The scene stops heating the MacBook

"Terribly high CPU usage, the MacBook gets really hot" - a fanless MacBook
Air on a 144Hz screen. Measured on that machine with headed engines
(process CPU plus the per-process GPU time macOS keeps): an idle Aero
library cost LibreWolf ~110% CPU and ~230ms/s of GPU, the study feed ~130%,
Chromium up to ~57% CPU and ~350ms/s of GPU, Safari ~220-250ms/s of
WindowServer GPU. Priced one by one:

- the gradient mask on .ice-floats re-rendered the animated layer offscreen
  on every frame (~75 points of Gecko CPU). The floats now rise through a
  plain rectangular band clear of the header, the bottom chrome and the
  rail, and fade in and out inside it, so the clip never cuts a visible one;
- the overlay grain forced a backdrop readback per frame for a texture that
  measured a mean <=0.11/255 difference: removed;
- the invisible blob drift made every frame a full-screen redraw: the blobs
  are painted once;
- static glass (answer tiles, feedback panel, chips, inputs, dropzones,
  lists, segmented controls, Aero hint chips) re-blurred the moving scene
  every frame: only floating glass blurs now, and Aero's baked chat chrome
  drops a live blur that never showed under the bake;
- the scene also parks while the window has no focus and under any dialog
  or sheet scrim (.scene-pause); the loading icon is a compositor-run CSS
  animation instead of a framer-motion main-thread loop.

After, focused and animating: LibreWolf library 109% -> 33% CPU, study
134% -> 34%, chat 130% -> 42%; Chromium GPU 2.5-4.4x lower with 7-22 points
less CPU; Safari's WindowServer GPU -20-26% in Aero, about half in dark.
Unfocused or under a sheet: nothing. bubbles-test sweeps every float through
41 phases against the band and pins the parking and the cost contract;
tests/heat-probe.mjs (macOS) repeats the measurement; the suites find
Playwright's Chromium on macOS.

All 15 suites pass, lint clean, the contrast scan lost a finding. Version
0.6.7, SW v89.

Co-authored-by: Cursor <cursoragent@cursor.com>

components/homework/HomeworkGuide.tsx

@@ -189,7 +189,7 @@ export function HomeworkGuide({
           >
             <div className="mx-auto flex min-h-full w-full max-w-xl flex-col gap-4 px-4 pb-24 pt-24 [justify-content:safe_center] [&>*]:shrink-0">
               <div className="flex flex-wrap items-center gap-2">
-                <span className="tint-sky inline-flex items-center gap-1.5 rounded-full px-3 py-1 text-xs font-semibold ring-1 ring-white/50 backdrop-blur-sm">
+                <span className="tint-sky inline-flex items-center gap-1.5 rounded-full px-3 py-1 text-xs font-semibold ring-1 ring-white/50">
                   {t("homework.guide.stepOf", { n: stepIndex + 1, total: steps.length })}
                 </span>
               </div>
@@ -293,7 +293,7 @@ export function HomeworkGuide({
         >
           <div className="mx-auto flex min-h-full w-full max-w-xl flex-col gap-4 px-4 pb-24 pt-24 [justify-content:safe_center] [&>*]:shrink-0">
             <div className="flex flex-wrap items-center gap-2">
-              <span className="tint-mint inline-flex items-center gap-1.5 rounded-full px-3 py-1 text-xs font-semibold ring-1 ring-white/50 backdrop-blur-sm">
+              <span className="tint-mint inline-flex items-center gap-1.5 rounded-full px-3 py-1 text-xs font-semibold ring-1 ring-white/50">
                 {t("homework.guide.solution")}
               </span>
             </div>

components/homework/HomeworkInput.tsx

@@ -204,7 +204,7 @@ export function HomeworkInput({
         autoComplete="off"
         autoCapitalize="sentences"
         spellCheck
-        className="w-full resize-y rounded-2xl border border-white/60 bg-white/55 px-4 py-3 text-sm text-frost-950 outline-none backdrop-blur-xl transition placeholder:text-frost-400 focus:border-accent-400 dark:border-white/12 dark:bg-white/[0.07] dark:text-frost-50"
+        className="w-full resize-y rounded-2xl border border-white/60 bg-white/55 px-4 py-3 text-sm text-frost-950 outline-none transition placeholder:text-frost-400 focus:border-accent-400 dark:border-white/12 dark:bg-white/[0.07] dark:text-frost-50"
       />
 
       <div className="flex flex-wrap items-center gap-2">
@@ -531,7 +531,7 @@ export function HomeworkInput({
                   autoComplete="off"
                   autoCapitalize="sentences"
                   spellCheck
-                  className="w-full resize-y rounded-2xl border border-white/60 bg-white/55 px-4 py-3 text-sm text-frost-950 outline-none backdrop-blur-xl transition placeholder:text-frost-400 focus:border-accent-400 dark:border-white/12 dark:bg-white/[0.07] dark:text-frost-50"
+                  className="w-full resize-y rounded-2xl border border-white/60 bg-white/55 px-4 py-3 text-sm text-frost-950 outline-none transition placeholder:text-frost-400 focus:border-accent-400 dark:border-white/12 dark:bg-white/[0.07] dark:text-frost-50"
                 />
               ) : null}
 
@@ -794,7 +794,7 @@ export function HomeworkInput({
           <button
             type="button"
             onClick={() => fileInputRef.current?.click()}
-            className="mt-4 flex w-full flex-col items-center gap-2 rounded-2xl border-2 border-dashed border-white/70 bg-white/40 px-4 py-10 text-center backdrop-blur-xl transition hover:border-accent-300 hover:bg-white/65 dark:border-white/15 dark:bg-white/[0.05] dark:hover:bg-white/[0.09]"
+            className="mt-4 flex w-full flex-col items-center gap-2 rounded-2xl border-2 border-dashed border-white/70 bg-white/40 px-4 py-10 text-center transition hover:border-accent-300 hover:bg-white/65 dark:border-white/15 dark:bg-white/[0.05] dark:hover:bg-white/[0.09]"
           >
             <span aria-hidden className="text-frost-500 dark:text-frost-200">
               <PlusIcon className="size-10" />