Track becomes a deck card, Departments become decks, and trains must be made up to leave, industry restrictions enforced, update display and add a new game button

src/engine/advance.ts

@@ -341,6 +341,35 @@ function mainlinePhase(s: GameState, events: GameEvent[]): AdvanceResult {
 
 type MoveOutcome = 'moved' | 'held' | 'needsClearance' | 'expedited';
 
+/**
+ * §8.2 — why this train is not fit to run, or null if it is.
+ *
+ * "The engine in front, cars behind, and if there is a caboose, the caboose at the rear."
+ *
+ * DIRECTION-FREE, deliberately. The engine may be at either end of the tray — pulling or pushing —
+ * and which of those counts as "in front" depends on which way the train is pointed, which the tray
+ * does not reliably record for a crew that has been shunting round a siding. What a train may NOT be
+ * is broken-backed: the engine buried among its own cars, with some ahead of it and some behind. The
+ * caboose then has to ride at the far end from the engine, which is the rear whichever way it runs.
+ *
+ * This is reachable purely through switching. A train arrives made up, and only comes apart because
+ * the player took cars onto the nose or picked up a cut in a run-around.
+ */
+function badlyMadeUp(tray: CrewTray): string | null {
+  const n = tray.consist.length;
+  if (n === 0) return null;
+  const pulling = tray.engineAt === 0;
+  const pushing = tray.engineAt === n;
+  if (!pulling && !pushing) {
+    return `not made up — the engine is buried in the train, ${tray.engineAt} car(s) ahead of it`;
+  }
+  const caboose = tray.consist.findIndex((c) => c.type === 'caboose');
+  if (caboose === -1) return null;
+  // The rear is the end away from the engine.
+  const rear = pulling ? n - 1 : 0;
+  return caboose === rear ? null : 'not made up — the caboose must be at the rear of the train';
+}
+
 /** Puts a train onto a Mainline card with its crossing time already computed. */
 function enterMainline(
   s: GameState,
@@ -449,6 +478,26 @@ function moveTrain(
       return 'held';
     }
 
+    /**
+     * §8.2 — A TRAIN MUST BE MADE UP BEFORE IT MAY LEAVE.
+     *
+     * The engine leads, the cars follow, and a caboose rides at the rear. A train that has been
+     * shunting can easily be in none of those states: taking cars on the nose puts them AHEAD of the
+     * engine ("pushing them into the Facility"), and cars picked up in a run-around land wherever the
+     * approach put them. Nothing checked, so a crew could shove a cut into a siding and then highball
+     * onto the Mainline engine-last with the caboose in the middle.
+     *
+     * The remedy is in the player's hands and is the reason both exist: run around the train, or
+     * spend a Move in a Small Yard, which re-makes it (`consistSorted` puts the engine back on the
+     * nose). Held rather than rejected — a train that cannot leave stays where it is, which is what
+     * makes an A/D track fill up and eventually bite.
+     */
+    const badOrder = badlyMadeUp(tray);
+    if (badOrder !== null) {
+      events.push({ type: 'trainHeld', trainNumber: tray.trainNumber ?? 0, reason: badOrder });
+      return 'held';
+    }
+
     const officeIndex = nodeIndexOfOffice(s, owner);
     const target = officeIndex + dir;
     const node = s.division.nodes[target];