various fixes. added version#s and added a playable browser build of the solitaire game (including deploy to filebrowser script)

package.json

@@ -9,7 +9,10 @@
   },
   "scripts": {
     "typecheck": "tsc --noEmit",
-    "test": "node --test test/**/*.test.ts"
+    "test": "node --test test/**/*.test.ts",
+    "build:web": "node scripts/build-web.ts",
+    "serve:web": "node scripts/build-web.ts && npx --yes http-server dist -p 8080 -c-1",
+    "deploy:web": "node scripts/deploy-web.ts"
   },
   "devDependencies": {
     "@types/node": "^26.1.2",

scripts/build-web.ts

@@ -0,0 +1,91 @@
+/**
+ * Build the static solitaire site into `dist/`.
+ *
+ * Everything here is BUILD-time. The output is plain files on disk — upload them anywhere that
+ * serves static content and the game runs entirely in the visitor's browser. No server, no API, no
+ * network call at runtime.
+ *
+ * The one thing a browser cannot do is run TypeScript: Node 22's type-stripping is a Node feature.
+ * So `tsc` emits ES2022 modules, rewriting the `.ts` import extensions the engine uses into `.js`.
+ */
+
+import { execFileSync } from 'node:child_process';
+import { mkdirSync, readFileSync, rmSync, writeFileSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const root = join(dirname(fileURLToPath(import.meta.url)), '..');
+const dist = join(root, 'dist');
+
+rmSync(dist, { recursive: true, force: true });
+mkdirSync(dist, { recursive: true });
+
+execFileSync(
+  'npx',
+  [
+    'tsc',
+    '--ignoreConfig',
+    'src/web/main.ts',
+    '--outDir', dist,
+    '--rootDir', 'src',
+    '--target', 'es2022',
+    '--module', 'es2022',
+    '--moduleResolution', 'bundler',
+    '--lib', 'es2022,dom',
+    '--types', '',
+    '--strict',
+    '--allowImportingTsExtensions',
+    '--rewriteRelativeImportExtensions',
+  ],
+  { cwd: root, stdio: 'inherit' },
+);
+
+/**
+ * Stamp the build into the page.
+ *
+ * Once this is published, "what is actually deployed?" stops being answerable by looking at the
+ * source. The stamp is written into index.html at copy time rather than generated into `src/`, so
+ * no generated file has to be ignored, imported, or kept in step.
+ *
+ * `-dirty` marks a build made from an uncommitted tree — the honest state of most test deploys, and
+ * exactly the thing you want to know when a fix appears to have had no effect.
+ */
+function buildStamp(): string {
+  const pkg = JSON.parse(readFileSync(join(root, 'package.json'), 'utf8')) as { version: string };
+  let git = 'nogit';
+  try {
+    const sha = execFileSync('git', ['rev-parse', '--short', 'HEAD'], { cwd: root })
+      .toString()
+      .trim();
+    const dirty =
+      execFileSync('git', ['status', '--porcelain'], { cwd: root }).toString().trim().length > 0;
+    git = sha + (dirty ? '-dirty' : '');
+  } catch {
+    // A build from a tarball with no git history is still a valid build.
+  }
+  const when = new Date().toISOString().replace('T', ' ').slice(0, 16);
+  return `v${pkg.version} · ${git} · ${when}Z`;
+}
+
+const stamp = buildStamp();
+const page = readFileSync(join(root, 'src/web/index.html'), 'utf8').replaceAll('__BUILD__', stamp);
+writeFileSync(join(dist, 'index.html'), page);
+
+// A tiny note for whoever unzips this later and wonders what it needs.
+writeFileSync(
+  join(dist, 'README.txt'),
+  [
+    'Station Master — solitaire, static build.',
+    '',
+    'Upload the contents of this folder to any static host and open index.html.',
+    'There is no server component. The game runs entirely in the browser and saves',
+    'to localStorage. Add ?seed=1234 to the URL for a reproducible deal.',
+    '',
+    'Note: ES modules require the files to be SERVED over http(s). Opening',
+    'index.html directly from the filesystem will be blocked by the browser.',
+    'To try it locally:  npx http-server dist   (or any static file server)',
+    '',
+  ].join('\n'),
+);
+
+console.log(`built -> ${dist}\n       ${stamp}`);

scripts/deploy-web.ts

@@ -0,0 +1,155 @@
+/**
+ * Build the solitaire site and push it to a File Browser instance.
+ *
+ * Written against File Browser v2.63's REST API, read from its own bundle rather than guessed:
+ *
+ *   POST /api/login                          {username, password, recaptcha} -> JWT as plain text
+ *   POST /api/resources/<dir>/               X-Auth: <jwt>                   -> create a directory
+ *   POST /api/resources/<file>?override=true X-Auth: <jwt>, body = bytes     -> upload
+ *
+ * File Browser is the STORE, not the server — Start9 Pages serves the uploaded folder as the site.
+ * So the job here is simply to land the built files in the right folder, intact.
+ *
+ * CREDENTIALS COME FROM THE ENVIRONMENT and are never written anywhere. Putting a password in a
+ * repo is how it ends up in a commit, and this repo is going to be pushed.
+ *
+ *   FB_USER=jesse FB_PASS='…' npm run deploy:web
+ *
+ * Optional:
+ *   FB_URL       default https://phoenix.local:58157
+ *   FB_DEST      default websites/stationmaster — the folder Start9 Pages serves from
+ *   FB_INSECURE  set to 1 for a self-signed certificate (usual for a .local StartOS host)
+ *   --dry-run    list what would be sent, contact nothing
+ */
+
+import { execFileSync } from 'node:child_process';
+import { readFileSync, readdirSync, statSync } from 'node:fs';
+import { dirname, join, posix, relative, sep } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const root = join(dirname(fileURLToPath(import.meta.url)), '..');
+const dist = join(root, 'dist');
+
+const URL_BASE = (process.env['FB_URL'] ?? 'https://phoenix.local:58157').replace(/\/+$/, '');
+const DEST = `/${(process.env['FB_DEST'] ?? 'websites/stationmaster').replace(/^\/+|\/+$/g, '')}`;
+const USER = process.env['FB_USER'] ?? '';
+const PASS = process.env['FB_PASS'] ?? '';
+const DRY = process.argv.includes('--dry-run');
+
+/**
+ * A .local StartOS host presents a certificate the system store does not know. Disabling
+ * verification is opt-in and announced rather than silent: it is the right call on a LAN box you
+ * own and the wrong one everywhere else, and that judgment is not the script's to make quietly.
+ */
+if (process.env['FB_INSECURE'] === '1') {
+  process.env['NODE_TLS_REJECT_UNAUTHORIZED'] = '0';
+  console.warn('! TLS verification disabled (FB_INSECURE=1)');
+}
+
+/** Every file in `dir`, as paths relative to it, with POSIX separators. */
+function walk(dir: string, base = dir): string[] {
+  const out: string[] = [];
+  for (const entry of readdirSync(dir)) {
+    const full = join(dir, entry);
+    if (statSync(full).isDirectory()) out.push(...walk(full, base));
+    else out.push(relative(base, full).split(sep).join('/'));
+  }
+  return out.sort();
+}
+
+const CONTENT_TYPES: Record<string, string> = {
+  '.html': 'text/html',
+  '.js': 'text/javascript',
+  '.css': 'text/css',
+  '.json': 'application/json',
+  '.txt': 'text/plain',
+};
+
+async function login(): Promise<string> {
+  const res = await fetch(`${URL_BASE}/api/login`, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({ username: USER, password: PASS, recaptcha: '' }),
+  });
+  const body = await res.text();
+  if (!res.ok) throw new Error(`login failed: ${res.status} ${body || res.statusText}`);
+  if (!body.trim()) throw new Error('login returned an empty token');
+  return body.trim();
+}
+
+async function makeDir(jwt: string, path: string): Promise<void> {
+  // Trailing slash is what marks a directory in this API. A 409 means it already exists, which is
+  // the normal case on every deploy after the first.
+  const res = await fetch(`${URL_BASE}/api/resources${encodePath(path)}/`, {
+    method: 'POST',
+    headers: { 'X-Auth': jwt },
+  });
+  if (!res.ok && res.status !== 409) {
+    throw new Error(`could not create ${path}: ${res.status} ${await res.text()}`);
+  }
+}
+
+async function upload(jwt: string, localPath: string, remotePath: string): Promise<void> {
+  const bytes = readFileSync(localPath);
+  const ext = remotePath.slice(remotePath.lastIndexOf('.'));
+  const res = await fetch(`${URL_BASE}/api/resources${encodePath(remotePath)}?override=true`, {
+    method: 'POST',
+    headers: {
+      'X-Auth': jwt,
+      'Content-Type': CONTENT_TYPES[ext] ?? 'application/octet-stream',
+      'Content-Length': String(bytes.byteLength),
+    },
+    body: new Uint8Array(bytes),
+  });
+  if (!res.ok) throw new Error(`upload ${remotePath} failed: ${res.status} ${await res.text()}`);
+}
+
+/** Encode each segment but keep the separators, so a path stays a path. */
+function encodePath(p: string): string {
+  return p.split('/').map(encodeURIComponent).join('/');
+}
+
+// ---------------------------------------------------------------------------
+
+console.log('building…');
+execFileSync('node', ['scripts/build-web.ts'], { cwd: root, stdio: 'inherit' });
+
+const files = walk(dist);
+if (files.length === 0) throw new Error('dist/ is empty — nothing to deploy');
+
+const dirs = [...new Set(files.map((f) => posix.dirname(f)).filter((d) => d !== '.'))].sort();
+const total = files.reduce((n, f) => n + statSync(join(dist, f)).size, 0);
+
+console.log(`\n${files.length} files, ${(total / 1024).toFixed(0)} KB`);
+console.log(`  from ${dist}`);
+console.log(`  to   ${URL_BASE}${DEST}\n`);
+
+if (DRY) {
+  for (const d of dirs) console.log(`  dir   ${DEST}/${d}`);
+  for (const f of files) console.log(`  file  ${DEST}/${f}`);
+  console.log('\ndry run — nothing was sent');
+} else {
+  if (!USER || !PASS) {
+    throw new Error(
+      'set FB_USER and FB_PASS.\n' +
+        "  e.g.  FB_USER=me FB_PASS='…' FB_INSECURE=1 npm run deploy:web\n" +
+        '  or run with --dry-run to see what would be sent',
+    );
+  }
+
+  const jwt = await login();
+  console.log('logged in');
+
+  await makeDir(jwt, DEST);
+  for (const d of dirs) await makeDir(jwt, `${DEST}/${d}`);
+
+  let done = 0;
+  for (const f of files) {
+    await upload(jwt, join(dist, f), `${DEST}/${f}`);
+    done++;
+    console.log(`  [${String(done).padStart(2)}/${files.length}] ${f}`);
+  }
+
+  console.log(`\ndeployed to ${URL_BASE}${DEST}`);
+  console.log('Start9 Pages serves these files as the site; File Browser is only the store.');
+}

src/engine/advance.ts

@@ -33,7 +33,7 @@ import {
 } from './content.ts';
 import type { Direction } from './content.ts';
 import type { GameEvent } from './events.ts';
-import { areaOf } from './apply.ts';
+import { acceptsCar, areaOf } from './apply.ts';
 import { legalActions } from './legal.ts';
 import type { CrewTray, DivisionNode, GameState, PlayerIndex, TrayId } from './state.ts';
 import { coordKey, freshTurn, totalRevenue } from './state.ts';
@@ -295,10 +295,9 @@ function trainNeedingCars(s: GameState): TrayId | null {
     if (tray.consist.length >= want) continue;
     // Consists are specified by CATEGORY — "Freight (2)" is any two freight cars — so any car in
     // the yard is potentially suitable unless the card narrows it.
-    const allowed = profile.consist.freightTypes;
+    // Ask the SAME predicate `check` uses. A separate copy of this test stalled the game: the phase
-    const suitable = s.yards.divisionYard.some(
+    // believed a car could be added while check rejected every option, so the Stage never ended.
-      (c) => c.type === 'caboose' || c.type === 'coach' || !allowed || allowed.includes(c.type),
+    const suitable = s.yards.divisionYard.some((c) => acceptsCar(tray, c.type));
-    );
     if (suitable) return id;
   }
   return null;

src/engine/apply.ts

@@ -27,12 +27,14 @@ import {
   modifierProfile,
   nextOfficeTier,
   officeProfile,
+  trainProfile,
 } from './content.ts';
 import type { CarType, FreightKind, Hand, MainlineKind, ModifierKind, TrackGeometry } from './content.ts';
 import type { GameEvent } from './events.ts';
 import type { Intent, RejectionCode } from './intents.ts';
 import type {
   CardId,
+  CrewTray,
   Facility,
   GameState,
   GridCoord,
@@ -468,7 +470,15 @@ export function check(s: GameState, player: PlayerIndex, i: Intent): RejectionCo
       if (!s.yards.divisionYard.some((c) => c.type === i.carType && c.loaded === i.loaded)) {
         return 'NO_SUITABLE_CAR';
       }
-      return null;
+
+      // §8.2 — "the train must be in the order listed on the train's card (engine on the front,
+      // Rolling Stock, and possibly a Caboose). It may depart with FEWER Rolling Stock than listed,
+      // but not out of order."
+      //
+      // This was not enforced at all: any car could be added in any quantity, so Train 9 "Heavy
+      // Freight" — a card calling for 3 freight AND a caboose — was made up with four hoppers and
+      // no caboose. Fewer is allowed; more, or of the wrong category, is not.
+      return acceptsCar(tray, i.carType) ? null : 'NO_SUITABLE_CAR';
     }
 
     case 'newTrain.secondSection': {
@@ -613,8 +623,15 @@ function checkPlay(
       // nothing, which is exactly the bug that made Modifiers dead weight for weeks.
       return 'NOT_IMPLEMENTED';
 
+    case 'timetabledTrain':
+    case 'extraTrain':
+      // A train card goes to the TIMETABLE, not onto the board. Accepting a placement made the UI
+      // offer the same play at six different grid squares with six rotations apiece — all identical,
+      // because the placement was then ignored. Same reasoning as the Office upgrade above: silently
+      // discarding a placement makes the event log claim the card was laid somewhere it was not.
+      return placement ? 'NO_PLACEMENT' : null;
+
     default:
-      // Train cards go to the timetable; the phase driver schedules them.
       return null;
   }
 }
@@ -1528,10 +1545,76 @@ function applyModifier(area: OfficeArea, coord: GridCoord, modifier: ModifierKin
 }
 
 /** §2.1, Gap 4a — extending the Running Track pushes the Limits sign outward. */
+/**
+ * §2.1 Gap 4a — "when you extend your Running Track, the Limits sign MOVES outwards with it".
+ *
+ * The sign is a physical card, not just a recorded column. Moving only the coordinate left the
+ * Limits card stranded mid-track: a district grew to
+ *   (0,-5) (0,-4) (0,-3) (0,-2)=Power Plant [LIMITS] (0,0)=Office [LIMITS] (0,2)=Freight House …
+ * with everything beyond (0,-2) built OUTSIDE a sign that never moved. That is not cosmetic —
+ * §8.1 and §10 both reason about "the track between the train and the Limits", Interlocking holds
+ * an arrival AT the Limits, and running past a player's Limits is what makes a collision his fault.
+ */
 function extendLimitsIfNeeded(area: OfficeArea, placed: GridCoord): void {
   if (placed.row !== area.runningRow) return;
-  if (placed.col <= area.limitsWest.col) area.limitsWest = { row: placed.row, col: placed.col - 1 };
+
-  if (placed.col >= area.limitsEast.col) area.limitsEast = { row: placed.row, col: placed.col + 1 };
+  if (placed.col <= area.limitsWest.col) {
+    area.limitsWest = { row: placed.row, col: placed.col - 1 };
+    area.grid.set(coordKey(area.limitsWest), limitsCard());
+  }
+  if (placed.col >= area.limitsEast.col) {
+    area.limitsEast = { row: placed.row, col: placed.col + 1 };
+    area.grid.set(coordKey(area.limitsEast), limitsCard());
+  }
+}
+
+/**
+ * §8.2 — may this car be coupled onto this train right now?
+ *
+ * "The train must be in the order listed on the train's card (engine on the front, Rolling Stock,
+ * and possibly a Caboose). It may depart with FEWER Rolling Stock than listed, but not out of
+ * order." Fewer is allowed; more, or of the wrong category, is not.
+ *
+ * SHARED. Both `check` and the New Train Phase's "is there a suitable car in the yard" test call
+ * this. A second copy stalled the game outright: the phase believed a car could be added while
+ * `check` rejected every option, so the Stage never completed.
+ */
+export function acceptsCar(tray: CrewTray, carType: CarType): boolean {
+  const profile = trainProfile(tray.trainNumber ?? 0, tray.trainIsExtra);
+  if (!profile) return true;
+
+  const cat = (t: CarType): 'coach' | 'caboose' | 'freight' =>
+    t === 'coach' ? 'coach' : t === 'caboose' ? 'caboose' : 'freight';
+  const adding = cat(carType);
+  const already = tray.consist.filter((c) => cat(c.type) === adding).length;
+  const allowed =
+    adding === 'coach'
+      ? profile.consist.coach
+      : adding === 'caboose'
+        ? profile.consist.caboose
+        : profile.consist.freight;
+  if (already >= allowed) return false;
+
+  // The caboose rides last (§A.3), so nothing may be coupled behind one.
+  if (adding !== 'caboose' && tray.consist.some((c) => c.type === 'caboose')) return false;
+
+  // The card also narrows WHICH freight types it will take.
+  const types = profile.consist.freightTypes;
+  if (adding === 'freight' && types && !types.includes(carType)) return false;
+
+  return true;
+}
+
+/** A fresh Limits sign. The set is "2N + spares" (§12), so relocating one is not a supply question. */
+function limitsCard(): TrackCard {
+  return {
+    geometry: { kind: 'limits' },
+    baseOperationalRail: true,
+    standing: [],
+    facility: null,
+    modifiers: [],
+    enhancements: [],
+  };
 }
 
