// Headless verification for Colorado Defense.
//   node tools/verifyColoradoDefense.js
// Exits non-zero on any failure.
//
// 1. Ground-layout invariants (9 slots, 3 bases + 6 cities, symmetric spacing).
// 2. City-pool draw correctness + malformed-pool fallback.
// 3. Difficulty escalation monotonicity across waves 1-40 (bounded).
// 4. MIRV step-unlock threshold.
// 4b. MIRV split-zone geometry (top-third once, top-third + halfway from wave 8).
// 5. Scripted explosion/collision fixture.
// 5c. Bonus plane fixture (unlock wave, crossing speed, hit/score/debris).
// 5d. Bonus UFO fixture (unlock wave, weaving/shots, hit/score/debris).
// 6. Palette-progression monotonicity.
// 7. Wave-complete bonus breakdown (recap data) matches the score delta.
// 8. Monte-carlo "always fire at nearest incoming missile" bot run.

import {
  BASE_SLOTS, CITY_SLOTS, GROUND_SLOTS, HEIGHT, WIDTH, GROUND_Y, slotX, mulberry32, pickCities,
  DEFAULT_CITIES, TUNE, spawnInterval, fallSpeed, waveQuota, mirvChance,
  PALETTES, paletteIndexForWave, createGame, step, pickFiringBase,
  fireInterceptor, lerpPos, explosionRadius,
} from '../src/games/coloradodefense/ColoradoDefenseLogic.js';

let failures = 0;
function check(name, cond, detail = '') {
  if (cond) { console.log(`  ok   ${name}`); return; }
  failures += 1;
  console.error(`  FAIL ${name}${detail ? ` — ${detail}` : ''}`);
}

// ── 1. Ground layout ─────────────────────────────────────────────────────────

console.log('Ground layout');
{
  check('9 slots total', GROUND_SLOTS === 9);
  check('3 base slots', BASE_SLOTS.length === 3);
  check('6 city slots', CITY_SLOTS.length === 6);
  const allSlots = [...BASE_SLOTS, ...CITY_SLOTS].sort((a, b) => a - b);
  check('slots partition 0..8 exactly', allSlots.join(',') === '0,1,2,3,4,5,6,7,8');
  check('classic arrangement Base,City,City,City,Base,City,City,City,Base',
    BASE_SLOTS.join(',') === '0,4,8' && CITY_SLOTS.join(',') === '1,2,3,5,6,7');

  const xs = Array.from({ length: GROUND_SLOTS }, (_, i) => slotX(i));
  let increasing = true;
  for (let i = 1; i < xs.length; i += 1) if (xs[i] <= xs[i - 1]) increasing = false;
  check('slot positions strictly increasing left to right', increasing);
  const mid = (xs[0] + xs[8]) / 2;
  check('layout symmetric around center', Math.abs((xs[4]) - mid) < 1, `slot4=${xs[4]} mid=${mid}`);
}

// ── 2. City pool ──────────────────────────────────────────────────────────────

console.log('City pool');
{
  const rng = mulberry32(42);
  for (const seed of [1, 2, 3, 999, 123456]) {
    const r = mulberry32(seed);
    const picked = pickCities(DEFAULT_CITIES, r);
    check(`seed ${seed}: exactly 6 cities`, picked.length === 6);
    check(`seed ${seed}: unique cities`, new Set(picked).size === 6, picked.join(','));
    check(`seed ${seed}: all from pool`, picked.every((n) => DEFAULT_CITIES.includes(n)));
  }
  const empty = pickCities([], rng);
  check('empty pool falls back safely (no throw, bounded length)', empty.length === 6);
  const small = pickCities(['A', 'B'], rng);
  check('pool smaller than 6 cycles without throwing', small.length === 6);
}

