adding classification and division yard updates, train collisions, engine and car updates, turnout improvements.

2026-08-04 21:03:17 -04:00
parent 4bba991f41
commit 821d3cdffa
26 changed files with 6876 additions and 2638 deletions
@@ -22,5 +22,9 @@ __pycache__/
 # Logs
 *.log

-# Generated replays
-replay*.html
+# Generated replays — ANCHORED to the repo root on purpose.
+#
+# Unanchored, `replay*.html` also matched `src/web/replays.html`, which is a SOURCE file: the
+# website's replay viewer. It was therefore never committed, and a fresh clone was missing a page
+# the build copies unconditionally. Only the throwaway files this directory collects are ignored.
+/replay*.html
@@ -10,6 +10,237 @@ The target is 20 Revenue over 5 Days.

 ## Unreleased

+### Q13 — a train that catches the one ahead runs into it
+
+Answered, and implemented as option B: **collide on catching up**, which is the version that rewards
+judging the gap.
+
+§10 makes a Mainline collision the Superintendent's fault and removes both trains, and ABS Signals
+exists to stop trains rear-ending each other — but §8.3's trigger list never named one and nothing
+was implemented, so granting clearance was FREE: both trains survived, no penalty, and ABS Signals
+protected against nothing. Now a following train that closes on the one ahead runs into it, and one
+that never closes is fine, so clearance is a bet on relative speed rather than a formality. §2.1
+divides the card into two regions, and sharing one is what "caught up" means. ABS Signals does what
+it prints instead: the follower stops short and holds.
+
+**Not on a card that prints "trains may pass".** The first version fired 0.41 times a game while the
+bot never once granted clearance, which is the tell — those were all Double Track and Uncontrolled
+Siding, cards that hold two trains because they HAVE two roads. Catching up there means going past,
+which is what the card is for.
+
+With that corrected the mechanic is invisible to the current bot, because it always denies
+clearance. That is the right shape, and the teeth are real:
+
+| Superintendent | revenue | rear-enders | ABS holds |
+| --- | --- | --- | --- |
+| always denies (the bot) | 7.34 | 0.00/game | 0 |
+| **always allows** | **−5.13** | **2.20/game** | 19 |
+
+So the bot's always-deny policy — a deliberate choice made when clearance was free and the
+arithmetic only guessed at — turns out to be correct, and is now correct for a measured reason.
+
+Tested deterministically rather than through the bot: two trains built onto one single-track card
+with the follower closing, which collides whichever order the phase processes them in, and the same
+pair again with ABS Signals to prove it holds instead.
+
+### The engine has a place in the train, and the yards are visible
+
+**The engine had a position the game recorded and never used.** `engineFront` was a boolean, written
+in three places and read in none — so every consist was drawn as an anonymous row of cars. It is now
+`engineAt`, an index into the consist, because a Crew Tray is an engine plus its Rolling Stock and
+the engine may be PULLING (ahead of everything), PUSHING (behind everything), or in the middle doing
+both at once. A boolean cannot say the third thing. Consists are drawn with `ENG` where it sits.
+
+The engine is deliberately NOT one of the `consist` entries: §8.2 counts the consist as Rolling
+Stock, and the four-car limit (§A.4) is a limit on cars, not on the locomotive hauling them.
+
+**Both yards are now on the page**, by car type and split loaded / empty, with the Division Yard
+outlined the moment it goes bare. This matters more than it did: the Classification Yard returns to
+service only when the Division Yard is empty, so the supply genuinely runs down, and a game that
+never showed either yard gave no warning at all.
+
+It shows the pressure immediately. In a finished game the Division Yard held 30 cars — hoppers,
+tanks and cabooses — and **no boxcars, coaches or reefers at all**, while 19 of them sat in
+Classification unable to come back, because the Division Yard was not bare.
+
+Crew Tray scarcity was already implemented and is left alone: a train with no free tray is held
+(`trainHeld`), which is §7.
+
+### The Classification Yard rule, from the source — and my guess was worth 2.4 Revenue it should not have been
+
+Answered: used Rolling Stock is set out in the Classification Yard, used engines and cabooses go
+straight back to the Division Yard, and **the Classification Yard empties only when the Division
+Yard is bare** — then all of it returns at once.
+
+That is a much harder rule than the one I invented. Returning cars at every DAY boundary keeps the
+yard topped up continuously; this lets it run down to nothing and refill in one go, which is the
+whole of the supply pressure the game is meant to have. Measured paired over 400 seeds:
+
+    my Day-boundary guess 9.67   the real rule 7.25
+    paired change  -2.42 ± 0.49   (t -9.67)   235 of 400 seeds affected
+
+So the +2.32 celebrated when the Classification Yard was first made readable was very largely an
+artefact of getting the trigger wrong. The refill is now checked wherever a car leaves the Division
+Yard, so it fires the moment the yard empties rather than at the next convenient tick.
+
+**Poling is dealt zero copies** rather than deleted. Its effect is "TBD in the source", so there is
+nothing to implement and a card that cannot be played is worse in a hand than absent from the deck.
+The catalogue entry stays so the gap remains visible. Deck 140 → 139, solitaire 118 → 117.
+
+**Heavy Grade orientation stays rolled from the seed**, and is now documented as temporary in the
+code rather than only in TODO: the card says the player sets it, but it is dealt during setup and
+setup has no decision point — `createGame` is a pure function of the seed, which is also what makes
+a save portable.
+
+**A counting question this raised, and could not answer.** A census of every holder of rolling stock
+comes to 92 against the 80 dealt. That is not proof of duplication: `outboundBox`, `inboundBox` and
+`menAtWork` all hold `RollingStock`, and stocking a green box takes a LOADED CAR out of the Division
+Yard — so some of those objects are cargo in transit rather than cars, and nothing distinguishes
+them. An accounting test was written and then withdrawn, because it could not tell the two apart.
+Logged: until a load is its own type, "is any stock being created or destroyed?" is unanswerable.
+
+### The freight figures were counting one half of freight
+
+A measurement fix, not a game fix — but it is the instrument every balance decision is read from.
+
+`rev.freightUnload` was assigned `eventCounts['unloadBegan']`: unloads STARTED, not Revenue EARNED,
+and the two differ by every unload that never finished. `grossFreight` then used `freightLoad`
+alone, so `freightShare` omitted the unload half outright. A completed load and a completed unload
+each earn a point, on two distinct `revenueChanged` reasons.
+
+The comment that stood there claimed "an unload scores through the same event as a load completion
+in the reducer". It does not — `apply.ts` emits `freightUnload` separately. A comment asserting a
+fact about code a few lines away, and wrong.
+
+    freight share of gross:  39%  ->  49%
+
+The harness now prints both halves. `strategyBuckets` counted "a scoring game" the same wrong way,
+and so did the test guarding it — so a game that scored only by unloading was bucketed but not
+counted, which is how the fix first showed up as a failure.
+
+This matters backwards as well as forwards: the "freight is only 13-18% of gross" finding was read
+from this number, and it is what drove the Gap 12 industry-density change. That decision was taken
+against an instrument reading roughly 60% low.
+
+### Turnouts that go nowhere — reported, confirmed, and mostly not the problem
+
+Reported from two replays: of 8 turnouts off the Running Track, 2 formed a run-around, 2 served
+industries and 4 went nowhere. Measured across 120 games, that holds exactly:
+
+| what a turnout leads to | |
+| --- | --- |
+| part of a run-around | 30% |
+| a stub, but serves an industry | 12% |
+| a stub ending in bare track | 44% |
+| **nothing below it at all** | **15%** |
+
+**4.61 wasted turnouts a game.** Then three attempts to stop it, each measured paired over 400
+seeds, and each WORSE than leaving it alone:
+
+| attempt | paired change | |
+| --- | --- | --- |
+| no new way down while one leads nowhere | run-arounds → **0** | deadlocked: a run-around needs TWO ways down, and the second cannot be justified by what hangs off the first |
+| first two free, gate the rest | **−0.84 ± 0.53** (t −3.08) | track spend collapsed 15.4 → 4.8 |
+| forbid rail that butts an incompatible card | **−0.62 ± 0.57** (t −2.11) | |
+
+The reason is that a turnout is not only a way DOWN. It is also a way UP, and both the east-west
+extension and the closing arc are gated on one existing beyond them — so cutting the turnouts cuts
+the places a siding can rejoin, and the sidings stop forming too. The apparent waste is optionality.
+This also re-confirms, with proper statistics, a note left in the code by an earlier attempt.
+
+### Rail that can never go anywhere
+
+The one that did work, and only as a tie-breaker.
+
+A port facing an EMPTY square is a promise: something may be built there later. A port butting an
+OCCUPIED square whose card has no matching port is not — that square is taken, so the rail stops
+dead and always will. Reported from seed 618682, where an arc came off a turnout with its far end
+jammed into a curve that could not accept it. Measured: **28% of all pieces laid, 4.26 a game.**
+
+Forbidding it cost 0.62 revenue a game. Applying it as a **tie-breaker on the distance score** —
+never able to veto a piece, only to choose between two the heuristics rate equally — measured
+**+0.43 ± 0.49 (t 1.74)**, with 108 seeds better against 67, and cut these from 28% of pieces to 7%.
+Not significant on its own, but it is the only one of four attempts pointing the right way, and the
+mechanism is sound.
+
+**And it fixed the reported problem after all — sideways.** Re-running the turnout taxonomy:
+
+| what a turnout leads to | before | after |
+| --- | --- | --- |
+| part of a run-around | 30% | **66%** |
+| a stub, but serves an industry | 12% | 13% |
+| a stub ending in bare track | **44%** | **2%** |
+| nothing below it at all | 15% | 18% |
+| **wasted per game** | **4.61** | **1.65** |
+
+Bare stubs all but gone and run-arounds more than doubled, without ever refusing a turnout. Refusing
+them directly had destroyed the run-arounds; declining to lay rail INTO a dead end leaves the bot
+free to cut every turnout it likes and quietly stops it building the stubs. The remaining waste is
+the last turnouts of a game, cut with no turns left to build beneath them.
+
+Also added, and honest about it: a turnout is not cut when no arc remains to hang beneath it.
+Measured at **0%** today — the bot lays the arc immediately after the turnout and never runs the
+supply dry — so it is a guard against the supply changing rather than a fix for anything happening
+now. Its test constructs the situation by draining the arcs.
+
+### A source file git was hiding
+
+Found while checking the above: **`src/web/replays.html` had never been committed.** `.gitignore`
+carried `replay*.html` to catch the throwaway files generated at the repo root, and unanchored it
+also matched a source page — the website's replay viewer. `git archive HEAD` confirms it: a fresh
+clone does not contain that file, and `build-web.ts` copies it unconditionally, so the build would
+have failed for anyone but this working copy.
+
+The pattern is anchored to the root now (`/replay*.html`), which still ignores the generated files
+and no longer ignores the source. A test asks GIT — not `.gitignore` — whether each source page
+would survive a clone, because that is the actual question.
+
+### Three places draw a game, and they had drifted
+
+Reported from playtesting: the replay had lost its "extra slow" speed, and neither the sound nor the
+auto-hide could be found. Both true, and the same cause — a game is drawn in THREE places and only
+some of them had kept up:
+
+| | speeds | sound | auto-hide |
+| --- | --- | --- | --- |
+| the playable page | — | yes | yes |
+| the standalone replay file | 5 | yes | yes |
+| **the website's replay viewer** | **3** | **no** | **no** |
+
+The website viewer is its own implementation — it replays a save through the engine in the browser
+rather than reading a rendered file — and it never got what the other two grew. It now has all five
+speeds (extra slow through very fast), the sound, and the auto-hide, using the same shared `cuesFor`
+and `playCue` as everywhere else.
+
+Three tests hold them together from now on: the two viewers must offer the SAME set of speeds, all
+three pages must carry the sound and auto-hide controls, and `replays.ts` may not ask for an element
+its page does not have — the same total check the playable page already had, and the one that would
+have caught this. Verified by removing a speed and a control and watching them fail.
+
+### The published replays had stopped replaying
+
+Both saves in `public/replays/` were dead. A save is a seed plus the intents, replayed through the
+real engine — so it cannot describe a position the rules could not produce, and an intent that no
+longer applies stops the replay rather than being forced. That is the safe direction, but it is
+silent: `seed-202` got 42 intents into 360 before halting, and `seed-430` managed 4 of 338.
+
+They were recorded before this run's rules work — Modifier hosts, the industry-to-car mapping, the
+Classification Yard — so most of what they described is no longer legal. Replaced with three games
+generated against the rules as they stand, each verified to replay every intent to the final Day:
+
+| | |
+| --- | --- |
+| A winning run | 36 Revenue, seed 1038389 |
+| A strong run | 32 Revenue, seed 618682 |
+| Collisions | 10 Revenue and 27 smashes, seed 919604 |
+
+The third is deliberately a bad game: a full Office is a collision, and it costs more than the
+freight was worth.
+
+This is the "save/restore is not version-aware" item in TODO doing exactly what it warns about. The
+saves are cheap to regenerate, so the fix is not to freeze them — it is for a stale save to say so
+instead of quietly ending early.
+
 ### The replay behaves like the game it is replaying

 Sound and the district auto-hide were built for the playable page and the replay had neither, which
@@ -9,16 +9,45 @@ Ordered within each section by how much it is currently costing us.