 // ---------------------------------------------------------------------------

src/engine/legal.ts

@@ -252,7 +252,11 @@ function placementCandidates(s: GameState, player: PlayerIndex): GridCoord[] {
       // Q7 — a district hangs BELOW the Running Track; there is nothing above it.
       if (c.row > area.runningRow) continue;
       const k = `${c.row},${c.col}`;
-      if (area.grid.has(k) || seen.has(k)) continue;
+      if (seen.has(k)) continue;
+      // The Limits signs are candidates even though they are occupied: laying track there is how
+      // the Running Track grows, and the sign moves outward (§2.1). `check` still has the final say.
+      const occupied = area.grid.get(k);
+      if (occupied && !(occupied.geometry.kind === 'limits' && c.row === area.runningRow)) continue;
       seen.add(k);
       out.push(c);
     }

src/engine/track.ts

@@ -330,7 +330,16 @@ export function allReachable(
  * stubs above and below so this is satisfiable from the opening Stage.
  */
 export function canPlaceAt(area: OfficeArea, coord: GridCoord, card: TrackCard): boolean {
-  if (cardAt(area, coord)) return false;
+  const existing = cardAt(area, coord);
+  // A Limits sign on the Running Track is the GROWTH POINT, not an obstacle. Extending means laying
+  // the card where the sign stands and moving the sign outward (§2.1, Gap 4a) — the physical act at
+  // the table. Treating the sign as occupied forced players to build PAST it, stranding the sign
+  // mid-track with everything beyond it nominally outside their own Limits.
+  const isMovableSign =
+    existing?.geometry.kind === 'limits' &&
+    coord.row === area.runningRow &&
+    existing.standing.length === 0;
+  if (existing && !isMovableSign) return false;
 
   const ports: Port[] = ['n', 's', 'e', 'w'];
   for (const p of ports) {

src/sim/bot.ts

@@ -56,17 +56,37 @@ function ruleOnClearance(options: Intent[]): Intent | null {
 
 // ---------------------------------------------------------------------------
 
+/**
+ * Why the developer bot made its last choice, for the replay's decision panel.
+ *
+ * WRITE-ONLY DIAGNOSTIC. Nothing reads this to make a decision, so it cannot affect play or
+ * determinism — it exists so the viewer can show the branch that fired instead of re-deriving the
+ * reasoning, which would drift from the bot exactly as a second copy of the rules would.
+ */
+let lastReason = '';
+
+export function lastChoiceReason(): string {
+  return lastReason;
+}
+
+/** Records the branch that fired and returns the intent unchanged. */
+function because(reason: string, intent: Intent): Intent {
+  lastReason = reason;
+  return intent;
+}
+
 export const developerBot: BotPolicy = {
   name: 'developer',
 
   choose(s, player, options) {
+    lastReason = 'no specific reason — first legal option';
     const clearance = ruleOnClearance(options);
-    if (clearance) return clearance;
+    if (clearance) return because('the Superintendent must rule on a following train (§8.1)', clearance);
 
     // Red Flags come before anything else — protection is only worth playing at the moment the
     // collision is actually pending, and that moment passes.
     const flags = worthFlagging(s, options);
-    if (flags) return flags;
+    if (flags) return because('a train of ours is stopped on a Mainline card with another train on it — Red Flags now or not at all', flags);
 
     // --- Load/Unload: spend every worker, then end. Each is a point, or a step toward one.
     //
@@ -87,7 +107,8 @@ export const developerBot: BotPolicy = {
       // jam costs a Freight Agent action to clear AND locks the industry track until it is cleared.
       // A first attempt kept a last-resort `startLoad` here "rather than idle", and the measured
       // result was identical to having no gate at all — 415 starts, 413 unjams, 13 completions.
-      return work ?? options.find((i) => i.type === 'loadUnload.end') ?? options[0]!;
+      if (work) return because(loadReason(work), work);
+      return because('every worker is spent or has nothing it can finish', options.find((i) => i.type === 'loadUnload.end') ?? options[0]!);
     }
 
     // --- New Train: fill the consist, but with the RIGHT cars.
@@ -102,9 +123,9 @@ export const developerBot: BotPolicy = {
         const match = options.find(
           (i) => i.type === 'newTrain.placeCar' && i.carType === w.type && i.loaded === w.loaded,
         );
-        if (match) return match;
+        if (match) return because(`the ${w.loaded ? 'loaded' : 'empty'} ${w.type} is what a facility is short of`, match);
       }
-      return pickFirst(options, 'newTrain.placeCar', 'newTrain.passCar') ?? options[0]!;
+      return because('no car on offer is one our facilities need', pickFirst(options, 'newTrain.placeCar', 'newTrain.passCar') ?? options[0]!);
     }
 
     // --- Local Operations.
@@ -140,43 +161,51 @@ function chooseLocalOption(s: GameState, player: PlayerIndex, options: Intent[])
   // An Office upgrade outranks even a train card: a train that arrives with nowhere to stand is a
   // collision, and collisions are the largest single drain on revenue.
   if (can('draw') && hand.some((id) => s.cards.get(id)?.kind.kind === 'office')) {
-    return can('draw')!;
+    return because('an Office upgrade is in hand — more A/D track means fewer collisions', can('draw')!);
   }
 
-  if (can('draw') && hand.some((id) => isTrainCard(s, id))) return can('draw')!;
+  if (can('draw') && hand.some((id) => isTrainCard(s, id))) {
+    return because('a train card is in hand and its value compounds every Day', can('draw')!);
+  }
 
   // A Mainline modifier is worth the option too: Realignment permanently converts a 30 card into a
   // 60, and Helpers/Brakeman take a Stage off every future crossing. Like a train card, the value
   // compounds — but only if it can be laid right now, so check for a legal target rather than for
   // the card sitting in hand.
-  if (can('draw') && options.some((i) => i.type === 'mainline.modify')) return can('draw')!;
+  if (can('draw') && options.some((i) => i.type === 'mainline.modify')) {
+    return because('a Mainline modifier can be laid — every later crossing pays less', can('draw')!);
+  }
 
   // 2. A train standing at the Office is a fleeting chance to spot cars — but ONLY if there is
   //    actually a car to spot or collect. Choosing to switch merely because a train is present
   //    wasted the whole Local Operations action shuttling back and forth: a passenger train needs
   //    no switching at all, because §9.2 works coaches straight off the A/D track.
   if (can('switch') && area.adOccupancy.length > 0 && usefulSwitching(s, player)) {
-    return can('switch')!;
+    return because('a train is at the Office and there is switching worth doing', can('switch')!);
   }
 
   // A crew stranded away from the Office is worth a whole turn on its own. A train may only
   // highball from the Office square, so one sitting anywhere else is out of the game permanently —
   // and the condition above never fires for it, because a crew down in the district has no work
   // left and would never claim the option needed to walk back.
-  if (can('switch') && strandedFromOffice(s, player)) return can('switch')!;
+  if (can('switch') && strandedFromOffice(s, player)) {
+    return because('the crew is away from the Office and can never depart from where it stands', can('switch')!);
+  }
 
   // 3. Stock a green box only when the load can actually finish — an empty car of the right type
   //    is already spotted. Stocking without one just fills the box.
-  if (can('freightAgent') && canStockProductively(s, player)) return can('freightAgent')!;
+  if (can('freightAgent') && canStockProductively(s, player)) {
+    return because('a green box can be stocked with a load that can actually finish', can('freightAgent')!);
+  }
 
   // 4. Rescue a jammed facility, or clear a full red box blocking further unloading.
   if (can('freightAgent') && (hasStuckLoad(s, player) || needsClearing(s, player))) {
-    return can('freightAgent')!;
+    return because('a facility is jammed or its red box is full, blocking the pipeline', can('freightAgent')!);
   }
 
   // 5. Otherwise develop. More facilities and a bigger Office are what make later Stages pay.
-  if (can('draw')) return can('draw')!;
+  if (can('draw')) return because('nothing urgent — develop the district instead', can('draw')!);
-  return can('freightAgent') ?? can('switch') ?? choices[0] ?? options[0]!;
+  return because('no option has a clear purpose this turn', can('freightAgent') ?? can('switch') ?? choices[0] ?? options[0]!);
 }
 
 /** A face-up card worth spending the draw on rather than gambling on the deck. */
@@ -317,6 +346,24 @@ function worthFlagging(s: GameState, options: Intent[]): Intent | null {
   return null;
 }
 
+/** A one-line account of which Load/Unload action was taken, and why it ranked first. */
+function loadReason(i: Intent): string {
+  switch (i.type) {
+    case 'porter.board':
+      return 'a Porter earns a point in ONE action — always the best use of a worker';
+    case 'porter.detrain':
+      return 'detraining passengers is a point for a single Porter action';
+    case 'laborer.advanceLoad':
+      return 'finish work already started — a load parked on WORK locks the industry track';
+    case 'laborer.startLoad':
+      return 'a matching empty car is spotted, so this load can actually finish';
+    case 'laborer.beginUnload':
+      return 'a loaded car is spotted and the red box has room';
+    default:
+      return 'the best remaining use of a worker';
+  }
+}
+
 /**
  * Is there already an empty car of the right type spotted to receive this load (§9.3)? Without one
  * the load can be started and walked across MEN|AT|WORK but can never come off.
@@ -376,11 +423,11 @@ function followThrough(s: GameState, player: PlayerIndex, options: Intent[]): In
         const useful = options.find(
           (i) => i.type === 'draw.fromDepartment' && isWorthTaking(s, i.slot),
         );
-        if (useful) return useful;
+        if (useful) return because('a face-up card is worth more than a blind draw right now', useful);
         const blind = options.find((i) => i.type === 'draw.fromHomeOffice');
-        if (blind) return blind;
+        if (blind) return because('no face-up card is worth taking — gamble on the deck', blind);
         const any = options.find((i) => i.type === 'draw.fromDepartment');
-        if (any) return any;
+        if (any) return because('the deck is empty, so take a face-up card', any);
       }
       // UPGRADE THE OFFICE FIRST. A Whistle Post has ONE A/D track, so a second arrival is an
       // automatic collision (§8.3, Gap 2a) — and measured, 25 of 26 collisions happened at Whistle
@@ -391,13 +438,13 @@ function followThrough(s: GameState, player: PlayerIndex, options: Intent[]): In
       const upgrade = options.find(
         (i) => i.type === 'card.play' && s.cards.get(i.cardId)?.kind.kind === 'office',
       );
-      if (upgrade) return upgrade;
+      if (upgrade) return because('upgrade the Office — a Whistle Post has ONE A/D track and a second arrival collides', upgrade);
 
       // Train cards next — they take no placement and their value compounds every Day.
       const train = options.find(
         (i) => i.type === 'card.play' && i.placement === undefined && isTrainCard(s, i.cardId),
       );
-      if (train) return train;
+      if (train) return because('a scheduled train runs every Day thereafter — the only card whose value compounds', train);
 
       // Mainline modifiers rank with train cards: every train that crosses afterwards pays the
       // lower price. Realignment first — converting Curves to Plains halves the crossing for
@@ -405,9 +452,9 @@ function followThrough(s: GameState, player: PlayerIndex, options: Intent[]): In
       const realign = options.find(
         (i) => i.type === 'mainline.modify' && isMainlineKey(s, i.cardId, 'realignment'),
       );
-      if (realign) return realign;
+      if (realign) return because('Realignment converts this Mainline card into a faster one for every future crossing', realign);
       const grade = options.find((i) => i.type === 'mainline.modify');
-      if (grade) return grade;
+      if (grade) return because('a grade modifier takes a Stage off every crossing in that direction', grade);
 
       // Enhancements next: Small Yard makes switching solvable, Interlocking stops the Office
       // overflowing into a collision, and the dispatch devices win meets. All are worth more than
@@ -420,12 +467,12 @@ function followThrough(s: GameState, player: PlayerIndex, options: Intent[]): In
           i.placement !== undefined &&
           isEnhancementKey(s, i.cardId, 'interlocking'),
       );
-      if (interlock) return interlock;
+      if (interlock) return because('Interlocking holds an arrival at the Limits instead of colliding into a full Office', interlock);
 
       const enh = options.find(
         (i) => i.type === 'card.play' && i.placement !== undefined && isEnhancement(s, i.cardId),
       );
-      if (enh) return enh;
+      if (enh) return because('an Enhancement is permanent and changes how the district works', enh);
 
       // Lay track before spending a card on the grid. Track is the scarce enabler, not the
       // consolation prize: nothing else in the deck can create the Running-Track and Secondary-Track
@@ -433,16 +480,16 @@ function followThrough(s: GameState, player: PlayerIndex, options: Intent[]): In
       // district exists. Measured with track absent, the hand held a playable Enhancement on 4,778
       // turns and could legally place one on 33.
       const track = bestTrackLay(s, player, options);
-      if (track) return track;
+      if (track) return because('lay track — nothing else creates the straights Enhancements need or the spurs freight needs', track);
 
       // Then real development: a card actually laid into the grid.
       const placed = options.find((i) => i.type === 'card.play' && i.placement !== undefined);
-      if (placed) return placed;
+      if (placed) return because('develop the district with a card that goes on the board', placed);
       const play = options.find((i) => i.type === 'card.play');
-      if (play) return play;
+      if (play) return because('play what is in hand', play);
       const end = options.find((i) => i.type === 'draw.end');
-      if (end) return end;
+      if (end) return because('nothing in hand can be played anywhere legal', end);
-      return pickFirst(options, 'card.discard') ?? options[0]!;
+      return because('nothing playable and nothing to draw — discard to a Department slot', pickFirst(options, 'card.discard') ?? options[0]!);
     }
 
     case 'switch': {
@@ -457,7 +504,7 @@ function followThrough(s: GameState, player: PlayerIndex, options: Intent[]): In
           i.count === 1 &&
           facilityWantsAt(s, player, i.to, trayOf(s, player)?.consist.slice(-1)[0]),
       );
-      if (flyingFirst) return flyingFirst;
+      if (flyingFirst) return because('a Flying Switch rolls the back car straight into an industry that wants it', flyingFirst);
 
       if (!usefulSwitching(s, player)) {
         // GO HOME. A train may only highball from the Office square itself (§8.1, Gap 2b) — from
@@ -467,9 +514,9 @@ function followThrough(s: GameState, player: PlayerIndex, options: Intent[]): In
         // the wrong column and 43 down in the district. A parked train earns nothing, holds its A/D
         // track, and is unavailable for the next load.
         const home = moveTowardOffice(s, player, options);
-        if (home) return home;
+        if (home) return because('no switching left worth doing — head back to the Office so the train can depart', home);
         const stop = options.find((i) => i.type === 'switch.end');
-        if (stop) return stop;
+        if (stop) return because('no switching left worth doing, and the crew is already at the Office', stop);
       }
 
       // Spotting the RIGHT car at the RIGHT facility is the whole point of switching.
@@ -499,7 +546,7 @@ function followThrough(s: GameState, player: PlayerIndex, options: Intent[]): In
             const sort = options.find(
               (i) => i.type === 'switch.sortConsist' && i.order.join() === order.join(),
             );
-            if (sort) return sort;
+            if (sort) return because('standing on a Small Yard — re-order so a car a facility wants ends up droppable', sort);
           }
         }
       }
@@ -512,7 +559,7 @@ function followThrough(s: GameState, player: PlayerIndex, options: Intent[]): In
         // Standing on a facility that wants the back car: put it down. This is the payoff move.
         if (hereFacility && facilityWants(hereFacility, endCar)) {
           const drop = options.find((i) => i.type === 'switch.dropCars' && i.count === 1);
-          if (drop) return drop;
+          if (drop) return because('standing on a facility that wants the back car — spot it', drop);
         }
 
         // SET OUT — and do it BEFORE travelling.
@@ -538,7 +585,14 @@ function followThrough(s: GameState, player: PlayerIndex, options: Intent[]): In
           const isSpur = here.row !== area.runningRow && !hereFacility;
           if (isSpur) {
             const setOut = options.find((i) => i.type === 'switch.dropCars' && i.count === 1);
-            if (setOut) return setOut;
+            if (setOut) {
+              return because(
+                tray.consist.length >= MAX_CONSIST
+                  ? 'the tray is full, so nothing can be coupled — set a car out here'
+                  : 'the back car is dead weight hiding a car a facility wants — set it out to expose it',
+                setOut,
+              );
+            }
           }
           const toSpur = options.find(
             (i) =>
@@ -546,7 +600,7 @@ function followThrough(s: GameState, player: PlayerIndex, options: Intent[]): In
               i.to.row !== area.runningRow &&
               !area.grid.get(`${i.to.row},${i.to.col}`)?.facility,
           );
-          if (toSpur) return toSpur;
+          if (toSpur) return because('looking for a plain spur to set out on — an industry track would silt with the wrong commodity', toSpur);
         }
 
         // Now travel — to a facility that wants SOMETHING aboard, not only the back car. Weighing
@@ -562,7 +616,7 @@ function followThrough(s: GameState, player: PlayerIndex, options: Intent[]): In
             i.type === 'switch.move' &&
             wanted.some((t) => t.row === i.to.row && t.col === i.to.col),
         );
-        if (toward) return toward;
+        if (toward) return because('heading for a facility that wants a car we are carrying', toward);
       }
 
       // Never take an arbitrary Move. Picking "the first legal move" is what produced the original
@@ -571,8 +625,8 @@ function followThrough(s: GameState, player: PlayerIndex, options: Intent[]): In
       // Moves oscillating between two cells. If there is no move with a purpose, the only useful
       // thing left is to head for the Office, because a train that is not on it can never depart.
       const goHome = moveTowardOffice(s, player, options);
-      if (goHome) return goHome;
+      if (goHome) return because('nothing productive left — head for the Office rather than shuttle aimlessly', goHome);
-      return options.find((i) => i.type === 'switch.end') ?? options[0]!;
+      return because('out of useful switching moves', options.find((i) => i.type === 'switch.end') ?? options[0]!);
     }
 
     case 'freightAgent': {
@@ -581,13 +635,13 @@ function followThrough(s: GameState, player: PlayerIndex, options: Intent[]): In
       // rescue it. §6.3's unjam exists for exactly this. Clear it before anything else.
       if (hasStuckLoad(s, player)) {
         const unjam = options.find((i) => i.type === 'freightAgent.unjam' && i.from === 'menAtWork');
-        if (unjam) return unjam;
+        if (unjam) return because('a jammed load blocks the pipeline AND strips the industry track of Operational Rail', unjam);
       }
       const clear = options.find((i) => i.type === 'freightAgent.clearInbound');
-      if (clear) return clear;
+      if (clear) return because('the red Inbound box is full and blocking further unloading', clear);
       const stock = options.find((i) => i.type === 'freightAgent.stockOutbound');
-      if (stock) return stock;
+      if (stock) return because('stock a green box so a Laborer has work next Stage', stock);
-      return pickFirst(options, 'freightAgent.unjam') ?? options[0]!;
+      return because('nothing productive at any facility — clear whatever is stuck', pickFirst(options, 'freightAgent.unjam') ?? options[0]!);
     }
 
     default:

src/sim/narrate.ts

@@ -34,6 +34,9 @@ export function clockTime(stage: number): string {
 }
 
 export function carLabel(c: RollingStock): string {
+  // A caboose carries the crew, not freight, so "loaded caboose" is nonsense on the page even
+  // though the supply marks every caboose loaded. Name it plainly.
+  if (c.type === 'caboose') return 'caboose';
   return `${c.loaded ? 'loaded' : 'empty'} ${c.type}`;
 }
 

src/sim/replay.ts

@@ -23,263 +23,24 @@ import { applyIntent, areaOf, facilityCarType, laborersLeft, portersLeft } from
 import type { GameLength } from '../engine/content.ts';
 import { MAINLINE_PROFILES, lengthProfile, officeProfile } from '../engine/content.ts';
 import type { GameEvent } from '../engine/events.ts';
+import type { Intent } from '../engine/intents.ts';
 import { legalActions } from '../engine/legal.ts';
 import { createGame } from '../engine/setup.ts';
-import type { GameConfig, GameState } from '../engine/state.ts';
+import type { Facility, GameConfig, GameState } from '../engine/state.ts';
-import { developerBot } from './bot.ts';
+import { developerBot, lastChoiceReason } from './bot.ts';
-import type { Impediment } from './narrate.ts';
+import { carLabel, idleNote, isVisible, narrate } from './narrate.ts';
-import { carLabel, clockTime, idleNote, impediments, isVisible, narrate, phaseLabel } from './narrate.ts';
+// The view-model lives in its own module so the browser build can import it without dragging in
+// this file's Node dependencies. Re-exported because tests and the web app import it from here.
+export type { CellView, DivisionView, FacilityView, Frame, Decision, TrainChip } from './view.ts';
+export { cardName, describeIntent, snapshot } from './view.ts';
+import type { Frame } from './view.ts';
+import type { Decision } from './view.ts';
+import { cardName, describeDecision, snapshot } from './view.ts';
 
