The battery pass: paint less, wake less

- opaque canvas: the compositor stops alpha-blending 2.5Mpx at 60Hz
- settled modals and the death summary idle at 20-24 fps; play untouched
- TUNE.lowPower caps RES at 3 (-44% pixels/frame), flippable live

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

main.js

@@ -18,9 +18,19 @@ let last = performance.now();
 // next frame without the scene moving on underneath you. Halting rAF instead (the old test recipe)
 // freezes the picture too, which is useless for looking at a shot.
 let paused = false;
+// CALM STATES RUN SLOW. The battery bill is fill-rate × frame-rate, and two screens can sit on a
+// phone for minutes while fully static: a SETTLED modal (the world is frozen behind it — only the
+// blink still moves) and the death summary once its fade and gore have played out. 20-odd fps
+// there is invisible and thirds the drain; live play stays at TUNE.fps, untouched — the 60 was a
+// feel decision and this deliberately never applies to anything that moves.
+const calmFps = () => G.modal && G.modal.in >= 1 ? 20
+  : G.mode === 'eaten' && G.eatenT > EATEN_RESTART + 1 ? 24 : 0;
+let lowPowerApplied = false; // the last lowPower state fitViewport was run under (T-panel flips it live)
 function frame(now) {
   requestAnimationFrame(frame); // schedule FIRST: one bad frame must never kill the loop (a thrown error froze the game for good)
-  if (TUNE.fps && now - last < 1000 / TUNE.fps - 2) return; // frame cap (battery): skip RAF ticks until it's our beat
+  if ((TUNE.lowPower >= 0.5) !== lowPowerApplied) { lowPowerApplied = TUNE.lowPower >= 0.5; fitViewport(); }
+  const cap = calmFps() || TUNE.fps;
+  if (cap && now - last < 1000 / cap - 2) return; // frame cap (battery): skip RAF ticks until it's our beat
   // THE MENU IS OPAQUE (#intro: fixed, inset 0, solid background). Painting the whole court at RES
   // density behind it — for the minutes a phone idles on the splash and stats screens — was pure
   // battery burn nobody could see. The world holds still too; nothing on it predates the menu.