Phase 3: procedural gore piles

Kills now grow 3D-ish gore mounds, not just flat stains. zombies.js gains
a piles array {x,z,size,seed}: a kill within 0.6m of a pile grows it
(size +1, cap 4), else starts a new one (cap 30, oldest shifts out).
Ball boys shave overlapping piles at size -= dt*0.25 — far slower than
stain mopping (dt*1.6) — so net growth wins over a long match. Splatter
particles bumped 14→24, ~1/3 dark and longer-lived (settling gore),
render reads pt.dark for colour.

render.js draws each pile as seeded pixel-art blobs (mulberry32 from
p.seed): N=6+size*5 blobs, offset within size*0.28m, lifted up to
size*0.14m so the pile has visible height, weighted gore colours + ~10%
bone flecks. Blobs are built once and rebuilt only when the pile GROWS
(builtSize guard) — never on the per-frame mop-shrink — and each pile
costs a single proj() call (blob screen positions offset from the base).
Piles draw split far/near of the net like zombies so height occludes
right. window.T exposes render/piles/gore/parts for verification.

Verified via window.T: clustered kills build tall dense mounds while
singles stay small (screenshot), avg render 0.61ms with 10 piles, 0 blob
rebuilds across 120 frames, mop shrinks a size-4 pile at exactly 0.25/s,
no console errors.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

zombies.js

@@ -9,8 +9,9 @@ import { splat, moan, pock, voice } from './audio.js';
 import { splatPoint, cheer } from './gameplay.js';
 
 export const zombies = []; // {x, z, v, walkT, variant: 'a'|'b'|'c'}
-export const gore = [];    // lawn decals {x, z, r, a}
-export const parts = [];   // splatter particles {x, y, z, vx, vy, vz, t}
+export const gore = [];    // lawn decals {x, z, r, a}  — the flat ground layer
+export const piles = [];   // 3D-ish gore mounds {x, z, size 1..4, seed} — grow where kills cluster
+export const parts = [];   // splatter particles {x, y, z, vx, vy, vz, t, dark}
 
 let spawnT = 1.5, moanT = 3;
 
@@ -25,11 +26,15 @@ function splatter(i) {
   ball.kills++;                   // this shot's running streak
   gore.push({ x: zb.x, z: zb.z, r: 0.45 + Math.random() * 0.35, a: 0.85 });
   if (gore.length > 40) gore.shift();
-  for (let k = 0; k < 14; k++) parts.push({
+  const pl = piles.find(p => Math.hypot(p.x - zb.x, p.z - zb.z) < 0.6); // stack up where kills cluster
+  if (pl) pl.size = Math.min(4, pl.size + 1);
+  else { piles.push({ x: zb.x, z: zb.z, size: 1, seed: Math.random() * 1e4, blobs: null, builtSize: 0 });
+         if (piles.length > 30) piles.shift(); }
+  for (let k = 0; k < 24; k++) { const dark = k >= 16; parts.push({ // ~1/3 dark & long-lived: settling gore
     x: zb.x, y: 0.9, z: zb.z,
     vx: (Math.random() * 2 - 1) * 3.5, vy: 1 + Math.random() * 3.5, vz: (Math.random() * 2 - 1) * 3.5,
-    t: 0.4 + Math.random() * 0.4,
-  });
+    t: dark ? 0.6 + Math.random() * 0.6 : 0.4 + Math.random() * 0.4, dark,
+  }); }
   splat();
   ball.vx *= TUNE.zPierce; ball.vz *= TUNE.zPierce; // keep enough pace to plow through the next
   sendBoy(zb.x, zb.z);            // a boy sprints out to mop
@@ -95,4 +100,9 @@ export function updateZombies(dt) {
     if (boy && Math.abs(boy.x - d.x) < 0.7 && Math.abs(boy.z - d.z) < 1.2) d.a -= dt * 1.6;
     if (d.a <= 0) gore.splice(i, 1);
   }
+  for (let i = piles.length - 1; i >= 0; i--) { // piles shave far slower than stains — net growth wins
+    const pl = piles[i];
+    if (boy && Math.abs(boy.x - pl.x) < 0.7 && Math.abs(boy.z - pl.z) < 1.2) pl.size -= dt * 0.25;
+    if (pl.size <= 0.3) piles.splice(i, 1);
+  }
 }