 // ---------------------------------------------------------------------------
 // Frame shape — only what the viewer draws
 // ---------------------------------------------------------------------------
 
-export type CellView = {
-  row: number;
-  col: number;
-  kind: string;
-  label: string;
-  running: boolean;
-  tray: string | null;
-  cars: string[];
-  facility: FacilityView | null;
-};
-
-export type FacilityView = {
-  name: string;
-  commodity: string;
-  flow: string;
-  green: string[];
-  greenCap: number;
-  maw: (string | null)[];
-  red: string[];
-  redCap: number;
-  track: string[];
-  trackCap: number;
-  laborers: string;
-  porters: string;
-};
-
-export type TrainChip = { label: string; consist: string[] };
-export type DivisionView = { kind: string; label: string; trains: TrainChip[][] };
-
-export type Frame = {
-  day: number;
-  stage: number;
-  clock: string;
-  phase: string;
-  actor: number | null;
-  superintendent: number;
-  revenue: number;
-  lines: { text: string; tone: string }[];
-  where: { row: number; col: number } | null;
-  /** Origin of a Move, so the crew's journey is visible rather than a chip teleporting. */
-  whereFrom: { row: number; col: number } | null;
-  division: DivisionView[];
-  cells: CellView[];
-  facilities: FacilityView[];
-  hand: string[];
-  deck: number;
-  departments: string[];
-  /** 12 slots; the train number due out at each Stage, or null. */
-  timetable: (number | null)[];
-  blocked: Impediment[];
-  trains: { label: string; where: string }[];
-};
-
-// ---------------------------------------------------------------------------
-// Snapshotting
-// ---------------------------------------------------------------------------
-
-const FACILITY_NAMES: Record<string, string> = {
-  mineTipple: 'Mine Tipple',
-  produceShed: 'Produce Shed',
-  grocersWarehouse: "Grocer's Warehouse",
-  oilRefinery: 'Oil Refinery',
-  powerPlant: 'Power Plant',
-};
-
-function facilityView(
-  card: { geometry: { kind: string; facility?: string }; facility: unknown },
-  officeName: string,
-): FacilityView | null {
-  const f = (card as { facility: import('../engine/state.ts').Facility | null }).facility;
-  // Passenger facilities were excluded entirely, so the Office's green and red slots never
-  // appeared — which is why stocking a coach into the green box looked like nothing happening.
-  if (!f) return null;
-  if (f.kind === 'passenger' && f.porters === 0 && f.capacity.outbound === 0) return null;
-  const key = card.geometry.kind === 'facility' ? (card.geometry.facility ?? '') : '';
-  return {
-    name: f.kind === 'passenger' ? officeName + ' (passengers)' : (FACILITY_NAMES[key] ?? key),
-    commodity: facilityCarType(f) ?? '?',
-    flow: f.kind === 'passenger'
-      ? 'passengers on and off'
-      : f.allows.outbound && f.allows.inbound ? 'both' : f.allows.outbound ? 'ships out' : 'receives',
-    green: f.outboundBox.map(carLabel),
-    greenCap: f.capacity.outbound,
-    maw: f.menAtWork.map((l) => (l ? `${l.type} ${l.dir === 'out' ? '→' : '←'}` : null)),
-    red: f.inboundBox.map(carLabel),
-    redCap: f.capacity.inbound,
-    track: f.industryTrack.cars.map(carLabel),
-    trackCap: f.industryTrack.length,
-    laborers: `${laborersLeft(f)}/${f.laborers}`,
-    porters: `${portersLeft(f)}/${f.porters}`,
-  };
-}
-
-function snapshot(
-  s: GameState,
-  lines: { text: string; tone: string }[],
-  where: { row: number; col: number } | null,
-  whereFrom: { row: number; col: number } | null = null,
-): Frame {
-  const area = areaOf(s, 0);
-  const trayAt = new Map<string, string>();
-  for (const [id, tray] of s.trays) {
-    if (tray.position.at === 'grid') {
-      const label = tray.trainNumber === null ? 'crew' : `T${tray.trainIsExtra ? 'X' : ''}${tray.trainNumber}`;
-      const carrying = tray.consist.length ? ` [${tray.consist.map(carLabel).join(', ')}]` : ' [empty]';
-      trayAt.set(`${tray.position.coord.row},${tray.position.coord.col}`, label + carrying);
-    }
-  }
-
-  const cells: CellView[] = [];
-  const facilities: FacilityView[] = [];
-  for (const [key, card] of area.grid) {
-    const [row, col] = key.split(',').map(Number);
-    const g = card.geometry;
-    const kind = g.kind;
-    let label: string;
-    if (g.kind === 'office') label = officeProfile(area.tier).name;
-    else if (g.kind === 'limits') label = 'Limits';
-    else if (g.kind === 'facility') label = FACILITY_NAMES[g.facility] ?? g.facility;
-    else if (g.kind === 'modifier') label = MODIFIER_NAMES[g.modifier] ?? g.modifier;
-    else if (g.kind === 'spaceUse') label = prettyKey(g.key);
-    else label = g.geometry === 'sharpCurved' ? 'sharp curve' : g.geometry;
-
-    const fv = facilityView(card as never, officeProfile(area.tier).name);
-    if (fv) facilities.push(fv);
-
-    cells.push({
-      row: row!,
-      col: col!,
-      kind,
-      label,
-      running: row === area.runningRow,
-      tray: trayAt.get(key) ?? null,
-      cars: (card.facility?.industryTrack.length ? card.facility.industryTrack.cars : card.standing).map(carLabel),
-      facility: fv,
-    });
-  }
-
-  const division: DivisionView[] = s.division.nodes.map((n) => {
-    if (n.kind === 'divisionPoint') {
-      return {
-        kind: 'dp',
-        label: n.side === 'west' ? 'West DP' : 'East DP',
-        trains: [n.holding.map((id) => trainChip(s, id))],
-      };
-    }
-    if (n.kind === 'mainline') {
-      // Crossing time is in Stages now, so a Mainline card shows its terrain and the trains on it
-      // with how long each still has to run.
-      const name = MAINLINE_PROFILES.find((m) => m.kind === n.card)?.name ?? n.card;
-      return {
-        kind: 'ml',
-        label: name,
-        trains: [n.transits.map((t) => {
-          const chip = trainChip(s, t.tray);
-          return { ...chip, label: `${chip.label} (${t.stagesRemaining})` };
-        })],
-      };
-    }
-    return {
-      kind: 'office',
-      label: officeProfile(areaOf(s, n.owner).tier).name,
-      trains: [areaOf(s, n.owner).adOccupancy.map((id) => trainChip(s, id))],
-    };
-  });
-
-  return {
-    day: s.clock.day,
-    stage: s.clock.stage,
-    clock: clockTime(s.clock.stage),
-    phase: phaseLabel(s.clock.phase),
-    actor: s.clock.currentActor,
-    superintendent: s.clock.superintendent,
-    revenue: s.players[0]?.revenue ?? 0,
-    lines,
-    where,
-    whereFrom,
-    division,
-    cells,
-    facilities,
-    hand: (s.decks.hands.get(0) ?? []).map((id) => cardName(s, id)),
-    deck: s.decks.homeOffice.length,
-    departments: s.decks.departments.map((id) => (id ? cardName(s, id) : '—')),
-    timetable: [...s.timetable],
-    blocked: impediments(s, 0),
-    trains: [...s.trays.values()].map((t) => ({
-      label: t.trainNumber === null ? 'local crew' : `Train ${t.trainIsExtra ? 'X' : ''}${t.trainNumber}`,
-      where:
-        t.position.at === 'divisionPoint'
-          ? `${t.position.side} Division Point`
-          : t.position.at === 'mainline'
-            ? `Mainline card ${t.position.index}`
-            : `Office Area (${t.position.coord.row},${t.position.coord.col})`,
-    })),
-  };
-}
-
-/** A card id turned into something a person can read. */
-export function cardName(s: GameState, id: string): string {
-  const k = s.cards.get(id)?.kind;
-  if (!k) return 'a card';
-  switch (k.kind) {
-    case 'timetabledTrain':
-      return `Train ${k.number}`;
-    case 'extraTrain':
-      return `Extra X${k.number}`;
-    case 'office':
-      return `${k.tier.replace(/([A-Z])/g, ' $1').replace(/^./, (c) => c.toUpperCase())} upgrade`;
-    case 'freightFacility':
-      return FACILITY_NAMES[k.facility] ?? k.facility;
-    case 'modifier':
-      return MODIFIER_NAMES[k.modifier] ?? k.modifier;
-    case 'track':
-      return k.geometry === 'sharpCurved' ? 'Sharp curve' : `${k.geometry} track`;
-    case 'spaceUse':
-    case 'enhancement':
-    case 'mainlineModifier':
-    case 'maneuver':
-    case 'action':
-      return prettyKey(k.key);
-  }
-}
-
-/** camelCase key → readable name, for the card categories that carry only a key. */
-function prettyKey(key: string): string {
-  return key.replace(/([A-Z])/g, ' $1').replace(/^./, (c) => c.toUpperCase());
-}
-
-const MODIFIER_NAMES: Record<string, string> = {
-  teamTrack: 'Team Track',
-  loadingDock: 'Loading Dock',
-  storageShed: 'Storage Shed',
-  extraPlatform: 'Extra Platform',
-  sectionGang: 'Section Gang',
-};
-
-/** A train on the board, with what it is carrying — otherwise a run looks identical empty or full. */
-function trainChip(s: GameState, id: string): TrainChip {
-  const t = s.trays.get(id);
-  if (!t) return { label: id, consist: [] };
-  return {
-    label: t.trainNumber === null ? 'crew' : `T${t.trainIsExtra ? 'X' : ''}${t.trainNumber}`,
-    consist: t.consist.map(carLabel),
-  };
-}
-
 // ---------------------------------------------------------------------------
 // Recording
 // ---------------------------------------------------------------------------
@@ -304,6 +65,8 @@ export function record(seed: number, length: GameLength, maxSteps = 100_000): Re
 
   // Tracks whether a phase did anything, so an empty one can say so rather than ending silently.
   let didSomething = false;
+  // The choice that produced the events about to be pushed.
+  let pendingDecision: Decision | null = null;
 
   const push = (events: GameEvent[]): void => {
     const visible = events.filter(isVisible);
@@ -328,7 +91,16 @@ export function record(seed: number, length: GameLength, maxSteps = 100_000): Re
     const where = visible.map((e) => narrate(e, narrateCtx)).find((n) => n.where)?.where ?? null;
     const moved = visible.find((e) => e.type === 'trayMoved');
     const from = moved && moved.type === 'trayMoved' ? moved.from : null;
-    frames.push(snapshot(s, lines, where ?? null, from));
+    const d = pendingDecision;
+    pendingDecision = null;
+    // A Local Operations turn that ended with nothing but the turn ending is a wasted action —
+    // six Moves and a card play spent on nothing. Among 600+ frames these are invisible unless
+    // marked, and they are the ones worth reviewing.
+    const wasted =
+      d !== null &&
+      (d.chose === 'switch.end' || d.chose === 'draw.end' || d.chose === 'loadUnload.end') &&
+      visible.every((e) => e.type === 'phaseEnded' || e.type === 'actorChanged');
+    frames.push(snapshot(s, lines, where ?? null, from, d, wasted));
   };
 
   frames.push(
@@ -345,8 +117,11 @@ export function record(seed: number, length: GameLength, maxSteps = 100_000): Re
     if (actor === null) break;
     const options = legalActions(s, actor);
     if (options.length === 0) break;
-    const applied = applyIntent(s, actor, developerBot.choose(s, actor, options));
+    const chosen = developerBot.choose(s, actor, options);
+    const decision = describeDecision(s, actor, chosen, options, lastChoiceReason());
+    const applied = applyIntent(s, actor, chosen);
     if (!applied.ok) break;
+    pendingDecision = decision;
     push(applied.events);
   }
 
@@ -363,6 +138,27 @@ export function record(seed: number, length: GameLength, maxSteps = 100_000): Re
 // HTML
 // ---------------------------------------------------------------------------
 
+/**
+ * Drop repeated board state from the serialised frames.
+ *
+ * Only the wire format changes: `record()` still returns complete frames, so tests and any other
+ * consumer are unaffected. The page resolves a null by walking back to the last frame that carried
+ * the field.
+ */
+function compress(frames: Frame[]): unknown[] {
+  const keys = ['cells', 'facilities', 'division'] as const;
+  let prev: Record<string, string> = {};
+  return frames.map((f, i) => {
+    const out: Record<string, unknown> = { ...f };
+    for (const k of keys) {
+      const json = JSON.stringify(f[k]);
+      if (i > 0 && prev[k] === json) out[k] = null;
+      prev[k] = json;
+    }
+    return out;
+  });
+}
+
 export function renderHtml(rec: Recording): string {
   const target = lengthProfile(rec.length);
   return `<!doctype html>
@@ -432,6 +228,21 @@ kbd{background:#2a3038;border:1px solid var(--line);border-radius:3px;padding:0
 .mini .box{padding:0 4px;font-size:9.5px}
 .cell.office{border-color:var(--clock)}
 .cell.modifier{border-style:dashed;opacity:.85}
+
+.chose{font-size:15px;margin-bottom:4px}
+.why{font-style:italic;opacity:.85;margin-bottom:2px}
+.rejected{list-style:none;margin:0;padding:0;max-height:210px;overflow:auto}
+.rejected li{padding:3px 0;border-top:1px solid rgba(128,128,128,.25);font-size:12px}
+.wasted{background:#b03030;color:#fff;font-weight:bold;padding:3px 6px;margin-bottom:5px;border-radius:3px}
+.fstat{margin-top:4px;font-size:11px;padding:2px 5px;border-radius:3px;display:inline-block}
+.fstat.good{background:rgba(40,140,60,.28)}
+.fstat.bad{background:rgba(190,50,50,.38);font-weight:bold}
+.fstat.idle{opacity:.6}
+.wastedmark{color:#e06060;font-weight:bold}
+
+.enh{font-size:10px;background:rgba(90,140,220,.30);border-radius:3px;padding:1px 4px;margin-top:2px}
+.mlmods{font-size:10px;background:rgba(200,150,60,.28);border-radius:3px;padding:1px 4px;margin-top:2px}
+.grade{font-size:10px;background:rgba(200,90,60,.35);border-radius:3px;padding:1px 4px;font-weight:normal}
 </style></head><body>
 
 <header>
@@ -455,6 +266,7 @@ kbd{background:#2a3038;border:1px solid var(--line);border-radius:3px;padding:0
   </div>
   <div>
     <section><h2>What just happened</h2><div id="now"></div></section>
+    <section><h2>Decision — what it chose, and what it passed over</h2><div id="decision"></div></section>
     <section><h2>Cards</h2>
       <div><span class="dim">your hand:</span> <span id="hand">—</span></div>
       <div style="margin-top:5px"><span class="dim">face-up Department slots:</span> <span id="depts">—</span></div>
@@ -468,7 +280,7 @@ kbd{background:#2a3038;border:1px solid var(--line);border-radius:3px;padding:0
 <div class="legend">
   <b>Keyboard:</b> <kbd>←</kbd>/<kbd>→</kbd> step · <kbd>space</kbd> play/pause ·
   <kbd>Home</kbd>/<kbd>End</kbd> first/last · <kbd>S</kbd> next Stage · <kbd>R</kbd> next revenue change ·
-  <kbd>C</kbd> next collision.<br>
+  <kbd>C</kbd> next collision · <kbd>W</kbd> next wasted turn · <kbd>J</kbd> next jam.<br>
   Running Track is the lighter row. <span class="chip">T4</span> is a train on the Division;
   <span style="background:var(--warn);color:#0d1117;font-weight:700;border-radius:3px;padding:0 4px">🚂 T4</span>
   is the crew in your yard — it carries the whole train with it as it moves, and a dashed outline
@@ -485,6 +297,8 @@ kbd{background:#2a3038;border:1px solid var(--line);border-radius:3px;padding:0
   <button id="stage">next Stage ⏭</button>
   <button id="money">next revenue 💰</button>
   <button id="crash">next collision ⚠</button>
+  <button id="waste">next wasted turn 🗑</button>
+  <button id="jam">next jam 🔒</button>
   <input type="range" id="scrub" min="0" value="0">
   <select id="speed">
     <option value="3000">extra slow</option>
@@ -496,7 +310,14 @@ kbd{background:#2a3038;border:1px solid var(--line);border-radius:3px;padding:0
 </footer>
 
 <script>
-const FRAMES = ${JSON.stringify(rec.frames)};
+const FRAMES = ${JSON.stringify(compress(rec.frames))};
+/* The board changes rarely, so cells/facilities/division are emitted as null when identical to the
+   previous frame and resolved by walking back. Re-serialising the full grid every frame was 63% of
+   a 5.2 MB page. The scrubber jumps anywhere, hence the walk rather than a running pointer. */
+function carry(i, key) {
+  for (let k = i; k >= 0; k--) if (FRAMES[k][key] !== null) return FRAMES[k][key];
+  return [];
+}
 let i = 0, timer = null;
 const $ = (id) => document.getElementById(id);
 const esc = (s) => String(s).replace(/[&<>]/g, (c) => ({'&':'&amp;','<':'&lt;','>':'&gt;'}[c]));
@@ -543,8 +364,13 @@ function render() {
   $('fno').textContent = i;
   $('scrub').value = i;
 
-  $('division').innerHTML = f.division.map((n) =>
+  const CELLS = carry(i, 'cells'), FACS = carry(i, 'facilities'), DIV = carry(i, 'division');
-    '<div class="node ' + (n.kind === 'office' ? 'office' : '') + '"><div class="nm">' + esc(n.label) + '</div>' +
+
+  $('division').innerHTML = DIV.map((n) =>
+    '<div class="node ' + (n.kind === 'office' ? 'office' : '') + '"><div class="nm">' + esc(n.label) +
+      (n.gradeUp ? ' <span class="grade">' + (n.gradeUp === 'east' ? 'climbs E ▲' : '▲ W climbs') + '</span>' : '') +
+    '</div>' +
+    (n.modifiers.length ? '<div class="mlmods">' + n.modifiers.map(esc).join(' · ') + '</div>' : '') +
     '<div class="regions">' + n.trains.map((r) =>
       '<div class="region">' + r.map((t) =>
         '<span class="chip">' + esc(t.label) + '</span>' +
@@ -552,14 +378,14 @@ function render() {
       ).join('') + '</div>').join('') +
     '</div></div>').join('');
 