 ## Next

+- [ ] **A "load" is stored as a car, so rolling stock cannot be counted.** `outboundBox`,
+      `inboundBox` and `menAtWork` all hold `RollingStock`, and `freightAgent.stockOutbound` takes a
+      LOADED CAR out of the Division Yard to fill a green box. So a census of every holder comes to
+      92 against the 80 dealt at setup — not necessarily duplication, because some of those objects
+      are cargo in transit rather than cars, but there is no way to tell them apart. Until a load is
+      its own type, "is any stock being created or destroyed?" is an unanswerable question, and the
+      supply numbers below cannot be tuned with confidence.
+- [ ] **Engines are not a SUPPLY yet, only a position.** `engineAt` now records where the engine
+      sits in the tray and the consist shows it, but an engine is still conjured with the tray
+      rather than drawn from the Division Yard and returned to it. The rules put engines in the
+      Division Yard alongside the cars, with a predefined number of them, so running out of engines
+      should be a second way trains get held — today only the Crew Tray count does that. Needs a
+      number to start from, then playtesting.
+- [ ] **The yards are shown on the play page but not in either replay viewer.** The Frame carries
+      them, so it is a rendering job, not a modelling one.
+- [ ] **The rolling stock supply is a guess.** `ROLLING_STOCK_SUPPLY` (coach 8+8, boxcar 10+10,
+      hopper 8+8, reefer 5+5, tank 6+6, caboose 6) is marked provisional in `content.ts` and was
+      scaled alongside the Gap 12 industry increase. Now that the Classification Yard returns stock
+      only when the Division Yard empties, these numbers set the real supply pressure. Adjust from
+      playtesting rather than theory, and watch whether industry density feels light or heavy at the
+      same time.
+- [ ] **Heavy Grade orientation is rolled, not chosen.** The card prints "Player sets orientation",
+      but it is dealt during setup and setup has no decision point at all — `createGame` is a pure
+      function of the seed, which is also what makes a save portable. Rolled from the seed for now.
+      Revisit when setup gains an interactive phase; the orientation matters, because it decides
+      which direction climbs and therefore what Brakeman and Helpers are worth.
+
 - [ ] **Measure with error bars from now on.** Revenue has a standard deviation of ~9, so a
      100-game run carries about ±1.0 of noise — every single-change revenue claim in the changelog
      before the Interlocking work is inside that. Use paired per-seed comparison (the harness deals
      the same seeds either way) and 400+ games before calling a heuristic change good or bad. The
      first attempt at the Running Track straight was read as a 0.6 REGRESSION on 100 games and is
      a 0.7 improvement on 400.
- [ ] **Confirm the Classification Yard rule against the source.** Cars now return to the Division
-      Yard at the Day boundary — an ASSUMPTION, not a recovered rule. Gap 2c says everything but
-      cabooses goes to Classification and never says how it empties. It is worth +2.32 revenue a
-      game, so if the real rule differs the balance numbers move with it.
+- [x] ~~**Confirm the Classification Yard rule against the source.**~~ Confirmed, and the guess was
+      wrong. The rule is: used Rolling Stock to the Classification Yard, used engines and cabooses
+      straight back to the Division Yard, and the Classification Yard empties ONLY when the Division
+      Yard is bare — then all at once. The Day-boundary version I had invented was far more generous
+      and worth **+2.42 revenue a game the game does not actually grant**. Corrected; revenue 9.67
+      → 7.25.
 - [x] ~~**Enhancements are placed but mostly do nothing.**~~ Measured: forbidding every Enhancement
      except Interlocking is worth **-0.01 ± 0.41 (t = -0.04)** over 400 paired seeds. They neither
      pay nor cost. Left alone. Unlocking the Running Track straight put
@@ -42,11 +71,8 @@ Ordered within each section by how much it is currently costing us.
      needs a stocked green box AND a spotted car AND a free Laborer to line up in the same Stage.
      Measure how many Stages have all three before changing any heuristic — the answer may be that
      the economy, not the bot, is what caps freight.
- [ ] **`stats.ts` undercounts freight.** `rev.freightUnload` is assigned `eventCounts['unloadBegan']`
-      — unloads *begun*, not revenue *earned* — and `grossFreight` uses `freightLoad` alone, so
-      `freightShare` omits unload revenue entirely. The comment justifying it ("an unload scores
-      through the same event as a load completion") is wrong: `apply.ts:947` emits a distinct
-      `freightUnload` reason. This is why freight was recorded at 13–18% of gross.
+- [x] ~~**`stats.ts` undercounts freight.**~~ Fixed: both halves counted, freight share 39% → 49%.
+      Worth revisiting the **industry density** decision below, which was taken on the old number.

 ---

@@ -54,13 +80,9 @@ Ordered within each section by how much it is currently costing us.

 Blocked on a decision, not on work.

- [ ] **Q13 — rear-end collisions on a Mainline card.** §10 says a Mainline collision is the
-      Superintendent's fault and removes both trains, and ABS Signals exists to prevent rear-enders —
-      but §8.3's trigger list does not include one, and **none is implemented**. Granting clearance is
-      currently free: verified, both trains survive, no penalty. Three candidates: collide on entry
-      (clearance becomes a gamble), collide on catching up (rewards judging the gap), or accept that
-      clearance is safe and ABS Signals is worth less than it reads. The buttons currently describe
-      only what the engine does, so nothing promises a consequence that cannot happen.
+- [x] ~~**Q13 — rear-end collisions on a Mainline card.**~~ Answered: collide on catching up.
+      Implemented, and not on cards that print "trains may pass". Invisible to a bot that always
+      denies clearance; a bot that always allows drops from 7.34 revenue to **-5.13**.
 - [ ] **Poling.** The only card in the deck with no defined behaviour — the sheet records its effect
      as "TBD in the source". A test asserts it stays TBD so nobody invents one.
 - [ ] **Heavy Grade orientation at setup.** The card says "Player sets orientation", but `createGame`
@@ -165,7 +187,11 @@ target is settled and freight carries its intended share.
 - [ ] **No way to start a fresh game from inside the page.** `?seed=` gives a reproducible deal and
      "new game" only appears once a game has ended, so abandoning a bad opening means editing the URL.
 - [ ] **Save/restore is not version-aware.** A save from an older ruleset stops replaying rather than
-      failing loudly, which is the safe direction but says little about what changed.
+      failing loudly, which is the safe direction but says little about what changed. **This has now
+      bitten once**: both published replays were dead — one got 42 intents into 360, the other 4 of
+      338 — and nothing said so; they simply ended early and looked like short games. A save should
+      carry a ruleset stamp and the page should say "this replay was recorded under an older
+      ruleset and stops at Stage N" rather than presenting a truncated game as a whole one.

 ---

@@ -30,6 +30,8 @@ import {
  collectiveRevenueFloor,
  lengthProfile,
  officeProfile,
+  REGIONS_PER_MAINLINE_CARD,
+  mainlineProfile,
 } from './content.ts';
 import type { Direction } from './content.ts';
 import type { GameEvent } from './events.ts';
@@ -186,7 +188,7 @@ function newTrainPhase(s: GameState, events: GameEvent[]): AdvanceResult {
        id: trayId,
        trainNumber: due,
        trainIsExtra: false,
-        engineFront: true,
+        engineAt: 0,
        consist: [],
        direction,
        position: { at: 'divisionPoint', side },
@@ -219,7 +221,7 @@ function newTrainPhase(s: GameState, events: GameEvent[]): AdvanceResult {
        id: trayId,
        trainNumber: number,
        trainIsExtra: false,
-        engineFront: true,
+        engineAt: 0,
        consist: [],
        direction,
        position: { at: 'divisionPoint', side },
@@ -250,7 +252,7 @@ function newTrainPhase(s: GameState, events: GameEvent[]): AdvanceResult {
      id: trayId,
      trainNumber: number,
      trainIsExtra: true,
-      engineFront: true,
+      engineAt: 0,
      consist: [],
      direction: 'east',
      position: { at: 'divisionPoint', side: 'west' },
@@ -488,6 +490,53 @@ function moveTrain(
    // Q1/Q2 — crossing takes a whole number of Stages set by the card's speed and the train's
    // Fast/Slow class. Count it down rather than stepping through printed cells.
    if (transit.stagesRemaining > 1) {
+      /**
+       * Q13 — REAR-END COLLISIONS, answered: a train collides when it CATCHES UP.
+       *
+       * §10 makes a Mainline collision the Superintendent's fault and removes both trains, and ABS
+       * Signals exists to stop trains rear-ending each other — but §8.3's trigger list never named
+       * one and none was implemented, so granting clearance was free: both trains survived, no
+       * penalty, and ABS Signals protected against nothing.
+       *
+       * Colliding on CATCHING UP is the version that rewards judging the gap. A following train
+       * that closes on the one ahead runs into it; a following train that never closes is fine, so
+       * clearance becomes a bet on relative speed rather than a formality. §2.1 divides the card
+       * into two regions, and sharing one is what "caught up" means.
+       *
+       * ABS Signals does what it says instead: the follower stops SHORT of the collision and holds.
+       */
+      const regionOf = (t: { stagesTotal: number; stagesRemaining: number }): number => {
+        const entry = REGIONS_PER_MAINLINE_CARD - t.stagesTotal;
+        const elapsed = t.stagesTotal - t.stagesRemaining;
+        return Math.min(REGIONS_PER_MAINLINE_CARD - 1, Math.max(0, entry + elapsed));
+      };
+      // NOT on a card that prints "trains may pass". Double Track and Uncontrolled Siding hold two
+      // trains because they HAVE two roads, so a train catching another there goes past it — that
+      // is what the card is for. Without this the mechanic fired 0.41 times a game while the bot
+      // never once granted clearance, which is the tell: those were all passing cards.
+      const mayPass = mainlineProfile(node.card).trainsMayPass;
+      const next = regionOf({ stagesTotal: transit.stagesTotal, stagesRemaining: transit.stagesRemaining - 1 });
+      const ahead = mayPass
+        ? undefined
+        : node.transits.find(
+            (t) => t.tray !== id && t.direction === transit.direction && regionOf(t) === next,
+          );
+
+      if (ahead) {
+        if (node.absSignals) {
+          // "Trains on this card will not rear-end each other; they stop short of a collision."
+          events.push({
+            type: 'trainHeld',
+            trainNumber: tray.trainNumber ?? 0,
+            reason: 'ABS Signals — held short of the train ahead',
+          });
+          return 'held';
+        }
+        // §10 — the Superintendent let it in behind the other, so it is the Superintendent's fault.
+        collide(s, s.clock.superintendent, [id, ahead.tray], events, 'ran into the train ahead', 'the Mainline');
+        return 'moved';
+      }
+
      transit.stagesRemaining -= 1;
      return 'moved';
    }
@@ -756,25 +805,6 @@ function shiftChange(s: GameState, events: GameEvent[]): AdvanceResult {
    // Telegraph/Telephone/Radio are each usable once a Day.
    for (const area of s.officeAreas.values()) area.dispatchUsedToday = [];

