retune tempest difficulty and fix death persistence

- Replace hard-capped difficulty curves with exponential ramp function
  that continues scaling deep into endless play without plateauing
- Reduce base speeds and shot counts for more deliberate gameplay
- Increase flipper, fuseball, and pulsar speeds for more pressure
- Flipper AI now chains hops toward the claw instead of resting,
  making it a true pursuer rather than a shuffler
- Change zapper to refill +1 per level instead of full reset, making
  charge management meaningful
- Death no longer resets the board: only enemies within threshold t
  die with the player, others remain mid-climb
- Improve enemy shot hit detection with lane distance check instead
  of exact lane match
- Add advanceShots() helper for cleaner shot advancement logic
- Update verification tests for new mechanics and difficulty curves
- Add michael background sprites and update tetrisattack characters

src/games/tempest/TempestGame.js

@@ -383,7 +383,11 @@ export default class TempestGame extends Phaser.Scene {
       case 'warpStart': {
         playSound(this, SFX.SCIFI_RISER);
         const spiked = this.sim.spikes.some((tip) => tip < 1);
-        this.showBanner(spiked ? 'AVOID SPIKES' : 'SUPERZAPPER RECHARGE', this.band.lane, 1500);
+        // The zapper only regains one charge per level, so only promise it
+        // when there is actually room for it.
+        const zapBack = this.sim.zapper.uses < TUNE.ZAPPER_USES ? 'SUPERZAPPER +1' : null;
+        const banner = spiked ? 'AVOID SPIKES' : zapBack;
+        if (banner) this.showBanner(banner, this.band.lane, 1500);
         break;
       }
       case 'warpDone': {

src/games/tempest/TempestLogic.js

@@ -238,81 +238,107 @@ export const TUNE = {
   LIVES: 3,
   EXTRA_LIFE_EVERY: 20000,
 
-  MOVE_LANES_PER_SEC: 14,
-  FIRE_COOLDOWN_MS: 110,
-  MAX_SHOTS: 8,               // arcade cap on live player shots
+  MOVE_LANES_PER_SEC: 10,
+  FIRE_COOLDOWN_MS: 150,
+  MAX_SHOTS: 4,               // live player shots — few enough that aim matters
   SHOT_SPEED: 2.3,            // t units per second, rim -> pit
 
   // Enemy climb speeds in t/sec (positive = toward the rim) and growth.
-  FLIPPER_SPEED: 0.16, FLIPPER_SPEED_GROWTH: 0.006, FLIPPER_SPEED_MAX: 0.42,
+  // The flipper's ramp is a soft cap (see `ramp`) plus a slow tail, so deep
+  // levels keep getting faster instead of flat-lining; HARD_MAX keeps it well
+  // under SHOT_SPEED so a climbing flipper always stays shootable.
+  FLIPPER_SPEED: 0.16, FLIPPER_SPEED_RATE: 0.05, FLIPPER_SPEED_CAP: 0.52,
+  FLIPPER_SPEED_TAIL: 0.0015, FLIPPER_SPEED_HARD_MAX: 1.0,
   TANKER_SPEED: 0.10,
   SPIKER_SPEED: 0.22,
-  FUSEBALL_SPEED: 0.30,
-  PULSAR_SPEED: 0.14,
+  FUSEBALL_SPEED: 0.50,
+  PULSAR_SPEED: 0.22,
 