-  const rows = f.cells.map((c) => c.row), cols = f.cells.map((c) => c.col);
+  const rows = CELLS.map((c) => c.row), cols = CELLS.map((c) => c.col);
   const r0 = Math.min(...rows), r1 = Math.max(...rows), c0 = Math.min(...cols), c1 = Math.max(...cols);
   const g = $('grid');
   g.style.gridTemplateColumns = 'repeat(' + (c1 - c0 + 1) + ', minmax(110px, 1fr))';
   let cellsHtml = '';
   for (let r = r1; r >= r0; r--) {
     for (let c = c0; c <= c1; c++) {
-      const cell = f.cells.find((x) => x.row === r && x.col === c);
+      const cell = CELLS.find((x) => x.row === r && x.col === c);
       if (!cell) { cellsHtml += '<div></div>'; continue; }
       const hl = f.where && f.where.row === r && f.where.col === c;
       const wasHere = f.whereFrom && f.whereFrom.row === r && f.whereFrom.col === c;
@@ -567,6 +393,9 @@ function render() {
         (cell.kind === 'modifier' ? 'modifier ' : '') + (hl ? 'hl ' : '') + (wasHere ? 'from' : '') + '">' +
         '<div class="nm">' + esc(cell.label) + '</div>' +
         '<div class="dim" style="font-size:10px">(' + r + ',' + c + ')</div>' +
+        (cell.enhancements.length
+          ? '<div class="enh">' + cell.enhancements.map(esc).join(' · ') + '</div>'
+          : '') +
         (cell.tray ? '<div class="crew">🚂 ' + esc(cell.tray) + '</div>' : '') +
         (cell.facility ? miniFacility(cell.facility) : '') +
         (cell.cars.length ? '<div class="cars">siding: ' + cell.cars.map(esc).join('<br>') + '</div>' : '') +
@@ -575,9 +404,9 @@ function render() {
   }
   g.innerHTML = cellsHtml;
 
-  $('facs').innerHTML = f.facilities.length === 0
+  $('facs').innerHTML = FACS.length === 0
     ? '<span class="dim">no freight facilities built yet</span>'
-    : f.facilities.map((x) =>
+    : FACS.map((x) =>
       '<div class="fac"><b>' + esc(x.name) + '</b> <span class="dim">' + esc(x.commodity) + ' · ' + esc(x.flow) +
       ' · laborers ' + esc(x.laborers) + ' · porters ' + esc(x.porters) + '</span>' +
       '<div class="boxes"><span class="dim">green</span>' + boxes(x.green, x.greenCap, 'g') + '</div>' +
@@ -585,9 +414,34 @@ function render() {
         x.maw.map((m) => '<span class="box ' + (m ? 'm' : 'empty') + '">' + (m ? esc(m) : '·') + '</span>').join('') + '</div>' +
       '<div class="boxes"><span class="dim">red</span>' + boxes(x.red, x.redCap, 'r') + '</div>' +
       '<div class="boxes"><span class="dim">siding</span>' + boxes(x.track, x.trackCap, 'g') + '</div>' +
+      '<div class="fstat ' + (x.jammed ? 'bad' : (x.canFinish ? 'good' : 'idle')) + '">' +
+        (x.jammed
+          ? 'JAMMED — a load is on WORK with no car spotted to receive it; the industry track is locked'
+          : (x.canFinish
+            ? 'ready — a matching empty car is spotted, so a load can finish'
+            : 'no car spotted — starting a load here would jam it')) +
+      '</div>' +
       '</div>').join('');
 
   $('now').innerHTML = f.lines.map((l) => '<div class="line t-' + l.tone + '">' + esc(l.text) + '</div>').join('');
+
+  var d = f.decision;
+  if (!d) {
+    $('decision').innerHTML = '<span class="dim">no choice here — the engine advanced on its own</span>';
+  } else {
+    var h = '';
+    if (f.wasted) h += '<div class="wasted">WASTED TURN — the whole action produced no change</div>';
+    h += '<div class="chose"><span class="dim">chose:</span> <b>' + esc(d.chose) + '</b></div>';
+    h += '<div class="why">why: ' + esc(d.why) + '</div>';
+    h += '<div class="dim" style="margin:6px 0 3px">passed over ' + (d.totalOptions - 1) +
+         ' other legal option' + ((d.totalOptions - 1) === 1 ? '' : 's') + ':</div>';
+    if (d.rejected.length === 0) h += '<div class="dim">none — this was the only legal action</div>';
+    else h += '<ul class="rejected">' + d.rejected.map(function (r) {
+      return '<li><b>' + esc(r.kind) + '</b> <span class="dim">x' + r.count + '</span><br>' +
+             '<span class="dim">' + esc(r.detail) + '</span></li>';
+    }).join('') + '</ul>';
+    $('decision').innerHTML = h;
+  }
   $('blocked').innerHTML = f.blocked.length === 0
     ? '<li class="dim">nothing blocked</li>'
     : f.blocked.map((b) => '<li class="sev-' + b.severity + '"><b>' + esc(b.where) + '</b> — ' + esc(b.why) + '</li>').join('');
@@ -604,7 +458,7 @@ function render() {
 }
 
 function go(n) { i = Math.max(0, Math.min(FRAMES.length - 1, n)); render(); }
-function findNext(pred) { for (let k = i + 1; k < FRAMES.length; k++) if (pred(FRAMES[k], FRAMES[k - 1])) return go(k); go(FRAMES.length - 1); }
+function findNext(pred) { for (let k = i + 1; k < FRAMES.length; k++) if (pred(FRAMES[k], FRAMES[k - 1], k)) return go(k); go(FRAMES.length - 1); }
 
 $('ftot').textContent = FRAMES.length - 1;
 $('scrub').max = FRAMES.length - 1;
@@ -615,6 +469,8 @@ $('fwd').onclick = () => go(i + 1);
 $('stage').onclick = () => findNext((f, p) => f.stage !== p.stage || f.day !== p.day);
 $('money').onclick = () => findNext((f, p) => f.revenue !== p.revenue);
 $('crash').onclick = () => findNext((f) => f.lines.some((l) => /COLLISION|collision/.test(l.text)));
+$('waste').onclick = () => findNext((f) => f.wasted);
+$('jam').onclick = () => findNext((f, p, idx) => carry(idx, 'facilities').some((x) => x.jammed));
 $('play').onclick = () => {
   if (timer) { clearInterval(timer); timer = null; $('play').textContent = '▶ play'; return; }
   $('play').textContent = '⏸ pause';
@@ -632,6 +488,8 @@ document.onkeydown = (e) => {
   else if (e.key === 's' || e.key === 'S') $('stage').click();
   else if (e.key === 'r' || e.key === 'R') $('money').click();
   else if (e.key === 'c' || e.key === 'C') $('crash').click();
+  else if (e.key === 'w' || e.key === 'W') $('waste').click();
+  else if (e.key === 'j' || e.key === 'J') $('jam').click();
   else if (e.key === ' ') { e.preventDefault(); $('play').click(); }
 };
 render();