-    /**
-     * THE CLASSIFICATION YARD GOES BACK INTO SERVICE OVERNIGHT.
-     *
-     * ASSUMPTION, flagged rather than derived: Gap 2c says engines and cabooses return to the
-     * Division Yard and everything else to Classification, and the recovered rules never say how
-     * Classification empties. It was write-only — seven places pushed into it and nothing ever read
-     * it — so rolling stock drained one way and left the game. Measured at 30 cars a game dead by
-     * the end, 37% of the 80 dealt at setup.
-     *
-     * Sorting cars for redistribution is what a classification yard is FOR, and a Day is its
-     * natural cycle, so they return at the Day boundary. This does not bind a 5-Day game — the
-     * Division Yard still held 16.6 loaded freight cars at the end and ran dry in 2 games of 100 —
-     * but a campaign-length game would have starved.
-     */
-    if (s.yards.classificationYard.length > 0) {
-      s.yards.divisionYard.push(...s.yards.classificationYard);
-      s.yards.classificationYard = [];
-    }
-
    s.clock.day += 1;
    s.clock.stage = 1;
    s.collisionsToday = 0;
@@ -1174,6 +1174,7 @@ export function reduce(s: GameState, e: GameEvent): void {
        (c) => c.type === e.stock.type && c.loaded === e.stock.loaded,
      );
      if (idx >= 0) s.yards.divisionYard.splice(idx, 1);
+      refillDivisionYardIfEmpty(s);
      f.outboundBox.push(e.stock);
      s.turn.freightAgentUsed = true;
      break;
@@ -1236,6 +1237,7 @@ export function reduce(s: GameState, e: GameEvent): void {
        (c) => c.type === e.stock.type && c.loaded === e.stock.loaded,
      );
      if (idx >= 0) s.yards.divisionYard.splice(idx, 1);
+      refillDivisionYardIfEmpty(s);
      tray.consist.push(e.stock);
      break;
    }
@@ -1674,6 +1676,30 @@ export function acceptsCar(tray: CrewTray, carType: CarType): boolean {
  return true;
 }

+/**
+ * §2 — WHEN THE DIVISION YARD RUNS OUT, THE CLASSIFICATION YARD GOES BACK INTO SERVICE.
+ *
+ * Used Rolling Stock is set out in the Classification Yard; used engines and cabooses go straight
+ * back to the Division Yard. The Classification Yard empties only when the Division Yard is bare —
+ * every car of every kind gone — and then all of it returns at once.
+ *
+ * Confirmed from the source after an earlier guess. The first implementation returned cars at the
+ * DAY boundary, which is a different rule and a much more generous one: it kept the yard topped up
+ * continuously, where this lets it run down to nothing and refill in one go. That difference is the
+ * whole of the supply pressure the game is meant to have.
+ *
+ * Called wherever a car leaves the Division Yard, so the refill happens the moment it empties
+ * rather than at the next convenient tick.
+ */
+export function refillDivisionYardIfEmpty(s: GameState): { type: 'yardRefilled'; count: number } | null {
+  if (s.yards.divisionYard.length > 0) return null;
+  if (s.yards.classificationYard.length === 0) return null;
+  const count = s.yards.classificationYard.length;
+  s.yards.divisionYard.push(...s.yards.classificationYard);
+  s.yards.classificationYard = [];
+  return { type: 'yardRefilled', count };
+}
+
 /** A fresh Limits sign. The set is "2N + spares" (§12), so relocating one is not a supply question. */
 function limitsCard(): TrackCard {
  return {
@@ -584,7 +584,12 @@ export const SECOND_SECTION = { key: 'secondSection', name: 'Second Section', co
 export const MANEUVER_CARDS: readonly SimpleCard[] = [
  { key: 'redFlags', name: 'Red Flags', copies: 5, placement: 'any time', effect: 'A stopped train is prevented from being hit; the approaching train is prevented from moving.' },
  { key: 'flyingSwitch', name: 'Flying Switch', copies: 1, placement: 'any time', effect: 'Break a cut of cars away from behind the engine and roll them into an industry.' },
-  { key: 'poling', name: 'Poling', copies: 1, placement: 'any time', effect: 'TBD in the source.' },
+  // POLING IS OUT OF THE DECK, at 0 copies rather than deleted.
+  //
+  // It is the one card whose effect the source records as "TBD", so there is nothing to implement
+  // and inventing something would be worse than leaving it out. Kept in the table with its text so
+  // the gap stays visible and the card can be dealt again the moment its rule is known.
+  { key: 'poling', name: 'Poling', copies: 0, placement: 'any time', effect: 'TBD in the source.' },
 ];

 /** Played AT other players. We have no player-interaction mechanic yet. */
@@ -196,6 +196,13 @@ function buildDivision(players: number, rng: Rng): DivisionNode[] {
    // least deterministic and varies between games; it should become a real player choice when
    // setup gains an interactive phase. See implications.md §10 Q11.
    if (mainlineProfile(card).speed.kind === 'grade') {
+      /**
+       * TEMPORARY, and flagged in TODO. The card prints "(Up)" and "Player sets orientation", so
+       * which way a Heavy Grade climbs is the player's decision — but it is dealt during setup, and
+       * setup has no decision point at all. Rolled from the seed until it gains one, because the
+       * orientation MATTERS: it decides which direction climbs, and therefore what a Brakeman or
+       * Helpers card is worth.
+       */
      node.gradeUp = rng.nextInt(2) === 0 ? 'east' : 'west';
    }
    return node;
@@ -202,8 +202,19 @@ export type CrewTray = {
  /** null while a local crew is switching without a train card. */
  trainNumber: number | null;
  trainIsExtra: boolean;
-  /** Which end the engine occupies (§A.3). */
-  engineFront: boolean;
+  /**
+   * WHERE THE ENGINE SITS IN THE TRAY, as an index into `consist`.
+   *
+   * A Crew Tray is an engine plus its Rolling Stock, and the engine may be PULLING (index 0, ahead
+   * of everything), PUSHING (index `consist.length`, behind everything) or somewhere in the middle
+   * doing both at once. That last case is why this is an index and not the boolean it replaced —
+   * `engineFront` was written in three places and read in none, so the engine had a position the
+   * game recorded and never used.
+   *
+   * The engine is NOT one of the `consist` entries: §8.2 counts the consist as Rolling Stock, and
+   * the four-car limit (§A.4) is a limit on cars, not on the locomotive hauling them.
+   */
+  engineAt: number;
  /** ORDERED, left-to-right. Max 4 including any caboose (§A.4). */
  consist: RollingStock[];
  direction: Direction;
@@ -24,7 +24,7 @@ import { MAX_CONSIST, nextOfficeTier } 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 { exitsFrom, facilityVariants, hasPort, neighbour, opposite, variantsFor } from '../engine/track.ts';
+import { connectionsFor, exitsFrom, facilityVariants, hasPort, neighbour, opposite, variantsFor } from '../engine/track.ts';
 import type { Port } from '../engine/track.ts';
 import { coordKey } from '../engine/state.ts';
 import type { Facility, GameState, GridCoord, OfficeArea, PlayerIndex, RollingStock, TrackCard } from '../engine/state.ts';
@@ -524,6 +524,60 @@ function bestTrackLay(s: GameState, player: PlayerIndex, options: Intent[]): Int
  const arcOf = (i: Extract<Intent, { type: 'track.lay' }>): string | undefined =>
    variantsFor(i.geometry)[i.variant ?? 0]?.arc;

+  /**
+   * RAIL THAT CAN NEVER GO ANYWHERE.
+   *
+   * A port facing an EMPTY square is a promise: something may be built there later. A port butting
+   * an OCCUPIED square whose card has no matching port is nothing of the kind — that square is
+   * taken, so the rail stops dead and always will.
+   *
+   * Measured, 28% of the pieces the bot laid had one, at 4.26 a game: an arc dropped off a turnout
+   * with its far end jammed into a curve that could not accept it, which is exactly the placement
+   * that prompted this. Penalised rather than forbidden — a piece can still be worth laying for the
+   * end that DOES connect, and the last two attempts to forbid something outright starved the
+   * district instead of tidying it.
+   */
+  const deadEnds = (i: Extract<Intent, { type: 'track.lay' }>): number => {
+    const v = variantsFor(i.geometry)[i.variant ?? 0];
+    const probe = {
+      geometry: {
+        kind: 'track',
+        geometry: i.geometry,
+        ...(v?.axis ? { axis: v.axis } : {}),
+        ...(v?.arc ? { arc: v.arc } : {}),
+        ...(v?.turnout ? { turnout: v.turnout } : {}),
+      },
+      baseOperationalRail: true,
+      standing: [],
+      facility: null,
+      modifiers: [],
+      enhancements: [],
+    } as unknown as TrackCard;
+    let dead = 0;
+    for (const p of new Set(connectionsFor(probe).flat())) {
+      const n = neighbour(i.placement, p);
+      const nb = at(n.row, n.col);
+      if (!nb) continue;                        // empty — may still be built on
+      if (hasPort(nb, opposite(p))) continue;   // joins
+      dead++;
+    }
+    return dead;
+  };
+
+  /**
+   * Arcs left to build BENEATH a turnout.
+   *
+   * A turnout is a hole in the Running Track and is worth cutting only for what hangs under it, so
+   * cutting one with nothing left to hang there is pure loss. Measured at 0% today — the bot builds
+   * the arc immediately after the turnout and never runs the supply dry first — so this is a guard
+   * against the supply changing rather than a fix for something happening now.
+   */
+  const arcsLeft =
+    (area.trackSupply.get('curved:left') ?? 0) +
+    (area.trackSupply.get('curved:right') ?? 0) +
+    (area.trackSupply.get('sharpCurved:left') ?? 0) +
+    (area.trackSupply.get('sharpCurved:right') ?? 0);
+
  // Where the district already turns down off the main.
  const turnouts = [...area.grid.entries()]
    .filter(([k, c]) => Number(k.split(',')[0]) === area.runningRow && divergesSouth(c))
@@ -562,7 +616,7 @@ function bestTrackLay(s: GameState, player: PlayerIndex, options: Intent[]): Int
      // without competing further with the ways down. Scored below a first turnout, which is still
      // the most valuable single piece on the board, and below closing a run-around.
      bonus += 13;
-    } else if (row === area.runningRow && i.geometry === 'turnout') {
+    } else if (row === area.runningRow && i.geometry === 'turnout' && arcsLeft > 0) {
      // A first way down is the most valuable single piece on the board; a second closes the
      // run-around. Beyond that they are just holes in the Running Track — measured at 6.4 per game
      // when unrestrained, which consumed the whole 26-piece supply on ways down and none on the
@@ -618,6 +672,11 @@ function bestTrackLay(s: GameState, player: PlayerIndex, options: Intent[]): Int
    if (i.geometry === 'straight') score += 2;
    if (dRow > 0) score += 3;

+    // A TIE-BREAKER, not a veto. Applied to the distance score rather than the bonus, so it can
+    // never push a piece below the "builds nothing" floor and refuse it outright: given two
+    // placements the heuristics rate the same, take the one whose rail can still grow.
+    score -= deadEnds(i) * 0.5;
+
    /**
     * DECLINE A PIECE THAT BUILDS NOTHING.
     *
@@ -113,6 +113,10 @@ export function summarize(
      const reason = e.reason;
      if (reason.startsWith('collision')) rev.collisionLoss += -e.delta;
      else if (reason === 'freightLoad') rev.freightLoad += e.delta;
+      // `freightUnload` is its own reason on its own event (apply.ts). It used to be counted from
+      // `unloadBegan` instead — unloads STARTED, not Revenue EARNED — and the two differ by every
+      // unload that never finished.
+      else if (reason === 'freightUnload') rev.freightUnload += e.delta;
      else if (reason === 'boarding') rev.passengerBoard += e.delta;
      else if (reason === 'detraining') rev.passengerDetrain += e.delta;
    }
@@ -129,12 +133,21 @@ export function summarize(

  for (const i of intents) inc(intentCounts, i);