// ── 3. Escalation monotonicity ────────────────────────────────────────────────

console.log('Escalation monotonicity (waves 1-40)');
{
  let spawnOk = true; let fallOk = true; let quotaOk = true;
  let spawnBounded = true; let fallBounded = true; let quotaBounded = true;
  for (let w = 2; w <= 40; w += 1) {
    if (spawnInterval(w) > spawnInterval(w - 1)) spawnOk = false;
    if (fallSpeed(w) < fallSpeed(w - 1)) fallOk = false;
    if (waveQuota(w) < waveQuota(w - 1)) quotaOk = false;
  }
  for (let w = 1; w <= 40; w += 1) {
    if (spawnInterval(w) < TUNE.SPAWN_MS_MIN) spawnBounded = false;
    if (fallSpeed(w) > TUNE.FALL_SPEED_MAX) fallBounded = false;
    if (waveQuota(w) > TUNE.WAVE_QUOTA_MAX) quotaBounded = false;
  }
  check('spawn interval never increases with wave', spawnOk);
  check('fall speed never decreases with wave', fallOk);
  check('wave quota never decreases with wave', quotaOk);
  check('spawn interval bounded at floor', spawnBounded);
  check('fall speed bounded at cap', fallBounded);
  check('wave quota bounded at cap', quotaBounded);
}

// ── 4. MIRV step-unlock ────────────────────────────────────────────────────────

console.log('MIRV step-unlock');
{
  let belowZero = true;
  for (let w = 1; w < TUNE.MIRV_WAVE; w += 1) if (mirvChance(w) !== 0) belowZero = false;
  check(`mirvChance is 0 before wave ${TUNE.MIRV_WAVE}`, belowZero);
  check(`mirvChance > 0 at wave ${TUNE.MIRV_WAVE}`, mirvChance(TUNE.MIRV_WAVE) > 0);
  check('mirvChance bounded at max', mirvChance(999) <= TUNE.MIRV_CHANCE_MAX);
}

// ── 4b. MIRV split-zone geometry ────────────────────────────────────────────────

console.log('MIRV split-zone geometry');
{
  // spawnEnemyMissile() itself: force isMirv=true (rng()=0 < any nonzero
  // mirvChance) and check the resulting splitsLeft/splitY at both tiers.
  const spawnLow = createGame(DEFAULT_CITIES, 3);
  spawnLow.wave = TUNE.MIRV_RESPLIT_WAVE - 1;
  spawnLow.rng = () => 0;
  const missileLow = spawnLow.spawnEnemyMissile();
  check('low-wave spawn becomes a MIRV with splitsLeft=1',
    missileLow.kind === 'mirv' && missileLow.splitsLeft === 1);
  check('low-wave MIRV splitY lands in SPLIT_ZONE_1',
    missileLow.splitY >= HEIGHT * TUNE.SPLIT_ZONE_1[0] && missileLow.splitY <= HEIGHT * TUNE.SPLIT_ZONE_1[1],
    `splitY=${missileLow.splitY}`);

  const spawnHigh = createGame(DEFAULT_CITIES, 3);
  spawnHigh.wave = TUNE.MIRV_RESPLIT_WAVE;
  spawnHigh.rng = () => 0;
  const missileHigh = spawnHigh.spawnEnemyMissile();
  check('wave>=MIRV_RESPLIT_WAVE spawn becomes a MIRV with splitsLeft=2',
    missileHigh.kind === 'mirv' && missileHigh.splitsLeft === 2);
  check('its first splitY still lands in SPLIT_ZONE_1',
    missileHigh.splitY >= HEIGHT * TUNE.SPLIT_ZONE_1[0] && missileHigh.splitY <= HEIGHT * TUNE.SPLIT_ZONE_1[1],
    `splitY=${missileHigh.splitY}`);