-  // Rim flippers hunt the player: rest between hops, then a hop that can be
-  // shot mid-flight. Flippers also flip lane-to-lane while still climbing
-  // (their arcade signature) — chance ramps up and cooldown shortens with
-  // level so early levels stay gentle and later ones get aggressive.
-  FLIP_DUR_MS: 260,
-  FLIP_REST_MS: 520, FLIP_REST_DECAY: 8, FLIP_REST_MIN_MS: 220,
-  FLIP_CLIMB_CHANCE_BASE: 0.3, FLIP_CLIMB_CHANCE_GROWTH: 0.01, FLIP_CLIMB_CHANCE_MAX: 0.55,
-  FLIP_CLIMB_COOLDOWN_MS: 1100, FLIP_CLIMB_COOLDOWN_DECAY: 20, FLIP_CLIMB_COOLDOWN_MIN_MS: 600,
+  // Rim flippers hunt the player: they chain hops toward the claw without
+  // resting while it is more than a lane away, and a hop that lands on the
+  // player's lane is a grab. Flippers also flip lane-to-lane while still
+  // climbing (their arcade signature) — chance ramps up and cooldown shortens
+  // with level.
+  FLIP_DUR_MS: 150,
+  FLIP_REST_MS: 260, FLIP_REST_DECAY: 10, FLIP_REST_MIN_MS: 90,
+  FLIP_CLIMB_CHANCE_BASE: 0.55, FLIP_CLIMB_CHANCE_GROWTH: 0.01, FLIP_CLIMB_CHANCE_MAX: 0.92,
+  FLIP_CLIMB_COOLDOWN_MS: 650, FLIP_CLIMB_COOLDOWN_DECAY: 25, FLIP_CLIMB_COOLDOWN_MIN_MS: 260,
 
   SPIKE_MIN_T: 0.22,          // how close to the rim a spike can grow
   SPIKE_TRIM: 0.06,           // how much one shot shaves off a spike tip
   SPIKE_POINTS: 1,
 
   FUSEBALL_MOVE_MS: [500, 1100],
-  FUSEBALL_PAUSE_MS: [350, 900],
-  FUSEBALL_EDGE_HOP_CHANCE: 0.35,
+  FUSEBALL_PAUSE_MS: [200, 500],
+  FUSEBALL_EDGE_HOP_CHANCE: 0.5,
+  FUSEBALL_CLIMB_BIAS: 0.85,  // chance a move phase heads for the rim
   FUSEBALL_CONTACT_T: 0.05,
 
-  PULSAR_PERIOD_MS: 3200, PULSAR_ACTIVE_MS: 700,
-  PULSAR_LETHAL_T: 0.18,      // a pulse only kills when the pulsar is near the rim
+  PULSAR_PERIOD_MS: 2400, PULSAR_ACTIVE_MS: 1000,
+  PULSAR_LETHAL_T: 0.30,      // a pulse only kills when the pulsar is near the rim
   PULSAR_TURN_T: 0.10,        // patrol: climb to here, retreat, climb again
   PULSAR_RETREAT_T: 0.72,
 
-  ENEMY_SHOT_SPEED: 0.34, ENEMY_SHOT_SPEED_GROWTH: 0.012, ENEMY_SHOT_SPEED_MAX: 0.62,
-  ENEMY_FIRE_PER_SEC: 0.16, ENEMY_FIRE_GROWTH: 0.012, ENEMY_FIRE_MAX: 0.55,
-  MAX_ENEMY_SHOTS: 8,
+  ENEMY_SHOT_SPEED: 0.70, ENEMY_SHOT_SPEED_RATE: 0.05, ENEMY_SHOT_SPEED_CAP: 1.25,
+  ENEMY_SHOT_SPEED_TAIL: 0.002, ENEMY_SHOT_SPEED_HARD_MAX: 1.9,
+  ENEMY_FIRE_PER_SEC: 0.50, ENEMY_FIRE_RATE: 0.05, ENEMY_FIRE_CAP: 1.6,
+  ENEMY_FIRE_TAIL: 0.004, ENEMY_FIRE_HARD_MAX: 4.0,
+  ENEMY_SHOT_HIT_LANES: 0.6,  // lane distance at which a rim shot connects
+  MAX_ENEMY_SHOTS: 14,
 