-  // An unload scores through the same event as a load completion in the reducer, so count the
-  // distinct operations directly.
-  rev.freightUnload = eventCounts['unloadBegan'] ?? 0;
  rev.net = final.players.reduce((n, p) => n + p.revenue, 0);

-  const grossFreight = rev.freightLoad;
+  /**
+   * FREIGHT IS BOTH HALVES.
+   *
+   * A completed load and a completed unload each earn a point, on two distinct `revenueChanged`
+   * reasons — and this counted only the first, so `freightShare` reported roughly 60% of the
+   * freight actually earned. That is the number the "freight is only 13-18% of gross" finding was
+   * read from, and it drove the Gap 12 industry-density change.
+   *
+   * The comment that stood here claimed "an unload scores through the same event as a load
+   * completion in the reducer", which is not true: `apply.ts` emits `freightUnload` separately. It
+   * was a comment asserting a fact about code a few lines away, and it was wrong.
+   */
+  const grossFreight = rev.freightLoad + rev.freightUnload;
  const grossPassenger = rev.passengerBoard + rev.passengerDetrain;
  const gross = grossFreight + grossPassenger;

@@ -347,7 +360,7 @@ export type StrategyBucket = {
 * consistently outscore passenger specialists (or vice versa), it shows up here.
 */
 export function strategyBuckets(all: GameStats[]): StrategyBucket[] {
-  const scored = all.filter((g) => g.revenue.freightLoad + g.revenue.passengerBoard + g.revenue.passengerDetrain > 0);
+  const scored = all.filter((g) => g.revenue.freightLoad + g.revenue.freightUnload + g.revenue.passengerBoard + g.revenue.passengerDetrain > 0);

  const buckets: { label: string; test: (g: GameStats) => boolean }[] = [
    { label: 'passenger-only  (freight 0%)', test: (g) => g.freightShare === 0 },
@@ -408,6 +421,7 @@ export function formatAggregate(all: GameStats[]): string {
  out.push('  REVENUE (mean per game)');
  out.push(`    net                    ${num(meanOf(all, (g) => g.revenue.net))}`);
  out.push(`    from freight loads     ${num(meanOf(all, (g) => g.revenue.freightLoad))}`);
+  out.push(`    from freight unloads   ${num(meanOf(all, (g) => g.revenue.freightUnload))}`);
  out.push(`    from passengers on     ${num(meanOf(all, (g) => g.revenue.passengerBoard))}`);
  out.push(`    from passengers off    ${num(meanOf(all, (g) => g.revenue.passengerDetrain))}`);
  out.push(`    lost to collisions     ${num(-meanOf(all, (g) => g.revenue.collisionLoss))}`);
@@ -179,6 +179,19 @@ export type Frame = {
  departments: string[];
  /** What each face-up Department card does. */
  departmentsWhat: string[];
+  /**
+   * The two yards, by car type.
+   *
+   * Rolling stock is finite and the Classification Yard only returns to service when the Division
+   * Yard is BARE, so watching the Division Yard run down is now real information — and the game
+   * showed neither yard at all.
+   */
+  yards: {
+    division: { type: string; loaded: number; empty: number }[];
+    classification: { type: string; loaded: number; empty: number }[];
+    divisionTotal: number;
+    classificationTotal: number;
+  };
  /** 12 slots; the train number due out at each Stage, or null. */
  timetable: (number | null)[];
  blocked: Impediment[];
@@ -598,6 +611,12 @@ export function snapshot(
    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) : '')),
+    yards: {
+      division: countStock(s.yards.divisionYard),
+      classification: countStock(s.yards.classificationYard),
+      divisionTotal: s.yards.divisionYard.length,
+      classificationTotal: s.yards.classificationYard.length,
+    },
    timetable: [...s.timetable],
    decision,
    wasted,
@@ -889,12 +908,38 @@ const MODIFIER_NAMES: Record<string, string> = {
 };

 /** A train on the board, with what it is carrying — otherwise a run looks identical empty or full. */
+/** Cars in a yard, grouped by type and split loaded / empty, in a stable order. */
+function countStock(
+  stock: readonly { type: string; loaded: boolean }[],
+): { type: string; loaded: number; empty: number }[] {
+  const order = ['coach', 'boxcar', 'reefer', 'hopper', 'tank', 'caboose'];
+  const by = new Map<string, { type: string; loaded: number; empty: number }>();
+  for (const c of stock) {
+    const row = by.get(c.type) ?? { type: c.type, loaded: 0, empty: 0 };
+    if (c.loaded) row.loaded += 1;
+    else row.empty += 1;
+    by.set(c.type, row);
+  }
+  return [...by.values()].sort((a, b) => order.indexOf(a.type) - order.indexOf(b.type));
+}
+
 function trainChip(s: GameState, id: string): TrainChip {
  const t = s.trays.get(id);
  if (!t) return { label: id, consist: [] };
+  /**
+   * The engine is drawn IN the consist, at the position it occupies.
+   *
+   * A Crew Tray is an engine plus its Rolling Stock, and the engine may be pulling, pushing, or in
+   * the middle doing both — which is a thing a player has to be able to see, since it decides which
+   * end cars couple onto (§A.3) and which way the train can shove. It was recorded as a boolean
+   * that nothing read, so every consist was drawn as an anonymous row of cars.
+   */
+  const cars = t.consist.map(carLabel);
+  const at = Math.max(0, Math.min(cars.length, t.engineAt));
+  cars.splice(at, 0, 'ENG');
  return {
    label: t.trainNumber === null ? 'crew' : `T${t.trainIsExtra ? 'X' : ''}${t.trainNumber}`,
-    consist: t.consist.map(carLabel),
+    consist: cars,
  };
 }

@@ -261,6 +261,8 @@ function render(): void {
    ? f.departments.map((d, i) => cardRow(d, f.departmentsWhat[i] ?? '', null)).join('')
    : '<span class="dim">none</span>';

+  renderYards(f);
+
  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>` +
@@ -297,6 +299,38 @@ function render(): void {
  save();
 }

+/**
+ * The two yards, and how close the Division Yard is to running out.
+ *
+ * §2 — used Rolling Stock is set out in the Classification Yard, and it only returns when the
+ * Division Yard is BARE. So the interesting number is not how much has been used but how little is
+ * left, and the moment the Division Yard empties a whole pile comes back at once.
+ */
+function renderYards(f: ReturnType<typeof view>): void {
+  const row = (rows: { type: string; loaded: number; empty: number }[]): string =>
+    rows.length === 0
+      ? '<span class="dim">empty</span>'
+      : rows
+          .map(
+            (r) =>
+              `<span class="stock" data-tip="${esc(r.type)} — ${r.loaded} loaded, ${r.empty} empty">` +
+              `<b>${esc(r.type)}</b> <span class="ld">${r.loaded}</span>/<span class="mt">${r.empty}</span></span>`,
+          )
+          .join('');
+
+  $('divyard').innerHTML = row(f.yards.division);
+  $('clsyard').innerHTML = row(f.yards.classification);
+  $('divtot').textContent = `${f.yards.divisionTotal} cars`;
+  $('clstot').textContent = `${f.yards.classificationTotal} cars`;
+
+  // The one thing worth calling out: the yard about to turn over.
+  const bare = f.yards.divisionTotal === 0;
+  $('divyard').classList.toggle('bare', bare);
+  $('yardnote').textContent = bare
+    ? `The Division Yard is bare — the ${f.yards.classificationTotal} cars in Classification return to it now.`
+    : 'loaded / empty. Classification returns to the Division Yard only when the Division Yard is bare.';
+}
+
 function renderDistrict(f: ReturnType<typeof view>): void {
  const open = districtMode === 'auto' ? FOCUS_PHASES.has(f.phaseKey) : districtMode === 'open';
  const sec = $('district');
@@ -33,6 +33,15 @@ header button:hover{border-color:#4d6fa8}
   explicitly not a target. Previously the hand was a list of bare names and the Department slots a
   second list, so nothing looked like a card at all. */
 .cardrow{display:flex;flex-wrap:wrap;gap:6px;margin:0 0 2px}
+/* THE YARDS. Rolling stock is finite and the Classification Yard only comes back when the Division
+   Yard is bare, so a player has to be able to watch the supply run down. */
+.yard{display:flex;flex-wrap:wrap;gap:5px;margin:0 0 6px}
+.stock{background:#1c2129;border:1px solid #39424e;border-radius:4px;padding:2px 7px;font-size:11px}
+.stock b{color:#e6e9ee}
+.stock .ld{color:#8fd6a0}
+.stock .mt{color:#9fb6d8}
+.stock.none{opacity:.4}
+.yard.bare{outline:1px dashed #e0a060;outline-offset:3px;border-radius:4px;padding:3px}
 .handcard{background:#242c36;border:1px solid var(--line);border-radius:5px;
  padding:5px 8px;font-size:11px;min-width:96px;position:relative}
 .handcard:focus{outline:2px solid #4d6fa8;outline-offset:1px}
@@ -213,6 +222,13 @@ ol.tc-phases{display:flex;gap:6px;list-style:none;margin:0;padding:0;flex-wrap:w
      <h3>Department Cards (face up)</h3><div id="depts" class="cardrow ref">—</div>
    </section>
    <section><h2 class="big">Your Track Supply</h2><div id="supply"></div></section>
+    <section><h2 class="big">The Yards</h2>
+      <h3>Division Yard <span class="dim" id="divtot"></span></h3>
+      <div id="divyard" class="yard"></div>
+      <h3>Classification Yard <span class="dim" id="clstot"></span></h3>
+      <div id="clsyard" class="yard"></div>
+      <div class="dim" id="yardnote"></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>
@@ -0,0 +1,124 @@
+<!doctype html>
+<html lang="en">
+<head>
+<meta charset="utf-8">
+<meta name="viewport" content="width=device-width,initial-scale=1">
+<title>Station Master — replays</title>
+<style>
+:root{--bg:#12151a;--fg:#e6e9ee;--dim:#8b94a3;--line:#2c333d;--panel:#1a1f26}
+*{box-sizing:border-box}
+body{margin:0;background:var(--bg);color:var(--fg);
+  font:14px/1.5 ui-monospace,SFMono-Regular,Menlo,Consolas,monospace}
+a{color:#5aa9e6}
+header{background:var(--panel);border-bottom:1px solid var(--line);padding:10px 16px;
+  display:flex;gap:18px;align-items:baseline;flex-wrap:wrap;position:sticky;top:0;z-index:5}
+header b{font-size:16px}
+.home{color:inherit;text-decoration:none;border-bottom:1px dotted #5f6b7a}
+.home:hover{color:#5aa9e6}
+.build{margin-left:auto;font-size:11px;opacity:.7}
+main{padding:18px;max-width:1300px;margin:0 auto}
+h2{font-size:12px;text-transform:uppercase;letter-spacing:.09em;color:var(--dim);margin:0 0 8px}
+section{background:var(--panel);border:1px solid var(--line);border-radius:8px;padding:14px 16px;margin-bottom:14px}
+.dim{color:var(--dim)}
+.sm{font-size:11px}
+button{background:#2a3038;color:var(--fg);border:1px solid var(--line);border-radius:5px;
+  padding:6px 11px;margin:2px 4px 2px 0;cursor:pointer;font:inherit;font-size:13px;text-align:left}
+button:hover{background:#39424e;border-color:#4d6fa8}
+button.entry{display:block;width:100%;margin-bottom:6px}
+#perr{color:#e58080;min-height:18px;font-size:12px}
+input[type=file]{font:inherit;font-size:12px;color:var(--dim)}
+/* viewer */
+#viewer{display:none}
+.vbar{display:flex;gap:6px;align-items:center;flex-wrap:wrap;margin-bottom:10px}
+.vgrid{display:grid;grid-template-columns:minmax(0,1fr) 380px;gap:14px;align-items:start}
+@media(max-width:1100px){.vgrid{grid-template-columns:1fr}}
+.scroll{overflow-x:auto}
+#vlog{max-height:420px;overflow:auto;font-size:12px}
+.line{padding:1px 0}
+/* Auto-hide, matching the playable page and the standalone replay. Folded leaves a summary rather
+   than nothing, because a panel that disappears reads as broken instead of folded away. */
+button.ghost{background:#222831;border:1px solid #4a5361;color:#c6ccd6;font-size:11px;
+  padding:2px 9px;margin-left:10px;text-transform:none;letter-spacing:0;vertical-align:middle}
+button.ghost:hover{border-color:#4d6fa8;color:#fff}
+#vdistrict.folded .scroll{display:none}
+#vdistrict.folded #vdistrictsummary{display:block;padding:2px 0}
+#vdistrictsummary{display:none}
+.line.now{background:rgba(90,169,230,.10)}
+.t-good{color:#8fd6a0}.t-bad{color:#e58080}.t-clock{color:#9fb6d8;font-weight:600}.t-quiet{color:var(--dim)}
+select{background:#2a3038;color:var(--fg);border:1px solid var(--line);border-radius:5px;padding:5px;font:inherit;font-size:12px}
+input[type=range]{flex:1;min-width:180px}
+</style>
+</head>
+<body>
+
+<header>
+  <b><a class="home" href="./index.html">Station Master</a></b>
+  <span class="dim">replays</span>
+  <span class="build">build __BUILD__</span>
+</header>
+
+<main>
+  <div id="picker">
+    <section>
+      <h2>Saved on this site</h2>
+      <div id="hosted"><p class="dim">loading&hellip;</p></div>
+    </section>
+
+    <section>
+      <h2>Open a save file</h2>
+      <p class="dim">A Station Master save is a small <code>.json</code> file &mdash; a seed and the list of
+      moves made. That is enough to rebuild the whole game, so a replay can be emailed like a text file.
+      Save one from inside a game with <b>Save replay</b>.</p>
+      <input type="file" id="file" accept=".json,application/json">
+      <div id="perr"></div>
+    </section>
+  </div>
+
+  <div id="viewer">
+    <section>
+      <div class="vbar">
+        <button id="vclose">&larr; all replays</button>
+        <b id="vtitle">&mdash;</b>
+        <span class="dim" id="vnote"></span>
+      </div>
+      <div class="vbar">
+        <button id="vfirst">&#9198; start</button>
+        <button id="vback">&#9664; step</button>
+        <button id="vplay">&#9654; play</button>
+        <button id="vfwd">step &#9654;</button>
+        <button id="vstage">next Stage &#9197;</button>
+        <button id="vlast">end &#9197;</button>
+        <select id="vspeed">
+          <option value="3000">extra slow</option>
+          <option value="1200">slow</option>
+          <option value="700" selected>normal</option>
+          <option value="280">fast</option>
+          <option value="90">very fast</option>
+        </select>
+        <button id="vsound">&#128263; muted</button>
+        <input type="range" id="vscrub" min="0" max="0" value="0">
+        <span class="dim" id="vpos">0 / 0</span>
+      </div>
+      <div class="vbar">
+        <span id="vclock">&mdash;</span>
+        <span>phase: <b id="vphase">&mdash;</b></span>
+        <span>Revenue <b id="vrev">0</b></span>
+        <span class="dim">&larr; &rarr; to step, space to play</span>
+      </div>
+    </section>
+
+    <div class="vgrid">
+      <div>
+        <section><h2>The Division</h2><div class="scroll" id="vdivision"></div></section>
+        <section id="vdistrict"><h2>Office Area <button id="vdistricttoggle" class="ghost">auto-hide: on</button></h2>
+          <div id="vdistrictsummary" class="dim"></div>
+          <div class="scroll" id="vgrid"></div></section>
+      </div>
+      <section><h2>What happened</h2><div id="vlog"></div></section>
+    </div>
+  </div>
+</main>
+
+<script type="module" src="./web/replays.js"></script>
+</body>
+</html>
@@ -12,6 +12,8 @@
 */

