnight: Boolean,
+        armed: ProgressType?,
+    ): String {
+        val me = seats.me
+        val onClock = CatanRules.currentSeat(state)
+        val mine = onClock == me
+        val turn = seats.label(state.turn)
+        val ck = state.ck!!
+
+        return when (state.phase) {
+            CatanPhase.GAME_OVER -> {
+                val winner = state.winner
+                if (winner == null) "The game is over." else "${seats.label(winner)} won the game."
+            }
+
+            CatanPhase.SETUP_FIRST, CatanPhase.SETUP_SECOND -> when {
+                !mine -> "${seats.label(onClock ?: state.turn)} is placing a settlement and a road…"
+                setupVertexChosen -> "Now tap the road to place beside that settlement."
+                state.phase == CatanPhase.SETUP_SECOND ->
+                    "Place your second piece: it is a city, and earns resources from the hexes around it."
+
+                else -> "Place a settlement, then a road."
+            }
+
+            CatanPhase.AWAIT_ROLL -> when {
+                !mine -> "$turn is rolling…"
+                armed != null -> armedPrompt(armed)
+                movingKnight -> "Tap where the knight should go."
+                else -> "Your turn. Roll the dice, or wake knights and play progress cards first."
+            }
+
+            CatanPhase.ROBBER -> when {
+                !mine -> "$turn is moving the robber…"
+                ck.bishop -> "The bishop: tap a hex. Everyone beside it pays you a card."
+                else -> "Move the robber. Tap a hex."
+            }
+
+            CatanPhase.PLAYING -> when {
+                !mine -> "$turn is playing…"
+                armed != null -> armedPrompt(armed)
+                movingKnight -> "Tap where the knight should go."
+                building == BuildKind.ROAD -> "Tap an edge to build a road."
+                building == BuildKind.SETTLEMENT -> "Tap an empty crossing to build a settlement."
+                building == BuildKind.CITY -> "Tap one of your settlements to upgrade it."
+                building == BuildKind.WALL -> "Tap one of your cities to raise a wall."
+                building == BuildKind.KNIGHT -> "Tap an empty crossing at the end of your road to hire a knight."
+                else -> "Your turn. Build, improve, trade, or end the turn. Tap a knight to use it."
+            }
+
+            CatanPhase.FREE_ROADS ->
+                if (mine) {
+                    "Place ${state.pendingFreeRoads} free " +
+                        if (state.pendingFreeRoads == 1) "road." else "roads."
+                } else {
+                    "$turn is placing free roads…"
+                }
+
+            CatanPhase.TRADE_PENDING -> {
+                val offer = ck.goodsOffer
+                val asking = offer?.asking?.takeIf { it >= 0 }
+                when {
+                    offer == null || asking == null -> "Waiting for a reply…"
+                    asking == me -> "${seats.label(offer.by)} offers you a trade."
+                    offer.by == me -> "Waiting for ${seats.label(asking)} to answer your offer…"
+                    else -> "${seats.label(offer.by)} has offered ${seats.label(asking)} a trade."
+                }
+            }
+
+            CatanPhase.TRADE_COUNTERS ->
+                if (mine) {
+                    "Nobody accepted, but there are counter-offers. Take one or turn them down."
+                } else {
+                    "$turn is weighing counter-offers…"
+                }
+
+            CatanPhase.DISCARDING -> "Discarding…"
+
+            CatanPhase.CHORE -> {
+                val chore = ck.chores.firstOrNull()
+                val who = seats.label(chore?.seat ?: state.turn)
+                if (chore == null || chore.seat != me) {
+                    when (chore) {
+                        is PillageChore -> "The barbarians have landed. $who must give up a city."
+                        is DiscardChore -> "$who must discard ${chore.count} cards."
+                        else -> "Waiting for $who…"
+                    }
+                } else {
+                    when (chore) {
+                        is DiscardChore -> "Discard ${chore.count} cards."
+                        is GiveChore -> "Give ${chore.count} card${if (chore.count == 1) "" else "s"} to ${seats.lower(chore.to)}."
+                        is PillageChore -> "The barbarians won. Tap a city of yours to give up."
+                        is PickDeckChore -> "Choose a progress deck to draw from."
+                        is DropProgressChore -> "You hold too many progress cards. Give one back."
+                        is MetropolisChore -> "Tap the city that will bear the ${track(chore.track).lowercase()} metropolis."
+                        is AqueductChore -> "Your aqueduct pays. Take any resource."
+                        is RelocateChore -> "Your knight was driven off. Tap where it goes."
+                        is RemoveKnightChore -> "Tap one of your knights to remove."
+                        is PlaceKnightChore -> "Tap where your free ${knightName(chore.level).lowercase()} stands."
+                        is SpyChore -> "Choose a progress card to take."
+                        is SmithChore -> "Tap a knight to promote (${chore.left} left), or stop."
+                    }
+                }
+            }
+        }
+    }
+
+    private fun armedPrompt(kind: ProgressType): String = when (kind) {
+        ProgressType.ENGINEER -> "Engineer: tap a city to wall."
+        ProgressType.MEDICINE -> "Medicine: tap a settlement to upgrade."
+        ProgressType.MERCHANT -> "Merchant: tap a hex beside one of your buildings."
+        ProgressType.DIPLOMAT -> "Diplomat: tap an open road to remove."
+        ProgressType.INTRIGUE -> "Intrigue: tap an enemy knight beside your road."
+        ProgressType.INVENTOR -> "Inventor: tap two hexes to swap their tokens."
+        else -> "Tap the board."
+    }
+
+    /** "6 steps away", "1 step away" for the barbarian ship. */
+    fun barbarianSteps(steps: Int): String = "$steps ${if (steps == 1) "step" else "steps"} away"
 }

app/src/test/java/org/prolibertate/games/game/catan/CatanAiTest.kt

@@ -142,4 +142,50 @@ class CatanAiTest {
         assertEquals(CatanPhase.PLAYING, after.phase)
         assertNull(after.pendingTrade)
     }
+
+    private fun tradeTable(offer: TradeOffer, vararg hands: Map<Resource, Int>): CatanState =
+        CatanRules.initialState(config(CatanOptions(), seed = 7L)).copy(
+            phase = CatanPhase.TRADE_PENDING,
+            turn = 0,
+            turnNumber = 1,
+            pendingTrade = offer,
+            resources = hands.toList(),
+        )
+
+    @Test
+    fun `the AI accepts an offer that gives it more than it costs, and declines the reverse`() {
+        val generous = tradeTable(
+            TradeOffer(by = 0, to = null, give = listOf(Resource.ORE, Resource.ORE), get = listOf(Resource.WOOL), asking = 1),
+            hand(Resource.ORE to 2), hand(Resource.WOOL to 2), hand(),
+        )
+        assertEquals(AcceptTrade, CatanAi().chooseMove(generous, 1, CatanRules.legalMoves(generous, 1)))
+
+        val stingy = tradeTable(
+            TradeOffer(by = 0, to = null, give = listOf(Resource.WOOL), get = listOf(Resource.ORE), asking = 1),
+            hand(Resource.WOOL to 1), hand(Resource.ORE to 2), hand(),
+        )
+        assertEquals(DeclineTrade, CatanAi().chooseMove(stingy, 1, CatanRules.legalMoves(stingy, 1)))
+    }
+
+    @Test
+    fun `an AI offerer takes the best counter and refuses a losing one`() {
+        val counters = listOf(
+            TradeCounter(by = 1, give = listOf(Resource.ORE), get = listOf(Resource.LUMBER)),
+            TradeCounter(by = 2, give = listOf(Resource.ORE, Resource.GRAIN), get = listOf(Resource.WOOL)),
+        )
+        val state = tradeTable(
+            TradeOffer(by = 0, to = null, give = listOf(Resource.WOOL), get = listOf(Resource.ORE), asking = -1, counters = counters),
+            hand(Resource.LUMBER to 1, Resource.WOOL to 1), hand(Resource.ORE to 1), hand(Resource.ORE to 1, Resource.GRAIN to 1),
+        ).copy(phase = CatanPhase.TRADE_COUNTERS)
+        val legal = CatanRules.legalMoves(state, 0)
+        assertEquals(AcceptCounter(2), CatanAi().chooseMove(state, 0, legal))
+
+        val bad = state.copy(
+            pendingTrade = state.pendingTrade!!.copy(
+                counters = listOf(TradeCounter(by = 1, give = listOf(Resource.WOOL), get = listOf(Resource.LUMBER))),
+            ),
+            resources = listOf(hand(Resource.LUMBER to 1), hand(Resource.WOOL to 1), hand()),
+        )
+        assertEquals(DismissCounters, CatanAi().chooseMove(bad, 0, CatanRules.legalMoves(bad, 0)))
+    }
 }