   // Spawn scheduling: per-level budget, concurrency cap, and cadence.
-  BUDGET_BASE: 10, BUDGET_GROWTH: 2.0, BUDGET_MAX: 40,
-  CONCURRENT_BASE: 4, CONCURRENT_MAX: 10,
-  SPAWN_MS_BASE: 1500, SPAWN_MS_DECAY: 0.97, SPAWN_MS_MIN: 480,
+  BUDGET_BASE: 14, BUDGET_RATE: 0.05, BUDGET_CAP: 46, BUDGET_TAIL: 0.35, BUDGET_HARD_MAX: 140,
+  CONCURRENT_BASE: 6, CONCURRENT_PER_LEVEL: 1 / 1.5, CONCURRENT_MAX: 16,
+  SPAWN_MS_BASE: 1100, SPAWN_MS_DECAY: 0.955, SPAWN_MS_MIN: 220,
 
   // Type unlock levels and relative spawn weights once unlocked.
-  UNLOCK: { flipper: 1, tanker: 3, spiker: 4, fuseball: 11, pulsar: 17 },
-  WEIGHT: { flipper: 1.0, tanker: 0.4, spiker: 0.35, fuseball: 0.3, pulsar: 0.35 },
+  UNLOCK: { flipper: 1, tanker: 2, spiker: 3, fuseball: 6, pulsar: 9 },
+  WEIGHT: { flipper: 1.0, tanker: 0.5, spiker: 0.35, fuseball: 0.45, pulsar: 0.5 },
 
   POINTS: { flipper: 150, tanker: 100, spiker: 50, pulsar: 200 },
   FUSEBALL_POINTS: [250, 500, 750], // by proximity to the rim when killed
 
-  ZAPPER_USES: 2,
+  ZAPPER_USES: 2,             // cap; a cleared level grants ZAPPER_REFILL back
+  ZAPPER_REFILL: 1,
   ZAP_CASCADE_MS: 40,
 
   DEATH_MS: 1300,
-  RESPITE_MS: 900,
+  RESPITE_MS: 600,
+  DEATH_CLEAR_T: 0.25,        // only enemies this close to the rim die with you
   WARP_MS: 2600,
 
   START_BONUS_SCALE: 700,     // start bonus ~ (level-1)^2 * this, rounded
 };
 
+// Approach `cap` quickly, then keep creeping by `tail` per level so endless
+// play never flat-lines the way a hard Math.min clamp does. `hardMax` is a
+// sanity ceiling, reached only hundreds of levels deep.
+export function ramp(base, rate, cap, tail, hardMax, level) {
+  const l = Math.max(0, level - 1);
+  const soft = cap - (cap - base) * Math.exp(-rate * l);
+  return Math.min(hardMax, soft + tail * l);
+}
+
 export function flipperSpeed(level) {
-  return Math.min(TUNE.FLIPPER_SPEED_MAX, TUNE.FLIPPER_SPEED + TUNE.FLIPPER_SPEED_GROWTH * (level - 1));
+  return ramp(TUNE.FLIPPER_SPEED, TUNE.FLIPPER_SPEED_RATE, TUNE.FLIPPER_SPEED_CAP,
+    TUNE.FLIPPER_SPEED_TAIL, TUNE.FLIPPER_SPEED_HARD_MAX, level);
 }
 export function enemyShotSpeed(level) {
-  return Math.min(TUNE.ENEMY_SHOT_SPEED_MAX, TUNE.ENEMY_SHOT_SPEED + TUNE.ENEMY_SHOT_SPEED_GROWTH * (level - 1));
+  return ramp(TUNE.ENEMY_SHOT_SPEED, TUNE.ENEMY_SHOT_SPEED_RATE, TUNE.ENEMY_SHOT_SPEED_CAP,
+    TUNE.ENEMY_SHOT_SPEED_TAIL, TUNE.ENEMY_SHOT_SPEED_HARD_MAX, level);
 }
 export function enemyFireRate(level) {
-  return Math.min(TUNE.ENEMY_FIRE_MAX, TUNE.ENEMY_FIRE_PER_SEC + TUNE.ENEMY_FIRE_GROWTH * (level - 1));
+  return ramp(TUNE.ENEMY_FIRE_PER_SEC, TUNE.ENEMY_FIRE_RATE, TUNE.ENEMY_FIRE_CAP,
+    TUNE.ENEMY_FIRE_TAIL, TUNE.ENEMY_FIRE_HARD_MAX, level);
 }
 export function levelBudget(level) {
-  return Math.min(TUNE.BUDGET_MAX, Math.round(TUNE.BUDGET_BASE + TUNE.BUDGET_GROWTH * (level - 1)));
+  return Math.round(ramp(TUNE.BUDGET_BASE, TUNE.BUDGET_RATE, TUNE.BUDGET_CAP,
+    TUNE.BUDGET_TAIL, TUNE.BUDGET_HARD_MAX, level));
 }
+// Capped for real: the scene redraws every live enemy as vector art each frame.
 export function maxConcurrent(level) {
-  return Math.min(TUNE.CONCURRENT_MAX, TUNE.CONCURRENT_BASE + Math.floor(level / 2));
+  return Math.min(TUNE.CONCURRENT_MAX,
+    TUNE.CONCURRENT_BASE + Math.floor(level * TUNE.CONCURRENT_PER_LEVEL));
 }
 export function spawnInterval(level) {
   return Math.max(TUNE.SPAWN_MS_MIN, TUNE.SPAWN_MS_BASE * TUNE.SPAWN_MS_DECAY ** (level - 1));
@@ -412,7 +438,14 @@ export class Sim {
     this.enemyShots = [];
     this.enemies = [];
     this.spikes = new Array(n).fill(1); // spike tip t per lane; 1 = no spike
-    this.zapper = { uses: TUNE.ZAPPER_USES, cascade: [], cascadeMs: 0 };
+    // The zapper is NOT refilled per level — surviving charge carries over and
+    // a cleared level hands back one, so burning both is a real cost.
+    if (!this.zapper) this.zapper = { uses: TUNE.ZAPPER_USES, cascade: [], cascadeMs: 0 };
+    else {
+      this.zapper.uses = Math.min(TUNE.ZAPPER_USES, this.zapper.uses + TUNE.ZAPPER_REFILL);
+      this.zapper.cascade = [];
+      this.zapper.cascadeMs = 0;
+    }
     this.spawn = { remaining: this.buildBudget(level), timerMs: 600 };
     this.warpT = 0;
   }
@@ -605,6 +638,18 @@ export class Sim {
     return e.lane;
   }
 