src/sim/view.ts

@@ -0,0 +1,638 @@
+/**
+ * The view-model: what a Station Master position LOOKS like.
+ *
+ * Split out of `replay.ts` so the playable browser build can use it. `replay.ts` writes files and
+ * reads `process.argv`, so importing it pulled `node:fs` into the bundle — and the engine's whole
+ * claim to run client-side rests on nothing in the import graph needing Node.
+ *
+ * Nothing here decides anything. It turns a `GameState` into boxes and labels, and turns an
+ * `Intent` into a sentence. The live game and the replay both render from this, so they cannot
+ * drift into two different pictures of the same board.
+ */
+
+import { areaOf, facilityCarType, laborersLeft, portersLeft } from '../engine/apply.ts';
+import {
+  ACTION_CARDS,
+  ENHANCEMENT_CARDS,
+  MAINLINE_MODIFIER_CARDS,
+  MAINLINE_PROFILES,
+  MANEUVER_CARDS,
+  SPACE_USE_CARDS,
+  industryProfile,
+  modifierProfile,
+  lengthProfile,
+  officeProfile,
+  trainProfile,
+} from '../engine/content.ts';
+import type { Intent } from '../engine/intents.ts';
+import type { Facility, GameState } from '../engine/state.ts';
+import type { TrackGeometry } from '../engine/content.ts';
+import { variantsFor } from '../engine/track.ts';
+import type { Impediment } from './narrate.ts';
+import { carLabel, clockTime, impediments, phaseLabel } from './narrate.ts';
+
+export type CellView = {
+  row: number;
+  col: number;
+  kind: string;
+  label: string;
+  running: boolean;
+  /**
+   * Enhancements laid ON this card. They were invisible: playing an Overpass onto the Office
+   * announced itself in the log and then changed nothing on the board, so a permanent change to how
+   * the district works left no trace you could see.
+   */
+  enhancements: string[];
+  tray: string | null;
+  cars: string[];
+  facility: FacilityView | null;
+};
+
+export type FacilityView = {
+  name: string;
+  commodity: string;
+  flow: string;
+  green: string[];
+  greenCap: number;
+  maw: (string | null)[];
+  red: string[];
+  redCap: number;
+  track: string[];
+  trackCap: number;
+  laborers: string;
+  porters: string;
+  /**
+   * Can a load actually come off WORK onto a spotted car (§9.3)? A load with nowhere to go parks on
+   * WORK and LOCKS the industry track, blocking the very car that would clear it — the deadlock
+   * that held freight to a 3% completion rate.
+   */
+  canFinish: boolean;
+  /** A load is sitting on WORK with no spotted car to receive it. */
+  jammed: boolean;
+};
+
+export type TrainChip = { label: string; consist: string[] };
+export type DivisionView = {
+  kind: string;
+  label: string;
+  trains: TrainChip[][];
+  /** Modifiers laid on a Mainline card (Brakeman, Helpers, Realignment …). */
+  modifiers: string[];
+  /**
+   * Which way a Heavy Grade climbs. The card prints "(Up)" and "Player sets orientation", so the
+   * direction is a property of the placed card — and without showing it, a Brakeman or Helpers card
+   * on that grade has no visible meaning.
+   */
+  gradeUp: string | null;
+};
+
+export type Frame = {
+  day: number;
+  stage: number;
+  clock: string;
+  phase: string;
+  actor: number | null;
+  superintendent: number;
+  revenue: number;
+  lines: { text: string; tone: string }[];
+  where: { row: number; col: number } | null;
+  /** Origin of a Move, so the crew's journey is visible rather than a chip teleporting. */
+  whereFrom: { row: number; col: number } | null;
+  division: DivisionView[];
+  cells: CellView[];
+  facilities: FacilityView[];
+  hand: string[];
+  /** What each hand card does, in the same order — names alone are not a playable hand. */
+  handWhat: string[];
+  deck: number;
+  departments: string[];
+  /** What each face-up Department card does. */
+  departmentsWhat: string[];
+  /** 12 slots; the train number due out at each Stage, or null. */
+  timetable: (number | null)[];
+  blocked: Impediment[];
+  trains: { label: string; where: string }[];
+  /**
+   * Where you stand against the target. Nothing on screen said what the game was FOR, so a player
+   * had the score but no way to know whether it was good.
+   */
+  objective: { target: number; days: number; daysLeft: number; onPace: boolean; note: string };
+  /**
+   * What is left of the player's personal track supply (§12.2). Track is NOT drawn from the deck —
+   * each player starts with 26 pieces and lays at most one a turn, so "how many straights have I
+   * got left" is a real planning question the board could not answer.
+   */
+  trackSupply: { piece: string; left: number }[];
+  /** What the bot chose here, why, and what it passed over. Null on engine-driven frames. */
+  decision: Decision | null;
+  /** A Local Operations turn that changed nothing — the frames worth your attention. */
+  wasted: boolean;
+};
+
+/**
+ * The choice behind a frame.
+ *
+ * The whole point is `rejected`: the replay could always show what happened, never what COULD have
+ * happened, so a daft move was visible but the alternatives it passed over were not — which is
+ * exactly what you need to say what it should have done instead.
+ */
+export type Decision = {
+  actor: number;
+  chose: string;
+  why: string;
+  /** Every legal option not taken, grouped by kind with a count. */
+  rejected: { kind: string; count: number; detail: string }[];
+  totalOptions: number;
+};
+
+// ---------------------------------------------------------------------------
+// Snapshotting
+// ---------------------------------------------------------------------------
+
+const FACILITY_NAMES: Record<string, string> = {
+  mineTipple: 'Mine Tipple',
+  produceShed: 'Produce Shed',
+  grocersWarehouse: "Grocer's Warehouse",
+  oilRefinery: 'Oil Refinery',
+  powerPlant: 'Power Plant',
+};
+
+function facilityView(
+  card: { geometry: { kind: string; facility?: string }; facility: unknown },
+  officeName: string,
+): FacilityView | null {
+  const f = (card as { facility: import('../engine/state.ts').Facility | null }).facility;
+  // Passenger facilities were excluded entirely, so the Office's green and red slots never
+  // appeared — which is why stocking a coach into the green box looked like nothing happening.
+  if (!f) return null;
+  if (f.kind === 'passenger' && f.porters === 0 && f.capacity.outbound === 0) return null;
+  const key = card.geometry.kind === 'facility' ? (card.geometry.facility ?? '') : '';
+  return {
+    name: f.kind === 'passenger' ? officeName + ' (passengers)' : (FACILITY_NAMES[key] ?? key),
+    commodity: facilityCarType(f) ?? '?',
+    flow: f.kind === 'passenger'
+      ? 'passengers on and off'
+      : f.allows.outbound && f.allows.inbound ? 'both' : f.allows.outbound ? 'ships out' : 'receives',
+    green: f.outboundBox.map(carLabel),
+    greenCap: f.capacity.outbound,
+    maw: f.menAtWork.map((l) => (l ? `${l.type} ${l.dir === 'out' ? '→' : '←'}` : null)),
+    red: f.inboundBox.map(carLabel),
+    redCap: f.capacity.inbound,
+    track: f.industryTrack.cars.map(carLabel),
+    trackCap: f.industryTrack.length,
+    laborers: `${laborersLeft(f)}/${f.laborers}`,
+    porters: `${portersLeft(f)}/${f.porters}`,
+    canFinish: canFinishHere(f),
+    jammed: f.menAtWork.some((l) => l !== null) && !canFinishHere(f),
+  };
+}
+
+/** Is a car spotted that a load on WORK could actually come off onto (§9.3)? */
+function canFinishHere(f: Facility): boolean {
+  const pending = f.menAtWork.find((l) => l !== null) ?? f.outboundBox[0];
+  if (!pending) return false;
+  return f.industryTrack.cars.some((c) => !c.loaded && c.type === pending.type);
+}
+
+/**
+ * Summarise the choice: what was taken, why, and what was passed over.
+ *
+ * Options are grouped by kind because a switching turn can offer 40 destinations, and a list that
+ * long hides the shape of the decision rather than showing it.
+ */
+export function describeDecision(
+  s: GameState,
+  actor: number,
+  chosen: Intent,
+  options: Intent[],
+  why: string,
+): Decision {
+  const groups = new Map<string, Intent[]>();
+  for (const o of options) {
+    if (o === chosen) continue;
+    const list = groups.get(o.type) ?? [];
+    list.push(o);
+    groups.set(o.type, list);
+  }
+  const rejected = [...groups.entries()]
+    .map(([kind, list]) => ({ kind, count: list.length, detail: sampleDetail(s, kind, list) }))
+    .sort((a, b) => b.count - a.count);
+
+  return { actor, chose: describeIntent(s, chosen), why, rejected, totalOptions: options.length };
+}
+
+/** A short, concrete example of what a group of rejected options would have done. */
+function sampleDetail(s: GameState, kind: string, list: Intent[]): string {
+  // Deduplicate by DESCRIPTION. Orientation variants and repeated copies of a card describe
+  // identically, so the raw list reads "play Overpass at (0,0)" three times over and hides the
+  // actual range of choices — the opposite of what this panel is for.
+  const seen = new Set<string>();
+  for (const i of list) seen.add(describeIntent(s, i));
+  const unique = [...seen];
+  const shown = unique.slice(0, 4);
+  const more = unique.length - shown.length;
+  return shown.join('; ') + (more > 0 ? ` … and ${more} more distinct` : '');
+}
+
+/** One readable line for a single intent. */
+export function describeIntent(s: GameState, i: Intent): string {
+  const at = (c: { row: number; col: number }): string => `(${c.row},${c.col})`;
+  switch (i.type) {
+    case 'localOps.choose':
+      // The most consequential decision of the Stage, and it was labelled "choose switch". Say what
+      // each option actually spends and buys.
+      return i.option === 'switch'
+        ? 'SWITCH — six Moves to shunt cars: spot empties at industries, collect loads'
+        : i.option === 'draw'
+          ? 'DRAW — take a card and play one, and you may lay a piece of track'
+          : 'FREIGHT AGENT — one car moved to or from a facility, or clear a jam';
+    case 'card.play':
+      return `play ${cardName(s, i.cardId)}${i.placement ? ` at ${at(i.placement)}` : ''}`;
+    case 'card.discard':
+      return `discard ${cardName(s, i.cardId)}`;
+    case 'track.lay':
+      return (
+        `lay ${i.hand === 'none' ? '' : i.hand + '-hand '}${geometryLabel(i.geometry)} ` +
+        `at ${at(i.placement)}${variantLabel(i.geometry, i.variant)}`
+      );
+    case 'switch.move':
+      return `move to ${at(i.to)}${i.reverse ? ' (reverse)' : ''}`;
+    case 'switch.dropCars':
+      return `drop ${i.count} car(s)`;
+    case 'switch.sortConsist':
+      return `re-order consist [${i.order.join(',')}]`;
+    case 'freightAgent.stockOutbound':
+      return `stock a ${i.carType} at ${at(i.at)}`;
+    case 'freightAgent.unjam':
+      return `unjam ${i.from} at ${at(i.at)}`;
+    case 'freightAgent.clearInbound':
+      return `clear red box at ${at(i.at)}`;
+    case 'laborer.startLoad':
+      return `start a load at ${at(i.at)}`;
+    case 'laborer.advanceLoad':
+      return `advance load in box ${i.box} at ${at(i.at)}`;
+    case 'laborer.beginUnload':
+      return `begin unloading car ${i.carIndex} at ${at(i.at)}`;
+    case 'porter.board':
+      return `board passengers at ${at(i.at)}`;
+    case 'porter.detrain':
+      return `detrain passengers at ${at(i.at)}`;
+    case 'newTrain.placeCar':
+      return `add ${i.loaded ? 'loaded' : 'empty'} ${i.carType}`;
+    case 'mainline.modify':
+      return `${cardName(s, i.cardId)} on Mainline card ${i.node}`;
+    case 'maneuver.redFlags':
+      return `Red Flags on ${i.trayId}`;
+    case 'maneuver.flyingSwitch':
+      return `Flying Switch ${i.count} car(s) into ${at(i.to)}`;
+    case 'mainline.clearance':
+      return i.allow ? 'grant clearance' : 'refuse clearance';
+    case 'draw.fromDepartment': {
+      // Naming the card is the whole point of a FACE-UP slot: "slot 2" tells a player nothing, and
+      // the choice between a visible card and a blind draw is unmakeable without it.
+      const id = s.decks.departments[i.slot];
+      return id ? `take ${cardName(s, id)} (face-up slot ${i.slot + 1})` : `slot ${i.slot + 1} (empty)`;
+    }
+    case 'draw.fromHomeOffice':
+      return `draw blind from the Home Office deck (${s.decks.homeOffice.length} left)`;
+    case 'draw.end':
+      return 'done drawing — end my turn';
+    case 'switch.end':
+      return 'done switching — end my turn';
+    case 'loadUnload.end':
+      return 'done working — end the Load/Unload phase';
+    case 'newTrain.passCar':
+      return 'add no more cars to this train';
+    case 'newTrain.secondSection':
+      return `run a Second Section behind Train ${i.trainNumber}`;
+    case 'redFlag.play':
+      return 'play your red flag';
+    case 'maneuver.redFlags':
+      return `Red Flags on ${i.trayId}`;
+    default: {
+      // Every Intent now has a sentence, so `i` narrows to never here. Keeping the assignment makes
+      // that a COMPILE error the day someone adds an intent without describing it — the playable UI
+      // labels its buttons from this function, so a missing case ships as a button reading
+      // "maneuver.poling".
+      const unhandled: never = i;
+      return String((unhandled as { type: string }).type);
+    }
+  }
+}
+
+/**
+ * Build the view-model for a state. Shared with the playable web app so the live game and the
+ * replay cannot drift into two different pictures of the same board.
+ */
+export function snapshot(
+  s: GameState,
+  lines: { text: string; tone: string }[],
+  where: { row: number; col: number } | null,
+  whereFrom: { row: number; col: number } | null = null,
+  decision: Decision | null = null,
+  wasted = false,
+): Frame {
+  const area = areaOf(s, 0);
+  const trayAt = new Map<string, string>();
+  for (const [id, tray] of s.trays) {
+    if (tray.position.at === 'grid') {
+      const label = tray.trainNumber === null ? 'crew' : `T${tray.trainIsExtra ? 'X' : ''}${tray.trainNumber}`;
+      const carrying = tray.consist.length ? ` [${tray.consist.map(carLabel).join(', ')}]` : ' [empty]';
+      trayAt.set(`${tray.position.coord.row},${tray.position.coord.col}`, label + carrying);
+    }
+  }
+
+  const cells: CellView[] = [];
+  const facilities: FacilityView[] = [];
+  for (const [key, card] of area.grid) {
+    const [row, col] = key.split(',').map(Number);
+    const g = card.geometry;
+    const kind = g.kind;
+    let label: string;
+    if (g.kind === 'office') label = officeProfile(area.tier).name;
+    else if (g.kind === 'limits') label = 'Limits';
+    else if (g.kind === 'facility') label = FACILITY_NAMES[g.facility] ?? g.facility;
+    else if (g.kind === 'modifier') label = MODIFIER_NAMES[g.modifier] ?? g.modifier;
+    else if (g.kind === 'spaceUse') label = prettyKey(g.key);
+    else label = geometryLabel(g.geometry);
+
+    const fv = facilityView(card as never, officeProfile(area.tier).name);
+    if (fv) facilities.push(fv);
+
+    cells.push({
+      row: row!,
+      col: col!,
+      kind,
+      label,
+      running: row === area.runningRow,
+      enhancements: card.enhancements.map(prettyKey),
+      tray: trayAt.get(key) ?? null,
+      cars: (card.facility?.industryTrack.length ? card.facility.industryTrack.cars : card.standing).map(carLabel),
+      facility: fv,
+    });
+  }
+
+  const division: DivisionView[] = s.division.nodes.map((n) => {
+    if (n.kind === 'divisionPoint') {
+      return {
+        kind: 'dp',
+        label: n.side === 'west' ? 'West DP' : 'East DP',
+        trains: [n.holding.map((id) => trainChip(s, id))],
+        modifiers: [],
+        gradeUp: null,
+      };
+    }
+    if (n.kind === 'mainline') {
+      // Crossing time is in Stages now, so a Mainline card shows its terrain and the trains on it
+      // with how long each still has to run.
+      const name = MAINLINE_PROFILES.find((m) => m.kind === n.card)?.name ?? n.card;
+      const isGrade = MAINLINE_PROFILES.find((m) => m.kind === n.card)?.speed.kind === 'grade';
+      return {
+        kind: 'ml',
+        label: name,
+        trains: [n.transits.map((t) => {
+          const chip = trainChip(s, t.tray);
+          return { ...chip, label: `${chip.label} (${t.stagesRemaining})` };
+        })],
+        modifiers: [
+          ...(n.modifiers ?? []).map(prettyKey),
+          ...(n.absSignals ? ['ABS Signals'] : []),
+        ],
+        gradeUp: isGrade ? (n.gradeUp ?? 'east') : null,
+      };
+    }
+    return {
+      kind: 'office',
+      label: officeProfile(areaOf(s, n.owner).tier).name,
+      trains: [areaOf(s, n.owner).adOccupancy.map((id) => trainChip(s, id))],
+      modifiers: [],
+      gradeUp: null,
+    };
+  });
+
+  return {
+    day: s.clock.day,
+    stage: s.clock.stage,
+    clock: clockTime(s.clock.stage),
+    phase: phaseLabel(s.clock.phase),
+    actor: s.clock.currentActor,
+    superintendent: s.clock.superintendent,
+    revenue: s.players[0]?.revenue ?? 0,
+    lines,
+    where,
+    whereFrom,
+    division,
+    cells,
+    facilities,
+    hand: (s.decks.hands.get(0) ?? []).map((id) => cardName(s, id)),
+    handWhat: (s.decks.hands.get(0) ?? []).map((id) => cardDescription(s, id)),
+    deck: s.decks.homeOffice.length,
+    departments: s.decks.departments.map((id) => (id ? cardName(s, id) : '—')),
+    departmentsWhat: s.decks.departments.map((id) => (id ? cardDescription(s, id) : '')),
+    timetable: [...s.timetable],
+    decision,
+    wasted,
+    objective: objectiveOf(s),
+    trackSupply: [...area.trackSupply.entries()]
+      .map(([key, left]) => {
+        const [geometry, hand] = key.split(':');
+        return { piece: `${hand === 'none' ? '' : hand + '-hand '}${geometryLabel(geometry ?? '')}`, left };
+      })
+      .sort((a, b) => a.piece.localeCompare(b.piece)),
+    blocked: impediments(s, 0),
+    trains: [...s.trays.values()].map((t) => ({
+      label: t.trainNumber === null ? 'local crew' : `Train ${t.trainIsExtra ? 'X' : ''}${t.trainNumber}`,
+      where:
+        t.position.at === 'divisionPoint'
+          ? `${t.position.side} Division Point`
+          : t.position.at === 'mainline'
+            ? `Mainline card ${t.position.index}`
+            : `Office Area (${t.position.coord.row},${t.position.coord.col})`,
+    })),
+  };
+}
+
+/** A card id turned into something a person can read. */
+export function cardName(s: GameState, id: string): string {
+  const k = s.cards.get(id)?.kind;
+  if (!k) return 'a card';
+  switch (k.kind) {
+    case 'timetabledTrain':
+      return `Train ${k.number}`;
+    case 'extraTrain':
+      return `Extra X${k.number}`;
+    case 'office':
+      return `${k.tier.replace(/([A-Z])/g, ' $1').replace(/^./, (c) => c.toUpperCase())} upgrade`;
+    // Fall back to prettyKey, never to the raw key: an unnamed card showed as "rotaryDumps" on a
+    // button a player is meant to read. The lookup tables are for names prettyKey cannot guess
+    // (Grocer's Warehouse), not the only source of a readable label.
+    case 'freightFacility':
+      return FACILITY_NAMES[k.facility] ?? prettyKey(k.facility);
+    case 'modifier':
+      return MODIFIER_NAMES[k.modifier] ?? prettyKey(k.modifier);
+    case 'track':
+      return `${geometryLabel(k.geometry)} track`;
+    case 'spaceUse':
+    case 'enhancement':
+    case 'mainlineModifier':
+    case 'maneuver':
+    case 'action':
+      return prettyKey(k.key);
+  }
+}
+
+/**
+ * What a card actually DOES, in one line.
+ *
+ * The hand showed names only, so "Steam Turbines" or "Facing Point Locks" told a player nothing
+ * about the effect — the difference between playing the game and clicking hopefully. Every fact
+ * here already existed in the content tables; none of it was reaching the screen.
+ */
+export function cardDescription(s: GameState, id: string): string {
+  const k = s.cards.get(id)?.kind;
+  if (!k) return '';
+
+  switch (k.kind) {
+    case 'timetabledTrain':
+    case 'extraTrain': {
+      const t = trainProfile(k.number, k.kind === 'extraTrain');
+      if (!t) return '';
+      const parts: string[] = [];
+      if (t.consist.freight > 0) {
+        const types = t.consist.freightTypes;
+        parts.push(`${t.consist.freight} freight${types ? ` (${types.join('/')})` : ''}`);
+      }
+      if (t.consist.coach > 0) parts.push(`${t.consist.coach} coach`);
+      if (t.consist.caboose > 0) parts.push('caboose');
+      const extra = k.kind === 'extraTrain' ? 'runs ONCE, unscheduled' : 'runs every Day once scheduled';
+      // Several Extras leave the direction to the player, so "playerChoicebound" is not a word.
+      const dir = t.direction === 'playerChoice' ? 'either direction' : `${t.direction}bound`;
+      const rule = t.rules.note ? ` · ${t.rules.note}` : '';
+      return `${t.name} · ${t.speed}, ${dir} · ${parts.join(' + ') || 'no cars'} · ${extra}${rule}`;
+    }
+    case 'office': {
+      const p = officeProfile(k.tier);
+      return (
+        `upgrade the Office: ${p.adTracks} A/D track${p.adTracks === 1 ? '' : 's'}, ` +
+        `${p.porters} porter${p.porters === 1 ? '' : 's'}, ` +
+        `${p.passengerOut} passenger out / ${p.passengerIn} in` +
+        (p.isControlPoint ? ' · a Control Point' : '')
+      );
+    }
+    case 'freightFacility': {
+      const f = industryProfile(k.facility);
+      const flow = f.flow === 'both' ? 'ships out AND receives' : f.flow === 'outbound' ? 'ships out' : 'receives';
+      const lock = f.lockouts.length
+        ? ` · cannot share a district with ${f.lockouts.map(facilityLabel).join(', ')}`
+        : '';
+      return `${flow} ${f.carTypes.join('/')} · ${f.baseLoaders} laborer${f.baseLoaders === 1 ? '' : 's'}${lock}`;
+    }
+    case 'modifier': {
+      const m = modifierProfile(k.modifier);
+      const adds: string[] = [];
+      if (m.addOut) adds.push(`+${m.addOut} out`);
+      if (m.addIn) adds.push(`+${m.addIn} in`);
+      if (m.addLoaders) adds.push(`+${m.addLoaders} laborer`);
+      if (m.addPorters) adds.push(`+${m.addPorters} porter`);
+      return `${adds.join(', ') || 'no change'} · goes beside ${m.hosts.map(facilityLabel).join(' or ')}`;
+    }
+    default: {
+      // The recovered categories carry their own prose — effect plus where it may be played.
+      const card = SIMPLE_CARDS.find((c) => c.key === (k as { key: string }).key);
+      return card ? `${card.effect} · played on ${card.placement}` : '';
+    }
+  }
+}
+
+/** An industry's name for the screen. `office` is the Passenger Facility, not an industry. */
+function facilityLabel(key: string): string {
+  return key === 'office' ? 'the Office' : (FACILITY_NAMES[key] ?? prettyKey(key));
+}
+
+/** Every card category that carries a written effect rather than a profile. */
+const SIMPLE_CARDS = [
+  ...ENHANCEMENT_CARDS,
+  ...MAINLINE_MODIFIER_CARDS,
+  ...MANEUVER_CARDS,
+  ...SPACE_USE_CARDS,
+  ...ACTION_CARDS,
+];
+
+/** The goal, and whether the current score is keeping up with the clock. */
+function objectiveOf(s: GameState): Frame['objective'] {
+  const profile = lengthProfile(s.config.length);
+  const revenue = s.players[0]?.revenue ?? 0;
+  const daysLeft = Math.max(0, profile.days - s.clock.day + 1);
+  const elapsed = profile.days - daysLeft + 1;
+  // Straight-line pace: by the end of Day N you want N/days of the target.
+  const expected = (profile.target * elapsed) / profile.days;
+  const onPace = revenue >= expected;
+  const note =
+    daysLeft === 0
+      ? 'the last Day is over'
+      : `${revenue} of ${profile.target} · ${daysLeft} Day${daysLeft === 1 ? '' : 's'} left · ` +
+        (onPace ? 'on pace' : `behind pace (about ${Math.ceil(expected)} by now)`);
+  return { target: profile.target, days: profile.days, daysLeft, onPace, note };
+}
+
+/**
+ * Which way a piece will point, in words.
+ *
+ * "rotation 2" is not a choice anyone can make — for a curve or a turnout the orientation IS the
+ * decision. Read from `variantsFor`, the same list the placement uses, so the label cannot describe
+ * one rotation while the engine lays another.
+ */
+export function variantLabel(geometry: TrackGeometry, variant: number | undefined): string {
+  const v = variantsFor(geometry)[variant ?? 0];
+  if (!v) return '';
+  if (v.axis) return v.axis === 'ew' ? ' — east–west' : ' — north–south';
+  if (v.turnout) {
+    const dir = (p: string): string =>
+      ({ n: 'north', s: 'south', e: 'east', w: 'west' })[p] ?? p;
+    return ` — stem ${dir(v.turnout.stem)}, through ${dir(v.turnout.through)}, diverges ${dir(v.turnout.diverge)}`;
+  }
+  return '';
+}
+
+/**
+ * A track shape in words. One place, because it is written on the board, in the action buttons and
+ * in the supply list — and `sharpCurved` was reaching the screen raw in two of the three.
+ */
+export function geometryLabel(geometry: string): string {
+  switch (geometry) {
+    case 'sharpCurved':
+      return 'sharp curve';
+    case 'curved':
+      return 'curve';
+    case 'turnout':
+      return 'turnout';
+    case 'straight':
+      return 'straight';
+    default:
+      return prettyKey(geometry);
+  }
+}
+
+/** camelCase key → readable name, for the card categories that carry only a key. */
+function prettyKey(key: string): string {
+  return key.replace(/([A-Z])/g, ' $1').replace(/^./, (c) => c.toUpperCase());
+}
+
+const MODIFIER_NAMES: Record<string, string> = {
+  teamTrack: 'Team Track',
+  loadingDock: 'Loading Dock',
+  storageShed: 'Storage Shed',
+  extraPlatform: 'Extra Platform',
+  sectionGang: 'Section Gang',
+};
+
+/** A train on the board, with what it is carrying — otherwise a run looks identical empty or full. */
+function trainChip(s: GameState, id: string): TrainChip {
+  const t = s.trays.get(id);
+  if (!t) return { label: id, consist: [] };
+  return {
+    label: t.trainNumber === null ? 'crew' : `T${t.trainIsExtra ? 'X' : ''}${t.trainNumber}`,
+    consist: t.consist.map(carLabel),
+  };
+}
+