  // Full flight, low wave: exactly one split, and the children never re-split.
  // (waveSpawned pinned to waveQuota so the sim's own spawn timer can't add
  // unrelated missiles that would pollute the length-based split count.)
  const simLow = createGame(DEFAULT_CITIES, 5);
  simLow.wave = TUNE.MIRV_RESPLIT_WAVE - 1;
  simLow.waveSpawned = simLow.waveQuota;
  const t1 = simLow.cities[0];
  simLow.enemyMissiles.push({
    id: simLow.nextId++, fromX: t1.x, fromY: 0, toX: t1.x, toY: t1.y,
    targetSlot: t1.slot, targetKind: 'city', t: 0, dur: 5000, kind: 'mirv',
    splitsLeft: 1, splitY: HEIGHT * 0.25,
  });
  let splitCountLow = 0;
  let childKinds = [];
  for (let i = 0; i < 250; i += 1) {
    const before = simLow.enemyMissiles.length;
    step(simLow, 16);
    if (simLow.enemyMissiles.length > before) {
      splitCountLow += 1;
      childKinds = simLow.enemyMissiles.filter((m) => m.kind !== 'mirv').map((m) => m.kind);
    }
  }
  check('low-wave MIRV splits exactly once over its full flight', splitCountLow === 1, `splitCount=${splitCountLow}`);
  check('its children never re-split', childKinds.length > 0 && childKinds.every((k) => k === 'single'));

  // Full flight, wave >= MIRV_RESPLIT_WAVE: splits twice, second time in zone 2.
  const simHigh = createGame(DEFAULT_CITIES, 6);
  simHigh.wave = TUNE.MIRV_RESPLIT_WAVE;
  simHigh.waveSpawned = simHigh.waveQuota;
  const t2 = simHigh.cities[0];
  simHigh.enemyMissiles.push({
    id: simHigh.nextId++, fromX: t2.x, fromY: 0, toX: t2.x, toY: t2.y,
    targetSlot: t2.slot, targetKind: 'city', t: 0, dur: 5000, kind: 'mirv',
    splitsLeft: 2, splitY: HEIGHT * 0.25,
  });
  let splitEvents = 0;
  let sawZone2SplitY = false;
  // Stops well before the trunk's own ~5000ms impact — once it lands and
  // completeWave() fires, waveSpawned resets and the spawn timer could add
  // unrelated missiles again, polluting the length-based split count.
  for (let i = 0; i < 280; i += 1) {
    const before = simHigh.enemyMissiles.length;
    step(simHigh, 16);
    if (simHigh.enemyMissiles.length > before) {
      splitEvents += 1;
      const trunk = simHigh.enemyMissiles.find((m) => m.kind === 'mirv');
      if (trunk && trunk.splitY !== null) {
        const frac = trunk.splitY / HEIGHT;
        if (frac >= TUNE.SPLIT_ZONE_2[0] && frac <= TUNE.SPLIT_ZONE_2[1]) sawZone2SplitY = true;
      }
    }
  }
  check('wave>=MIRV_RESPLIT_WAVE MIRV splits exactly twice', splitEvents === 2, `splitEvents=${splitEvents}`);
  check('its second split is scheduled in SPLIT_ZONE_2', sawZone2SplitY);
}

// ── 5. Explosion/collision fixture ────────────────────────────────────────────

console.log('Explosion/collision fixture');
{
  const sim = createGame(DEFAULT_CITIES, 7);
  const target = sim.cities[0];
  // A slow-descending missile (long dur) barely drifts during the
  // interceptor's flight time, so a shot at its current position still lands.
  sim.enemyMissiles.push({
    id: sim.nextId++, fromX: target.x, fromY: 0, toX: target.x, toY: target.y,
    targetSlot: target.slot, targetKind: 'city', t: 0.5, dur: 60000, kind: 'single', splitsLeft: 0,
  });
  const missilePos = lerpPos(sim.enemyMissiles[0]);
  const base = pickFiringBase(sim, missilePos.x, missilePos.y);
  fireInterceptor(sim, base, missilePos.x, missilePos.y);
  let destroyed = false;
  let steps = 0;
  while (!destroyed && steps < 200) {
    const events = step(sim, 16);
    if (events.some((e) => e.type === 'missileDestroyed')) destroyed = true;
    steps += 1;
  }
  check('interceptor blast destroys missile within radius', destroyed, `steps=${steps}`);
  check('score increased on kill', sim.score > 0, `score=${sim.score}`);