+  // Unsigned lane gap between a lane index and the claw's fractional position,
+  // taking the short way around a closed web.
+  laneDistanceToPlayer(lane) {
+    const n = laneCount(this.web);
+    let d = lane - this.player.pos;
+    if (this.web.closed) {
+      d = ((d % n) + n) % n;
+      if (d > n / 2) d -= n;
+    }
+    return Math.abs(d);
+  }
+
   adjacentLaneToward(fromLane, targetLane) {
     const n = laneCount(this.web);
     if (this.web.closed) {
@@ -650,11 +695,23 @@ export class Sim {
       if (e.flipMs >= TUNE.FLIP_DUR_MS) {
         e.lane = e.flipTo;
         e.state = e.flipReturn;
-        if (e.state === 'rest') e.restMs = flipRest(this.level);
+        // A rim flipper chains hops without resting while the claw is still
+        // more than a lane away — this is what makes it a pursuer rather than
+        // a shuffler the player can simply outrun.
+        if (e.state === 'rest') {
+          const to = this.adjacentLaneToward(e.lane, this.playerLane());
+          if (to !== e.lane) {
+            e.state = 'flip'; e.flipFrom = e.lane; e.flipTo = to; e.flipMs = 0;
+          } else {
+            e.restMs = flipRest(this.level);
+          }
+        }
       }
     }
-    // A rim flipper sharing the player's lane is a grab — instant death.
-    if (e.t <= 0.02 && e.state !== 'climb' && this.visualLane(e) === this.playerLane() && e.state !== 'flip') {
+    // A rim flipper sharing the player's lane is a grab — instant death. A hop
+    // that lands on the claw counts: past the halfway point of a flip
+    // `visualLane` already reports the destination lane.
+    if (e.t <= 0.02 && e.state !== 'climb' && this.visualLane(e) === this.playerLane()) {
       this.killPlayer('grabbed');
     }
   }
@@ -695,7 +752,7 @@ export class Sim {
       e.state = 'move';
       e.phaseMs = this.randRange(TUNE.FUSEBALL_MOVE_MS);
       // Mostly climbs, sometimes dives back down, sometimes hops an edge.
-      e.dir = this.rng() < 0.72 ? -1 : 1;
+      e.dir = this.rng() < TUNE.FUSEBALL_CLIMB_BIAS ? -1 : 1;
       if (this.rng() < TUNE.FUSEBALL_EDGE_HOP_CHANCE) {
         const edges = this.edgeCount();
         let edge = e.edge + (this.rng() < 0.5 ? -1 : 1);
@@ -727,8 +784,8 @@ export class Sim {
   }
 