app/src/test/java/org/prolibertate/games/game/catan/CatanCkSelfPlayTest.kt

@@ -0,0 +1,182 @@
+package org.prolibertate.games.game.catan
+
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.prolibertate.games.game.GameCatalog
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+/**
+ * Engines playing Cities & Knights against each other. These are the
+ * playtests: every move is checked for legality, the state is round-tripped
+ * through its wire format as it goes, nothing may leave a seat without a move,
+ * and the game has to reach a result.
+ */
+class CatanCkSelfPlayTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun config(options: CatanOptions, seed: Long) = TableConfig(
+        gameId = GameCatalog.CATAN,
+        seats = (0 until options.playerCount).map {
+            PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = it)
+        },
+        optionsJson = json.encodeToString(options),
+        seed = seed,
+    )
+
+    /** What one game looked like, for the summary printed at the end. */
+    private data class Report(
+        val seed: Long,
+        val moves: Int,
+        val turns: Int,
+        val attacks: Int,
+        val progressPlayed: Int,
+        val metropolises: Int,
+        val winner: Int?,
+        val points: List<Int>,
+    )
+
+    private fun playOut(options: CatanOptions, seed: Long, cap: Int = 30_000): Pair<CatanState, Report> {
+        val ai = CatanAi()
+        var state = CatanRules.initialState(config(options, seed))
+        var moves = 0
+        var attacks = 0
+        var progress = 0
+        while (!CatanRules.isFinished(state)) {
+            assertTrue("seed $seed ran past $cap moves; log tail: ${state.log.takeLast(8)}", moves++ < cap)
+            val seat = CatanRules.currentSeat(state)
+                ?: error("seed $seed: nobody on the clock in ${state.phase}; log tail: ${state.log.takeLast(8)}")
+            val legal = CatanRules.legalMoves(state, seat)
+            assertTrue("seed $seed: seat $seat has no legal move in ${state.phase}", legal.isNotEmpty())
+            val move = ai.chooseMove(state, seat, legal)
+            assertTrue(
+                "seed $seed: seat $seat chose the illegal move $move in ${state.phase}; " +
+                    "log tail: ${state.log.takeLast(5)}",
+                CatanRules.isLegalMove(state, seat, move),
+            )
+            val before = state.ck!!.attacked
+            val wasAttacks = state.log.count { it.contains("The barbarians land") }
+            state = CatanRules.applyMove(state, seat, move)
+            attacks += state.log.count { it.contains("The barbarians land") } - wasAttacks
+            if (move is PlayProgress) progress++
+            if (!before && state.ck!!.attacked) Unit
+
+            if (moves % 97 == 0) {
+                val back = CatanRules.decodeState(CatanRules.encodeState(state))
+                assertEquals("seed $seed: the state did not survive its wire format", state, back)
+                // A seat's view never carries another seat's progress cards or the decks.
+                for (viewer in 0 until options.playerCount) {
+                    val view = CatanRules.viewFor(state, viewer)
+                    assertTrue(view.ck!!.decks.values.all { it.isEmpty() })
+                    for (other in 0 until options.playerCount) {
+                        if (other != viewer) {
+                            val spied = (state.ck!!.chores.firstOrNull() as? SpyChore)
+                            val allowed = spied != null && spied.seat == viewer && spied.target == other
+                            if (!allowed) assertTrue(view.ck!!.progressHands[other].isEmpty())
+                        }
+                    }
+                }
+            }
+            checkInvariants(state, seed)
+        }
+        val ck = state.ck!!
+        return state to Report(
+            seed = seed,
+            moves = moves,
+            turns = state.turnNumber,
+            attacks = attacks,
+            progressPlayed = progress,
+            metropolises = ck.metropolises.size,
+            winner = state.winner,
+            points = CatanRules.publicVictoryPoints(state),
+        )
+    }
+
+    /** Things that must hold in every state of every game. */
+    private fun checkInvariants(state: CatanState, seed: Long) {
+        val ck = state.ck!!
+        val tag = "seed $seed turn ${state.turnNumber}"
+        // Cards are conserved: no good is held in more copies than the bank started with.
+        for (good in Good.entries) {
+            val held = (0 until state.playerCount).sumOf { CatanCk.goodsOf(state, it)[good] ?: 0 }
+            val cap = if (good.isCommodity) BANK_PER_COMMODITY else BANK_PER_RESOURCE
+            assertTrue("$tag: $held ${good} cards exist, the bank only had $cap", held in 0..cap)
+        }
+        for (seat in 0 until state.playerCount) {
+            assertTrue(
+                "$tag: seat $seat holds negative cards",
+                CatanCk.goodsOf(state, seat).values.all { it >= 0 },
+            )
+            for (level in 1..3) {
+                assertTrue(
+                    "$tag: seat $seat has more than two level-$level knights",
+                    ck.knights.count { it.owner == seat && it.level == level } <= KNIGHTS_PER_LEVEL,
+                )
+            }
+            assertTrue("$tag: too many progress cards in seat $seat's hand", ck.progressHands[seat].size <= PROGRESS_HAND_MAX + 1)
+            assertTrue("$tag: seat $seat has more than three walls", CatanCk.wallsOf(state, seat) <= MAX_WALLS)
+            assertTrue(
+                "$tag: seat $seat has more than five settlements",
+                state.buildings.count { it == CatanBuilding(BuildingType.SETTLEMENT, seat) } <= MAX_SETTLEMENTS,
+            )
+            assertTrue(
+                "$tag: seat $seat has more than four cities",
+                state.buildings.count { it == CatanBuilding(BuildingType.CITY, seat) } <= MAX_CITIES,
+            )
+        }
+        // A knight stands on a crossing nothing else stands on, and no two share one.
+        assertEquals("$tag: two knights share a crossing", ck.knights.size, ck.knights.map { it.vertex }.toSet().size)
+        for (k in ck.knights) {
+            assertTrue("$tag: a knight stands on a building at ${k.vertex}", state.buildings[k.vertex] == null)
+        }
+        // Metropolises stand on cities of their owners.
+        for ((_, m) in ck.metropolises) {
+            assertEquals(
+                "$tag: a metropolis is not on its owner's city",
+                CatanBuilding(BuildingType.CITY, m.seat),
+                state.buildings[m.vertex],
+            )
+        }
+        // Every progress card exists exactly once, in a deck or a hand, or was played face up.
+        val cards = ck.decks.values.sumOf { it.size } + ck.progressHands.sumOf { it.size } + ck.progressVp.sum()
+        assertEquals("$tag: progress cards were lost or duplicated", 54, cards)
+        assertTrue("$tag: barbarians out of range", ck.barbarians in 1..BARBARIAN_STEPS)
+    }
+
+    @Test
+    fun `three engines play Cities and Knights to a finish`() {
+        val reports = (1L..12L).map { seed ->
+            val (state, report) = playOut(
+                CatanOptions(playerCount = 3, pointsToWin = 13, ruleSet = CatanRuleSet.CITIES_AND_KNIGHTS),
+                seed,
+            )
+            assertEquals("seed $seed", CatanPhase.GAME_OVER, state.phase)
+            val winner = state.winner
+            assertTrue("seed $seed finished without a winner", winner != null)
+            assertTrue(
+                "seed $seed: the winner fell short of the target",
+                CatanRules.victoryPoints(state, winner!!) >= 13,
+            )
+            report
+        }
+        reports.forEach { println("CK3 $it") }
+    }
+
+    @Test
+    fun `four engines play Cities and Knights to a finish`() {
+        val reports = (101L..108L).map { seed ->
+            val (state, report) = playOut(
+                CatanOptions(playerCount = 4, pointsToWin = 13, ruleSet = CatanRuleSet.CITIES_AND_KNIGHTS),
+                seed,
+            )
+            assertEquals("seed $seed", CatanPhase.GAME_OVER, state.phase)
+            report
+        }
+        reports.forEach { println("CK4 $it") }
+    }
+}