  const sim2 = createGame(DEFAULT_CITIES, 8);
  const target2 = sim2.cities[0];
  sim2.enemyMissiles.push({
    id: sim2.nextId++, fromX: target2.x, fromY: 0, toX: target2.x, toY: target2.y,
    targetSlot: target2.slot, targetKind: 'city', t: 0.5, dur: 4000, kind: 'single', splitsLeft: 0,
  });
  const far = lerpPos(sim2.enemyMissiles[0]);
  fireInterceptor(sim2, sim2.bases[1], far.x + 5000, far.y);
  for (let i = 0; i < 60; i += 1) step(sim2, 16);
  check('missile far outside blast radius survives', sim2.enemyMissiles.length === 1);
}

// ── 5b. Chain-reaction fixture ─────────────────────────────────────────────────

console.log('Chain-reaction fixture');
{
  const durSim = createGame(DEFAULT_CITIES, 1);
  durSim.spawnExplosion(0, 0, 'player');
  const normalTotal = durSim.explosions[0].totalMs;
  durSim.spawnExplosion(0, 0, 'chain', {
    lethal: true, extraGrow: TUNE.CHAIN_EXTRA_GROW_MS, maxR: TUNE.BLAST_R_BASE * TUNE.CHAIN_R_MULT,
  });
  const chainExp = durSim.explosions[1];
  check('chain explosion lasts exactly CHAIN_EXTRA_GROW_MS longer than a normal one',
    chainExp.totalMs - normalTotal === TUNE.CHAIN_EXTRA_GROW_MS, `normal=${normalTotal} chain=${chainExp.totalMs}`);
  check('the extra time is spent growing to full size, not lingering at it',
    explosionRadius({ t: TUNE.BLAST_GROW_MS + 1, maxR: 90, extraGrow: TUNE.CHAIN_EXTRA_GROW_MS }) < 90,
    'radius already maxed before the slower grow phase finished');
  check('chain explosion max radius is CHAIN_R_MULT times a normal one',
    chainExp.maxR === TUNE.BLAST_R_BASE * TUNE.CHAIN_R_MULT,
    `expected ${TUNE.BLAST_R_BASE * TUNE.CHAIN_R_MULT} got ${chainExp.maxR}`);

  const sim = createGame(DEFAULT_CITIES, 21);
  const target = sim.cities[0];
  sim.enemyMissiles.push({
    id: sim.nextId++, fromX: target.x, fromY: 0, toX: target.x, toY: target.y,
    targetSlot: target.slot, targetKind: 'city', t: 0.5, dur: 60000, kind: 'single', splitsLeft: 0,
  });
  const primaryPos = lerpPos(sim.enemyMissiles[0]);
  const base = pickFiringBase(sim, primaryPos.x, primaryPos.y);
  fireInterceptor(sim, base, primaryPos.x, primaryPos.y);
  // Note: the interceptor itself takes real flight time to arrive (the
  // original blast doesn't start at t=0), so a fixed-schedule secondary
  // missile can't be pre-timed reliably. Instead, inject a near-stationary
  // missile inside the chain's radius only once the chain blast is confirmed
  // under way (well after the original — which shares the same radius —
  // would have already faded), so the chain is unambiguously the killer.