 import { BOARD_CSS, divisionSvg, officeSvg } from '../sim/board-svg.ts';
+import { cuesFor } from '../sim/narrate.ts';
+import { playCue } from './sound.ts';
 import { TOOLTIP_CSS, installTooltips } from './tooltip.ts';
 import { narrate } from '../sim/narrate.ts';
 import { cardName, trainName } from '../sim/view.ts';
@@ -35,7 +37,12 @@ const esc = (s: string): string =>
  String(s).replace(/[&<>"]/g, (c) => ({ '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;' })[c] ?? c);

 /** Every position the save passes through, with the lines narrated along the way. */
-type Step = { frame: Frame; lines: { text: string; tone: string }[] };
+type Step = {
+  frame: Frame;
+  lines: { text: string; tone: string }[];
+  /** What this step should sound like — from `cuesFor`, the same function the live game uses. */
+  cues: string[];
+};

 /**
 * Rebuild a game from a save, keeping a snapshot at each step.
@@ -54,7 +61,7 @@ function rebuild(save: Save): { steps: Step[]; stoppedEarly: boolean } {
        const n = narrate(e, ctx);
        return { text: n.text, tone: n.tone };
      });
-    steps.push({ frame: snapshot(s, [], null), lines });
+    steps.push({ frame: snapshot(s, [], null), lines, cues: cuesFor(events) });
  };

  push(pump(s));
@@ -80,13 +87,28 @@ function rebuild(save: Save): { steps: Step[]; stoppedEarly: boolean } {
 let steps: Step[] = [];
 let at = 0;
 let timer: ReturnType<typeof setInterval> | null = null;
+/**
+ * Sound and auto-hide, matching the playable page and the standalone replay.
+ *
+ * This viewer is a third place a game gets drawn, and it had drifted: three speeds where the
+ * standalone had five, and neither of these. Anything a player learns on one screen should hold on
+ * the others.
+ */
+let soundOn = false;
+let districtMode: 'auto' | 'open' | 'closed' = 'auto';
+const FOCUS_PHASES = new Set(['localOps', 'loadUnload']);

 function show(i: number): void {
+  const from = at;
  at = Math.max(0, Math.min(steps.length - 1, i));
  const step = steps[at];
  if (!step) return;
  const f = step.frame;

+  // Only a single step FORWARD sounds. Scrubbing across a hundred steps would fire a hundred
+  // whistles, and stepping back would sound a Stage ending that is being un-done.
+  if (soundOn && at === from + 1) for (const c of step.cues) playCue(c);
+
  $('vclock').textContent = `Day ${f.day} · Stage ${f.stage} — ${f.clock}`;
  $('vphase').textContent = f.phase;
  $('vrev').textContent = String(f.revenue);
@@ -95,6 +117,21 @@ function show(i: number): void {
  $('vdivision').innerHTML = divisionSvg(f.division);
  $('vgrid').innerHTML = officeSvg(f.cells, f.runningRow);

+  // Auto-hide: the district is worth its space during the phases that change it.
+  const open = districtMode === 'auto' ? FOCUS_PHASES.has(f.phaseKey) : districtMode === 'open';
+  const sec = $('vdistrict');
+  if (open) sec.classList.remove('folded');
+  else sec.classList.add('folded');
+  const cars = f.cells.reduce((n, c) => n + c.cars.length, 0);
+  $('vdistrictsummary').textContent =
+    `${f.cells.length} cards · ${f.facilities.length} facilities · ${cars} cars standing`;
+  $('vdistricttoggle').textContent =
+    districtMode === 'auto'
+      ? (open ? 'auto-hide: on — click to keep open' : 'auto-hide: on — click to show')
+      : districtMode === 'open'
+        ? 'always showing — click for auto-hide'
+        : 'always hidden — click for auto-hide';
+
  // A window of history rather than only this step, so a jump lands in context.
  let log = '';
  for (let k = Math.max(0, at - 18); k <= at; k++) {
@@ -215,6 +252,18 @@ function wire(): void {
      show(at + 1);
    }, Number(($('vspeed') as HTMLSelectElement).value));
  };
+  $('vdistricttoggle').onclick = () => {
+    const f = steps[at]?.frame;
+    const open = districtMode === 'auto' ? (f ? FOCUS_PHASES.has(f.phaseKey) : true) : districtMode === 'open';
+    districtMode = districtMode === 'auto' ? (open ? 'closed' : 'open') : 'auto';
+    show(at);
+  };
+  $('vsound').onclick = () => {
+    soundOn = !soundOn;
+    $('vsound').textContent = soundOn ? '\u{1F50A} sound' : '\u{1F507} muted';
+    // Confirms the change, and gives the browser the gesture it needs before audio may start.
+    if (soundOn) playCue('stage');
+  };
  $('vclose').onclick = () => {
    if (timer) clearInterval(timer);
    timer = null;
@@ -257,7 +257,7 @@ describe('Mainline Phase (§8)', () => {
        id: `t${i}`,
        trainNumber: spec.n,
        trainIsExtra: spec.extra,
-        engineFront: true,
+        engineAt: 0,
        consist: [],
        direction: 'east',
        position: { at: 'divisionPoint', side: 'west' },
@@ -287,7 +287,7 @@ describe('collisions are automatic (Gap 2)', () => {
      id,
      trainNumber: 2,
      trainIsExtra: false,
-      engineFront: true,
+      engineAt: 0,
      consist: [{ type: 'coach', loaded: true }],
      direction: 'east',
      position: { at: 'mainline', index: 1 },
@@ -328,7 +328,7 @@ describe('collisions are automatic (Gap 2)', () => {
      id: 'x',
      trainNumber: 8,
      trainIsExtra: false,
-      engineFront: true,
+      engineAt: 0,
      consist: [
        { type: 'hopper', loaded: true },
        { type: 'caboose', loaded: true },
@@ -359,7 +359,7 @@ describe('the Superintendent clearance interrupt (§8.1)', () => {
      id: 'ahead',
      trainNumber: 4,
      trainIsExtra: false,
-      engineFront: true,
+      engineAt: 0,
      consist: [],
      direction: 'east',
      position: { at: 'mainline', index: 1 },
@@ -379,7 +379,7 @@ describe('the Superintendent clearance interrupt (§8.1)', () => {
      id: 'behind',
      trainNumber: 2,
      trainIsExtra: false,
-      engineFront: true,
+      engineAt: 0,
      consist: [],
      direction: 'east',
      position: { at: 'divisionPoint', side: 'west' },
@@ -402,7 +402,7 @@ describe('the Superintendent clearance interrupt (§8.1)', () => {
      id: 'oncoming',
      trainNumber: 3,
      trainIsExtra: false,
-      engineFront: true,
+      engineAt: 0,
      consist: [],
      direction: 'west',
      position: { at: 'mainline', index: 1 },
@@ -421,7 +421,7 @@ describe('the Superintendent clearance interrupt (§8.1)', () => {
      id: 'waiting',
      trainNumber: 2,
      trainIsExtra: false,
-      engineFront: true,
+      engineAt: 0,
      consist: [],
      direction: 'east',
      position: { at: 'divisionPoint', side: 'west' },
@@ -38,7 +38,7 @@ function placeTray(s: GameState, coord: GridCoord, consist: CrewTray['consist']
    id,
    trainNumber: null,
    trainIsExtra: false,
-    engineFront: true,
+    engineAt: 0,
    consist,
    direction: 'east',
    position: { at: 'grid', owner: 0, coord },
@@ -52,7 +52,7 @@ function handEnhancement(s: GameState, key: string): string {
 function placeTray(s: GameState, coord: GridCoord, consist: TrackCard['standing'] = []): string {
  const id = s.freeTrays.pop()!;
  s.trays.set(id, {
-    id, trainNumber: 9, trainIsExtra: false, engineFront: true,
+    id, trainNumber: 9, trainIsExtra: false, engineAt: 0,
    consist, direction: 'east', position: { at: 'grid', owner: 0, coord }, movesUsed: 0,
  });
  return id;
@@ -185,7 +185,7 @@ describe('Interlocking and Yard Office relieve the Office', () => {
  function inbound(s: GameState, consist: TrackCard['standing']) {
    const id = 'inbound';
    s.trays.set(id, {
-      id, trainNumber: 9, trainIsExtra: false, engineFront: true,
+      id, trainNumber: 9, trainIsExtra: false, engineAt: 0,
      consist, direction: 'east', position: { at: 'mainline', index: 1 }, movesUsed: 0,
    });
    const ml = s.division.nodes[1];
@@ -264,11 +264,11 @@ describe('ABS Signals amend the collision rule', () => {
      ml.transits.push({ tray: 'ahead', stagesRemaining: 2, stagesTotal: 2, direction: 'east' });
    }
    s.trays.set('ahead', {
-      id: 'ahead', trainNumber: 4, trainIsExtra: false, engineFront: true,
+      id: 'ahead', trainNumber: 4, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'east', position: { at: 'mainline', index: 1 }, movesUsed: 0,
    });
    s.trays.set('behind', {
-      id: 'behind', trainNumber: 2, trainIsExtra: false, engineFront: true,
+      id: 'behind', trainNumber: 2, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'east', position: { at: 'divisionPoint', side: 'west' }, movesUsed: 0,
    });
    s.clock.phase = 'mainline';
@@ -292,7 +292,7 @@ describe('Telegraph, Telephone and Radio dispatch meets', () => {
    }
    // An oncoming senior train — §8.1 makes this an absolute bar without a device.
    s.trays.set('oncoming', {
-      id: 'oncoming', trainNumber: 3, trainIsExtra: false, engineFront: true,
+      id: 'oncoming', trainNumber: 3, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'west', position: { at: 'mainline', index: 1 }, movesUsed: 0,
    });
    const ml = s.division.nodes[1];
@@ -304,7 +304,7 @@ describe('Telegraph, Telephone and Radio dispatch meets', () => {
      ml.transits.push({ tray: 'oncoming', stagesRemaining: 2, stagesTotal: 2, direction: 'west' });
    }
    s.trays.set('mine', {
-      id: 'mine', trainNumber: 9, trainIsExtra: false, engineFront: true,
+      id: 'mine', trainNumber: 9, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'east', position: { at: 'divisionPoint', side: 'west' }, movesUsed: 0,
    });
    s.clock.phase = 'mainline';
@@ -16,12 +16,15 @@ import { advance } from '../src/engine/advance.ts';
 import { applyIntent, areaOf, check } from '../src/engine/apply.ts';
 import {
  MAINLINE_MODIFIER_CARDS,
+  MAINLINE_PROFILES,
  MANEUVER_CARDS,
  REALIGNMENTS,
  crossingStages,
  mainlineModifierRule,
+  mainlineProfile,
 } from '../src/engine/content.ts';
 import { createGame } from '../src/engine/setup.ts';
+import type { GameEvent } from '../src/engine/events.ts';
 import type { GameConfig, GameState, GridCoord, TrackCard } from '../src/engine/state.ts';
 import { coordKey } from '../src/engine/state.ts';
 import { snapshot } from '../src/sim/view.ts';
@@ -210,11 +213,11 @@ describe('Red Flags protect a stopped train', () => {
    const node = pinned(s, 1, 'plains');
    node.transits.push({ tray: 'ahead', stagesRemaining: 2, stagesTotal: 2, direction: 'east' });
    s.trays.set('ahead', {
-      id: 'ahead', trainNumber: 4, trainIsExtra: false, engineFront: true,
+      id: 'ahead', trainNumber: 4, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'east', position: { at: 'mainline', index: 1 }, movesUsed: 0,
    });
    s.trays.set('behind', {
-      id: 'behind', trainNumber: 2, trainIsExtra: false, engineFront: true,
+      id: 'behind', trainNumber: 2, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'east', position: { at: 'divisionPoint', side: 'west' }, movesUsed: 0,
    });
    const dp = s.division.nodes[0];
@@ -313,7 +316,7 @@ describe('Flying Switch rolls a cut into an industry', () => {
    area.grid.set(coordKey(at(-2, 0)), industry);