app/src/test/java/org/prolibertate/games/game/catan/CatanRulesTest.kt

@@ -340,6 +340,89 @@ class CatanRulesTest {
         )
     }
 
+    /** Seat 0 owns a settlement at vertex 0 and a two-road chain v0 - w - x; `beyond` continues past x. */
+    private data class Chain(val state: CatanState, val x: Int, val beyond: Int, val spur: Int?)
+
+    private fun chain(): Chain {
+        val e1 = CatanBoard.VERTEX_EDGES[0][0]
+        val w = CatanBoard.otherEnd(e1, 0)
+        val e2 = CatanBoard.VERTEX_EDGES[w].first { it != e1 }
+        val x = CatanBoard.otherEnd(e2, w)
+        val beyond = CatanBoard.VERTEX_EDGES[x].first { it != e2 }
+        val spur = CatanBoard.VERTEX_EDGES[w].firstOrNull { it != e1 && it != e2 }
+        val state = craft()
+            .copy(resources = hands(hand(Resource.LUMBER to 5, Resource.BRICK to 5)))
+            .withBuilding(0, BuildingType.SETTLEMENT, 0)
+            .withRoad(e1, 0)
+            .withRoad(e2, 0)
+        return Chain(state, x, beyond, spur)
+    }
+
+    @Test
+    fun `a road cannot be built past an opponent's settlement`() {
+        val (open, x, beyond, spur) = chain()
+        assertTrue("open crossing: the road continues", BuildRoad(beyond) in CatanRules.legalMoves(open, 0))
+
+        val blocked = open.withBuilding(x, BuildingType.SETTLEMENT, 1)
+        assertFalse(
+            "an opponent's settlement on the crossing breaks the network",
+            BuildRoad(beyond) in CatanRules.legalMoves(blocked, 0),
+        )
+        // The same through a city, and while laying free roads from Road Building.
+        val city = open.withBuilding(x, BuildingType.CITY, 1)
+        assertFalse(BuildRoad(beyond) in CatanRules.legalMoves(city, 0))
+        val free = blocked.copy(phase = CatanPhase.FREE_ROADS, pendingFreeRoads = 2)
+        assertFalse(BuildRoad(beyond) in CatanRules.legalMoves(free, 0))
+        // The rest of the network is untouched: the spur at the other crossing still works.
+        if (spur != null) assertTrue(BuildRoad(spur) in CatanRules.legalMoves(blocked, 0))
+    }
+
+    @Test
+    fun `your own settlement on the crossing does not block your road`() {
+        val (open, x, beyond, _) = chain()
+        val own = open.withBuilding(x, BuildingType.SETTLEMENT, 0)
+        assertTrue(BuildRoad(beyond) in CatanRules.legalMoves(own, 0))
+    }
+
+    @Test
+    fun `a player runs out of pieces`() {
+        val rich = hands(
+            hand(
+                Resource.LUMBER to 9, Resource.BRICK to 9, Resource.WOOL to 9,
+                Resource.GRAIN to 9, Resource.ORE to 9,
+            ),
+        )
+
+        // Roads: fifteen, and no sixteenth - in the main phase or from Road Building.
+        var roads = craft().copy(resources = rich).withBuilding(0, BuildingType.SETTLEMENT, 0)
+        repeat(14) {
+            roads = roads.withRoad(CatanRules.legalMoves(roads, 0).filterIsInstance<BuildRoad>().first().edge, 0)
+        }
+        assertTrue("fourteen laid: one more is allowed", CatanRules.legalMoves(roads, 0).any { it is BuildRoad })
+        roads = roads.withRoad(CatanRules.legalMoves(roads, 0).filterIsInstance<BuildRoad>().first().edge, 0)
+        assertEquals(15, roads.roads.count { it == 0 })
+        assertTrue("fifteen laid: none left", CatanRules.legalMoves(roads, 0).none { it is BuildRoad })
+        val free = roads.copy(phase = CatanPhase.FREE_ROADS, pendingFreeRoads = 2)
+        assertEquals(listOf<CatanMove>(EndFreeRoads), CatanRules.legalMoves(free, 0))
+
+        // Settlements: five.
+        val homes = scattered(7)
+        var settled = craft().copy(resources = rich)
+        for (i in 0 until 4) settled = settled.withBuilding(homes[i], BuildingType.SETTLEMENT, 0)
+        settled = settled.withRoad(CatanBoard.VERTEX_EDGES[homes[5]][0], 0)
+        assertTrue("four standing: a fifth is allowed", BuildSettlement(homes[5]) in CatanRules.legalMoves(settled, 0))
+        settled = settled.withBuilding(homes[4], BuildingType.SETTLEMENT, 0)
+        assertFalse("five standing: no sixth", BuildSettlement(homes[5]) in CatanRules.legalMoves(settled, 0))
+
+        // Cities: four. A raised settlement returns to the supply, so five settlements stays possible.
+        var raised = craft().copy(resources = rich)
+        for (i in 0 until 3) raised = raised.withBuilding(homes[i], BuildingType.CITY, 0)
+        raised = raised.withBuilding(homes[3], BuildingType.SETTLEMENT, 0)
+        assertTrue("three cities: a fourth is allowed", BuildCity(homes[3]) in CatanRules.legalMoves(raised, 0))
+        raised = raised.withBuilding(homes[3], BuildingType.CITY, 0).withBuilding(homes[4], BuildingType.SETTLEMENT, 0)
+        assertFalse("four cities: no fifth", BuildCity(homes[4]) in CatanRules.legalMoves(raised, 0))
+    }
+
     @Test
     fun `a settlement needs an open vertex on the network, a city one of yours`() {
         val base = craft()
@@ -437,6 +520,113 @@ class CatanRulesTest {
         assertEquals(listOf<CatanMove>(DeclineTrade), CatanRules.legalMoves(offered, 1))
     }
 
+    private val twoLumberForBrick =
+        OfferTrade(to = null, give = listOf(Resource.LUMBER, Resource.LUMBER), get = listOf(Resource.BRICK))
+
+    private fun openTable() = craft().copy(
+        resources = hands(
+            hand(Resource.LUMBER to 3),
+            hand(Resource.BRICK to 2),
+            hand(Resource.BRICK to 1, Resource.WOOL to 1),
+        ),
+    )
+
+    @Test
+    fun `an open offer asks each other seat in turn until one accepts`() {
+        val state = openTable()
+        assertTrue(CatanRules.isLegalMove(state, 0, twoLumberForBrick))
+        val asked1 = CatanRules.applyMove(state, 0, twoLumberForBrick)
+        assertEquals(CatanPhase.TRADE_PENDING, asked1.phase)
+        assertEquals(1, CatanRules.currentSeat(asked1))
+
+        val asked2 = CatanRules.applyMove(asked1, 1, DeclineTrade)
+        assertEquals("a decline passes the offer on", 2, CatanRules.currentSeat(asked2))
+        assertEquals(CatanPhase.TRADE_PENDING, asked2.phase)
+
+        val done = CatanRules.applyMove(asked2, 2, AcceptTrade)
+        assertEquals(CatanPhase.PLAYING, done.phase)
+        assertNull(done.pendingTrade)
+        assertEquals(hand(Resource.LUMBER to 1, Resource.BRICK to 1), done.resources[0])
+        assertEquals(hand(Resource.LUMBER to 2, Resource.WOOL to 1), done.resources[2])
+        assertEquals("seat 1 never took part", state.resources[1], done.resources[1])
+    }
+
+    @Test
+    fun `an open offer nobody wants lapses back to the offerer`() {
+        var table = CatanRules.applyMove(openTable(), 0, twoLumberForBrick)
+        table = CatanRules.applyMove(table, 1, DeclineTrade)
+        table = CatanRules.applyMove(table, 2, DeclineTrade)
+        assertEquals(CatanPhase.PLAYING, table.phase)
+        assertNull(table.pendingTrade)
+        assertEquals(0, CatanRules.currentSeat(table))
+    }
+
+    @Test
+    fun `seats with no cards are not asked`() {
+        val state = openTable().copy(resources = hands(hand(Resource.LUMBER to 3), hand(), hand(Resource.BRICK to 1)))
+        val table = CatanRules.applyMove(state, 0, twoLumberForBrick)
+        assertEquals(2, CatanRules.currentSeat(table))
+    }
+
+    @Test
+    fun `a counter is kept and the offerer chooses once everyone has answered`() {
+        var table = CatanRules.applyMove(openTable(), 0, twoLumberForBrick)
+        // Seat 1 will not give a brick for two lumber but would for three.
+        val counter = CounterTrade(give = listOf(Resource.BRICK), get = listOf(Resource.LUMBER, Resource.LUMBER, Resource.LUMBER))
+        assertTrue(CatanRules.isLegalMove(table, 1, counter))
+        table = CatanRules.applyMove(table, 1, counter)
+        assertEquals(2, CatanRules.currentSeat(table))
+        table = CatanRules.applyMove(table, 2, DeclineTrade)
+
+        assertEquals(CatanPhase.TRADE_COUNTERS, table.phase)
+        assertEquals("the offerer chooses", 0, CatanRules.currentSeat(table))
+        assertEquals(
+            listOf<CatanMove>(AcceptCounter(1), DismissCounters),
+            CatanRules.legalMoves(table, 0),
+        )
+
+        val taken = CatanRules.applyMove(table, 0, AcceptCounter(1))
+        assertEquals(CatanPhase.PLAYING, taken.phase)
+        assertNull(taken.pendingTrade)
+        assertEquals(hand(Resource.BRICK to 1), taken.resources[0])
+        assertEquals(hand(Resource.LUMBER to 3, Resource.BRICK to 1), taken.resources[1])
+    }
+
+    @Test
+    fun `counters can all be turned down`() {
+        var table = CatanRules.applyMove(openTable(), 0, twoLumberForBrick)
+        table = CatanRules.applyMove(
+            table, 1,
+            CounterTrade(listOf(Resource.BRICK), listOf(Resource.LUMBER, Resource.LUMBER, Resource.LUMBER)),
+        )
+        table = CatanRules.applyMove(table, 2, DeclineTrade)
+        val after = CatanRules.applyMove(table, 0, DismissCounters)
+        assertEquals(CatanPhase.PLAYING, after.phase)
+        assertNull(after.pendingTrade)
+        assertEquals(openTable().resources, after.resources)
+    }
+
+    @Test
+    fun `a counter must differ from the offer and be affordable`() {
+        val table = CatanRules.applyMove(openTable(), 0, twoLumberForBrick)
+        assertFalse(
+            "the offer as made is an accept, not a counter",
+            CatanRules.isLegalMove(table, 1, CounterTrade(listOf(Resource.BRICK), listOf(Resource.LUMBER, Resource.LUMBER))),
+        )
+        assertFalse(
+            "cannot promise cards not held",
+            CatanRules.isLegalMove(table, 1, CounterTrade(listOf(Resource.ORE), listOf(Resource.LUMBER))),
+        )
+        assertFalse(
+            "cannot ask for cards the offerer lacks",
+            CatanRules.isLegalMove(table, 1, CounterTrade(listOf(Resource.BRICK), listOf(Resource.ORE))),
+        )
+        assertFalse(
+            "only the seat being asked may counter",
+            CatanRules.isLegalMove(table, 2, CounterTrade(listOf(Resource.WOOL), listOf(Resource.LUMBER))),
+        )
+    }
+
     @Test
     fun `the bank trades four for one and harbours do better`() {
         val base = craft()
@@ -829,6 +1019,10 @@ class CatanRulesTest {
             OfferTrade(1, listOf(Resource.LUMBER, Resource.LUMBER), listOf(Resource.ORE)),
             AcceptTrade,
             DeclineTrade,
+            OfferTrade(null, listOf(Resource.LUMBER), listOf(Resource.ORE)),
+            CounterTrade(listOf(Resource.WOOL), listOf(Resource.GRAIN, Resource.GRAIN)),
+            AcceptCounter(2),
+            DismissCounters,
             MaritimeTrade(Resource.WOOL, Resource.GRAIN),
             EndTurn,
             EndFreeRoads,