  let primaryKillElapsed = null;
  let chainExplosionElapsed = null;
  let secondaryInjected = false;
  let secondaryKilledByChain = false;
  let elapsed = 0;
  for (let steps = 0; steps < 300; steps += 1) {
    const events = step(sim, 16);
    elapsed += 16;
    for (const ev of events) {
      if (ev.type === 'missileDestroyed' && !ev.chained && primaryKillElapsed === null) primaryKillElapsed = elapsed;
      if (ev.type === 'explosion' && ev.owner === 'chain' && chainExplosionElapsed === null) chainExplosionElapsed = elapsed;
      if (ev.type === 'missileDestroyed' && ev.chained) secondaryKilledByChain = true;
    }
    // The original blast is only guaranteed faded 670ms after IT spawns
    // (~primaryKillElapsed). The chain (spawned ~250ms after the kill) grows
    // to a 135px max over 1100ms, passing the 50px test distance ~407ms into
    // its own life (250+407=657ms after the kill) — wait past both before
    // injecting, well inside its 1670ms total lethal window.
    if (!secondaryInjected && primaryKillElapsed !== null && elapsed >= primaryKillElapsed + 1000) {
      sim.enemyMissiles.push({
        id: sim.nextId++, fromX: primaryPos.x - 50, fromY: primaryPos.y, toX: primaryPos.x - 50, toY: primaryPos.y,
        targetSlot: sim.cities[1].slot, targetKind: 'city', t: 0.5, dur: 60000, kind: 'single', splitsLeft: 0,
      });
      secondaryInjected = true;
    }
  }
  check('primary missile destroyed by direct hit', primaryKillElapsed !== null);
  check('a chain explosion follows ~CHAIN_DELAY_MS later',
    chainExplosionElapsed !== null
      && Math.abs((chainExplosionElapsed - primaryKillElapsed) - TUNE.CHAIN_DELAY_MS) <= 16,
    `primary=${primaryKillElapsed} chain=${chainExplosionElapsed}`);
  check('missile dropped inside the chain blast is destroyed by it', secondaryKilledByChain);
  check('chain reaction bounded to one extra tier (no dangling pending chains)', sim.pendingChains.length === 0);
}

// ── 5c. Bonus plane fixture ────────────────────────────────────────────────────

console.log('Bonus plane fixture');
{
  // Locked before PLANE_WAVE, even given plenty of time. waveQuota pinned to
  // Infinity so a real wave can never complete mid-test and silently bump
  // `wave` past the threshold being tested (ordinary missile spawning is
  // left running — it's irrelevant noise for these plane-only assertions).
  const simLocked = createGame(DEFAULT_CITIES, 40);
  simLocked.wave = TUNE.PLANE_WAVE - 1;
  simLocked.waveQuota = Infinity;
  for (let i = 0; i < Math.ceil((TUNE.PLANE_SPAWN_MAX_MS + 2000) / 16); i += 1) step(simLocked, 16);
  check('no plane spawns before PLANE_WAVE', simLocked.plane === null);

  // Unlocked: spawns once its timer elapses.
  const simSpawn = createGame(DEFAULT_CITIES, 41);
  simSpawn.wave = TUNE.PLANE_WAVE;
  simSpawn.nextPlaneAt = 100; // force a near-immediate spawn, deterministically
  for (let i = 0; i < 20 && !simSpawn.plane; i += 1) step(simSpawn, 16);
  check('plane spawns once its timer elapses at/after PLANE_WAVE', simSpawn.plane !== null);
  if (simSpawn.plane) {
    const { x, dir } = simSpawn.plane;
    check('plane starts just off the correct edge for its direction',
      (dir === 1 && x < 0) || (dir === -1 && x > WIDTH), `dir=${dir} x=${x}`);
    check('plane speed crosses the full width in exactly PLANE_CROSS_MS',
      Math.abs(simSpawn.plane.speed * TUNE.PLANE_CROSS_MS - WIDTH) < 1e-6);
  }