   enemyFireTick(e, dt) {
-    if (e.type !== 'flipper' && e.type !== 'tanker') return;
-    if (e.t < 0.12 || e.t > 0.92) return; // only while riding the well
+    if (e.type === 'fuseball') return; // fuseballs ram, they don't shoot
+    if (e.t < 0.03 || e.t > 0.98) return; // only while riding the well
     if (this.enemyShots.length >= TUNE.MAX_ENEMY_SHOTS) return;
     if (this.rng() < enemyFireRate(this.level) * (dt / 1000)) {
       this.enemyShots.push({ lane: this.visualLane(e), t: e.t, prevT: e.t });
@@ -736,6 +793,20 @@ export class Sim {
     }
   }
 
+  // Advance both sides' shots. A player shot that reaches the pit is pinned
+  // there and flagged spent: it still gets its final collision pass in
+  // resolveShots, which then drops it. Pinning rather than letting it overshoot
+  // matters because a death cuts the tick short before resolveShots runs, which
+  // would otherwise strand shots far past t=1.
+  advanceShots(dt) {
+    for (const shot of this.shots) {
+      shot.prevT = shot.t;
+      shot.t += TUNE.SHOT_SPEED * (dt / 1000);
+      if (shot.t >= 1) { shot.t = 1; shot.spent = true; }
+    }
+    for (const es of this.enemyShots) { es.prevT = es.t; es.t -= enemyShotSpeed(this.level) * (dt / 1000); }
+  }
+
   // -- collisions -----------------------------------------------------------
 
   crossed(a, b) {
@@ -787,7 +858,7 @@ export class Sim {
         this.emit('spikeTrimmed', { lane: shot.lane, t: tip });
       }
     }
-    this.shots = this.shots.filter((s) => !s.dead && s.t < 1);
+    this.shots = this.shots.filter((s) => !s.dead && !s.spent);
     this.enemyShots = this.enemyShots.filter((s) => !s.dead);
   }
 
@@ -823,13 +894,11 @@ export class Sim {
       this.emit('warpStart', { level: this.level, refly: true });
       return;
     }
-    // Survivors sink back into the pit and rejoin the spawn queue; the
-    // fight resumes where it left off (zapper charges are NOT refilled).
-    for (const e of this.enemies) {
-      const key = e.type;
-      this.spawn.remaining[key] += 1;
-    }
-    this.enemies = [];
+    // Dying is not a reset. Only the enemies that actually cornered the claw
+    // go up with it — the rest of the wave stays on the web mid-climb, and
+    // none of them are refunded into the spawn budget. Zapper charges are NOT
+    // refilled either.
+    this.enemies = this.enemies.filter((e) => e.t >= TUNE.DEATH_CLEAR_T);
     this.enemyShots = [];
     this.shots = [];
     this.phase = 'respite';
@@ -854,7 +923,7 @@ export class Sim {
     this.warpT = Math.min(1, this.warpT + dt / TUNE.WARP_MS);
     this.movePlayer(dt);
     this.fireTick(dt);
-    for (const shot of this.shots) { shot.prevT = shot.t; shot.t += TUNE.SHOT_SPEED * (dt / 1000); }
+    this.advanceShots(dt);
     // Shots ahead of the diving player shave spikes down.
     for (const shot of this.shots) {
       const tip = this.spikes[shot.lane];
@@ -865,7 +934,7 @@ export class Sim {
         this.emit('spikeTrimmed', { lane: shot.lane, t: tip });
       }
     }
-    this.shots = this.shots.filter((s) => !s.dead && s.t < 1);
+    this.shots = this.shots.filter((s) => !s.dead && !s.spent);
     // Flying into a spike costs a life and the warp restarts.
     const tip = this.spikes[this.playerLane()];
     if (tip < 1 && prev < tip && this.warpT >= tip) {
@@ -931,8 +1000,7 @@ export class Sim {
       }
     }
 