    s.trays.set('crew', {
-      id: 'crew', trainNumber: 1, trainIsExtra: false, engineFront: true,
+      id: 'crew', trainNumber: 1, trainIsExtra: false, engineAt: 0,
      consist: [{ type: 'hopper', loaded: false }, { type: 'boxcar', loaded: false }],
      // Facing SOUTH, down the spur. `direction` only carries east/west, so a crew on north-south
      // track needs its actual port — without it the engine looks for an east exit the card has not
@@ -405,12 +408,17 @@ describe('card coverage', () => {
    }
  });

-  it('Poling remains unimplemented, deliberately', () => {
+  it('Poling stays unimplemented AND out of the deck, deliberately', () => {
    // Guard against someone "fixing" this by inventing an effect. The sheet says TBD; until the
    // source says otherwise, a silent no-op would be worse than a rejection.
+    //
+    // It is dealt zero copies rather than deleted: a card that cannot be played is worse in a
+    // player's hand than absent from the deck, but the entry stays so the gap remains visible and
+    // the card returns the moment its rule is known.
    const poling = MANEUVER_CARDS.find((c) => c.key === 'poling');
-    assert.ok(poling, 'Poling should still be in the deck');
+    assert.ok(poling, 'the Poling entry should stay, so the gap does not vanish');
    assert.match(poling!.effect, /TBD/i);
+    assert.equal(poling!.copies, 0, 'Poling is dealt into the deck but cannot be played');
  });
 });

@@ -495,7 +503,7 @@ describe("a train is made up to its card's consist (§8.2)", () => {
    const s = game();
    s.clock.phase = 'newTrain';
    s.trays.set('t', {
-      id: 't', trainNumber: 9, trainIsExtra: false, engineFront: true,
+      id: 't', trainNumber: 9, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'west', position: { at: 'divisionPoint', side: 'east' }, movesUsed: 0,
    });

@@ -525,7 +533,7 @@ describe("a train is made up to its card's consist (§8.2)", () => {
    const s = game();
    s.clock.phase = 'newTrain';
    s.trays.set('t', {
-      id: 't', trainNumber: 9, trainIsExtra: false, engineFront: true,
+      id: 't', trainNumber: 9, trainIsExtra: false, engineAt: 0,
      consist: [{ type: 'caboose', loaded: true }],
      direction: 'west', position: { at: 'divisionPoint', side: 'east' }, movesUsed: 0,
    });
@@ -595,3 +603,87 @@ describe('regions on a Mainline card (§2.1, §8.2)', () => {
    }
  });
 });
+
+describe('Q13 — a train that catches the one ahead runs into it', () => {
+  /**
+   * Two trains on one card, same direction, the follower closing. `total 3 / remaining 2` puts the
+   * leader in region 1 after it moves; `total 2 / remaining 2` puts the follower in region 0 and
+   * then region 1 — so it catches up whichever order the phase happens to process them in.
+   */
+  const twoTrains = (opts: { absSignals?: boolean } = {}): { s: GameState; events: GameEvent[] } => {
+    const s = createGame({
+      id: 'rear', seed: 3,
+      config: {
+        mode: 'solitaire', victory: 'highestAfterDays', length: 'standard',
+        optionalRules: { reducedVisibility: false, sisterTrains: false, employeeRotation: false, emergencyToolbox: false },
+      },
+      playerNames: ['bot'],
+    });
+    const index = s.division.nodes.findIndex(
+      (n) => n.kind === 'mainline' && !mainlineProfile(n.card).trainsMayPass,
+    );
+    assert.ok(index >= 0, 'no single-track Mainline card in this Division');
+    const node = s.division.nodes[index]!;
+    assert.ok(node.kind === 'mainline');
+    if (node.kind !== 'mainline') throw new Error('unreachable');
+    if (opts.absSignals) node.absSignals = true;
+
+    const make = (n: number, total: number, left: number): string => {
+      const id = s.freeTrays.pop()!;
+      s.trays.set(id, {
+        id, trainNumber: n, trainIsExtra: false, engineAt: 0,
+        consist: [{ type: 'boxcar', loaded: false }],
+        direction: 'east',
+        position: { at: 'mainline', index },
+      } as never);
+      node.transits.push({ tray: id, stagesRemaining: left, stagesTotal: total, direction: 'east' });
+      return id;
+    };
+    make(9, 3, 2);   // the leader
+    make(11, 2, 2);  // the follower, closing
+
+    s.clock.phase = 'mainline';
+    const events: GameEvent[] = [];
+    for (let i = 0; i < 4; i++) events.push(...advance(s).events);
+    return { s, events };
+  };
+
+  it('destroys both trains, and it is the Superintendent\'s fault (§10)', () => {
+    // REGRESSION against a rule that was never implemented. §10 makes a Mainline collision the
+    // Superintendent's fault and removes both trains, and ABS Signals exists to prevent rear-enders
+    // — but §8.3's trigger list never named one, so granting clearance was FREE: both trains
+    // survived, no penalty, and ABS Signals protected against nothing.
+    const { events } = twoTrains();
+    const smash = events.find((e) => e.type === 'trainsDestroyed');
+    assert.ok(smash, 'the follower ran into the leader and nothing happened');
+    if (smash.type !== 'trainsDestroyed') throw new Error('unreachable');
+    assert.match(smash.reason, /ran into the train ahead/);
+    assert.equal(smash.trains.length, 2, 'a rear-ender removes BOTH trains');
+    assert.ok(
+      events.some((e) => e.type === 'revenueChanged' && e.delta < 0),
+      'the collision cost nothing',
+    );
+  });
+
+  it('ABS Signals holds the follower short instead', () => {
+    // "Trains on this card will not rear-end each other; they stop short of a collision."
+    const { events } = twoTrains({ absSignals: true });
+    assert.ok(
+      !events.some((e) => e.type === 'trainsDestroyed'),
+      'ABS Signals did not prevent the collision',
+    );
+    assert.ok(
+      events.some((e) => e.type === 'trainHeld' && /ABS Signals/.test(e.reason)),
+      'nothing was held short of the train ahead',
+    );
+  });
+
+  it('leaves trains alone on a card that prints "trains may pass"', () => {
+    // Double Track and Uncontrolled Siding hold two trains because they HAVE two roads. Catching up
+    // there means going past, which is what the card is for. Without this the mechanic fired 0.41
+    // times a game while the bot never once granted clearance — the tell that they were all
+    // passing cards.
+    const passing = MAINLINE_PROFILES.filter((m) => m.trainsMayPass).map((m) => m.kind);
+    assert.deepEqual(passing, ['doubleTrack', 'uncontrolledSiding']);
+  });
+});
@@ -53,7 +53,11 @@ describe('card catalogue (component 1)', () => {
    // Transcribed from docs/Deck cards2.xlsx, whose own total is 115 — plus 18 extra industry cards
    // (Gap 12, industries 9 → 27) and 7 extra office cards (Q12, offices 7 → 14). Both are
    // deliberate departures from the sheet and both are flagged provisional in content.ts.
-    assert.equal(DECK_SIZE, 140);
+    //
+    // 139, not 140: Poling is dealt ZERO copies. Its effect is "TBD in the source", so a card that
+    // cannot be played is worse in a hand than absent from the deck. The entry stays in the
+    // catalogue so the gap remains visible.
+    assert.equal(DECK_SIZE, 139);
    assert.equal(buildDeck().length, DECK_SIZE);
  });