app/src/test/java/org/prolibertate/games/ui/game/catan/CatanCkInteractionTest.kt

@@ -0,0 +1,291 @@
+package org.prolibertate.games.ui.game.catan
+
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.prolibertate.games.game.GameCatalog
+import org.prolibertate.games.game.catan.AcceptCounter
+import org.prolibertate.games.game.catan.AcceptTrade
+import org.prolibertate.games.game.catan.CounterGoods
+import org.prolibertate.games.game.catan.DismissCounters
+import org.prolibertate.games.game.catan.ActivateKnight
+import org.prolibertate.games.game.catan.BuildCity
+import org.prolibertate.games.game.catan.BuildRoad
+import org.prolibertate.games.game.catan.BuildSettlement
+import org.prolibertate.games.game.catan.BuildWall
+import org.prolibertate.games.game.catan.BuyImprovement
+import org.prolibertate.games.game.catan.CatanAi
+import org.prolibertate.games.game.catan.CatanBoard
+import org.prolibertate.games.game.catan.CatanMove
+import org.prolibertate.games.game.catan.CatanOptions
+import org.prolibertate.games.game.catan.CatanPhase
+import org.prolibertate.games.game.catan.CatanRuleSet
+import org.prolibertate.games.game.catan.CatanRules
+import org.prolibertate.games.game.catan.CatanState
+import org.prolibertate.games.game.catan.ChaseRobber
+import org.prolibertate.games.game.catan.DeclineTrade
+import org.prolibertate.games.game.catan.DiscardGoods
+import org.prolibertate.games.game.catan.DropProgress
+import org.prolibertate.games.game.catan.EndFreeRoads
+import org.prolibertate.games.game.catan.EndSmith
+import org.prolibertate.games.game.catan.EndTurn
+import org.prolibertate.games.game.catan.GiveGoods
+import org.prolibertate.games.game.catan.GoodsBankTrade
+import org.prolibertate.games.game.catan.HireKnight
+import org.prolibertate.games.game.catan.MoveKnight
+import org.prolibertate.games.game.catan.MoveRobber
+import org.prolibertate.games.game.catan.OfferGoods
+import org.prolibertate.games.game.catan.PickDeck
+import org.prolibertate.games.game.catan.PillageCity
+import org.prolibertate.games.game.catan.PlaceKnight
+import org.prolibertate.games.game.catan.PlaceMetropolis
+import org.prolibertate.games.game.catan.PlayProgress
+import org.prolibertate.games.game.catan.PromoteKnight
+import org.prolibertate.games.game.catan.RelocateKnight
+import org.prolibertate.games.game.catan.RemoveKnight
+import org.prolibertate.games.game.catan.RollDice
+import org.prolibertate.games.game.catan.SetupPlace
+import org.prolibertate.games.game.catan.SpyTake
+import org.prolibertate.games.game.catan.TakeAqueduct
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+/**
+ * Cities & Knights has no device in this test suite, so the screen's logic is
+ * checked another way: engines play whole games, and at every position the
+ * player on the clock is treated as the local one. For every move the engine says
+ * is legal, [CatanInteraction] (and the dialogs' own filters) must offer a way to
+ * make it — a tap, a button or a dialog choice. A legal move that no control can
+ * produce would be a stuck game on a real phone.
+ */
+class CatanCkInteractionTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun config(players: Int, seed: Long) = TableConfig(
+        gameId = GameCatalog.CATAN,
+        seats = (0 until players).map { PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = it) },
+        optionsJson = json.encodeToString(
+            CatanOptions(players, pointsToWin = 13, ruleSet = CatanRuleSet.CITIES_AND_KNIGHTS),
+        ),
+        seed = seed,
+    )
+
+    /** How a move reaches the engine from the screen, or null if nothing can produce it. */
+    private fun reachable(state: CatanState, legal: List<CatanMove>, move: CatanMove): String? {
+        fun tapVertex(vertex: Int, building: BuildKind? = null, moving: Int? = null, armed: ArmedCard? = null): TapOutcome =
+            CatanInteraction.onVertexTap(vertex, legal, building, null, moving, armed)
+
+        return when (move) {
+            is SetupPlace -> {
+                val vertex = CatanInteraction.targets(state, legal, null, null).vertices
+                val edges = CatanInteraction.targets(state, legal, null, move.vertex).edges
+                "setup".takeIf {
+                    move.vertex in vertex && move.edge in edges &&
+                        CatanInteraction.onVertexTap(move.vertex, legal, null, null) is TapOutcome.PickSetupVertex &&
+                        CatanInteraction.onEdgeTap(move.edge, legal, null, move.vertex) == TapOutcome.Submit(move)
+                }
+            }
+
+            is BuildRoad -> {
+                val targets = CatanInteraction.targets(state, legal, BuildKind.ROAD, null)
+                "road".takeIf {
+                    move.edge in targets.edges &&
+                        CatanInteraction.onEdgeTap(move.edge, legal, BuildKind.ROAD, null) == TapOutcome.Submit(move)
+                }
+            }
+
+            is BuildSettlement -> viaBuild(state, legal, BuildKind.SETTLEMENT, move.vertex, move)
+            is BuildCity -> viaBuild(state, legal, BuildKind.CITY, move.vertex, move)
+            is BuildWall -> viaBuild(state, legal, BuildKind.WALL, move.vertex, move)
+            is HireKnight -> viaBuild(state, legal, BuildKind.KNIGHT, move.vertex, move)
+
+            is MoveRobber -> {
+                val hex = CatanBoard.hexIndex.getValue(move.hex)
+                val targets = CatanInteraction.targets(state, legal, null, null)
+                val tap = CatanInteraction.onHexTap(hex, legal)
+                "robber".takeIf {
+                    hex in targets.hexes &&
+                        (tap == TapOutcome.Submit(move) || (tap is TapOutcome.PickRobberVictim && move.victim in tap.victims))
+                }
+            }
+
+            is MoveKnight -> {
+                val targets = CatanInteraction.targets(state, legal, null, null, movingKnight = move.from)
+                "moveKnight".takeIf {
+                    move.to in targets.vertices && tapVertex(move.to, moving = move.from) == TapOutcome.Submit(move) &&
+                        move.from in CatanInteraction.targets(state, legal, null, null).knights &&
+                        CatanInteraction.knightActions(legal, move.from).any { it is MoveKnight }
+                }
+            }
+
+            is ActivateKnight, is ChaseRobber, is PromoteKnight -> {
+                val vertex = when (move) {
+                    is ActivateKnight -> move.vertex
+                    is ChaseRobber -> move.vertex
+                    else -> (move as PromoteKnight).vertex
+                }
+                val smith = legal.any { it is EndSmith }
+                if (move is PromoteKnight && smith) {
+                    val targets = CatanInteraction.targets(state, legal, null, null)
+                    "smith".takeIf {
+                        vertex in targets.vertices && tapVertex(vertex) == TapOutcome.Submit(move)
+                    }
+                } else {
+                    val targets = CatanInteraction.targets(state, legal, null, null)
+                    "knightMenu".takeIf {
+                        vertex in targets.knights && tapVertex(vertex) == TapOutcome.PickKnight(vertex) &&
+                            move in CatanInteraction.knightActions(legal, vertex)
+                    }
+                }
+            }
+
+            is PillageCity -> viaChore(state, legal, move.vertex, move)
+            is PlaceMetropolis -> viaChore(state, legal, move.vertex, move)
+            is RelocateKnight -> viaChore(state, legal, move.to, move)
+            is RemoveKnight -> viaChore(state, legal, move.vertex, move)
+            is PlaceKnight -> viaChore(state, legal, move.vertex, move)
+
+            is PlayProgress -> viaCard(state, legal, move)
+
+            is BuyImprovement -> "improve".takeIf { move.track in CatanInteraction.improvable(legal) }
+
+            is GoodsBankTrade ->
+                "bankTrade".takeIf { move.get in CatanInteraction.goodsBankTrades(legal)[move.give].orEmpty() }
+
+            RollDice(), is RollDice -> "roll".takeIf { CatanInteraction.canRoll(legal) }
+            EndTurn -> "endTurn".takeIf { CatanInteraction.canEndTurn(legal) }
+            EndFreeRoads -> "endRoads".takeIf { CatanInteraction.canEndFreeRoads(legal) }
+            EndSmith -> "endSmith".takeIf { CatanInteraction.canEndSmith(legal) }
+            AcceptTrade, DeclineTrade -> "tradeReply".takeIf { CatanInteraction.tradeResponses(legal) != (false to false) }
+
+            // Answered in a dialog that offers exactly the moves in the legal list.
+            is PickDeck, is DropProgress, is TakeAqueduct, is SpyTake -> "choreDialog"
+
+            // Structural: the discard and give dialogs build these and ask the engine.
+            is DiscardGoods, is GiveGoods -> "goodsDialog"
+            is OfferGoods, is CounterGoods -> "tradeDialog"
+            is AcceptCounter, DismissCounters -> "counterDialog"
+
+            else -> null
+        }
+    }
+
+    private fun viaBuild(state: CatanState, legal: List<CatanMove>, kind: BuildKind, vertex: Int, move: CatanMove): String? {
+        val targets = CatanInteraction.targets(state, legal, kind, null)
+        return "build $kind".takeIf {
+            vertex in targets.vertices &&
+                CatanInteraction.onVertexTap(vertex, legal, kind, null) == TapOutcome.Submit(move) &&
+                kind in CatanInteraction.canBuild(legal)
+        }
+    }
+
+    private fun viaChore(state: CatanState, legal: List<CatanMove>, vertex: Int, move: CatanMove): String? {
+        val targets = CatanInteraction.targets(state, legal, null, null)
+        return "chore".takeIf {
+            vertex in targets.vertices &&
+                CatanInteraction.onVertexTap(vertex, legal, null, null) == TapOutcome.Submit(move)
+        }
+    }
+
+    private fun viaCard(state: CatanState, legal: List<CatanMove>, move: PlayProgress): String? {
+        val seat = CatanRules.currentSeat(state) ?: return null
+        val entry = CatanInteraction.progressHand(state, seat, legal).firstOrNull { it.card.id == move.card }
+            ?: return null
+        val kind = entry.card.kind
+        if (move !in entry.plays) return null
+        if (kind !in CatanInteraction.BOARD_CARDS) return "cardDialog"
+
+        val armed = ArmedCard(kind, entry.plays)
+        val targets = CatanInteraction.targets(state, legal, null, null, armed = armed)
+        return when (kind) {
+            org.prolibertate.games.game.catan.ProgressType.DIPLOMAT ->
+                "armed".takeIf {
+                    move.edge in targets.edges &&
+                        CatanInteraction.onEdgeTap(move.edge!!, legal, null, null, armed) == TapOutcome.Submit(move)
+                }
+
+            org.prolibertate.games.game.catan.ProgressType.MERCHANT ->
+                "armed".takeIf {
+                    move.hexA in targets.hexes &&
+                        CatanInteraction.onHexTap(move.hexA!!, legal, armed) == TapOutcome.Submit(move)
+                }
+
+            org.prolibertate.games.game.catan.ProgressType.INVENTOR -> {
+                val first = CatanInteraction.onHexTap(move.hexA!!, legal, armed)
+                if (first != TapOutcome.PickFirstHex(move.hexA!!)) return null
+                val second = armed.copy(firstHex = move.hexA)
+                val partners = CatanInteraction.targets(state, legal, null, null, armed = second).hexes
+                "armed".takeIf {
+                    move.hexB in partners &&
+                        CatanInteraction.onHexTap(move.hexB!!, legal, second) == TapOutcome.Submit(move)
+                }
+            }
+
+            else ->
+                "armed".takeIf {
+                    move.vertex in targets.vertices &&
+                        CatanInteraction.onVertexTap(move.vertex!!, legal, null, null, null, armed) == TapOutcome.Submit(move)
+                }
+        }
+    }
+
+    private fun playAndCheck(players: Int, seed: Long): Map<String, Int> {
+        val ai = CatanAi()
+        var state = CatanRules.initialState(config(players, seed))
+        val seen = mutableMapOf<String, Int>()
+        var moves = 0
+        while (!CatanRules.isFinished(state) && moves++ < 20_000) {
+            val seat = CatanRules.currentSeat(state) ?: break
+            val legal = CatanRules.legalMoves(state, seat)
+            for (move in legal) {
+                val how = reachable(state, legal, move)
+                assertTrue(
+                    "seed $seed: no control produces $move in ${state.phase} " +
+                        "(chore ${state.ck?.chores?.firstOrNull()}); log tail: ${state.log.takeLast(3)}",
+                    how != null,
+                )
+                seen.merge(how!!, 1, Int::plus)
+            }
+            state = CatanRules.applyMove(state, seat, ai.chooseMove(state, seat, legal))
+        }
+        return seen
+    }
+
+    @Test
+    fun `every legal move in a full game has a control that produces it`() {
+        val total = mutableMapOf<String, Int>()
+        listOf(3 to 21L, 4 to 22L, 3 to 23L, 4 to 24L).forEach { (players, seed) ->
+            playAndCheck(players, seed).forEach { (k, v) -> total.merge(k, v, Int::plus) }
+        }
+        println("CK UI coverage: ${total.toSortedMap()}")
+        // The ways the screen builds, moves and answers all got exercised.
+        listOf("setup", "road", "build SETTLEMENT", "build CITY", "knightMenu", "improve", "bankTrade", "roll", "endTurn")
+            .forEach { assertTrue("never exercised: $it in $total", (total[it] ?: 0) > 0) }
+    }
+
+    @Test
+    fun `a sleeping knight with nothing to do can still be tapped for its menu`() {
+        val base = CatanRules.initialState(config(3, 5L))
+            .copy(phase = CatanPhase.PLAYING, turn = 0, turnNumber = 1)
+        val state = base.copy(
+            ck = base.ck!!.copy(knights = listOf(org.prolibertate.games.game.catan.Knight(10, 0, 1))),
+        )
+        val legal = CatanRules.legalMoves(state, 0)
+        assertTrue("no grain, so nothing to do", CatanInteraction.knightActions(legal, 10).isEmpty())
+
+        val targets = CatanInteraction.targets(state, legal, null, null, localSeat = 0)
+        assertTrue(10 in targets.idleKnights)
+        assertTrue("no tap ring for a knight with nothing to do", 10 !in targets.knights)
+        assertTrue(10 in targets.tappableVertices)
+        assertEquals(
+            TapOutcome.PickKnight(10),
+            CatanInteraction.onVertexTap(10, legal, null, null, ownKnights = setOf(10)),
+        )
+        // On somebody else's turn the legal list is empty and nothing is offered.
+        assertTrue(CatanInteraction.targets(state, emptyList(), null, null, localSeat = 0).idleKnights.isEmpty())
+    }
+}

