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/activities/shared.tsx

@@ -55,7 +55,7 @@ export function ActivityHeader({
     <div className="flex flex-wrap items-center gap-2">
       <span
         className={cn(
-          "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",
+          "inline-flex items-center gap-1.5 rounded-full px-3 py-1 text-xs font-semibold ring-1 ring-white/50",
           meta.tint,
         )}
       >
@@ -129,7 +129,7 @@ export function OptionTile({
       onClick={onClick}
       disabled={disabled}
       className={cn(
-        "flex w-full items-center gap-3 rounded-2xl border px-4 py-3.5 text-left text-[15px] font-medium backdrop-blur-xl transition-all duration-200 disabled:cursor-default",
+        "flex w-full items-center gap-3 rounded-2xl border px-4 py-3.5 text-left text-[15px] font-medium transition-all duration-200 disabled:cursor-default",
         states[state],
         !disabled && "active:scale-[0.99]",
         className,
@@ -179,7 +179,7 @@ export function FeedbackPanel({
       animate={{ opacity: 1, y: 0 }}
       transition={{ type: "spring", stiffness: 380, damping: 32 }}
       className={cn(
-        "rounded-3xl border p-4 shadow-lift backdrop-blur-xl",
+        "rounded-3xl border p-4 shadow-lift",
         correct
           ? "border-emerald-200/80 bg-gradient-to-b from-emerald-50/95 to-emerald-100/70 dark:border-emerald-400/30 dark:from-emerald-500/15 dark:to-emerald-500/5"
           : "border-rose-200/80 bg-gradient-to-b from-rose-50/95 to-rose-100/70 dark:border-rose-400/30 dark:from-rose-500/15 dark:to-rose-500/5",