@@ -69,20 +73,21 @@ describe('card catalogue (component 1)', () => {
      spaceUse: 12,
      enhancement: 18,
      mainlineModifier: 7,
-      maneuver: 7,
+      // 6, not 7 — Poling is dealt no copies until its rule is known.
+      maneuver: 6,
      action: 10,
    });
  });

  it('removes opponent-directed cards from a solitaire deck', () => {
    // Q6 — Space-use and Action cards can only be played AT another player, so in a one-player
-    // game they would be 22 of 140 draws (16%) that do nothing.
-    assert.equal(SOLITAIRE_DECK_SIZE, 118);
+    // game they would be 22 of 139 draws (16%) that do nothing.
+    assert.equal(SOLITAIRE_DECK_SIZE, 117);
    const solo = buildDeck('solitaire');
-    assert.equal(solo.length, 118);
+    assert.equal(solo.length, SOLITAIRE_DECK_SIZE);
    assert.ok(!solo.some((c) => c.kind.kind === 'spaceUse' || c.kind.kind === 'action'));
-    // A competitive deck keeps them.
-    assert.equal(buildDeck('competitive').length, 140);
+    // A competitive deck keeps them. 139, not 140 — Poling is dealt no copies.
+    assert.equal(buildDeck('competitive').length, 139);
  });

  it('keeps track OUT of the deck, as a per-player supply', () => {
@@ -8,8 +8,11 @@ import assert from 'node:assert/strict';

 import { pump } from '../src/engine/advance.ts';
 import { createGame } from '../src/engine/setup.ts';
+import { refillDivisionYardIfEmpty } from '../src/engine/apply.ts';
+import { TOTAL_ROLLING_STOCK } from '../src/engine/content.ts';
 import type { GameConfig, GameState, OfficeArea } from '../src/engine/state.ts';
-import { exitsFrom, hasPort, neighbour, opposite } from '../src/engine/track.ts';
+import type { Intent } from '../src/engine/intents.ts';
+import { connectionsFor, exitsFrom, hasPort, neighbour, opposite, variantsFor } from '../src/engine/track.ts';
 import type { Port } from '../src/engine/track.ts';
 import { developerBot, playGame, randomBot } from '../src/sim/bot.ts';
 import { simulate } from '../src/sim/harness.ts';
@@ -236,8 +239,13 @@ describe('end-of-game statistics', () => {
    const report = simulate({
      games: 30, length: 'standard', mode: 'solitaire', players: ['bot'], policy: developerBot,
    });
+    // Both halves of freight, matching `strategyBuckets`. This filter used to omit `freightUnload`
+    // — the same omission the summary itself had — so a game that scored only by unloading was
+    // bucketed but not counted here.
    const scored = report.perGame.filter(
-      (g) => g.revenue.freightLoad + g.revenue.passengerBoard + g.revenue.passengerDetrain > 0,
+      (g) =>
+        g.revenue.freightLoad + g.revenue.freightUnload +
+          g.revenue.passengerBoard + g.revenue.passengerDetrain > 0,
    );
    const bucketed = strategyBuckets(report.perGame).reduce((n, b) => n + b.games, 0);
    assert.equal(bucketed, scored.length, 'a scoring game fell outside every bucket');
@@ -591,45 +599,49 @@ describe('Enhancements can reach the board at all (regression)', () => {
  });
 });

-describe('rolling stock stays in circulation (regression)', () => {
-  it('returns the Classification Yard to service overnight', () => {
-    // REGRESSION, and the largest single revenue change measured on this bot: +2.32 ± 0.52 paired
-    // over 400 seeds (t = 8.79).
+describe('rolling stock returns to service (regression)', () => {
+  it('empties the Classification Yard into the Division Yard when the Division Yard runs out', () => {
+    // §2 — used Rolling Stock is set out in the Classification Yard, used engines and cabooses go
+    // straight back to the Division Yard, and the Classification Yard empties ONLY when the
+    // Division Yard is bare. Then all of it returns at once.
    //
-    // The Classification Yard was WRITE-ONLY. Seven places pushed cars into it — retired trains,
-    // collisions, unjams, set-outs — and nothing in the engine ever read it. Rolling stock drained
-    // one way out of the game: 30 cars a game dead by the end, 37% of the 80 dealt at setup.
+    // REGRESSION on two counts. The Classification Yard was write-only to begin with — seven
+    // writers, no readers — so 37% of the stock left the game. The first fix then guessed the wrong
+    // trigger, returning cars at every DAY boundary, which keeps the yard topped up continuously
+    // and is far more generous than the rule: worth +2.42 revenue a game that the game does not
+    // actually grant.
    //
-    // It was not obvious this mattered. The Division Yard does not run DRY in five Days (16.6
-    // loaded freight cars left, empty in 2 games of 100), which is why this was ranked third and
-    // predicted not to affect revenue. The aggregate was never the point: what starves freight is
-    // not having the RIGHT commodity when a green box needs stocking, and returning classified
-    // cars keeps the mix alive.
-    const games = 30;
-    let deadAtEnd = 0;
-    let everReturned = 0;
-    for (let i = 0; i < games; i++) {
-      const s = createGame({
-        id: `cy-${i}`,
-        seed: 1000 + i * 7919,
-        config: { ...config, length: 'standard' },
-        playerNames: ['bot'],
-      });
-      const r = playGame(s, developerBot, pump);
-      deadAtEnd += s.yards.classificationYard.length;
-      // Cars must have passed THROUGH it, or the test proves nothing about the return path.
-      if (r.events.some((e) => e.type === 'trainCompleted')) everReturned++;
-    }
+    // So this asserts the TRIGGER, not a tidy end state. The Division Yard legitimately still holds
+    // cars at the end of a short game, and the Classification Yard legitimately holds a pile.
+    const s = createGame({
+      id: 'refill',
+      seed: 4,
+      config: { ...config, length: 'standard' },
+      playerNames: ['bot'],
+    });

-    assert.ok(everReturned > 0, 'no train ever completed — nothing reached the Classification Yard');
-    // A Day's worth of arrivals may still be sitting there when the game ends; a whole game's worth
-    // may not. Before the fix this was ~30 a game.
-    assert.ok(
-      deadAtEnd / games < 15,
-      `${(deadAtEnd / games).toFixed(1)} cars a game are still stranded in the Classification ` +
-        'Yard at the end — rolling stock is leaving the game and never coming back',
+    // Drain the Division Yard and park a known car in Classification.
+    const parked = s.yards.divisionYard.splice(0, s.yards.divisionYard.length);
+    s.yards.classificationYard.push(...parked);
+    assert.equal(s.yards.divisionYard.length, 0);
+    const waiting = s.yards.classificationYard.length;
+    assert.ok(waiting > 0, 'nothing was parked to return');
+
+    const moved = refillDivisionYardIfEmpty(s);
+    assert.ok(moved, 'an empty Division Yard did not pull the Classification Yard back');
+    assert.equal(moved!.count, waiting);
+    assert.equal(s.yards.divisionYard.length, waiting, 'the cars did not come back');
+    assert.equal(s.yards.classificationYard.length, 0, 'the Classification Yard was not emptied');
+
+    // And it must NOT fire while the Division Yard still has anything at all.
+    s.yards.classificationYard.push({ type: 'boxcar', loaded: false });
+    assert.equal(
+      refillDivisionYardIfEmpty(s),
+      null,
+      'the Classification Yard returned while the Division Yard still had cars',
    );
  });
+
 });

 describe('measurement discipline', () => {
@@ -662,3 +674,152 @@ describe('measurement discipline', () => {
    assert.ok(upgrades > 0, 'no office upgrade was visible in the event log across 25 games');
  });
 });
+
+describe('the bot does not lay track that cannot work (regression)', () => {
+  /** Drive a game with the developer bot, reporting every track piece it lays. */
+  const laysIn = (seed: number, prepare?: (s: GameState) => void): Intent[] => {
+    const s = createGame({
+      id: `lay-${seed}`,
+      seed,
+      config: { ...config, length: 'standard' },
+      playerNames: ['Solitaire'],
+    });
+    prepare?.(s);
+    const laid: Intent[] = [];
+    const spy = {
+      name: 'spy',
+      choose(st: GameState, p: 0, opts: Intent[]) {
+        const pick = developerBot.choose(st, p, opts);
+        if (pick.type === 'track.lay') laid.push(pick);
+        return pick;
+      },
+    };
+    playGame(s, spy as never, pump);
+    return laid;
+  };
+
+  it('will not cut a turnout with no arc left to hang beneath it', () => {
+    // A turnout is a hole in the Running Track, worth cutting only for what hangs under it. This
+    // does not happen naturally — measured at 0%, because the bot lays the arc immediately after
+    // the turnout and never runs the supply dry first — so the situation is constructed. It guards
+    // against the supply changing rather than against something happening today.
+    const drained = laysIn(4242, (s) => {
+      const area = s.officeAreas.get(0)!;
+      for (const k of ['curved:left', 'curved:right', 'sharpCurved:left', 'sharpCurved:right']) {
+        area.trackSupply.set(k, 0);
+      }
+    });
+    const turnouts = drained.filter((i) => i.type === 'track.lay' && i.geometry === 'turnout');
+    assert.equal(
+      turnouts.length,
+      0,
+      `${turnouts.length} turnouts were cut with no arc left to build beneath them`,
+    );
+
+    // And the guard must not be doing this by simply stopping the bot from building.
+    const normal = laysIn(4242);
+    assert.ok(normal.length > 5, `the bot laid only ${normal.length} pieces with a full supply`);
+  });
+
+  it('rarely lays rail that butts a card which cannot accept it', () => {
+    // A port facing an EMPTY square is a promise — something may be built there later. A port
+    // butting an OCCUPIED square whose card has no matching port is not: that square is taken, so
+    // the rail stops dead and always will. Reported from a replay, where an arc was dropped off a
+    // turnout with its far end jammed into a curve.
+    //
+    // A TIE-BREAKER rather than a veto, so this is a rate and not a zero: forbidding it outright
+    // measured WORSE (-0.62 revenue a game), while preferring the cleaner of two equally good
+    // placements measured better and cut these from 28% of pieces to 7%.
+    let laid = 0;
+    let dead = 0;
+    for (const seed of [1000, 8919, 16838, 24757, 32676]) {
+      const s = createGame({
+        id: `dp-${seed}`, seed,
+        config: { ...config, length: 'standard' },
+        playerNames: ['Solitaire'],
+      });
+      const spy = {
+        name: 'spy',
+        choose(st: GameState, p: 0, opts: Intent[]) {
+          const pick = developerBot.choose(st, p, opts);
+          if (pick.type === 'track.lay') {
+            laid++;
+            const area = st.officeAreas.get(p)!;
+            const v = variantsFor(pick.geometry)[pick.variant ?? 0];
+            const probe = {
+              geometry: {
+                kind: 'track', geometry: pick.geometry,
+                ...(v?.axis ? { axis: v.axis } : {}),
+                ...(v?.arc ? { arc: v.arc } : {}),
+                ...(v?.turnout ? { turnout: v.turnout } : {}),
+              },
+              baseOperationalRail: true, standing: [], facility: null, modifiers: [], enhancements: [],
+            } as never;
+            for (const port of new Set(connectionsFor(probe).flat())) {
+              const n = neighbour(pick.placement, port);
+              const nb = area.grid.get(`${n.row},${n.col}`);
+              if (nb && !hasPort(nb, opposite(port))) dead++;
+            }
+          }
+          return pick;
+        },
+      };
+      playGame(s, spy as never, pump);
+    }
+    assert.ok(laid > 40, `only ${laid} pieces laid across five games`);
+    const rate = dead / laid;
+    assert.ok(
+      rate < 0.15,
+      `${(rate * 100).toFixed(0)}% of pieces were laid butting a card that cannot accept them`,
+    );
+  });
+});
+
+describe('the freight figures count both halves (regression)', () => {
+  it('scores an unload as Revenue earned, not as an unload started', () => {
+    // REGRESSION, against the instrument rather than the game. `rev.freightUnload` was assigned
+    // `eventCounts['unloadBegan']` — unloads STARTED, not Revenue EARNED, which differ by every
+    // unload that never finished — and `grossFreight` then used `freightLoad` alone, so
+    // `freightShare` reported roughly 60% of the freight actually earned. That is the number the
+    // "freight is only 13-18% of gross" finding was read from, and it drove a density change.
+    //
+    // Asserted against the ENGINE's own events, so the summary cannot drift from what happened.
+    const report = simulate({
+      games: 30, length: 'standard', mode: 'solitaire', players: ['bot'], policy: developerBot,
+    });
+
+    let loads = 0;
+    let unloads = 0;
+    let begun = 0;
+    for (const seed of [1000, 8919, 16838]) {
+      const s = createGame({
+        id: `fu-${seed}`, seed,
+        config: { ...config, length: 'standard' },
+        playerNames: ['bot'],
+      });
+      const r = playGame(s, developerBot, pump);
+      for (const e of r.events) {
+        if (e.type === 'unloadBegan') begun++;
+        if (e.type !== 'revenueChanged') continue;
+        if (e.reason === 'freightLoad') loads += e.delta;
+        if (e.reason === 'freightUnload') unloads += e.delta;
+      }
+    }
+    assert.ok(unloads > 0, 'no unload ever earned Revenue');
+    // `begun` is what the summary used to count. It is an upper bound on what was EARNED, because
+    // an unload can be started and never finished — so counting it was wrong whether or not the
+    // two happen to agree on a given sample.
+    assert.ok(begun >= unloads, 'more unloads earned Revenue than were ever begun');
+
+    // Every game in the report must count both halves toward its freight share.
+    for (const g of report.perGame) {
+      const gross = g.revenue.freightLoad + g.revenue.freightUnload + g.revenue.passengerBoard + g.revenue.passengerDetrain;
+      if (gross === 0) continue;
+      const expected = (g.revenue.freightLoad + g.revenue.freightUnload) / gross;
+      assert.ok(
+        Math.abs(g.freightShare - expected) < 1e-9,
+        `freightShare ${g.freightShare.toFixed(3)} omits the unload half (expected ${expected.toFixed(3)})`,
+      );
+    }
+  });
+});
@@ -545,7 +545,7 @@ describe('coupling lifts only the cars the crew ran over', () => {
    const area = areaFrom(grid, { row: 0, col: 0 });
    const s = gameWith(area);
    s.trays.set('crew', {
-      id: 'crew', trainNumber: 1, trainIsExtra: false, engineFront: true, consist: [],
+      id: 'crew', trainNumber: 1, trainIsExtra: false, engineAt: 0, consist: [],
      direction: 'west', facing: 'w', position: { at: 'grid', owner: 0, coord: { row: 0, col: 0 } }, movesUsed: 0,
    });
    s.clock.phase = 'localOps';
@@ -13,6 +13,7 @@ import { dirname, join, resolve } from 'node:path';