app/src/test/java/org/prolibertate/games/ui/game/catan/CatanCkTextTest.kt

@@ -0,0 +1,75 @@
+package org.prolibertate.games.ui.game.catan
+
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.prolibertate.games.game.GameCatalog
+import org.prolibertate.games.game.catan.CatanAi
+import org.prolibertate.games.game.catan.CatanOptions
+import org.prolibertate.games.game.catan.CatanRuleSet
+import org.prolibertate.games.game.catan.CatanRules
+import org.prolibertate.games.game.catan.ProgressType
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+import org.prolibertate.games.ui.catanDefaultPoints
+import org.prolibertate.games.ui.catanPointsChoices
+import org.prolibertate.games.ui.catanSwitchRules
+
+class CatanCkTextTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    @Test
+    fun `every position of a Cities and Knights game has a prompt for every seat`() {
+        val config = TableConfig(
+            gameId = GameCatalog.CATAN,
+            seats = (0 until 3).map { PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = it) },
+            optionsJson = json.encodeToString(
+                CatanOptions(3, 13, CatanRuleSet.CITIES_AND_KNIGHTS),
+            ),
+            seed = 31L,
+        )
+        var state = CatanRules.initialState(config)
+        val ai = CatanAi()
+        var moves = 0
+        while (!CatanRules.isFinished(state) && moves++ < 20_000) {
+            for (me in 0 until 3) {
+                val seats = CatanSeats(me, listOf("A", "B", "C"))
+                val text = CatanText.prompt(state, seats, setupVertexChosen = false, building = null)
+                assertTrue("blank prompt in ${state.phase} for seat $me", text.isNotBlank())
+            }
+            val seat = CatanRules.currentSeat(state) ?: break
+            state = CatanRules.applyMove(state, seat, ai.chooseMove(state, seat, CatanRules.legalMoves(state, seat)))
+        }
+    }
+
+    @Test
+    fun `every progress card has a name and a description`() {
+        ProgressType.entries.forEach {
+            assertTrue(CatanText.progress(it).isNotBlank())
+            assertTrue("no help for $it", CatanText.progressHelp(it).length > 10)
+        }
+    }
+
+    @Test
+    fun `the setup screen offers each rule set its own targets and switches sensibly`() {
+        assertEquals(listOf(5, 8, 10, 12), catanPointsChoices(CatanRuleSet.BASE))
+        assertEquals(listOf(8, 10, 13, 15), catanPointsChoices(CatanRuleSet.CITIES_AND_KNIGHTS))
+        assertEquals(10, catanDefaultPoints(CatanRuleSet.BASE))
+        assertEquals(13, catanDefaultPoints(CatanRuleSet.CITIES_AND_KNIGHTS))
+
+        val base = CatanOptions()
+        val ck = catanSwitchRules(base, CatanRuleSet.CITIES_AND_KNIGHTS)
+        assertEquals(CatanRuleSet.CITIES_AND_KNIGHTS, ck.ruleSet)
+        assertEquals("the published target for the new rules", 13, ck.pointsToWin)
+        assertEquals(10, catanSwitchRules(ck, CatanRuleSet.BASE).pointsToWin)
+
+        // A short game picked on purpose is kept when both menus have it.
+        val short = catanSwitchRules(base.copy(pointsToWin = 8), CatanRuleSet.CITIES_AND_KNIGHTS)
+        assertEquals(8, short.pointsToWin)
+        assertEquals(3, ck.playerCount)
+    }
+}