src/web/game.ts

@@ -0,0 +1,306 @@
+/**
+ * Station Master — solitaire, playable in a browser.
+ *
+ * The whole game runs client-side. There is no server and no network call at any point: the engine
+ * is pure, imports nothing outside itself, and never touches `Math.random`, `Date` or `crypto`, so
+ * a static host is all this needs. (Proven, not assumed — a test runs full games with every Node
+ * global replaced by a throwing stub.)
+ *
+ * WHAT THIS MODULE IS. Everything here is presentation and input. It builds no rules of its own:
+ *
+ *   - what you may do  -> `legalActions(state, actor)`
+ *   - what it means    -> `describeIntent()`, shared with the replay
+ *   - what the board looks like -> `snapshot()`, shared with the replay
+ *   - what just happened -> `narrate()`, shared with the replay
+ *
+ * That is the same discipline the engine holds itself to. A second opinion about which moves are
+ * legal would eventually disagree with `check`, and the failure mode is a UI that offers an illegal
+ * move or refuses a legal one.
+ *
+ * SAVING. The event log is the game (`state = fold(events)`), and the RNG is seeded, so a save is
+ * the seed plus the list of intents submitted. Replaying them reconstructs the position exactly,
+ * which is far smaller and far more robust than serialising the state graph.
+ */
+
+import { pump } from '../engine/advance.ts';
+import { applyIntent } from '../engine/apply.ts';
+import type { GameEvent } from '../engine/events.ts';
+import type { Intent } from '../engine/intents.ts';
+import { legalActions } from '../engine/legal.ts';
+import { createGame } from '../engine/setup.ts';
+import type { GameConfig, GameState, PlayerIndex } from '../engine/state.ts';
+import { narrate } from '../sim/narrate.ts';
+// Import from the view module, NOT replay.ts — replay.ts writes files and reads process.argv,
+// which would pull node:fs into a browser bundle.
+import { cardName, describeIntent, geometryLabel, snapshot, variantLabel } from '../sim/view.ts';
+import type { TrackGeometry } from '../engine/content.ts';
+import { variantsFor } from '../engine/track.ts';
+import type { Frame } from '../sim/view.ts';
+
+export const SOLO_CONFIG: GameConfig = {
+  mode: 'solitaire',
+  victory: 'highestAfterDays',
+  length: 'standard',
+  optionalRules: {
+    reducedVisibility: false,
+    sisterTrains: false,
+    employeeRotation: false,
+    emergencyToolbox: false,
+  },
+};
+
+/** A group of legal actions of one kind, ready to put on screen. */
+export type ActionGroup = {
+  kind: string;
+  title: string;
+  actions: { index: number; label: string }[];
+};
+
+export type Game = {
+  state: GameState;
+  seed: number;
+  /** Every intent submitted, in order — the save file. */
+  history: Intent[];
+  /** Narrated lines, newest last. */
+  log: { text: string; tone: string }[];
+};
+
+/** How each intent kind is introduced in the action list, in the order they should appear. */
+const GROUP_ORDER: readonly { prefix: string; title: string }[] = [
+  { prefix: 'mainline.clearance', title: 'Superintendent — rule on this train' },
+  { prefix: 'localOps.choose', title: 'Local Operations — choose ONE' },
+  { prefix: 'switch.', title: 'Switching' },
+  { prefix: 'draw.', title: 'Draw' },
+  { prefix: 'card.', title: 'Cards' },
+  { prefix: 'track.lay', title: 'Lay track from your supply' },
+  { prefix: 'mainline.modify', title: 'Mainline modifiers' },
+  { prefix: 'maneuver.', title: 'Manoeuvres' },
+  { prefix: 'freightAgent.', title: 'Freight Agent' },
+  { prefix: 'newTrain.', title: 'Making up the train' },
+  { prefix: 'porter.', title: 'Porters' },
+  { prefix: 'laborer.', title: 'Laborers' },
+  { prefix: 'loadUnload.', title: 'Finish' },
+  { prefix: 'redFlag.', title: 'Red flag' },
+];
+
+export function newGame(seed: number, config: GameConfig = SOLO_CONFIG): Game {
+  const state = createGame({ id: `web-${seed}`, seed, config, playerNames: ['You'] });
+  const game: Game = { state, seed, history: [], log: [] };
+  drain(game);
+  return game;
+}
+
+/**
+ * Run the engine forward until it needs a decision.
+ *
+ * Most of a Stage is automatic — the Mainline Phase moves trains, the clock turns over — so the
+ * player is only ever asked when `advance` genuinely stops.
+ */
+export function drain(game: Game): void {
+  record(game, pump(game.state));
+}
+
+/** Whose turn it is, or null if the game is over or waiting on nothing. */
+export function currentActor(game: Game): PlayerIndex | null {
+  if (game.state.status !== 'active') return null;
+  return game.state.clock.pendingDecision !== null
+    ? game.state.clock.superintendent
+    : game.state.clock.currentActor;
+}
+
+/** Every legal action right now, grouped for display. Empty when there is nothing to decide. */
+export function actionGroups(game: Game): { options: Intent[]; groups: ActionGroup[] } {
+  const actor = currentActor(game);
+  if (actor === null) return { options: [], groups: [] };
+
+  const options = legalActions(game.state, actor);
+  const byKind = new Map<string, { index: number; label: string }[]>();
+  options.forEach((intent, index) => {
+    const label = describeIntent(game.state, intent);
+    const list = byKind.get(intent.type) ?? [];
+    // Orientation variants and duplicate copies describe identically; showing one is enough, and a
+    // list of forty identical rows hides the real choice rather than presenting it.
+    if (!list.some((a) => a.label === label)) list.push({ index, label });
+    byKind.set(intent.type, list);
+  });
+
+  const groups: ActionGroup[] = [];
+  const used = new Set<string>();
+  for (const { prefix, title } of GROUP_ORDER) {
+    const kinds = [...byKind.keys()].filter((k) => k.startsWith(prefix) && !used.has(k));
+    const actions = kinds.flatMap((k) => {
+      used.add(k);
+      return byKind.get(k) ?? [];
+    });
+    if (actions.length > 0) groups.push({ kind: prefix, title, actions });
+  }
+  // Anything the table above does not name still has to be offered — silently dropping a legal
+  // action would make the game unplayable in a way that is very hard to notice.
+  const leftovers = [...byKind.entries()].filter(([k]) => !used.has(k));
+  for (const [kind, actions] of leftovers) groups.push({ kind, title: kind, actions });
+
+  return { options, groups };
+}
+
+/**
+ * A thing you might do, and — if it goes on the board — where it could go.
+ *
+ * Placeable actions are presented as SUBJECT then LOCATION rather than as one flat list of every
+ * (card x square x rotation) combination. A single turn offered 29 track buttons and 7 card buttons
+ * with no way to tell which square each referred to; picking the card first and the square second is
+ * how the choice is actually made at the table.
+ */
+export type Placeable = {
+  /** Groups every option that plays the same card or lays the same piece. */
+  subjectKey: string;
+  subject: string;
+  /**
+   * Where it may go. `coord` drives board highlighting; several spots can share one square when the
+   * piece has more than one legal rotation there, which is why the label carries the rotation too.
+   */
+  spots: { label: string; index: number; coord: { row: number; col: number } }[];
+};
+
+export type Menu = {
+  options: Intent[];
+  /** Actions with no further choice to make. */
+  direct: ActionGroup[];
+  /** Actions needing a location, grouped under their card or track piece. */
+  placeable: { title: string; items: Placeable[] }[];
+};
+
+/** The action list as the page shows it: direct actions, plus subject-then-location for the rest. */
+export function actionMenu(game: Game): Menu {
+  const { options, groups } = actionGroups(game);
+  const direct: ActionGroup[] = [];
+  const placeableByTitle = new Map<string, Map<string, Placeable>>();
+
+  for (const g of groups) {
+    const plain: ActionGroup['actions'] = [];
+    for (const a of g.actions) {
+      const intent = options[a.index]!;
+      const key = subjectOf(game, intent);
+      if (key === null) {
+        plain.push(a);
+        continue;
+      }
+      const bucket = placeableByTitle.get(g.title) ?? new Map<string, Placeable>();
+      const entry = bucket.get(key.subjectKey) ?? {
+        subjectKey: key.subjectKey,
+        subject: key.subject,
+        spots: [],
+      };
+      if (!entry.spots.some((sp) => sp.label === key.spot)) {
+        entry.spots.push({ label: key.spot, index: a.index, coord: key.coord });
+      }
+      bucket.set(key.subjectKey, entry);
+      placeableByTitle.set(g.title, bucket);
+    }
+    if (plain.length > 0) direct.push({ ...g, actions: plain });
+  }
+
+  const placeable = [...placeableByTitle.entries()].map(([title, m]) => ({
+    title,
+    items: [...m.values()],
+  }));
+  return { options, direct, placeable };
+}
+
+/** Split an intent into "what" and "where", or null if it needs no location. */
+function subjectOf(
+  game: Game,
+  i: Intent,
+): { subjectKey: string; subject: string; spot: string; coord: { row: number; col: number } } | null {
+  const at = (c: { row: number; col: number }): string => `(${c.row}, ${c.col})`;
+  if (i.type === 'card.play' && i.placement) {
+    return {
+      subjectKey: `card:${i.cardId}`,
+      subject: cardName(game.state, i.cardId),
+      spot: `${at(i.placement)}${rotationNote(null, i.variant)}`,
+      coord: i.placement,
+    };
+  }
+  if (i.type === 'track.lay') {
+    const hand = i.hand === 'none' ? '' : `${i.hand}-hand `;
+    return {
+      subjectKey: `track:${i.geometry}:${i.hand}`,
+      subject: `${hand}${geometryLabel(i.geometry)}`,
+      spot: `${at(i.placement)}${rotationNote(i.geometry, i.variant)}`,
+      coord: i.placement,
+    };
+  }
+  return null;
+}
+
+/**
+ * Rotations share a square, so the square alone does not identify the choice — and "rotation 2"
+ * does not tell a player which way the rail will run, which for a curve or turnout is the entire
+ * decision. Only shown when there is more than one way to lay the piece.
+ */
+function rotationNote(geometry: TrackGeometry | null, variant: number | undefined): string {
+  if (geometry === null) return variant === undefined || variant === 0 ? '' : ` — option ${variant + 1}`;
+  return variantsFor(geometry).length > 1 ? variantLabel(geometry, variant) : '';
+}
+
+/** Submit an action. Returns false and changes nothing if the engine rejects it. */
+export function submit(game: Game, intent: Intent): boolean {
+  const actor = currentActor(game);
+  if (actor === null) return false;
+
+  const result = applyIntent(game.state, actor, intent);
+  if (!result.ok) {
+    game.log.push({ text: `That is not allowed: ${result.code}`, tone: 'bad' });
+    return false;
+  }
+  game.history.push(intent);
+  record(game, result.events);
+  drain(game);
+  return true;
+}
+
+/** The board as the replay draws it, so the live game and the replay agree. */
+export function view(game: Game): Frame {
+  return snapshot(game.state, [], null);
+}
+
+function record(game: Game, events: GameEvent[]): void {
+  for (const e of events) {
+    // The same filter the replay uses: actor changes and phase bookkeeping are noise on screen.
+    if (e.type === 'actorChanged') continue;
+    const n = narrate(e, { cardName: (id) => cardName(game.state, id) });
+    game.log.push({ text: n.text, tone: n.tone });
+  }
+  // Keep the log bounded; the full history lives in `history` and can be replayed.
+  if (game.log.length > 400) game.log.splice(0, game.log.length - 400);
+}
+
+// ---------------------------------------------------------------------------
+// Saving — seed plus intents, replayed
+// ---------------------------------------------------------------------------
+
+export type Save = { seed: number; history: Intent[] };
+
+export function toSave(game: Game): Save {
+  return { seed: game.seed, history: game.history };
+}
+
+/**
+ * Rebuild a game from a save.
+ *
+ * Replays the intents through the real engine rather than restoring a serialised state, so a save
+ * can never describe a position the rules could not have produced. An intent that no longer applies
+ * stops the replay rather than being forced — better a short game than a corrupt one.
+ */
+export function fromSave(save: Save, config: GameConfig = SOLO_CONFIG): Game {
+  const game = newGame(save.seed, config);
+  for (const intent of save.history) {
+    const actor = currentActor(game);
+    if (actor === null) break;
+    const result = applyIntent(game.state, actor, intent);
+    if (!result.ok) break;
+    game.history.push(intent);
+    record(game, result.events);
+    drain(game);
+  }
+  return game;
+}

src/web/index.html

@@ -0,0 +1,128 @@
+<!doctype html>
+<html lang="en">
+<head>
+<meta charset="utf-8">
+<meta name="viewport" content="width=device-width,initial-scale=1">
+<title>Station Master — solitaire</title>
+<style>
+:root{--bg:#12151a;--fg:#e6e9ee;--dim:#8b94a3;--line:#2c333d;--panel:#1a1f26;--run:#3a4250}
+*{box-sizing:border-box}
+body{margin:0;background:var(--bg);color:var(--fg);
+  font:14px/1.45 ui-monospace,SFMono-Regular,Menlo,Consolas,monospace}
+h1{font-size:17px;margin:0}
+h2{font-size:12px;text-transform:uppercase;letter-spacing:.09em;color:var(--dim);
+  margin:0 0 6px;font-weight:600}
+h3{font-size:11px;text-transform:uppercase;letter-spacing:.07em;color:var(--dim);margin:9px 0 4px}
+.dim{color:var(--dim)}
+header{position:sticky;top:0;z-index:5;background:var(--panel);border-bottom:1px solid var(--line);
+  padding:9px 14px;display:flex;gap:20px;align-items:baseline;flex-wrap:wrap}
+header b{font-size:16px}
+.build{margin-left:auto;font-size:11px;opacity:.7}
+.pace{font-size:12px;padding:1px 7px;border-radius:10px}
+.pace.good{background:rgba(40,140,60,.32)}
+.pace.behind{background:rgba(190,120,40,.28)}
+.handcard{border-top:1px solid var(--line);padding:4px 0}
+.handcard:first-child{border-top:0}
+.handcard .what{font-size:11px;line-height:1.35}
+main{display:grid;grid-template-columns:minmax(0,1fr) 400px;gap:14px;padding:14px;align-items:start}
+@media(max-width:1100px){main{grid-template-columns:1fr}}
+section{background:var(--panel);border:1px solid var(--line);border-radius:7px;
+  padding:10px 12px;margin-bottom:12px}
+/* division strip */
+#division{display:flex;gap:7px;overflow-x:auto;padding-bottom:4px}
+.node{border:1px solid var(--line);border-radius:6px;padding:6px 9px;min-width:112px;flex:0 0 auto}
+.node.office{border-color:#4d6fa8;background:rgba(60,100,170,.13)}
+.node .nm{font-weight:600;font-size:12px}
+.chip{display:inline-block;background:#2f6b3d;border-radius:4px;padding:1px 6px;margin:3px 3px 0 0;font-size:11px}
+.consist{font-size:10px;color:var(--dim)}
+.grade{font-size:10px;background:rgba(200,90,60,.35);border-radius:3px;padding:1px 4px;font-weight:400}
+.mlmods{font-size:10px;background:rgba(200,150,60,.28);border-radius:3px;padding:1px 4px;margin-top:2px}
+/* board */
+#grid{display:grid;gap:5px;overflow-x:auto}
+.cell{border:1px solid var(--line);border-radius:5px;padding:5px 6px;min-height:64px;background:#161b21}
+.cell.run{background:var(--run)}
+.cell.office{border-color:#4d6fa8}
+.cell.modifier{background:#2b2333;border-style:dashed}
+.cell.legal{outline:2px solid #5aa9e6;outline-offset:-2px;cursor:pointer;
+  box-shadow:0 0 0 3px rgba(90,169,230,.18) inset}
+.cell.legal:hover{background:#233246}
+.cell.ghost{border-style:dashed;background:rgba(90,169,230,.07);
+  display:flex;flex-direction:column;justify-content:center;align-items:center;text-align:center}
+.cell.ghost .nm{font-weight:400;color:#5aa9e6;font-size:11px}
+.cell .nm{font-size:12px;font-weight:600}
+.coord{font-size:10px}
+.enh{font-size:10px;background:rgba(90,140,220,.30);border-radius:3px;padding:1px 4px;margin-top:2px}
+.crew{font-size:11px;margin-top:3px;color:#8fd6a0}
+.cars{font-size:10px;color:var(--dim)}
+/* facilities */
+.fac{border-top:1px solid var(--line);padding:7px 0}
+.fac:first-child{border-top:0}
+.boxes{display:flex;gap:3px;align-items:center;margin-top:3px;flex-wrap:wrap}
+.box{display:inline-block;min-width:22px;text-align:center;border-radius:3px;padding:1px 4px;font-size:10px}
+.box.empty{background:#242a32;color:#5a6472}
+.box.f{background:#2f6b3d}
+.box.m{background:#8a6d1f}
+.fstat{margin-top:4px;font-size:11px;padding:2px 5px;border-radius:3px;display:inline-block}
+.fstat.good{background:rgba(40,140,60,.28)}
+.fstat.bad{background:rgba(190,50,50,.38);font-weight:700}
+.fstat.idle{opacity:.6}
+/* actions */
+#actions{max-height:none}
+.grp{margin-bottom:6px}
+button{background:#2a3038;color:var(--fg);border:1px solid var(--line);border-radius:5px;
+  padding:5px 9px;margin:2px 3px 2px 0;cursor:pointer;font:inherit;font-size:12px;text-align:left}
+button:hover{background:#39424e;border-color:#4d6fa8}
+button.act{display:inline-block}
+.over{padding:9px;border-radius:5px;font-weight:700;margin-bottom:8px}
+.over.win{background:rgba(40,140,60,.35)}
+.over.loss{background:rgba(160,60,60,.3)}
+/* cards, log, blocked */
+.card.gone{opacity:.35;text-decoration:line-through}
+.subj{display:block;width:100%;margin:2px 0}
+.subj.open{border-color:#4d6fa8;background:#39424e}
+.spots{margin:0 0 6px 12px;padding-left:8px;border-left:2px solid #4d6fa8}
+.card{display:inline-block;background:#242c36;border:1px solid var(--line);border-radius:4px;
+  padding:2px 6px;margin:2px 2px 0 0;font-size:11px}
+#log{max-height:230px;overflow:auto;font-size:12px}
+.line{padding:1px 0}
+.t-good{color:#8fd6a0}.t-bad{color:#e58080}.t-clock{color:#9fb6d8;font-weight:600}.t-quiet{color:var(--dim)}
+ul.blocked{list-style:none;margin:0;padding:0;font-size:12px}
+ul.blocked li{padding:2px 0}
+.sev-warn{color:#e0b060}.sev-stop{color:#e58080}
+</style>
+</head>
+<body>
+
+<header>
+  <b>Station Master</b>
+  <span id="clock">—</span>
+  <span>phase: <b id="phase">—</b></span>
+  <span>Revenue <b id="revenue">0</b></span>
+  <span id="objective" class="pace">—</span>
+  <span class="dim">seed <span id="seed">—</span></span>
+  <span class="dim">saved in this browser · add ?seed=1234 to the address for a set deal</span>
+  <span class="dim build" title="what is actually deployed">__BUILD__</span>
+</header>
+
+<main>
+  <div>
+    <section><h2>The Division — west to east</h2><div id="division"></div></section>
+    <section><h2>Your Office Area</h2><div id="grid"></div></section>
+    <section><h2>History</h2><div id="log"></div></section>
+  </div>
+
+  <div>
+    <section><h2>Your move</h2><div id="actions"></div></section>
+    <section><h2>Cards</h2>
+      <div><span class="dim">hand:</span> <span id="hand">—</span></div>
+      <div style="margin-top:5px"><span class="dim">face-up Department slots:</span> <span id="depts">—</span></div>
+    </section>
+    <section><h2>Your track supply</h2><div id="supply"></div></section>
+    <section><h2>Blocked — why nothing is moving</h2><ul class="blocked" id="blocked"></ul></section>
+    <section><h2>Facilities</h2><div id="facs"></div></section>
+  </div>
+</main>
+
+<script type="module" src="./web/main.js"></script>
+</body>
+</html>

