diff --git a/config.js b/config.js
index 9e7785c..98a4351 100644
--- a/config.js
+++ b/config.js
@@ -39,7 +39,9 @@ export const TUNE = {
   hordeRate: 2.5,   // zombies spawned per second during a horde
   mgRate: 6,        // machine-gun pellets fired per second during a horde
   mgPickupLen: 8,   // s the machine-gun tin (4th delivery) auto-fires outside hordes
+  fps: 30,          // frame cap — pixel art reads fine at 30 and it halves battery/heat; set 60 to compare
   runnerSpeed: 3.2, // runner ('f') speed multiplier over the shamble
+  runnerVMax: 4.2,  // hard runner speed cap — the late-game ramp must stay humanly reactable
   bruteHp: 2,       // splat-quality hits (or pellets) a brute ('g') soaks before it dies
   shieldDown: 1.5,  // s a shield zombie's ('s') chair stays dropped after a block — the kill window
   meleeRange: 1.7,  // m — a racket swish cleaves shamblers this close to you
diff --git a/main.js b/main.js
index d68308f..aee52fb 100644
--- a/main.js
+++ b/main.js
@@ -15,7 +15,8 @@ import './input.js';
 let last = performance.now();
 function frame(now) {
   requestAnimationFrame(frame); // schedule FIRST: one bad frame must never kill the loop (a thrown error froze the game for good)
-  const dt = Math.min(0.033, (now - last) / 1000); last = now;
+  if (TUNE.fps && now - last < 1000 / TUNE.fps - 2) return; // frame cap (battery): skip RAF ticks until it's our beat
+  const dt = Math.min(0.04, (now - last) / 1000); last = now;
   update(dt); render();
 }
 
diff --git a/render.js b/render.js
index 4d8df19..d9d5945 100644
--- a/render.js
+++ b/render.js
@@ -33,6 +33,7 @@ function palette() {
 }
 
 // ---------------------------------------------------------------- camera ----
+const IS_TOUCH = matchMedia('(pointer: coarse)').matches; // hoisted: a matchMedia call per frame churns GC
 export const RES = 3; // physical pixels per logical pixel — 3x so phone screens downscale (crisp) instead of upscaling (soft)
 export let W = 480, H = 270;
 