  // Hit: a lethal explosion at the plane's position destroys it, scores
  // PLANE_SCORE exactly, and spawns debris that keeps the plane's heading.
  const simHit = createGame(DEFAULT_CITIES, 42);
  simHit.wave = TUNE.PLANE_WAVE;
  simHit.waveQuota = Infinity;
  const planeY = HEIGHT * TUNE.PLANE_Y_FRAC;
  const planeSpeed = WIDTH / TUNE.PLANE_CROSS_MS;
  simHit.plane = { id: simHit.nextId++, x: 500, y: planeY, dir: 1, speed: planeSpeed, vx: planeSpeed, vy: 0 };
  const scoreBefore = simHit.score;
  simHit.spawnExplosion(500, planeY, 'player');
  let planeDestroyedEvent = null;
  for (let i = 0; i < 50 && !planeDestroyedEvent; i += 1) {
    const events = step(simHit, 16);
    planeDestroyedEvent = events.find((e) => e.type === 'planeDestroyed') || planeDestroyedEvent;
  }
  check('a lethal explosion at the plane destroys it', planeDestroyedEvent !== null);
  check('plane kill awards exactly PLANE_SCORE', simHit.score === scoreBefore + TUNE.PLANE_SCORE,
    `before=${scoreBefore} after=${simHit.score}`);
  check('plane is cleared after being destroyed', simHit.plane === null);
  const [dLo, dHi] = TUNE.PLANE_DEBRIS_COUNT;
  check('debris count is within PLANE_DEBRIS_COUNT range',
    simHit.debris.length >= dLo && simHit.debris.length <= dHi, `count=${simHit.debris.length}`);
  check("debris keeps the plane's horizontal momentum (rightward here)",
    simHit.debris.length > 0 && simHit.debris.every((p) => p.vx > 0));

  // Debris eventually falls and clears, without exceeding the ground band.
  let debrisSteps = 0;
  let maxY = 0;
  while (simHit.debris.length > 0 && debrisSteps < 3000) {
    for (const p of simHit.debris) maxY = Math.max(maxY, p.y);
    step(simHit, 16);
    debrisSteps += 1;
  }
  check('debris eventually clears (lands) within a bounded number of steps',
    simHit.debris.length === 0, `steps=${debrisSteps}`);
  check('debris never falls past the ground band', maxY <= GROUND_Y + 40, `maxY=${maxY}`);
}

// ── 5d. Bonus UFO fixture ───────────────────────────────────────────────────────

console.log('Bonus UFO fixture');
{
  // Locked before UFO_WAVE, even given plenty of time.
  const simLocked = createGame(DEFAULT_CITIES, 50);
  simLocked.wave = TUNE.UFO_WAVE - 1;
  simLocked.waveQuota = Infinity;
  for (let i = 0; i < Math.ceil((TUNE.UFO_SPAWN_MAX_MS + 2000) / 16); i += 1) step(simLocked, 16);
  check('no UFO spawns before UFO_WAVE', simLocked.ufo === null);

  // Unlocked: spawns with the right edge/speed, weaves within ±UFO_MAX_ANGLE_DEG,
  // and fires exactly UFO_SHOTS MIRVs (3-4s apart) if left alive.
  const simUfo = createGame(DEFAULT_CITIES, 51);
  simUfo.wave = TUNE.UFO_WAVE;
  simUfo.waveQuota = Infinity;
  simUfo.nextUfoAt = 100;
  for (let i = 0; i < 20 && !simUfo.ufo; i += 1) step(simUfo, 16);
  check('UFO spawns once its timer elapses at/after UFO_WAVE', simUfo.ufo !== null);

  if (simUfo.ufo) {
    const { x, dir, speed } = simUfo.ufo;
    check('UFO starts just off the correct edge for its direction',
      (dir === 1 && x < 0) || (dir === -1 && x > WIDTH), `dir=${dir} x=${x}`);
    check('UFO speed crosses the full width in exactly UFO_CROSS_MS',
      Math.abs(speed * TUNE.UFO_CROSS_MS - WIDTH) < 1e-6);
    check('UFO turn count is within UFO_TURNS range',
      simUfo.ufo.turnSchedule.length >= TUNE.UFO_TURNS[0] && simUfo.ufo.turnSchedule.length <= TUNE.UFO_TURNS[1],
      `turns=${simUfo.ufo.turnSchedule.length}`);