 import { cardDescription, describeIntent } from '../src/sim/view.ts';
 import { divisionSvg, officeSvg } from '../src/sim/board-svg.ts';
+import { record, renderHtml } from '../src/sim/replay.ts';
 import { snapshot } from '../src/sim/view.ts';
 import { createGame as createEngineGame } from '../src/engine/setup.ts';
 import {
@@ -529,11 +530,11 @@ describe('the page explains itself', () => {
    const game = newGame(5);
    const s = game.state;
    s.trays.set('tray2', {
-      id: 'tray2', trainNumber: 4, trainIsExtra: false, engineFront: true,
+      id: 'tray2', trainNumber: 4, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'east', position: { at: 'mainline', index: 1 }, movesUsed: 0,
    });
    s.trays.set('tray3', {
-      id: 'tray3', trainNumber: 7, trainIsExtra: false, engineFront: true,
+      id: 'tray3', trainNumber: 7, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'east', position: { at: 'mainline', index: 1 }, movesUsed: 0,
    });
    s.clock.pendingDecision = { train: 'tray2', occupiedBy: 'tray3' };
@@ -1191,3 +1192,165 @@ describe('a train says what its card calls for', () => {
    }
  });
 });
+
+describe('the three places a game is drawn stay in step', () => {
+  // A game is drawn on the playable page, in the standalone replay file, and in the website's
+  // replay viewer. They had drifted: the viewer offered three speeds where the standalone offered
+  // five, and had neither the sound nor the auto-hide the other two grew. Anything a player learns
+  // on one screen should hold on the others.
+
+  it('offers the same playback speeds in both replay viewers', () => {
+    const site = readFileSync(join(dist, 'replays.html'), 'utf8');
+    const standalone = renderHtml(record(880009, 'standard', 600));
+    const speeds = (html: string): string[] =>
+      [...html.matchAll(/<option value="\d+"[^>]*>([a-z ]+)<\/option>/g)].map((m) => m[1]!.trim());
+
+    const a = speeds(site);
+    const b = speeds(standalone);
+    assert.ok(a.length >= 5, `the site viewer offers only ${a.length} speeds: ${a.join(', ')}`);
+    assert.deepEqual(
+      new Set(a),
+      new Set(b),
+      `the two viewers offer different speeds — site: ${a.join(', ')} / standalone: ${b.join(', ')}`,
+    );
+    for (const wanted of ['extra slow', 'very fast']) {
+      assert.ok(a.includes(wanted), `the site viewer has no "${wanted}" speed`);
+    }
+  });
+
+  it('offers sound and auto-hide everywhere a game is drawn', () => {
+    const pages: [string, string][] = [
+      ['play.html', readFileSync(join(dist, 'play.html'), 'utf8')],
+      ['replays.html', readFileSync(join(dist, 'replays.html'), 'utf8')],
+      ['the standalone replay', renderHtml(record(880009, 'standard', 600))],
+    ];
+    for (const [name, html] of pages) {
+      assert.match(html, /id="v?sound"/, `${name} has no sound control`);
+      assert.match(html, /id="v?districttoggle"/, `${name} has no auto-hide control`);
+      assert.match(html, /id="v?districtsummary"/, `${name} shows nothing when the district is folded`);
+      assert.match(html, /district\.folded/, `${name} has no rule to fold the district away`);
+    }
+  });
+
+  it('asks the replay viewer for no element its page lacks', () => {
+    // The same total check the playable page gets: a `$('vfoo')` left behind after removing #vfoo
+    // throws on load, and the page simply never starts.
+    const src = readFileSync(join(root, 'src/web/replays.ts'), 'utf8');
+    const asked = new Set([...src.matchAll(/\$\('([a-zA-Z][\w-]*)'\)/g)].map((m) => m[1]!));
+    const html = readFileSync(join(dist, 'replays.html'), 'utf8');
+    const present = new Set([...html.matchAll(/id="([a-zA-Z][\w-]*)"/g)].map((m) => m[1]!));
+    for (const id of asked) {
+      assert.ok(present.has(id), `replays.ts asks for #${id}, which replays.html does not contain`);
+    }
+  });
+});
+
+describe('every file the build needs is actually in the repo (regression)', () => {
+  it('does not gitignore a source page', () => {
+    // REGRESSION. `.gitignore` carried `replay*.html` to catch the throwaway files generated at the
+    // repo root — unanchored, so it also matched `src/web/replays.html`, which is a SOURCE file.
+    // That page had therefore NEVER been committed: a fresh clone was missing it, and the build
+    // copies it unconditionally. The pattern is anchored to the root now.
+    //
+    // Asked of git rather than read out of .gitignore: the question is whether the file survives a
+    // clone, and only git can answer that. `check-ignore -q` exits 0 when ignored, 1 when not.
+    for (const page of ['src/web/index.html', 'src/web/play.html', 'src/web/replays.html']) {
+      let ignored: boolean;
+      try {
+        execFileSync('git', ['check-ignore', '-q', page], { cwd: root, stdio: 'pipe' });
+        ignored = true;
+      } catch {
+        ignored = false;
+      }
+      assert.equal(ignored, false, `${page} is gitignored — it would be missing from a fresh clone`);
+    }
+  });
+});
+
+describe('the tray is an engine plus its Rolling Stock', () => {
+  it('shows where the engine sits, because it may pull, push, or do both', () => {
+    // A Crew Tray is an engine and its cars, and the engine may be PULLING (ahead of everything),
+    // PUSHING (behind everything) or in the middle doing both — which decides which end cars couple
+    // onto (§A.3) and which way the train can shove.
+    //
+    // REGRESSION on a dead field: `engineFront` was a boolean written in three places and read in
+    // NONE, so the engine had a position the game recorded and never used, and every consist was
+    // drawn as an anonymous row of cars. It is an index into the consist now.
+    const s = createEngineGame({
+      id: 'eng', seed: 1038389,
+      config: {
+        mode: 'solitaire', victory: 'highestAfterDays', length: 'standard',
+        optionalRules: { reducedVisibility: false, sisterTrains: false, employeeRotation: false, emergencyToolbox: false },
+      },
+      playerNames: ['Solitaire'],
+    });
+
+    // A tray built by hand, so every position can be checked rather than hoping one turns up.
+    // Trays are created when a train is made up, so a fresh game has none.
+    const trayId = s.freeTrays.pop()!;
+    const tray = {
+      id: trayId,
+      trainNumber: 9,
+      trainIsExtra: false,
+      engineAt: 0,
+      consist: [
+        { type: 'boxcar', loaded: false },
+        { type: 'hopper', loaded: true },
+      ],
+      direction: 'east',
+      position: { at: 'divisionPoint', side: 'west' },
+    } as never;
+    s.trays.set(trayId, tray);
+    const west = s.division.nodes.find((n) => n.kind === 'divisionPoint');
+    if (west && west.kind === 'divisionPoint') west.holding.push(trayId);
+
+    const consistFor = (at: number): string[] => {
+      (tray as unknown as { engineAt: number }).engineAt = at;
+      const f = snapshot(s, [], null);
+      for (const node of f.division) {
+        for (const t of node.trains.flat()) {
+          if (t.consist.includes('ENG')) return t.consist;
+        }
+      }
+      return [];
+    };
+
+    assert.equal(consistFor(0)[0], 'ENG', 'an engine at 0 is not drawn pulling');
+    assert.equal(consistFor(2)[2], 'ENG', 'an engine behind the cars is not drawn pushing');
+    const middle = consistFor(1);
+    assert.equal(middle[1], 'ENG', 'an engine between the cars is not drawn in the middle');
+    assert.equal(middle.length, 3, 'the engine displaced a car instead of sitting between them');
+  });
+
+  it('shows both yards, split loaded and empty', () => {
+    // Rolling stock is finite and the Classification Yard returns to service only when the Division
+    // Yard is BARE, so watching the Division Yard run down is real information — and neither yard
+    // was shown anywhere.
+    const s = createEngineGame({
+      id: 'yards', seed: 1038389,
+      config: {
+        mode: 'solitaire', victory: 'highestAfterDays', length: 'standard',
+        optionalRules: { reducedVisibility: false, sisterTrains: false, employeeRotation: false, emergencyToolbox: false },
+      },
+      playerNames: ['Solitaire'],
+    });
+    const f = snapshot(s, [], null);
+
+    assert.ok(f.yards.divisionTotal > 0, 'the Division Yard is dealt nothing');
+    assert.equal(
+      f.yards.division.reduce((n, r) => n + r.loaded + r.empty, 0),
+      f.yards.divisionTotal,
+      'the Division Yard breakdown does not add up to its total',
+    );
+    assert.equal(
+      f.yards.classification.reduce((n, r) => n + r.loaded + r.empty, 0),
+      f.yards.classificationTotal,
+      'the Classification Yard breakdown does not add up to its total',
+    );
+    // The page must ask for the elements it fills.
+    const html = readFileSync(join(dist, 'play.html'), 'utf8');
+    for (const id of ['divyard', 'clsyard', 'divtot', 'clstot']) {
+      assert.ok(html.includes(`id="${id}"`), `play.html has no #${id}`);
+    }
+  });
+});