@@ -181,15 +182,24 @@ function buildBlobs(pl) {
   pl.builtSize = pl.size;
 }
 function drawGorePile(pl) {
-  if (!pl.blobs || pl.size > pl.builtSize) buildBlobs(pl); // rebuild only on growth, never on the mop-shrink
+  if (!pl.blobs || pl.size > pl.builtSize) { buildBlobs(pl); pl.cv = null; } // rebuild only on growth, never on the mop-shrink
   const base = proj(pl.x, 0, pl.z), s = base.s, sz = pl.size;
-  for (const b of pl.blobs) {
-    const sx = base.x + b.nx * sz * 0.28 * s;
-    const sy = base.y + b.nz * sz * 0.28 * s * 0.4 - b.lift * sz * 0.14 * s; // depth squished onto ground; lift raises it
-    const r = Math.max(1.2, b.pr * s * 0.035);
-    ctx.fillStyle = b.color;
-    ctx.beginPath(); ctx.ellipse(sx, sy, r, Math.max(1, r * 0.72), 0, 0, 7); ctx.fill();
+  const key = Math.round(s * 4); // proj scale is constant per pile until growth or an orientation change
+  if (!pl.cv || pl.cvKey !== key) { // pre-render: 1 drawImage per frame instead of ~26 ellipses (battery)
+    const pad = Math.ceil(sz * 0.28 * s + 4);
+    const off = document.createElement('canvas');
+    off.width = off.height = pad * 2;
+    const oc = off.getContext('2d');
+    for (const b of pl.blobs) {
+      const sx = pad + b.nx * sz * 0.28 * s;
+      const sy = pad + b.nz * sz * 0.28 * s * 0.4 - b.lift * sz * 0.14 * s; // depth squished onto ground; lift raises it
+      const r = Math.max(1.2, b.pr * s * 0.035);
+      oc.fillStyle = b.color;
+      oc.beginPath(); oc.ellipse(sx, sy, r, Math.max(1, r * 0.72), 0, 0, 7); oc.fill();
+    }
+    pl.cv = off; pl.cvKey = key; pl.cvPad = pad;
   }
+  ctx.drawImage(pl.cv, base.x - pl.cvPad, base.y - pl.cvPad);
 }
 function drawPiles(near) { // split at the net like zombies so height occludes correctly
   for (const pl of piles.filter(p => near ? p.z > COURT.netZ : p.z <= COURT.netZ).sort((a, b) => a.z - b.z))
@@ -418,7 +428,7 @@ export function render() {
   }
   if (G.phase === 'pretoss' && score.server === 'P' && G.mode !== 'eaten' && !G.horde && !(G.mgT > 0)) {
     ctx.fillStyle = '#f8e048'; ctx.font = 'bold 8px monospace';
-    const touch = matchMedia('(pointer: coarse)').matches;
+    const touch = IS_TOUCH;
     const stock = G.bombs ? 'BOMB' : G.triples ? 'TRIPLE' : G.flames ? 'FIRE' : null;
     const txt = G.mode === 'splatter'
       ? (G.aim ? (stock ? `RELEASE FIRES THE ${stock} · DRAG BACK TO CANCEL` : 'RELEASE TO SERVE · DRAG BACK TO CANCEL')
diff --git a/zombies.js b/zombies.js
index 2202bab..d849b51 100644
--- a/zombies.js
+++ b/zombies.js
@@ -20,7 +20,7 @@ let spawnT = 1.5, moanT = 3;
 export function spawnZombie(x, z, variant) {
   const ramp = 1 + Math.min(1.5, G.splatT / 70); // they get faster the longer you survive
   const zb = { x, z, v: TUNE.zSpeed * ramp * (0.8 + Math.random() * 0.4), walkT: Math.random() * 9, variant };
-  if (variant === 'f') { zb.v *= TUNE.runnerSpeed; shriek(); } // the shriek is the fairness contract
+  if (variant === 'f') { zb.v = Math.min(TUNE.runnerVMax, zb.v * TUNE.runnerSpeed); shriek(); } // shriek = the fairness contract; capped so late runners stay reactable
   if (variant === 'g') { zb.v *= 0.55; zb.hp = TUNE.bruteHp; } // slow, but soaks hits
   if (variant === 's') zb.shieldT = 0;                         // chair up; > 0 = seconds of stagger left
   zombies.push(zb);
@@ -243,6 +243,7 @@ export function updateZombies(dt) {
           ball.vx *= 0.4; ball.vz *= -0.2; ball.lastHit = 'X'; // ball caroms off the chair, spent
           continue;
         }
+        if (zb.variant === 'f') { splatter(i); continue; } // the sprinter is GLASS — any touch, any quality, it bursts
         // chair-down shield zombies (and anything hit from behind) obey the normal rules:
         if ((ball.pow || 0) >= TUNE.zSplatQ) { splatter(i); continue; }
         zb.z -= TUNE.zPushback; // weak sitters only stagger them
@@ -280,7 +281,7 @@ export function updateZombies(dt) {
       if (!zb || zb.variant === 'r') continue; // side balls pass the boss; !zb: kills can sweep mid-loop
       if (Math.hypot(zb.x - e.x, zb.z - e.z) < (zb.variant === 'g' ? 0.75 : 0.55)) {
         if (zb.variant === 's' && e.vz < 0 && !(zb.shieldT > 0)) { zb.shieldT = TUNE.shieldDown; pock(0.9, 1800); } // chair blocks these too
-        else if (e.pow >= TUNE.zSplatQ) {
+        else if (e.pow >= TUNE.zSplatQ || zb.variant === 'f') {
           if (zb.variant === 'g' && --zb.hp > 0) splat(0.4); // wounds the brute
           else killZombie(j, !!G.horde);
         } else { zb.z -= TUNE.zPushback; pock(0.5, 300); }