src/web/main.ts

@@ -0,0 +1,357 @@
+/**
+ * Browser entry point — wires the DOM to `game.ts`.
+ *
+ * Presentation only. Every question of what is legal, what it means, or what the board looks like
+ * is answered by the engine or by the shared view helpers.
+ */
+
+import type { Game } from './game.ts';
+import {
+  actionMenu,
+  currentActor,
+  fromSave,
+  newGame,
+  submit,
+  toSave,
+  view,
+} from './game.ts';
+
+const SAVE_KEY = 'station-master.save.v1';
+
+let game: Game;
+/** Which card or track piece is picked, waiting for a location. */
+let selected: string | null = null;
+/** A square picked on the board, waiting for a rotation. */
+let pendingAt: string | null = null;
+
+const $ = (id: string): HTMLElement => {
+  const el = document.getElementById(id);
+  if (!el) throw new Error(`missing element: ${id}`);
+  return el as HTMLElement;
+};
+
+const esc = (s: string): string =>
+  s.replace(/[&<>"]/g, (c) => ({ '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;' })[c] ?? c);
+
+// ---------------------------------------------------------------------------
+
+function start(): void {
+  const params = new URLSearchParams(location.search);
+  const requested = params.get('seed');
+
+  const saved = load();
+  if (saved && requested === null) {
+    game = fromSave(saved);
+  } else {
+    // A seed in the URL makes a game shareable and reproducible: same link, same deal.
+    const seed = requested !== null ? Number(requested) || 1 : Math.floor(Math.random() * 1e9);
+    game = newGame(seed);
+  }
+  render();
+}
+
+function render(): void {
+  const f = view(game);
+  const menu = actionMenu(game);
+
+  // Which squares the selected card or track piece may go on. Highlighting them is what turns the
+  // coordinate list into a board: you pick the thing, then click where it goes.
+  const chosen = menu.placeable.flatMap((g) => g.items).find((it) => it.subjectKey === selected);
+  const spotsAt = new Map<string, { label: string; index: number }[]>();
+  for (const sp of chosen?.spots ?? []) {
+    const key = `${sp.coord.row},${sp.coord.col}`;
+    spotsAt.set(key, [...(spotsAt.get(key) ?? []), sp]);
+  }
+
+  $('clock').textContent = `Day ${f.day} · Stage ${f.stage} — ${f.clock}`;
+  $('phase').textContent = f.phase;
+  $('revenue').textContent = String(f.revenue);
+  const obj = $('objective');
+  obj.textContent = f.objective.note;
+  obj.className = f.objective.onPace ? 'pace good' : 'pace behind';
+  $('seed').textContent = String(game.seed);
+
+  // -- division
+  $('division').innerHTML = f.division
+    .map(
+      (n) =>
+        `<div class="node ${n.kind === 'office' ? 'office' : ''}">` +
+        `<div class="nm">${esc(n.label)}` +
+        (n.gradeUp
+          ? ` <span class="grade">${n.gradeUp === 'east' ? 'climbs E ▲' : '▲ W climbs'}</span>`
+          : '') +
+        `</div>` +
+        (n.modifiers.length ? `<div class="mlmods">${n.modifiers.map(esc).join(' · ')}</div>` : '') +
+        `<div class="regions">` +
+        n.trains
+          .map(
+            (r) =>
+              `<div class="region">` +
+              r
+                .map(
+                  (t) =>
+                    `<span class="chip">${esc(t.label)}</span>` +
+                    `<div class="consist">${t.consist.length ? esc(t.consist.join(', ')) : 'empty'}</div>`,
+                )
+                .join('') +
+              `</div>`,
+          )
+          .join('') +
+        `</div></div>`,
+    )
+    .join('');
+
+  // -- grid
+  // Include the legal squares in the bounds. A placement is usually just OUTSIDE the current
+  // extent — that is what extending the district means — so a grid sized to the existing cards
+  // would highlight nothing at exactly the moment highlighting matters.
+  const spotCoords = [...spotsAt.keys()].map((k) => k.split(',').map(Number));
+  const rows = [...f.cells.map((c) => c.row), ...spotCoords.map((c) => c[0]!)];
+  const cols = [...f.cells.map((c) => c.col), ...spotCoords.map((c) => c[1]!)];
+  const r0 = Math.min(...rows);
+  const r1 = Math.max(...rows);
+  const c0 = Math.min(...cols);
+  const c1 = Math.max(...cols);
+  const grid = $('grid');
+  grid.style.gridTemplateColumns = `repeat(${c1 - c0 + 1}, minmax(104px, 1fr))`;
+  let cells = '';
+  for (let r = r1; r >= r0; r--) {
+    for (let c = c0; c <= c1; c++) {
+      const cell = f.cells.find((x) => x.row === r && x.col === c);
+      const spots = spotsAt.get(`${r},${c}`);
+      if (!cell) {
+        // An empty square is still a legal destination — render it as a target rather than a gap,
+        // or the most common placement of all would have nothing to click.
+        cells += spots
+          ? `<div class="cell ghost legal" data-at="${r},${c}">` +
+            `<div class="nm">place here</div><div class="dim coord">(${r},${c})</div>` +
+            (spots.length > 1 ? `<div class="dim">${spots.length} rotations</div>` : '') +
+            `</div>`
+          : '<div></div>';
+        continue;
+      }
+      cells +=
+        `<div class="cell ${cell.running ? 'run ' : ''}${cell.kind === 'office' ? 'office ' : ''}` +
+        `${cell.kind === 'modifier' ? 'modifier ' : ''}${spots ? 'legal' : ''}"` +
+        `${spots ? ` data-at="${r},${c}"` : ''}>` +
+        `<div class="nm">${esc(cell.label)}</div>` +
+        `<div class="dim coord">(${r},${c})</div>` +
+        (cell.enhancements.length
+          ? `<div class="enh">${cell.enhancements.map(esc).join(' · ')}</div>`
+          : '') +
+        (cell.tray ? `<div class="crew">🚂 ${esc(cell.tray)}</div>` : '') +
+        (cell.cars.length ? `<div class="cars">${esc(cell.cars.join(', '))}</div>` : '') +
+        `</div>`;
+    }
+  }
+  grid.innerHTML = cells;
+
+  // Clicking a highlighted square plays there. With more than one rotation available it narrows to
+  // that square instead, so the rotation is a second click rather than a guess.
+  for (const el of Array.from(grid.querySelectorAll('[data-at]'))) {
+    const node = el as HTMLElement;
+    node.onclick = () => {
+      const spots = spotsAt.get(node.dataset['at'] ?? '') ?? [];
+      if (spots.length === 1) {
+        const intent = menu.options[spots[0]!.index];
+        if (intent) submit(game, intent);
+        selected = null;
+        pendingAt = null;
+      } else if (spots.length > 1) {
+        pendingAt = node.dataset['at'] ?? null;
+      }
+      render();
+    };
+  }
+
+  // -- facilities
+  $('facs').innerHTML =
+    f.facilities.length === 0
+      ? '<div class="dim">no facilities yet</div>'
+      : f.facilities
+          .map(
+            (x) =>
+              `<div class="fac"><div class="nm">${esc(x.name)}</div>` +
+              `<div class="dim">${esc(x.commodity)} · ${esc(x.flow)} · laborers ${esc(x.laborers)}</div>` +
+              `<div class="boxes"><span class="dim">green</span>${boxes(x.green, x.greenCap)}</div>` +
+              `<div class="boxes"><span class="dim">MEN AT WORK</span>` +
+              x.maw
+                .map(
+                  (m) => `<span class="box ${m ? 'm' : 'empty'}">${m ? esc(m) : '·'}</span>`,
+                )
+                .join('') +
+              `</div>` +
+              `<div class="boxes"><span class="dim">red</span>${boxes(x.red, x.redCap)}</div>` +
+              `<div class="boxes"><span class="dim">siding</span>${boxes(x.track, x.trackCap)}</div>` +
+              `<div class="fstat ${x.jammed ? 'bad' : x.canFinish ? 'good' : 'idle'}">` +
+              (x.jammed
+                ? 'JAMMED — a load is on WORK with no car spotted; the siding is locked'
+                : x.canFinish
+                  ? 'ready — a matching empty car is spotted'
+                  : 'no car spotted — a load started here would jam') +
+              `</div></div>`,
+          )
+          .join('');
+
+  // Name AND effect. A hand of names alone tells a player nothing about what they can do.
+  const cardRow = (name: string, why: string): string =>
+    `<div class="handcard"><b>${esc(name)}</b>` +
+    (why ? `<div class="dim what">${esc(why)}</div>` : '') +
+    `</div>`;
+
+  $('hand').innerHTML = f.hand.length
+    ? f.hand.map((h, i) => cardRow(h, f.handWhat[i] ?? '')).join('')
+    : '<span class="dim">empty</span>';
+  $('depts').innerHTML = f.departments.length
+    ? f.departments.map((d, i) => cardRow(d, f.departmentsWhat[i] ?? '')).join('')
+    : '<span class="dim">none</span>';
+
+  const total = f.trackSupply.reduce((n, t) => n + t.left, 0);
+  $('supply').innerHTML =
+    `<div class="dim">${total} pieces left · one may be laid per turn, during the DRAW option</div>` +
+    f.trackSupply
+      .map(
+        (t) =>
+          `<span class="card ${t.left === 0 ? 'gone' : ''}">${esc(t.piece)} <b>${t.left}</b></span>`,
+      )
+      .join(' ');
+
+  $('blocked').innerHTML =
+    f.blocked.length === 0
+      ? '<li class="dim">nothing blocked</li>'
+      : f.blocked
+          .map((b) => `<li class="sev-${b.severity}"><b>${esc(b.where)}</b> — ${esc(b.why)}</li>`)
+          .join('');
+
+  // -- log
+  const log = $('log');
+  log.innerHTML = game.log
+    .slice(-60)
+    .map((l) => `<div class="line t-${l.tone}">${esc(l.text)}</div>`)
+    .join('');
+  log.scrollTop = log.scrollHeight;
+
+  renderActions(menu);
+  save();
+}
+
+function boxes(items: string[], cap: number): string {
+  let out = '';
+  for (let i = 0; i < Math.max(cap, items.length); i++) {
+    const v = items[i];
+    out += `<span class="box ${v ? 'f' : 'empty'}">${v ? esc(v) : '·'}</span>`;
+  }
+  return out || '<span class="dim">—</span>';
+}
+
+function renderActions(menu: ReturnType<typeof actionMenu>): void {
+  const el = $('actions');
+
+  if (game.state.status !== 'active') {
+    const o = game.state.outcome;
+    el.innerHTML =
+      `<div class="over ${o?.result === 'win' ? 'win' : 'loss'}">` +
+      `${o?.result === 'win' ? 'YOU WIN' : 'GAME OVER'} — ${esc(String(o?.reason ?? ''))}<br>` +
+      `final Revenue ${game.state.players[0]?.revenue ?? 0} against a target of ${view(game).objective.target}</div>` +
+      `<button id="again">new game</button>`;
+    $('again').onclick = () => {
+      clearSave();
+      location.search = '';
+    };
+    return;
+  }
+
+  if (menu.direct.length === 0 && menu.placeable.length === 0) {
+    el.innerHTML = '<div class="dim">nothing to decide — the engine is running the Division</div>';
+    return;
+  }
+
+  const apply = (index: number): void => {
+    const intent = menu.options[index];
+    if (intent) submit(game, intent);
+    selected = null;
+    pendingAt = null;
+    render();
+  };
+
+  let html = menu.direct
+    .map(
+      (g) =>
+        `<div class="grp"><h3>${esc(g.title)}</h3>` +
+        g.actions.map((a) => `<button class="act" data-i="${a.index}">${esc(a.label)}</button>`).join('') +
+        `</div>`,
+    )
+    .join('');
+
+  // Subject first, location second. Picking a card then a square is how the choice is actually made;
+  // one flat list of every card-square-rotation combination was unreadable.
+  for (const group of menu.placeable) {
+    html += `<div class="grp"><h3>${esc(group.title)}</h3>`;
+    for (const item of group.items) {
+      const open = selected === item.subjectKey;
+      html +=
+        `<button class="subj ${open ? 'open' : ''}" data-subj="${esc(item.subjectKey)}">` +
+        `${esc(item.subject)} <span class="dim">${item.spots.length} spot${item.spots.length === 1 ? '' : 's'}</span>` +
+        `</button>`;
+      if (open) {
+        // Once a square is picked, show only that square's rotations — the rest is noise.
+        const shown = pendingAt
+          ? item.spots.filter((sp) => `${sp.coord.row},${sp.coord.col}` === pendingAt)
+          : item.spots;
+        html +=
+          `<div class="spots"><div class="dim">` +
+          (pendingAt ? `choose a rotation for (${esc(pendingAt.replace(',', ', '))}):` : 'click a highlighted square, or:') +
+          `</div>` +
+          shown.map((sp) => `<button class="act" data-i="${sp.index}">${esc(sp.label)}</button>`).join('') +
+          `</div>`;
+      }
+    }
+    html += `</div>`;
+  }
+  el.innerHTML = html;
+
+  for (const b of Array.from(el.querySelectorAll('button.act'))) {
+    const node = b as HTMLElement;
+    node.onclick = () => apply(Number(node.dataset['i']));
+  }
+  for (const b of Array.from(el.querySelectorAll('button.subj'))) {
+    const node = b as HTMLElement;
+    node.onclick = () => {
+      const key = node.dataset['subj'] ?? null;
+      selected = selected === key ? null : key;
+      pendingAt = null;
+      render();
+    };
+  }
+}
+
+// ---------------------------------------------------------------------------
+// Saving. localStorage only — nothing leaves the browser.
+// ---------------------------------------------------------------------------
+
+function save(): void {
+  try {
+    localStorage.setItem(SAVE_KEY, JSON.stringify(toSave(game)));
+  } catch {
+    // A full or disabled localStorage must not take the game down with it.
+  }
+}
+
+function load(): ReturnType<typeof toSave> | null {
+  try {
+    const raw = localStorage.getItem(SAVE_KEY);
+    return raw ? (JSON.parse(raw) as ReturnType<typeof toSave>) : null;
+  } catch {
+    return null;
+  }
+}
+
+function clearSave(): void {
+  try {
+    localStorage.removeItem(SAVE_KEY);
+  } catch {
+    /* nothing to do */
+  }
+}
+
+start();

test/mainline-cards.test.ts

@@ -412,3 +412,85 @@ describe('card coverage', () => {
     assert.match(poling!.effect, /TBD/i);
   });
 });
+
+// ---------------------------------------------------------------------------
+
+describe('the Limits sign moves with the Running Track (§2.1, Gap 4a)', () => {
+  it('keeps the Limits at the ends, never stranded mid-track', () => {
+    // Found by watching a replay: a district grew to
+    //   (0,-5) (0,-4) (0,-3) (0,-2)=Power Plant [LIMITS] (0,0)=Office [LIMITS] (0,2) …
+    // with everything beyond (0,-2) built OUTSIDE a sign that never moved. Not cosmetic — §8.1 and
+    // §10 both reason about "the track between the train and the Limits", and running past a
+    // player's Limits is what makes a collision his fault.
+    const s = game();
+    const area = areaOf(s, 0);
+    s.turn.option = 'draw';
+
+    for (let n = 0; n < 4; n++) {
+      s.turn.laidThisTurn = false;
+      const target = { row: area.runningRow, col: area.limitsWest.col };
+      const r = applyIntent(s, 0, {
+        type: 'track.lay', geometry: 'straight', hand: 'none', placement: target, variant: 0,
+      });
+      assert.ok(r.ok, `extending onto the Limits should be legal (attempt ${n + 1})`);
+    }
+
+    const onRunning = [...area.grid.entries()]
+      .map(([k, c]) => ({ col: Number(k.split(',')[1]), kind: c.geometry.kind }))
+      .filter((x) => !Number.isNaN(x.col));
+    const limits = onRunning.filter((x) => x.kind === 'limits').map((x) => x.col).sort((a, b) => a - b);
+    const cols = onRunning.map((x) => x.col);
+
+    assert.equal(limits.length, 2, 'there must be exactly two Limits signs');
+    assert.equal(limits[0], Math.min(...cols), 'the west sign must be the westernmost card');
+    assert.equal(limits[1], Math.max(...cols), 'the east sign must be the easternmost card');
+  });
+});
+
+describe("a train is made up to its card's consist (§8.2)", () => {
+  it('takes a caboose when the card calls for one, and refuses a fourth freight car', () => {
+    // Train 9 "Heavy Freight" is freight 3 + caboose 1. It was being made up with FOUR hoppers and
+    // no caboose, because placeCar checked only MAX_CONSIST and yard availability.
+    const s = game();
+    s.clock.phase = 'newTrain';
+    s.trays.set('t', {
+      id: 't', trainNumber: 9, trainIsExtra: false, engineFront: true,
+      consist: [], direction: 'west', position: { at: 'divisionPoint', side: 'east' }, movesUsed: 0,
+    });
+
+    for (let n = 0; n < 3; n++) {
+      const r = applyIntent(s, 0, { type: 'newTrain.placeCar', trayId: 't', carType: 'hopper', loaded: true });
+      assert.ok(r.ok, `hopper ${n + 1} of 3 should be accepted`);
+    }
+    assert.equal(
+      check(s, 0, { type: 'newTrain.placeCar', trayId: 't', carType: 'hopper', loaded: true }),
+      'NO_SUITABLE_CAR',
+      'a fourth freight car exceeds the card',
+    );
+    assert.equal(
+      check(s, 0, { type: 'newTrain.placeCar', trayId: 't', carType: 'coach', loaded: true }),
+      'NO_SUITABLE_CAR',
+      'this card carries no coaches',
+    );
+    assert.equal(
+      check(s, 0, { type: 'newTrain.placeCar', trayId: 't', carType: 'caboose', loaded: true }),
+      null,
+      'the card calls for a caboose',
+    );
+  });
+
+  it('couples nothing behind the caboose', () => {
+    // §A.3 — the caboose rides last.
+    const s = game();
+    s.clock.phase = 'newTrain';
+    s.trays.set('t', {
+      id: 't', trainNumber: 9, trainIsExtra: false, engineFront: true,
+      consist: [{ type: 'caboose', loaded: true }],
+      direction: 'west', position: { at: 'divisionPoint', side: 'east' }, movesUsed: 0,
+    });
+    assert.equal(
+      check(s, 0, { type: 'newTrain.placeCar', trayId: 't', carType: 'hopper', loaded: true }),
+      'NO_SUITABLE_CAR',
+    );
+  });
+});

test/replay.test.ts

@@ -191,7 +191,7 @@ describe('replay HTML', () => {
   });
 
   it('offers the controls that make it usable', () => {
-    for (const id of ['play', 'back', 'fwd', 'scrub', 'stage', 'money', 'crash']) {
+    for (const id of ['play', 'back', 'fwd', 'scrub', 'stage', 'money', 'crash', 'waste', 'jam', 'decision']) {
       assert.ok(html.includes(`id="${id}"`), `missing control: ${id}`);
     }
   });
@@ -207,7 +207,7 @@ describe('replay HTML', () => {
 
   it('wires a handler to every control', () => {
     const js = html.slice(html.lastIndexOf('<script>') + 8, html.lastIndexOf('</script>'));
-    for (const id of ['play', 'back', 'fwd', 'first', 'stage', 'money', 'crash']) {
+    for (const id of ['play', 'back', 'fwd', 'first', 'stage', 'money', 'crash', 'waste', 'jam']) {
       assert.match(js, new RegExp(`\\$\\('${id}'\\)\\.onclick`), `no handler bound to ${id}`);
     }
     assert.match(js, /\$\('scrub'\)\.oninput/, 'no handler bound to scrub');
@@ -233,6 +233,65 @@ describe('replay HTML', () => {
     assert.match(String(els.get('when')?.textContent ?? ''), /Day \d+/);
   });
 
+  it('records what the bot chose, why, and what it passed over', () => {
+    // The replay could always show what happened, never what COULD have happened — so a daft move
+    // was visible but the alternatives it declined were not, which is what you need to say what it
+    // should have done instead.
+    const rec = record(202, 'standard');
+    const decided = rec.frames.filter((f) => f.decision !== null);
+    assert.ok(decided.length > 0, 'no frame carried a decision');
+
+    for (const f of decided) {
+      assert.ok(f.decision!.chose.length > 0, 'a decision with no chosen action');
+      assert.ok(f.decision!.why.length > 0, 'a decision with no stated reason');
+      assert.ok(f.decision!.totalOptions >= 1, 'a decision offering nothing');
+    }
+
+    // The reasons must come from the bot's own branches, not a generic fallback for everything.
+    const reasons = new Set(decided.map((f) => f.decision!.why));
+    assert.ok(reasons.size > 5, `only ${reasons.size} distinct reasons — the branches are not reporting`);
+
+    // Turns with real alternatives must show them, or the panel is decoration.
+    assert.ok(
+      decided.some((f) => f.decision!.rejected.length > 0),
+      'no frame ever recorded a rejected option',
+    );
+  });
+
+  it('flags jammed facilities and can tell them from ready ones', () => {
+    const rec = record(202, 'standard');
+    for (const f of rec.frames) {
+      for (const x of f.facilities) {
+        // A jam is precisely "work on WORK that cannot come off", so it can never be 'ready'.
+        assert.ok(!(x.jammed && x.canFinish), `${x.name} reported both jammed and ready`);
+      }
+    }
+  });
+
+  it('renders a LATER frame, where the board state is carried forward', () => {
+    // The page omits cells/facilities/division when unchanged and resolves them by walking back —
+    // 63% of a 5.2 MB payload was the same grid re-serialised every frame. Rendering only frame 0
+    // would never exercise that path, because frame 0 always carries everything.
+    const js = html.slice(html.lastIndexOf('<script>') + 8, html.lastIndexOf('</script>'));
+    const els = new Map<string, Record<string, unknown>>();
+    const stub = {
+      getElementById: (id: string) => {
+        if (!els.has(id)) els.set(id, { textContent: '', innerHTML: '', value: '', style: {}, max: 0 });
+        return els.get(id);
+      },
+    };
+    // Append a jump to a late frame so render() runs against carried-forward state.
+    const run = new Function('document', 'setInterval', 'clearInterval', js + '\n;go(FRAMES.length - 1);');
+    assert.doesNotThrow(
+      () => run(stub, () => 0, () => undefined),
+      'the page threw rendering a frame whose board state was carried forward',
+    );
+    assert.ok(
+      String(els.get('grid')?.innerHTML ?? '').length > 0,
+      'the grid rendered empty on a carried-forward frame',
+    );
+  });
+
   it('stays a sane size', () => {
     const mb = Buffer.byteLength(html) / 1024 / 1024;
     assert.ok(mb < 5, `replay is ${mb.toFixed(1)} MB`);