-    for (const shot of this.shots) { shot.prevT = shot.t; shot.t += TUNE.SHOT_SPEED * (dt / 1000); }
-    for (const es of this.enemyShots) { es.prevT = es.t; es.t -= enemyShotSpeed(this.level) * (dt / 1000); }
+    this.advanceShots(dt);
 
     for (const e of this.enemies.slice()) {
       if (e.dead) continue;
@@ -949,10 +1017,11 @@ export class Sim {
     this.resolveShots();
     if (this.phase !== 'playing') return this.events;
 
-    // Enemy shots that reach the rim in the player's lane connect.
+    // Enemy shots that reach the rim near the claw connect — a shot grazing
+    // the lane boundary counts, so half-a-lane dodges are not free.
     for (const es of this.enemyShots) {
       if (es.t <= 0) {
-        if (es.lane === this.playerLane()) {
+        if (this.laneDistanceToPlayer(es.lane) < TUNE.ENEMY_SHOT_HIT_LANES) {
           this.killPlayer('shot');
           break;
         }

tools/verifyTempest.js

@@ -21,7 +21,7 @@ import {
   laneCount, webForLevel, rimPoint, depthScale, makeProjector, aimLaneForAngle,
   bandIndexForLevel, startBonus, startLevelOptions,
   flipperSpeed, enemyShotSpeed, enemyFireRate, levelBudget, maxConcurrent,
-  spawnInterval, flipRest, createGame, step, setAim, setFiring, superzap,
+  spawnInterval, flipRest, flipClimbCooldown, createGame, step, setAim, setFiring, superzap,
 } from '../src/games/tempest/TempestLogic.js';
 
 let failures = 0;
@@ -333,13 +333,17 @@ console.log('Enemy fixtures');
   sim9.spawn.remaining = { flipper: 0, tanker: 0, spiker: 0, fuseball: 0, pulsar: 0 };
   const deep = sim9.makeEnemy('pulsar', sim9.playerLane(), 0.6);
   sim9.enemies.push(deep);
-  let deepDeath = false;
+  let deepPulseDeath = false; let deepFired = false;
   for (let i = 0; i < 60 * 8; i += 1) {
     deep.t = 0.6; deep.dir = 1; // pin it deep in the well
-    for (const e of step(sim9, DT)) if (e.type === 'playerHit') deepDeath = true;
+    for (const e of step(sim9, DT)) {
+      if (e.type === 'playerHit' && e.cause === 'pulsar') deepPulseDeath = true;
+      if (e.type === 'enemyShotFired') deepFired = true;
+    }
     if (sim9.phase !== 'playing') break;
   }
-  check('pulsar deep in the well is harmless', !deepDeath);
+  check('a pulsar\'s pulse is harmless deep in the well', !deepPulseDeath);
+  check('but a deep pulsar still shoots', deepFired);
 }
 
 // ── 7. Superzapper ───────────────────────────────────────────────────────────
@@ -374,8 +378,17 @@ console.log('Superzapper');
   step(sim, DT);
   check('empty zapper does nothing', sim.enemies.length === 1);
 
