Game Loop & State Machine

4.1GameTask: the per-frame loop

When the menu hands over (setNextProc(2)), trainMain starts GameTask (@ 0x1e718c) as task 99 with a 24 KB stack; six times every other process, because this function coordinates physics, streaming, camera, effects and scoring in one frame. Its initialization runs once:

CdSyncRead();              // flush pending asset reads
SetDiaDecisionGameData();  // commit the selected diagram into game data
setJoinGame(-1);           // resolve join (multi-segment) state → station status
setStationStatus(...);     // set current/next station indices
MapInit(); initMapMainBefore(); MapRead();   // load route map data
chgMapTrain(); MapSet(); initMapMainAfter(); // place train, cameras, mode=0
startDemo(2);              // pre-departure intro cinematic (below)

Then the loop, annotated, from the decompilation:

/* GameTask @ 0x1e718c — one iteration = one 60 Hz frame */
do {
  GameCondition = GameConditionBk;      // 1. snapshot world switches
  gameMode = getGameMode();             // 0=driver 1=lecture 2/3=conductor 4=replay
  mode    = setMainMapMode(-1);         // read current phase (no change)

  // 2. game-over / replay-end detection (bit 0x200 or replay buffer end)
  if (gameMode == 4 && (replayBufferDone || GameCondition & 0x200)) { …fade out… }

  // 3. station-stop transition: running==0 while at a platform
  if (mode == 2 && !(GameCondition & 1)) {
      SaveStationStopTime();
      switch (gameMode) {
        case 1:  EndRunLecture(1); break;              // tutorial wrap
        case 2,3: setMainMapMode(10); break;           // conductor doors
        case 4:  setEndMapMode(0); setMainMapMode(9); break;
        default: setMainMapMode(3); break;             // station result screen
      }
  }

  setNochBrake();                       // 4. input → notch/brake (Chapter 7)
  if (gameMode != 4) checkPause();      // 5. Enter during driving → pause mode

  // 6. dispatch current phase; run its per-frame function
  if (setMainMapMode(-1) == 2 && mainMap() != 0) {
      // 7. ACTIVE DRIVING FRAME — the ordered pipeline:
      ttTrainGo();          // physics integration      (Chapter 7)
      moveMap();            // move along route
      procSReplay(_RunRoutePos); // record replay frame
      MainGameMapCheck(_MainRailTagID); // area streaming / bank switch
      GameViewProc();       // camera
      commonMapFunc();      // events, TimeCtl, judges, game-over check
      RendMap();            // queue world drawing
      setMapTrain(); procRilTrain();       // train position + models
      DispFallRain(); drawEffectAll();     // weather + effects
      LectDispCheck(); procLecture();      // tutorial overlays
      procGameSp();         // HUD: speed, notch, score, life, navi…
      procDispConductor(); procGradeStg(); // conductor UI, grades
      DispStationInt(); procWordMenu();    // station interior, text
      procSprMove(); procSprAttach(); procSprShade(); // 2D layers
      OldViewType = ViewType;
  }
  ttDelayTask(1);                       // yield until next tick
} while (true);

The pre-departure cinematic

Before the loop starts, startDemo(2) runs playDemo (@ 0x1e41a0), a five-state flyover showing the train and station, with the “Yamanote Line Diagram #01” title card. It ends after 269 frames, or after 79 frames if the player presses decide (checked against denkeyP+0x2c & 0x60), then cross-fades out and hands over to the loop:

case 1:                                   // hold
    cnt++;
    if (cnt > 0x10d ||                    // ~4.5 s at 60 fps
       (cnt > 0x4f && (*(uint *)((int)denkeyP + 0x2c) & 0x60) != 0)) {
        mode = 2; cnt = 0;                // → fade out
    }
    break;

4.2The 12 map modes

Every gameplay phase is one function in a 12-entry table at 0x42C348. A phase is initialized once (called with -1) and then called with 0 every frame until it reports done:

/* setMainMapMode @ 0x1e7974 — the whole dispatch mechanism */
int setMainMapMode(int param_1)
{
  if ((GameCondition.mainMapMode != param_1) && (-1 < param_1)) {
    GameCondition.mainMapModeBk = GameCondition.mainMapMode;
    GameCondition.mainMapMode = param_1;
    (*(code *)(&mainFunc)[param_1])(0xffffffff);   // init new phase
    return GameCondition.mainMapMode;
  }
  return GameCondition.mainMapMode;
}

4.3GameCondition: the world's switchboard

Two globals form a snapshot pair: game logic flips bits in GameConditionBk (@ 0x6d74d0); once per frame the loop copies it into GameCondition (@ 0x6d74cc) so every subsystem reads a consistent snapshot. The decompiled bit table:

4.4Time and the timetable

Game time is an integer second counter at gameStatus+0x314 (@ 0x6d360c), advanced by TimeCtl once per active frame (masked off by pause/replay: GameCondition & 0x402). The scheduled arrival second for the current station sits at gameStatus+0x318 (@ 0x6d3610), and the difference drives the late-arrival judgment (Chapter 8). Departure rewinds the clock by the station's dwell time (startMapFunc mode 3: gameStatus+0x314 -= schedule.dwell_seconds_14), so the timetable stays coherent across stops.

4.5Events, streaming, and the replay recorder

• Event scanning — commonMapFunc → trEvCheckEventI walks an event cursor along the route each frame: signal changes, tunnel lights, overtake triggers, roof events (types 0xb4–0xb7), and the taikou (opposing-train) meet events all fire from per-rail trigger records.
• Area streaming — MainGameMapCheck watches the train's rail-tag position against the current map-area's range; near a boundary it preloads the adjacent areapacNN into the inactive bank (GameLoadDataMap(area, MapBank^1)), waits out in-flight reads, then flips the bank (ChangeMapBank). This is why the world fades in piecewise on slow loads (screenshots in Chapter 1 show the green placeholder state.
• Replay recorder — every active frame appends packed controller bits to a 6000-frame circular buffer with 0x70-byte headers; the station-result screen replays the approach from a cinematic camera (Chapter 10).