app/src/test/java/org/prolibertate/games/ui/game/catan/CatanGeometryTest.kt

@@ -111,7 +111,7 @@ class CatanGeometryTest {
             val anchor = layout.portAnchor(e)
             val mid = layout.edgeMidpoint(e)
             assertTrue("harbour on edge $e should be past the coast", dist(anchor, centre) > dist(mid, centre))
-            assertTrue("and not floating far from it", abs(dist(anchor, mid) - layout.radius * 0.62f) < 1f)
+            assertTrue("and not floating far from it", abs(dist(anchor, mid) - layout.radius * PORT_OFFSET) < 1f)
         }
     }
 }

app/src/test/java/org/prolibertate/games/ui/game/catan/CatanInteractionTest.kt

@@ -322,4 +322,27 @@ class CatanInteractionTest {
         val short = pending.withHand(1, hand())
         assertEquals(false to true, CatanInteraction.tradeResponses(CatanRules.legalMoves(short, 1)))
     }
+
+    // --- Rolled-hex highlight --------------------------------------------------
+
+    @Test
+    fun `rolled hexes are those carrying the number, minus the robber's`() {
+        val base = playing(turn = 0)
+        val number = base.numbers.first { it != 0 && it != 7 }
+        val state = base.copy(lastDice = if (number <= 7) listOf(number - 1, 1) else listOf(6, number - 6))
+        val all = (0 until CatanBoard.HEX_COUNT).filter { state.numbers[it] == number }
+        assertTrue(all.isNotEmpty())
+        assertEquals(all.filter { it != state.robber }.toSet(), CatanInteraction.rolledHexes(state))
+        val blocked = state.copy(robber = all.first())
+        assertFalse(all.first() in CatanInteraction.rolledHexes(blocked))
+    }
+
+    @Test
+    fun `nothing is highlighted before this turn's roll, on a seven, or in setup`() {
+        val rolled = playing(turn = 0).copy(lastDice = listOf(3, 3))
+        assertTrue(CatanInteraction.rolledHexes(rolled.copy(phase = CatanPhase.AWAIT_ROLL)).isEmpty())
+        assertTrue(CatanInteraction.rolledHexes(rolled.copy(lastDice = listOf(3, 4))).isEmpty())
+        assertTrue(CatanInteraction.rolledHexes(rolled.copy(phase = CatanPhase.SETUP_FIRST)).isEmpty())
+        assertTrue(CatanInteraction.rolledHexes(rolled.copy(lastDice = emptyList())).isEmpty())
+    }
 }

docs/README.md

@@ -24,7 +24,7 @@ Naming: the catalogue id, lowercase, e.g. `crazy8s` → `RULES-crazy8s.md`.
 | Golf | [RULES-golf.md](RULES-golf.md) |
 | Hearts | — (TODO) |
 | Kaiser | [RULES-kaiser.md](RULES-kaiser.md) |
-| Katan (catalogue id `catan`) | [RULES-catan.md](RULES-catan.md) |
+| Katan (catalogue id `catan`) | [RULES-catan.md](RULES-catan.md) — and its expansion rule set, [RULES-catan-ck.md](RULES-catan-ck.md) |
 | Klondike | — (TODO) |
 | Mastermind | [RULES-mastermind.md](RULES-mastermind.md) |
 | Morris | [RULES-morris.md](RULES-morris.md) |