+  // A cleared level hands back one charge, not a full refill — burning both
+  // has to cost something.
   sim.enterLevel(sim.level + 1);
-  check('zapper recharges on a new level', sim.zapper.uses === TUNE.ZAPPER_USES);
+  check('a new level grants exactly one zapper charge',
+    sim.zapper.uses === TUNE.ZAPPER_REFILL, `uses=${sim.zapper.uses}`);
+  sim.enterLevel(sim.level + 1);
+  check('zapper charge caps at ZAPPER_USES',
+    sim.zapper.uses === TUNE.ZAPPER_USES, `uses=${sim.zapper.uses}`);
+  sim.enterLevel(sim.level + 1);
+  check('zapper does not exceed its cap',
+    sim.zapper.uses === TUNE.ZAPPER_USES, `uses=${sim.zapper.uses}`);
 }
 
 // ── 8. Scoring, extra lives, skill step ──────────────────────────────────────
@@ -455,11 +468,13 @@ console.log('Level flow');
   check('flying into a spike costs a life', spiked && sim2.lives < livesBefore);
   check('spike death re-flies the warp', reflew);
 
-  // Death and respite: survivors rejoin the spawn budget.
+  // Death is not a reset: only the enemies that cornered the claw go up with
+  // it, the rest of the wave stays on the web, and nothing is refunded.
   const sim3 = createGame({ seed: 53 });
   sim3.spawn.remaining = { flipper: 0, tanker: 0, spiker: 0, fuseball: 0, pulsar: 0 };
   sim3.enemies.push(sim3.makeEnemy('flipper', (sim3.playerLane() + 5) % LANES, 0.5));
   sim3.enemies.push(sim3.makeEnemy('spiker', (sim3.playerLane() + 8) % LANES, 0.9));
+  sim3.enemies.push(sim3.makeEnemy('flipper', (sim3.playerLane() + 2) % LANES, 0.1));
   sim3.killPlayer('shot');
   check('death costs a life', sim3.lives === TUNE.LIVES - 1);
   let respited = false;
@@ -468,8 +483,13 @@ console.log('Level flow');
     if (sim3.phase === 'playing') break;
   }
   check('respite follows a death with lives left', respited && sim3.phase === 'playing');
-  check('survivors rejoined the spawn budget',
-    sim3.spawn.remaining.flipper === 1 && sim3.spawn.remaining.spiker === 1 && sim3.enemies.length === 0);
+  check('deep enemies survive the player\'s death',
+    sim3.enemies.length === 2 && sim3.enemies.every((e) => e.t >= TUNE.DEATH_CLEAR_T),
+    `left=${sim3.enemies.length}`);
+  check('the enemies that cornered the claw are cleared',
+    !sim3.enemies.some((e) => e.t < TUNE.DEATH_CLEAR_T));
+  check('death does not refund the spawn budget', sim3.budgetTotal() === 0,
+    `budget=${sim3.budgetTotal()}`);
 