    const maxVyAllowed = speed * Math.sin(TUNE.UFO_MAX_ANGLE_DEG * Math.PI / 180) + 1e-9;
    let turnsSeen = 0;
    let shots = 0;
    const shotTimes = [];
    let elapsed = 0;
    let vyMaxSeen = 0;
    for (let i = 0; i < 700 && simUfo.ufo; i += 1) {
      const events = step(simUfo, 16);
      elapsed += 16;
      for (const ev of events) {
        if (ev.type === 'ufoTurn') turnsSeen += 1;
        if (ev.type === 'ufoShot') { shots += 1; shotTimes.push(elapsed); }
      }
      if (simUfo.ufo) vyMaxSeen = Math.max(vyMaxSeen, Math.abs(simUfo.ufo.vy));
    }
    check('UFO performs its scheduled direction changes',
      turnsSeen >= TUNE.UFO_TURNS[0], `turnsSeen=${turnsSeen}`);
    check('UFO never exceeds the ±UFO_MAX_ANGLE_DEG heading',
      vyMaxSeen <= maxVyAllowed, `vyMaxSeen=${vyMaxSeen} allowed=${maxVyAllowed}`);
    check('UFO fires exactly UFO_SHOTS MIRV shots if left alive', shots === TUNE.UFO_SHOTS, `shots=${shots}`);
    if (shotTimes.length === 2) {
      const gap = shotTimes[1] - shotTimes[0];
      check('gap between the two shots is within the configured 3-4s window',
        gap >= TUNE.UFO_SHOT_GAP_MIN_MS - 16 && gap <= TUNE.UFO_SHOT_GAP_MAX_MS + 16, `gap=${gap}`);
    }
  }

  // Hit: any lethal explosion at the UFO's position destroys it, scores
  // UFO_SCORE exactly, and spawns debris that keeps its current heading.
  const simHit = createGame(DEFAULT_CITIES, 52);
  simHit.wave = TUNE.UFO_WAVE;
  simHit.waveQuota = Infinity;
  const ufoY = HEIGHT * 0.15;
  const ufoSpeed = WIDTH / TUNE.UFO_CROSS_MS;
  simHit.ufo = {
    id: simHit.nextId++, x: 600, y: ufoY, dir: 1, speed: ufoSpeed,
    vx: ufoSpeed * 0.9, vy: ufoSpeed * 0.3, // mid-weave heading
    elapsed: 0, turnSchedule: [], turnIdx: 0, shotsLeft: 0, nextShotAt: 999999, shotGap: 3500,
  };
  const ufoScoreBefore = simHit.score;
  simHit.spawnExplosion(600, ufoY, 'player');
  let ufoDestroyedEvent = null;
  for (let i = 0; i < 50 && !ufoDestroyedEvent; i += 1) {
    const events = step(simHit, 16);
    ufoDestroyedEvent = events.find((e) => e.type === 'ufoDestroyed') || ufoDestroyedEvent;
  }
  check('a lethal explosion at the UFO destroys it', ufoDestroyedEvent !== null);
  check('UFO kill awards exactly UFO_SCORE', simHit.score === ufoScoreBefore + TUNE.UFO_SCORE,
    `before=${ufoScoreBefore} after=${simHit.score}`);
  check('UFO is cleared after being destroyed', simHit.ufo === null);
  const [uLo, uHi] = TUNE.UFO_DEBRIS_COUNT;
  check('UFO debris count is within UFO_DEBRIS_COUNT range',
    simHit.debris.length >= uLo && simHit.debris.length <= uHi, `count=${simHit.debris.length}`);
  check("UFO debris keeps its current heading's momentum",
    simHit.debris.length > 0 && simHit.debris.every((p) => p.vx > 0));
}

// ── 6. Palette progression ────────────────────────────────────────────────────

console.log('Palette progression');
{
  let monotonic = true;
  for (let w = 2; w <= 60; w += 1) {
    if (paletteIndexForWave(w) < paletteIndexForWave(w - 1)) monotonic = false;
  }
  check('palette index monotonic non-decreasing', monotonic);
  check('palette index clamps at array end', paletteIndexForWave(9999) === PALETTES.length - 1);
}