docs/RULES-catan-ck.md

@@ -0,0 +1,222 @@
+# Katan: Cities & Knights — implemented rules
+
+This is the second rule set of Katan (see [RULES-catan.md](RULES-catan.md) for the
+base game). It is chosen on the setup screen — **Rules: Base game / Cities &
+Knights** — and stored as `CatanOptions.ruleSet` (`CatanRuleSet.CITIES_AND_KNIGHTS`).
+A table plays one or the other; the choice reaches guests with the rest of the
+options.
+
+The expansion is a whole rule set rather than a toggle, because it replaces rules
+(no development cards, no Largest Army, a different seven) as well as adding them.
+Everything it needs lives behind `CatanState.ck`, which is `null` in the base game,
+so a base game's state and rules are untouched. The code is:
+
+| File | Holds |
+| --- | --- |
+| `CatanCkModel.kt` | the data: commodities, improvement tracks, progress cards, knights, the chore queue, every new move |
+| `CatanCk.kt` | the rules: legal moves, applying them, the roll, the barbarians, scoring |
+| `CatanCkAi.kt` | the computer opponent for this rule set |
+| `CatanRules.kt` | the single entry point; calls into `CatanCk` whenever `state.ck != null` |
+
+Behaviour is pinned by `CatanCkRulesTest` (each rule on a crafted position) and
+`CatanCkSelfPlayTest` (whole games, engine against engine). Three or four players,
+as in the base game.
+
+## Verification
+
+The rules were checked against the in-game almanac of Catan Universe (rules text
+only: costs, card wordings, the barbarian and improvement rules). Where the almanac
+is silent or ambiguous the reading chosen is listed under *Choices made here* below.
+
+## What changes from the base game
+
+| | Base game | Cities & Knights |
+| --- | --- | --- |
+| Points to win | 10 | **13** (setup offers 8 / 10 / 13 / 15) |
+| Development cards | 25-card deck | **none** — knights and progress cards replace them |
+| Largest Army | 5 *(see RULES-catan.md)* | **none** |
+| Longest Road | 5 *(see RULES-catan.md)* | **2** |
+| Second setup piece | settlement | **city** (resources only, no commodities) |
+| Dice | two | **two number dice + the event die** |
+| A seven | discard half over 7; robber moves | discard half over **7 + 2 per wall**; the robber **only moves after the first barbarian attack** |
+| Cities | 2 of a resource | forest: 1 lumber + **1 paper**; pasture: 1 wool + **1 cloth**; mountains: 1 ore + **1 coin**; hills / fields: 2 of the resource |
+
+## The dice
+
+The yellow die and the red die are added for production, as in the base game. The
+**event die** has three ships and one gate each of yellow (trade), blue (politics)
+and green (science). It is resolved **before** production:
+
+- **Ship** — the barbarians come one step nearer (they start 7 steps out).
+- **Gate** — every player with at least one level of improvement in that colour,
+  **in turn order from the roller**, whose **red die is no higher than their level**
+  in that track, draws a progress card of that colour.
+
+`RollDice(forced, event)` stages both for tests, like the base game's forced roll.
+An **Alchemist** played before the roll sets the two number dice (the event die is
+still rolled).
+
+## Commodities
+
+Three commodities — **cloth, coin, paper** — join the five resources. The bank holds
+12 of each (19 of each resource). Hands, discards, thefts and trades all treat them as
+cards; progress cards are not cards for any of these purposes.
+
+When the bank cannot meet the demand for a card type: with **one** seat owed it,
+that seat takes what is left; with **two or more** owed, nobody receives it.
+
+## The barbarians
+
+The strip shows how many steps away the ship is. On the seventh ship it **lands**:
+
+- Barbarian strength is the **number of cities on the board** (a metropolis is a city).
+- Catan's strength is the sum of the strengths of every **active** knight (basic 1,
+  strong 2, mighty 3).
+- If Catan's strength is **at least** the barbarians', Catan holds: the player with
+  the strictly highest contribution takes a **Defender of Catan** card (one point);
+  if several tie for highest, **each draws a progress card from a deck of their
+  choice** instead.
+- Otherwise Catan falls: among the players who own a city that is not a metropolis,
+  those who contributed **least** each lose one city, **to their own choice**. A lost
+  city becomes a settlement (or, if the seat has no settlement piece left, is removed),
+  and its wall goes. **A metropolis can never be pillaged.**
+- Either way every knight stands down, the ship returns to seven steps, and the
+  **robber wakes** — until now it has not been on the board.
+
+## Knights
+
+Each seat has **two knights of each strength** (six in all).
+
+| Action | Cost | Rule |
+| --- | --- | --- |
+| Hire | 1 ore + 1 wool | a **basic** knight on an empty crossing at the end of one of your roads; only if one of your two basic knights is free |
+| Activate | 1 grain | a sleeping knight wakes; only active knights count against the barbarians |
+| Promote | 1 ore + 1 wool | one level, once per knight per turn; a **mighty** knight needs **level three of politics** (the fortress); the next level's pieces must be free |
+| Move | — | an active knight moves along **its own roads** to an empty crossing, or onto a **strictly weaker** foreign knight, driving it off; it then rests |
+| Chase the robber | — | an active knight on a crossing of the robber's hex sends the robber off (only once the robber is awake); it then rests, and the robber move follows |
+
+- **A knight cannot act on the turn it woke.** It can be woken again after it acts.
+- A driven-off knight is moved by **its owner** along its own roads to any empty
+  crossing it can reach; if there is none, it is lost.
+- A knight is a wall, like an opposing building: roads cannot be laid past an enemy
+  knight, a settlement cannot be built on a knight, and the knight cuts **Longest Road**.
+- Knights can act (wake, move, chase) **before the roll** as well as after.
+
+## City walls
+
+2 brick, on a city without a wall, **three per player**. Each wall raises the hand
+limit on a seven by two (so a seven discards when you hold more than `7 + 2 × walls`).
+
+## City improvements
+
+Three tracks, five levels each, bought with the track's commodity: **trade (cloth,
+yellow), politics (coin, blue), science (paper, green)**. Level *n* costs *n* of the
+commodity. You must own a city to improve.
+
+| Track | Level 3 gives |
+| --- | --- |
+| Trade | commodities trade with the bank **2:1** |
+| Politics | knights may be promoted to **mighty** |
+| Science | the **aqueduct**: when the dice pay you nothing, take any resource |
+
+The level names (Trading Post … Grand Bazaar, Town Hall … Palace, Abbey … University)
+are this app's own.
+
+### Metropolises
+
+The first player to reach **level four** in a track takes that track's **metropolis**
+(a marker on one of their cities: +2 points; a city carries at most one). Reaching
+**level five** takes it from a holder who is still on four. A player with several
+cities chooses which; with one it is placed at once; a player with no free city
+**waits**, and claims it when a city is built.
+
+## Progress cards
+
+54 cards: 18 in each of three decks. A card played returns to the **bottom** of its
+deck. A hand holds **four**; a fifth must be given back at once. They can be played at
+any point of your own turn (before or after the roll), except where noted.
+
+**Science (green)** — Alchemist ×2 *(before the roll only)*, Crane ×2, Engineer, Inventor ×2,
+Irrigation ×2, Medicine ×2, Mining ×2, Printer, Road Building ×2, Smith ×2.
+
+**Politics (blue)** — Bishop ×2 *(after the first attack)*, Constitution, Deserter ×2,
+Diplomat ×2, Intrigue ×2, Saboteur ×2, Spy ×3, Warlord ×2, Wedding ×2.
+
+**Trade (yellow)** — Commercial Harbor ×2, Master Merchant ×2, Merchant ×6,
+Merchant Fleet ×2, Resource Monopoly ×4, Trade Monopoly ×2.
+
+**Printer** and **Constitution** are one point each and are **laid face up the moment
+they are drawn**; they never sit in a hand.
+
+How each plays is shown on the card in the app (`CatanText.progressHelp`); the engine's
+behaviour is in `CatanCk.applyProgress`. Points worth knowing:
+
+- **Saboteur** hits every other player with **as many points as you or more**, who each
+  discard half their cards (rounded down). **Wedding** takes two cards (or what they
+  have) from each player with **more** points. **Master Merchant** needs a victim with
+  more points, and takes two cards you choose.
+- **Spy**: you see the target's progress cards and take one; nobody else sees them.
+- **Merchant**: placed beside one of your buildings; you trade that hex's resource 2:1
+  and hold a victory point until someone else plays a Merchant.
+- **Deserter**: the victim removes a knight of *their* choice; you place a free one of the
+  same strength (or a basic if yours is not free), awake or asleep as theirs was.
+- **Diplomat**: removes a road with a loose end (an end touching no other road, building
+  or knight); if it was yours you may rebuild it anywhere for free.
+- **Inventor** swaps two tokens, never a 2, 6, 8 or 12.
+
+## The chore queue
+
+Anything that needs an answer from somebody — a discard, a city to lose, a progress card
+to hand over, a metropolis site, a knight to place — is queued as a **chore**
+(`CatanPhase.CHORE`, `CkState.chores`). The game waits on the seat the first chore names
+(not always the player whose turn it is), then resumes where `CkState.back` says. This is
+how a seven, a barbarian landing, a wedding or a spy are all one mechanism, and why
+the AI and the network driver needed no new concepts.
+
+The two free-form chores — **discarding** and **handing over** cards — are structural
+like the base game's trade offers: the engine checks them in `isLegalMove` and the legal
+list carries one example, so a seat is never without a move.
+
+## Scoring and winning
+
+Settlement 1, city 2, **metropolis +2**, **Longest Road 2**, **Defender of Catan 1** each,
+**Printer / Constitution 1** each, **the Merchant 1**. Nothing is hidden. Win at 13 (default),
+checked after every move and when a turn arrives.
+
+## Choices made here, and why
+
+- **The red die must be no higher than the improvement level** to draw a progress card
+  (level 1 draws on a 1, level 5 on 1–5). The almanac says the red die must match a
+  number on one of your improvements and that the number rises with the level; this is
+  the reading that makes both true.
+- **One resource is offered to every player for a Commercial Harbor.** The printed card
+  lets you offer a different one to each.
+- **The merchant cannot go on the desert**, which produces nothing to trade.
+- **Improvements need a city** to be built.
+- **A 3:1 harbour trades commodities too**; a 2:1 harbour trades only its own resource.
+- **A knight that cannot find a refuge is lost**, as the almanac says of an intrigue.
+- **A claim on a metropolis with no city to carry it waits** and is made when a city is
+  built.
+- **Domestic trade** works as in the base game — an offer to one seat or to the whole
+  table, asked in seat order, each seat accepting, declining or countering — and may
+  include commodities (`OfferGoods`, `CounterGoods`; accepting and dismissing counters
+  reuse the base game's `AcceptCounter` and `DismissCounters`).
+- **No Seafarers, no 5–6 player extension**, no scenario or variant of any kind.
+
+## The computer opponent
+
+`CatanCkAi` plays a safe, unambitious game: it settles and raises cities as the base AI
+does, spends commodities on improvements as soon as it can (leaning to politics), hires
+and wakes knights as the barbarians draw near, chases the robber off hexes it needs, plays
+the progress cards whose value is obvious, and answers every chore with the card it values
+least. It never plans a knight's route, never plays an Alchemist, Inventor, Diplomat,
+Deserter or Intrigue, and makes no domestic offers (though it answers them). Every engine
+game in `CatanCkSelfPlayTest` ends in a win at thirteen points.
+
+## Known gaps
+
+- The screen is built and its logic is tested, but **not yet verified on two real
+  devices**; the catalogue entry stays a dev-channel preview.
+- No animation for the event die, the barbarian landing or a knight's move.
+- The Commercial Harbor offers a single resource type (see above).
+- The AI is not a strong opponent and makes no claim to be.

docs/RULES-catan.md

@@ -12,14 +12,27 @@ players, as published.
 The engine is a pure state machine (`CatanRules`) with no Android types, and its
 behaviour is pinned by `CatanBoardTest`, `CatanRulesTest` and `CatanAiTest`.
 
+## Rule sets
+
+A table plays one of two rule sets, chosen on the setup screen
+(`CatanOptions.ruleSet`):
+
+- **Base game** — everything in this document.
+- **Cities & Knights** — the expansion, documented in
+  [RULES-catan-ck.md](RULES-catan-ck.md). It reuses this document's board, setup,
+  building, robber and trade rules and changes or replaces the rest; its state lives
+  behind `CatanState.ck`, which is `null` in the base game.
+
 ## Table
 
+- **Rules — *toggle*.** Base game or Cities & Knights (`CatanOptions.ruleSet`).
 - **Players — *toggle*.** Three or four. `CatanOptions.playerCount`; the engine
   refuses anything else.
 - **Points to win — *toggle*.** Defaults to 10. `CatanOptions.pointsToWin`, at
   least 2. A lower target makes a test game short.
 
-The setup screen exposes both (players: 3 or 4; game to 5, 8, 10 or 12 points).
+The setup screen exposes all three (players: 3 or 4; game to 5, 8, 10 or 12 points in the
+base game, 8, 10, 13 or 15 in Cities & Knights, whose published target is 13).
 
 ## Board
 
@@ -122,17 +135,32 @@ is the same code path.
 