   // Game over at zero lives.
   const sim4 = createGame({ seed: 54 });
@@ -497,11 +517,30 @@ console.log('Difficulty escalation (levels 1-60)');
     if (flipRest(l) > flipRest(l - 1)) ok = false;
   }
   check('all difficulty curves monotonic', ok);
-  check('curves stay bounded',
-    flipperSpeed(999) <= TUNE.FLIPPER_SPEED_MAX
-    && levelBudget(999) <= TUNE.BUDGET_MAX
-    && spawnInterval(999) >= TUNE.SPAWN_MS_MIN
-    && flipRest(999) >= TUNE.FLIP_REST_MIN_MS);
+
+  // Timings genuinely cannot fall to zero, so they keep hard floors.
+  check('timing curves respect their floors',
+    spawnInterval(999) >= TUNE.SPAWN_MS_MIN
+    && flipRest(999) >= TUNE.FLIP_REST_MIN_MS
+    && flipClimbCooldown(999) >= TUNE.FLIP_CLIMB_COOLDOWN_MIN_MS);
+
+  // The growth curves must NOT plateau — endless play has to keep ramping
+  // instead of replaying level 44 forever.
+  check('growth curves still rise deep into an endless run',
+    flipperSpeed(200) > flipperSpeed(100)
+    && enemyShotSpeed(200) > enemyShotSpeed(100)
+    && enemyFireRate(200) > enemyFireRate(100)
+    && levelBudget(200) > levelBudget(100));
+
+  // ...but stay sane: a flipper must always be slower than a player shot, or
+  // it could never be shot down on approach.
+  check('growth curves stay under their sanity ceilings',
+    flipperSpeed(9999) <= TUNE.FLIPPER_SPEED_HARD_MAX
+    && TUNE.FLIPPER_SPEED_HARD_MAX < TUNE.SHOT_SPEED
+    && enemyShotSpeed(9999) <= TUNE.ENEMY_SHOT_SPEED_HARD_MAX
+    && enemyFireRate(9999) <= TUNE.ENEMY_FIRE_HARD_MAX
+    && levelBudget(9999) <= TUNE.BUDGET_HARD_MAX
+    && maxConcurrent(9999) <= TUNE.CONCURRENT_MAX);
   check('unlock order matches the arcade schedule',
     TUNE.UNLOCK.flipper < TUNE.UNLOCK.tanker
     && TUNE.UNLOCK.tanker < TUNE.UNLOCK.spiker
@@ -522,9 +561,11 @@ console.log('Difficulty escalation (levels 1-60)');
 console.log('Monte-carlo bot soak (40 games)');
 {
   let cleared = 0; let deaths = 0; let maxLevel = 0; let bad = 0; let overs = 0;
+  let gained = 0; // total levels *gained*, since games start at 1/5/9/13
   const started = Date.now();
   for (let g = 0; g < 40; g += 1) {
-    const sim = createGame({ seed: 9000 + g, startLevel: 1 + (g % 4) * 4 });
+    const startLevel = 1 + (g % 4) * 4;
+    const sim = createGame({ seed: 9000 + g, startLevel });
     setFiring(sim, true);
     let steps = 0;
     const stepCap = 60 * 60 * 6; // six simulated minutes per game
@@ -564,11 +605,26 @@ console.log('Monte-carlo bot soak (40 games)');
       if (sim.shots.length > TUNE.MAX_SHOTS) bad += 1;
     }
     maxLevel = Math.max(maxLevel, sim.level);
+    gained += sim.level - startLevel;
   }
+  const avgRun = gained / 40;
   check('no invariant violations across the soak', bad === 0, `violations=${bad}`);
-  check('bot makes real progress', cleared >= 40 && maxLevel >= 5, `cleared=${cleared} maxLevel=${maxLevel}`);
-  check('deaths occur (the game bites back)', deaths > 0, `deaths=${deaths}`);
-  console.log(`  info soak: cleared=${cleared} deaths=${deaths} gameovers=${overs} maxLevel=${maxLevel} in ${((Date.now() - started) / 1000).toFixed(1)}s`);
+
+  // Difficulty regression guard. This bot is deliberately naive (aim at the
+  // nearest enemy, hold fire, panic-zap) — it stands in for a careless player.
+  // Before the retune it posted deaths=2, gameovers=0, maxLevel=22 across
+  // these same 40 games, i.e. it could not lose. It now has to lose.
+  check('a careless player actually loses', overs >= 30, `gameovers=${overs}/40`);
+  check('deaths are common, not incidental', deaths / 40 >= 3,
+    `deaths=${deaths} (${(deaths / 40).toFixed(1)}/game)`);
+  check('but level 1 is still winnable', cleared >= 40, `cleared=${cleared}`);
+  // Mean levels gained per run — far stabler across seeds than a max, and the
+  // number to watch if this is ever retuned again. Too low means level 1 got
+  // unfair; too high means the retune has eroded.
+  check('the naive bot does not cruise', avgRun <= 6, `avgRun=${avgRun.toFixed(1)}`);
+  check('runs are not instantly fatal', avgRun >= 1, `avgRun=${avgRun.toFixed(1)}`);
+  console.log(`  info soak: cleared=${cleared} deaths=${deaths} gameovers=${overs}`
+    + ` maxLevel=${maxLevel} avgRun=+${avgRun.toFixed(1)} in ${((Date.now() - started) / 1000).toFixed(1)}s`);
 }
 
 // ── Result ───────────────────────────────────────────────────────────────────