test/web.test.ts

@@ -0,0 +1,448 @@
+/**
+ * The playable browser build.
+ *
+ * These tests drive `game.ts` exactly as the page does — take the offered actions, submit one, look
+ * at the new position — so "it compiles" is never mistaken for "it plays".
+ */
+
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import { execFileSync } from 'node:child_process';
+import { existsSync, readFileSync, readdirSync } from 'node:fs';
+import { join } from 'node:path';
+
+import { cardDescription, describeIntent } from '../src/sim/view.ts';
+import {
+  actionGroups,
+  actionMenu,
+  currentActor,
+  fromSave,
+  newGame,
+  submit,
+  toSave,
+  view,
+} from '../src/web/game.ts';
+
+/** Play a whole game by always taking the first offered action. */
+function playThrough(seed: number, maxTurns = 20_000) {
+  const game = newGame(seed);
+  let turns = 0;
+  for (; turns < maxTurns; turns++) {
+    if (currentActor(game) === null) break;
+    const { options, groups } = actionGroups(game);
+    if (groups.length === 0 || options.length === 0) break;
+    const first = groups[0]!.actions[0]!;
+    if (!submit(game, options[first.index]!)) break;
+  }
+  return { game, turns };
+}
+
+describe('the browser game plays', () => {
+  it('reaches the end of a game through the same calls the page makes', () => {
+    const { game, turns } = playThrough(77);
+    assert.ok(turns > 50, `only ${turns} decisions — the game stalled`);
+    assert.equal(game.state.status, 'finished');
+    assert.ok(game.state.outcome !== null, 'a finished game must have an outcome');
+  });
+
+  it('never offers an action the engine then refuses', () => {
+    // The action list comes from legalActions, which delegates to check — so every button on the
+    // page must be accepted. A rejection here means the UI and the rules disagree.
+    const game = newGame(21);
+    for (let i = 0; i < 300; i++) {
+      if (currentActor(game) === null) break;
+      const { options, groups } = actionGroups(game);
+      if (groups.length === 0) break;
+      const pick = groups[groups.length - 1]!.actions[0]!;
+      assert.ok(submit(game, options[pick.index]!), 'the engine refused an offered action');
+    }
+  });
+
+  it('offers every legal action somewhere, dropping none', () => {
+    // Grouping is presentation. If a kind is not named in GROUP_ORDER it must still appear, or a
+    // legal move becomes unreachable in a way that is very hard to notice.
+    const game = newGame(5);
+    for (let i = 0; i < 120; i++) {
+      if (currentActor(game) === null) break;
+      const { options, groups } = actionGroups(game);
+      if (options.length === 0) break;
+      const shown = new Set(groups.flatMap((g) => g.actions.map((a) => a.index)));
+      const kinds = new Set(options.map((o) => o.type));
+      const shownKinds = new Set([...shown].map((i2) => options[i2]!.type));
+      assert.deepEqual(shownKinds, kinds, 'a kind of legal action was not offered at all');
+      submit(game, options[[...shown][0]!]!);
+    }
+  });
+
+  it('restores a saved game to the same position', () => {
+    // A save is the seed plus the intents; replaying them must reproduce the game exactly. That is
+    // the payoff of event sourcing, and it is only true while the RNG stays seeded.
+    const game = newGame(909);
+    for (let i = 0; i < 80; i++) {
+      if (currentActor(game) === null) break;
+      const { options, groups } = actionGroups(game);
+      if (groups.length === 0) break;
+      submit(game, options[groups[0]!.actions[0]!.index]!);
+    }
+
+    const restored = fromSave(toSave(game));
+    assert.equal(restored.state.players[0]!.revenue, game.state.players[0]!.revenue);
+    assert.equal(restored.state.clock.day, game.state.clock.day);
+    assert.equal(restored.state.clock.stage, game.state.clock.stage);
+    assert.equal(restored.state.status, game.state.status);
+    assert.deepEqual(view(restored).cells, view(game).cells, 'the board differs after restore');
+  });
+
+  it('is deterministic — the same seed deals the same game', () => {
+    const a = playThrough(4242).game;
+    const b = playThrough(4242).game;
+    assert.equal(a.state.players[0]!.revenue, b.state.players[0]!.revenue);
+    assert.deepEqual(view(a).cells, view(b).cells);
+  });
+});
+
+describe('the action menu presents choices the way they are made', () => {
+  it('offers a card ONCE, with its locations underneath', () => {
+    // A single turn offered 29 track buttons and 7 card buttons in one flat list, with no way to
+    // tell which square each referred to. Subject first, location second.
+    const game = newGame(555);
+    submit(game, actionGroups(game).options.find((o) => o.type === 'localOps.choose' && o.option === 'draw')!);
+
+    const menu = actionMenu(game);
+    const items = menu.placeable.flatMap((g) => g.items);
+    assert.ok(items.length > 0, 'nothing placeable was offered');
+
+    const keys = items.map((i) => i.subjectKey);
+    assert.equal(new Set(keys).size, keys.length, 'the same card appeared as two subjects');
+    for (const item of items) {
+      const labels = item.spots.map((sp) => sp.label);
+      assert.equal(new Set(labels).size, labels.length, `${item.subject} lists a spot twice`);
+      assert.ok(item.spots.length > 0, `${item.subject} has nowhere to go but was offered`);
+    }
+  });
+
+  it('loses no legal action in the reshuffle', () => {
+    // Splitting into direct + placeable must not drop anything: every option must still be reachable.
+    const game = newGame(88);
+    for (let i = 0; i < 120; i++) {
+      if (currentActor(game) === null) break;
+      const menu = actionMenu(game);
+      if (menu.options.length === 0) break;
+      const reachable = new Set([
+        ...menu.direct.flatMap((g) => g.actions.map((a) => a.index)),
+        ...menu.placeable.flatMap((g) => g.items.flatMap((it) => it.spots.map((sp) => sp.index))),
+      ]);
+      const kinds = new Set(menu.options.map((o) => o.type));
+      const shown = new Set([...reachable].map((k) => menu.options[k]!.type));
+      assert.deepEqual(shown, kinds, 'a kind of legal action became unreachable');
+      submit(game, menu.options[[...reachable][0]!]!);
+    }
+  });
+
+  it('names the card in every face-up slot', () => {
+    // "slot 2" is unusable information: the whole point of a face-up slot is choosing it on sight.
+    const game = newGame(555);
+    submit(game, actionGroups(game).options.find((o) => o.type === 'localOps.choose' && o.option === 'draw')!);
+    const draw = actionMenu(game).direct.find((g) => g.title === 'Draw');
+    assert.ok(draw, 'no draw group');
+    for (const a of draw!.actions) {
+      assert.ok(!/^draw\.|^slot \d+$/.test(a.label), `raw intent name on a button: ${a.label}`);
+    }
+    assert.ok(
+      draw!.actions.some((a) => /face-up slot/.test(a.label)),
+      'face-up slots are not named',
+    );
+  });
+
+  it('never offers a train card a place on the board', () => {
+    // A train card goes to the TIMETABLE. Seed 555 offered Extra X15 at six squares with six
+    // rotations each — all identical, because the placement was accepted and then ignored.
+    const game = newGame(555);
+    for (let i = 0; i < 200; i++) {
+      if (currentActor(game) === null) break;
+      const { options } = actionGroups(game);
+      if (options.length === 0) break;
+      for (const o of options) {
+        if (o.type !== 'card.play') continue;
+        const kind = game.state.cards.get(o.cardId)?.kind.kind;
+        if (kind === 'timetabledTrain' || kind === 'extraTrain') {
+          assert.equal(o.placement, undefined, 'a train card was offered a board square');
+        }
+      }
+      submit(game, options[0]!);
+    }
+  });
+
+  it('reports what is left of the personal track supply', () => {
+    // Track is not drawn from the deck — 26 pieces per player, at most one laid a turn — so the
+    // board alone could never answer "how many straights have I got left".
+    const game = newGame(31);
+    const supply = view(game).trackSupply;
+    assert.ok(supply.length > 0, 'no track supply reported');
+    assert.equal(supply.reduce((n, t) => n + t.left, 0), 26, 'the opening supply should be 26');
+    assert.ok(supply.every((t) => !/none/.test(t.piece)), 'un-handed pieces should not say "none"');
+  });
+});
+
+describe('board highlighting', () => {
+  it('gives every spot a coordinate to highlight', () => {
+    const game = newGame(555);
+    submit(game, actionGroups(game).options.find((o) => o.type === 'localOps.choose' && o.option === 'draw')!);
+    const items = actionMenu(game).placeable.flatMap((g) => g.items);
+    assert.ok(items.length > 0);
+    for (const it of items) {
+      for (const sp of it.spots) {
+        assert.equal(typeof sp.coord.row, 'number', `${it.subject} has a spot with no coordinate`);
+        assert.equal(typeof sp.coord.col, 'number', `${it.subject} has a spot with no coordinate`);
+        assert.ok(sp.label.includes(`(${sp.coord.row}, ${sp.coord.col})`), 'label and coord disagree');
+      }
+    }
+  });
+
+  it('highlights squares OUTSIDE the current district', () => {
+    // The commonest placement is just beyond the existing cards — that is what extending means. A
+    // grid sized only to the cards already down would highlight nothing exactly when it matters.
+    const game = newGame(555);
+    submit(game, actionGroups(game).options.find((o) => o.type === 'localOps.choose' && o.option === 'draw')!);
+
+    const cells = view(game).cells;
+    const minCol = Math.min(...cells.map((c) => c.col));
+    const maxCol = Math.max(...cells.map((c) => c.col));
+    const spots = actionMenu(game).placeable.flatMap((g) => g.items).flatMap((i) => i.spots);
+
+    assert.ok(
+      spots.some((sp) => sp.coord.col < minCol || sp.coord.col > maxCol || sp.coord.row < 0),
+      'no legal spot lies outside the current cards — the bounds test would be vacuous',
+    );
+  });
+});
+
+describe('the page explains itself', () => {
+  it('says what every card in hand and every face-up slot does', () => {
+    // A hand of bare names is unplayable: "Steam Turbines" carries no hint of its effect, and all of
+    // this text already existed in the content tables without reaching the screen.
+    for (const seed of [555, 430, 7, 99]) {
+      const f = view(newGame(seed));
+      assert.equal(f.handWhat.length, f.hand.length, 'a hand card has no description slot');
+      f.hand.forEach((name, i) => {
+        const what = f.handWhat[i]!;
+        assert.ok(what.length > 0, `${name} has no description`);
+        // camelCase leaking to the screen is the recurring failure here.
+        assert.doesNotMatch(what, /[a-z][A-Z]/, `raw camelCase in "${name}": ${what}`);
+        assert.doesNotMatch(what, /playerChoicebound|undefined|NaN/, `broken text: ${what}`);
+      });
+      f.departments.forEach((name, i) => {
+        if (name === '—') return;
+        assert.ok(f.departmentsWhat[i]!.length > 0, `face-up ${name} has no description`);
+      });
+    }
+  });
+
+  it('describes every card kind in the deck, not just the easy ones', () => {
+    // Walk the whole deck rather than one hand: the categories differ, and a missing branch would
+    // show as a blank line under a card name only for the seeds that happen to deal it.
+    const game = newGame(1);
+    const seen = new Set<string>();
+    for (const [id, card] of game.state.cards) {
+      const what = cardDescription(game.state, id);
+      assert.ok(what.length > 0, `${card.kind.kind} has no description`);
+      seen.add(card.kind.kind);
+    }
+    assert.ok(seen.size >= 7, `only ${seen.size} card kinds seen — the deck should hold more`);
+  });
+
+  it('states the objective and whether you are keeping up', () => {
+    const f = view(newGame(430));
+    assert.equal(f.objective.target, 20);
+    assert.equal(f.objective.days, 5);
+    assert.match(f.objective.note, /of 20/);
+    assert.match(f.objective.note, /Days? left/);
+  });
+
+  it('explains what each Local Operations option spends', () => {
+    // The most consequential decision of the Stage, previously labelled "choose switch".
+    const game = newGame(555);
+    const choices = actionGroups(game)
+      .options.filter((o) => o.type === 'localOps.choose')
+      .map((o) => describeIntent(game.state, o));
+    assert.ok(choices.length > 0);
+    for (const c of choices) {
+      assert.ok(c.length > 25, `too terse to be an explanation: "${c}"`);
+      assert.match(c, /—/, `no explanation after the option name: "${c}"`);
+    }
+  });
+
+  it('says which way a piece will point, never "rotation 2"', () => {
+    const game = newGame(555);
+    submit(game, actionGroups(game).options.find((o) => o.type === 'localOps.choose' && o.option === 'draw')!);
+    const track = actionMenu(game)
+      .placeable.flatMap((g) => g.items)
+      .filter((i) => /straight|curve|turnout/.test(i.subject));
+    assert.ok(track.length > 0, 'no track pieces offered');
+
+    for (const item of track) {
+      for (const sp of item.spots) {
+        assert.doesNotMatch(sp.label, /rotation \d/, `opaque rotation label: ${sp.label}`);
+      }
+      // A piece with more than one orientation must say which is which, or the spots are ambiguous.
+      const perSquare = new Map<string, number>();
+      for (const sp of item.spots) {
+        const k = `${sp.coord.row},${sp.coord.col}`;
+        perSquare.set(k, (perSquare.get(k) ?? 0) + 1);
+      }
+      if ([...perSquare.values()].some((n) => n > 1)) {
+        assert.ok(
+          item.spots.some((sp) => /east|west|north|south/.test(sp.label)),
+          `${item.subject} offers two orientations on one square without naming them`,
+        );
+      }
+    }
+  });
+});
+
+describe('the static build', () => {
+  const root = join(import.meta.dirname, '..');
+  const dist = join(root, 'dist');
+
+  it('builds, and needs nothing but a static host', () => {
+    execFileSync('node', ['scripts/build-web.ts'], { cwd: root, stdio: 'pipe' });
+
+    assert.ok(existsSync(join(dist, 'index.html')), 'no index.html');
+    assert.ok(existsSync(join(dist, 'web/main.js')), 'no entry script');
+    assert.ok(existsSync(join(dist, 'engine/apply.js')), 'the engine did not emit');
+  });
+
+  it('emits no import that a browser cannot resolve', () => {
+    // Node's type-stripping lets the source import './x.ts'; a browser cannot. The build rewrites
+    // those to .js, and nothing may reach for a bare module or a node: builtin.
+    const files: string[] = [];
+    const walk = (dir: string): void => {
+      for (const e of readdirSync(dir, { withFileTypes: true })) {
+        if (e.isDirectory()) walk(join(dir, e.name));
+        else if (e.name.endsWith('.js')) files.push(join(dir, e.name));
+      }
+    };
+    walk(dist);
+    assert.ok(files.length > 5, 'suspiciously few emitted files');
+
+    for (const f of files) {
+      const src = readFileSync(f, 'utf8');
+      // Anchor to real import/export statements. A loose `from '...'` also matches PROSE — the
+      // turnout comment "a train entering a turnout from \"A\"" was read as importing a module
+      // called A, which is the kind of false alarm that trains you to ignore a failing test.
+      const imports = /^\s*(?:import|export)[^'"\n]*?from\s+['"]([^'"]+)['"]/gm;
+      for (const m of src.matchAll(imports)) {
+        const spec = m[1]!;
+        assert.ok(!spec.endsWith('.ts'), `${f} imports a .ts path: ${spec}`);
+        assert.ok(!spec.startsWith('node:'), `${f} imports a Node builtin: ${spec}`);
+        assert.ok(spec.startsWith('.') || spec.startsWith('/'), `${f} imports bare module: ${spec}`);
+      }
+      assert.ok(!/^[^/*]*\bprocess\.\w/m.test(src), `${f} references process`);
+      assert.ok(!/\brequire\(/.test(src), `${f} uses require()`);
+    }
+  });
+
+  it('renders clickable highlights on the board when a card is picked', async () => {
+    // The real check: load the EMITTED bundle with a DOM stub, click a card, and confirm the board
+    // came back with highlighted squares wired to handlers. Asserting the data has coordinates says
+    // nothing about whether the page draws them.
+    const els = new Map<string, Record<string, unknown>>();
+    const make = (): Record<string, unknown> => {
+      let html = '';
+      // Cache per selector and clear it when innerHTML changes. Returning fresh objects each call
+      // would drop the handlers the page assigns — the test would then report "no button" for a
+      // page that works perfectly.
+      let cache = new Map<string, Record<string, unknown>[]>();
+      const node: Record<string, unknown> = {
+        textContent: '', style: {}, dataset: {}, onclick: null, scrollTop: 0, scrollHeight: 0,
+        querySelectorAll(sel: string) {
+          const hit = cache.get(sel);
+          if (hit) return hit;
+          const out: Record<string, unknown>[] = [];
+          const re = sel.startsWith('[')
+            ? /data-at="([^"]*)"/g
+            : new RegExp(`<button class="${sel.split('.')[1]}[^"]*"([^>]*)>`, 'g');
+          let m: RegExpExecArray | null;
+          while ((m = re.exec(html)) !== null) {
+            const data: Record<string, string> = {};
+            if (sel.startsWith('[')) data['at'] = m[1]!;
+            else {
+              const attr = /data-(\w+)="([^"]*)"/g;
+              let a: RegExpExecArray | null;
+              while ((a = attr.exec(m[1]!)) !== null) data[a[1]!] = a[2]!;
+            }
+            out.push({ dataset: data, onclick: null });
+          }
+          cache.set(sel, out);
+          return out;
+        },
+      };
+      Object.defineProperty(node, 'innerHTML', {
+        get: () => html,
+        set: (v: string) => {
+          html = v;
+          cache = new Map();
+        },
+      });
+      return node;
+    };
+
+    const g = globalThis as Record<string, unknown>;
+    g['document'] = {
+      getElementById: (id: string) => {
+        if (!els.has(id)) els.set(id, make());
+        return els.get(id);
+      },
+    };
+    g['location'] = { search: '?seed=555' };
+    const store = new Map<string, string>();
+    g['localStorage'] = {
+      getItem: (k: string) => store.get(k) ?? null,
+      setItem: (k: string, v: string) => void store.set(k, v),
+      removeItem: (k: string) => void store.delete(k),
+    };
+    // No parameter properties — `erasableSyntaxOnly` forbids them, since Node strips types rather
+    // than compiling them.
+    g['URLSearchParams'] = class {
+      search: string;
+      constructor(search: string) {
+        this.search = search;
+      }
+      get(k: string): string | null {
+        return new RegExp(`${k}=([^&]*)`).exec(this.search)?.[1] ?? null;
+      }
+    };
+
+    await import(`file://${join(dist, 'web/main.js')}?t=${Date.now()}`);
+
+    const actions = els.get('actions')!;
+    const grid = els.get('grid')!;
+
+    // Take the draw option, then pick the first placeable subject.
+    const clickFirst = (el: Record<string, unknown>, sel: string): boolean => {
+      const fn = el['querySelectorAll'] as (s: string) => Record<string, unknown>[];
+      const nodes = fn.call(el, sel);
+      const target = nodes[0];
+      if (!target) return false;
+      (target['onclick'] as (() => void) | null)?.();
+      return true;
+    };
+
+    assert.ok(clickFirst(actions, 'button.act'), 'no action button rendered');
+    assert.ok(clickFirst(actions, 'button.subj'), 'no card/track subject to pick');
+
+    const html = String(grid['innerHTML']);
+    assert.match(html, /class="cell[^"]*legal/, 'picking a card highlighted nothing');
+    assert.match(html, /data-at="/, 'highlighted squares carry no click target');
+    assert.match(html, /ghost/, 'no empty square was offered as a destination');
+  });
+
+  it('serves a page that loads the game as a module', () => {
+    const html = readFileSync(join(dist, 'index.html'), 'utf8');
+    assert.match(html, /<script type="module" src="\.\/web\/main\.js">/);
+    assert.ok(!/https?:\/\//.test(html.replace(/<!--[\s\S]*?-->/g, '')), 'page fetches something external');
+    for (const id of ['grid', 'division', 'actions', 'log', 'facs', 'hand', 'blocked']) {
+      assert.ok(html.includes(`id="${id}"`), `page is missing #${id}`);
+    }
+  });
+});