// ── 7. Wave-complete bonus breakdown ──────────────────────────────────────────

console.log('Wave-complete bonus breakdown');
{
  const sim = createGame(DEFAULT_CITIES, 99);
  sim.cities[0].alive = false; // 5 cities survive
  sim.bases[0].ammo = 4;
  sim.bases[1].ammo = 0;
  sim.bases[2].ammo = 7;
  const scoreBefore = sim.score;

  const events = [];
  const origEmit = sim.emit.bind(sim);
  sim.emit = (type, data) => { events.push({ type, ...data }); origEmit(type, data); };
  sim.completeWave();

  const e = events.find((ev) => ev.type === 'waveComplete');
  check('waveComplete event emitted', !!e);
  check('aliveCityCount matches surviving cities', e.aliveCityCount === 5, `got ${e.aliveCityCount}`);
  check('cityBonus = aliveCityCount * CITY_BONUS', e.cityBonus === 5 * TUNE.CITY_BONUS);
  check('preAmmo snapshot matches pre-refill ammo', e.preAmmo.join(',') === '4,0,7', e.preAmmo.join(','));
  check('totalAmmo sums preAmmo', e.totalAmmo === 11, `got ${e.totalAmmo}`);
  check('ammoBonus = totalAmmo * SCORE_PER_KILL', e.ammoBonus === 11 * TUNE.SCORE_PER_KILL);
  check('score increased by exactly cityBonus + ammoBonus',
    sim.score === scoreBefore + e.cityBonus + e.ammoBonus,
    `before=${scoreBefore} after=${sim.score}`);
  check('surviving bases refilled to full ammo after transition',
    sim.bases[0].ammo === TUNE.BASE_AMMO && sim.bases[2].ammo === TUNE.BASE_AMMO);
}

// ── 8. Monte-carlo bot run ────────────────────────────────────────────────────

console.log('Monte-carlo bot run');
{
  for (const seed of [1, 2, 3, 4, 5]) {
    const sim = createGame(DEFAULT_CITIES, seed);
    let steps = 0;
    let scoreRegressed = false;
    let cityCountIncreased = false;
    let nanFound = false;
    let prevScore = 0;
    let prevCities = sim.aliveCities().length;
    const MAX_STEPS = 20000; // ~320s of sim time at 16ms/step

    while (sim.status === 'playing' && steps < MAX_STEPS) {
      // Bot: fire at whichever enemy missile is closest to impact (highest t),
      // but only one interceptor in flight at a time so ammo isn't wasted on
      // redundant shots at the same target.
      if (sim.enemyMissiles.length && sim.interceptors.length === 0) {
        let soonest = null; let soonestT = -1;
        for (const m of sim.enemyMissiles) {
          if (m.t > soonestT) { soonestT = m.t; soonest = m; }
        }
        if (soonest) {
          const pos = lerpPos(soonest);
          const base = pickFiringBase(sim, pos.x, pos.y);
          if (base) fireInterceptor(sim, base, pos.x, pos.y);
        }
      }
      step(sim, 16);
      steps += 1;

      if (sim.score < prevScore) scoreRegressed = true;
      prevScore = sim.score;
      const aliveCities = sim.aliveCities().length;
      if (aliveCities > prevCities) cityCountIncreased = true;
      prevCities = aliveCities;

      const planeList = sim.plane ? [sim.plane] : [];
      for (const list of [sim.enemyMissiles, sim.interceptors, sim.explosions, planeList, sim.debris]) {
        for (const e of list) {
          if (Number.isNaN(e.x ?? e.fromX) || Number.isNaN(e.y ?? e.fromY)) nanFound = true;
        }
      }
    }

    check(`seed ${seed}: no NaN values`, !nanFound);
    check(`seed ${seed}: score never regressed`, !scoreRegressed);
    check(`seed ${seed}: city count never increased`, !cityCountIncreased);
    check(`seed ${seed}: game over exactly when all cities dead`,
      sim.status === 'gameover' ? sim.aliveCities().length === 0 : true);
    check(`seed ${seed}: terminates within step bound`, steps < MAX_STEPS, `steps=${steps}`);
    console.log(`       seed ${seed}: status=${sim.status} wave=${sim.wave} score=${sim.score} steps=${steps}`);
  }
}

console.log(failures ? `\n${failures} FAILURE(S)` : '\nAll checks passed.');
process.exit(failures ? 1 : 0);