 ### Domestic
 
-An offer names **one** addressee and two card multisets: what the offerer gives,
-what they want. There are no counter-offers and no open auctions in v1.
+An offer is addressed to **one** seat or, with `to = null`, to **everyone**, and
+names two card multisets: what the offerer gives, what they want.
+
+Seats are asked **one at a time**, in seat order after the offerer (seats holding
+no cards are skipped; an addressed offer asks only its addressee). The seat being
+asked may:
+
+- **accept** — the trade happens at once and the offer closes (first accept wins);
+- **decline** — the offer moves on to the next seat;
+- **counter** (`CounterTrade`) — propose different terms: what they would give and
+  what they want from the offerer. A counter must differ from the offer as made
+  (that is an accept), and both sides must hold the cards. The offer moves on.
+
+When every seat has answered and nobody accepted: with no counters the offer
+simply lapses; with counters the phase becomes `TRADE_COUNTERS` and the offerer
+either **takes one** (`AcceptCounter(seat)`, still checked for affordability) or
+**turns them all down** (`DismissCounters`).
 
 An offer is legal only when the offerer's turn is in PLAYING, the addressee is
 another seat, both legs are non-empty, the two legs are not the same multiset
 (`countOf(give) != countOf(get)` — like-for-like is not a trade), and the
 offerer actually holds the cards being offered.
 
-The addressee may **accept** only if they hold what was asked and the offerer
-still holds what was promised; otherwise only **decline** is offered. A decline
-clears the table and leaves every card where it was.
+A seat may **accept** only if it holds what was asked and the offerer still holds
+what was promised; otherwise only decline (or counter) is offered. A refusal
+leaves every card where it was.
 
 Offers are free-form intents rather than enumerated moves (the space of card
 multisets is combinatorial), so they are validated structurally by
@@ -159,7 +187,19 @@ its edge.
 A settlement goes on an **empty vertex** at least two edges from every standing
 building and connected to the seat's own road network. A city upgrades one of
 the seat's own settlements. A road goes on an empty edge that connects to the
-seat's network (a road or a building at one of its ends).
+seat's network: it must start from a crossing where the seat has a building, or
+where one of its roads ends.
+
+**An opponent's settlement or city on a crossing breaks the network there.** A
+road cannot be laid past it, even from a crossing where one of your own roads
+ends — only a crossing you own a building on is a way through. The same rule
+applies to the free roads of a Road Building card, and it is the same wall that
+cuts Longest Road (below).
+
+**Pieces are limited**: each player has **15 roads, 5 settlements and 4 cities**.
+A player who has laid them all cannot build another of that kind. Raising a
+settlement into a city returns the settlement to the supply, so the five
+settlements remain available to be laid again.
 
 The development deck is the published 25 cards: **14 Knights, 2 Road Building,
 2 Monopoly, 2 Year of Plenty, 5 Victory Point**. Cards are bought blind from the
@@ -280,15 +320,18 @@ timing rules; Longest Road and Largest Army worth five; victory at ten.
 - **Year of Plenty two-of-a-kind needs the bank to hold both cards**, not one.
 - **The robber must move.** Some printings allow staying put; this engine always
   requires a different hex.
-- **Offers are one-to-one, no auctions or counter-offers** in v1.
+- **Offers may be open to the whole table** and can be countered; the first accept wins (see Trading).
 
 ## Known gaps
 
-- **No domestic auction or counter-offer.** An offer is addressed to a single
-  seat. Open trading to the whole table, and counter-offers, are the obvious next
-  step and are not implemented.
-- **No player-to-player trade over the wire beyond accept/decline.** The engine
-  supports it; whether the UI surfaces it is the screen task's concern.
+- **Longest Road and Largest Army are worth 5 each here.** The published base game awards
+  **2** each (Catan Universe's almanac says so for Largest Army, and the printed rules
+  for both). Cities & Knights scores Longest Road at 2, as printed. Left unchanged in
+  the base game so far; it is a one-constant change in `publicVictoryPoints`.
+- **A bank short of a resource pays nobody that roll**, even when only one player is owed
+  it. The published ruling lets a lone claimant take what is left; Cities & Knights does.
+- **No timer or cancel on offers.** An offer waits for each asked seat in turn; the offerer cannot withdraw it mid-round, and a player who never answers stalls the table.
+- **The AI never counters.** It accepts, declines, and picks among counters it is sent, but does not propose them.
 - **No trading away a development card.** Not part of the base game.
 - **The screen is built, not yet verified on two devices.** The Katan screen and
   setup options exist (see [UI-catan.md](UI-catan.md)); the catalogue entry is a

docs/UI-catan.md

@@ -71,6 +71,14 @@ screen's UI state. The legal-move list stays the gate.
    size of the deck; it is not known to a client. Card *counts* (`resourceCount`,
    `devHandCounts`) are public.
 5. **The state is immutable.** Never mutate it; submit a move.
+6. **The layout must not move.** Everything outside the board has a *fixed
+   height*, and the board takes whatever is left, so the island's scale is the
+   same all game. Concretely: a control is *enabled or disabled*, never
+   *present or absent* (the action bar always shows every button); text that can
+   vary in length is pinned to a fixed number of lines (`minLines = maxLines`);
+   a line that is sometimes empty is still drawn (a non-breaking space), as the
+   award line on a player card is. A change that makes any non-board element
+   taller or shorter at runtime will rescale the board under the player's thumb.
 
 ## Interaction model (what the player actually does)
 
@@ -81,7 +89,8 @@ screen's UI state. The legal-move list stays the gate.
 | Seven | **Discard** dialog (forced); then taps a hex to move the robber; a victim dialog appears only if more than one player can be robbed |
 | Main turn | arms **Road / Settlement / City** and taps a highlighted spot; **Buy card**; **Play card**; **Trade**; **End turn** |
 | Road Building | taps highlighted edges, or **Done with roads** |
-| Offered a trade | **Accept / Decline** dialog (forced) |
+| Offered a trade | **Accept / Decline / Counter…** dialog (forced); *Counter…* opens a picker pre-filled with the mirror of the offer |
+| Counter-offers received | **Counter-offers** dialog: *Accept* beside the one to take, or *No deal* |
 | Game over | result dialog |
 
 Trade offers are free-form (two card multisets), so they are validated with
@@ -112,6 +121,34 @@ and play a game on a dev build.
 - The board has a content description but no per-hex semantics; a screen-reader
   mode would need one.
 
+## Cities & Knights on the screen
+
+The same layers carry the expansion; the screen only adds pieces, and **none of them
+decides what is legal** — each reads the engine's legal-move list.
+
+| Layer | What it adds |
+| --- | --- |
+| `CatanStyle.kt` | commodity colours, a colour per improvement track, the wall and barbarian colours, the awake-knight halo |
+| `CatanText.kt` | goods, track, knight and progress-card names and help text; the prompts for every chore |
+| `CatanInteraction.kt` | `BuildKind.WALL` / `KNIGHT`; chore taps; the moving-knight and armed-card modes; `knightActions`, `progressHand`, `goodsBankTrades` |
+| `CatanBoardView.kt` | shields for knights (strength dots; faded when asleep, white halo when awake), dashed walls, a pennant for each metropolis, the merchant coin, a faint robber until the first attack |
+| `CatanPanels.kt` | commodity tiles in the hand, the barbarian strip, the yellow / red / event dice, the extra player-card lines, the Improve and Progress buttons |
+| `CatanCkDialogs.kt` | goods picker (discard, wedding, harbour), improvements, progress cards, the knight menu, deck / aqueduct / spy / drop choices, goods trade |
+| `CatanScreen.kt` | the visual state: knight menu, moving knight, armed card, and which chore dialog shows |
+
+**Interaction model.** Tap one of your own knights (it gets a yellow ring when it can do
+something) for its menu: wake, promote, move or chase the robber. *Move* arms the board
+with the crossings the knight can reach. A progress card that needs a place on the board
+(Engineer, Medicine, Merchant, Diplomat, Intrigue, Inventor) closes the dialog and
+**arms** the board; the next tap plays it. Chores that are answered with a place — a city
+to lose, a metropolis site, a driven knight's refuge, a free knight — light the crossings
+on the board and the prompt line says what to tap; the others open a dialog that cannot
+be dismissed, because the game is waiting on it.
+
+**Testing.** `CatanCkInteractionTest` plays whole games and checks that for *every* legal
+move at *every* position some control (a tap, a button or a dialog choice) produces it, so
+a legal move with no way to make it — a stuck phone — fails the build.
+
 ## Status and known gaps
 
 The screen is **playable and feature-complete for the engine's rules**, but is
@@ -129,6 +166,6 @@ Not done yet, in rough priority order:
    it does not say which hexes paid out, so that needs either a diff of two states
    or an engine addition.
 3. Art: terrain textures, resource and harbour icons, a real robber pawn.
-4. Open trade to the whole table and counter-offers (an engine limitation too).
+4. A timer or cancel button on offers (the engine has neither).
 5. A board that shows the *last* move (a faint highlight of what just changed).
 6. Landscape polish on large tablets; the right-hand panel scrolls but is plain.