A new run rewinds the clock; the camera flashes did not rewind with it

Oliver: "I start a new zombie tennis match. when playing and scoring no
fotograph flashes appear, but at a random place in the crowd some frozen
midflash circle is visible. after a few points the flashes unfreeze."

Both halves are the same cause. resetState() puts G.idleT back to 0 for every
new run, while the flash list and its "next at" live in render.js's own closure
and survive it. So the new run inherited a flashNext from the old one — no
photographs at all until the clock climbed back past it — and any flash still in
flight was left with a t0 in its own future, which makes its fade
1 - (now - t0)/life permanently greater than 1: a shutter stuck at full
brightness in the stand until something else cleared it.

tickFlashes now notices the clock moving backwards and clears and re-arms. One
guard, in the only place that owns the state, so it covers any future mode that
rewinds the clock as well. Verified on the canvas: after a rewind there is no
permanently-bright pixel in the stand, and the photographers resume within
seconds instead of staying dark.

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

PROJECT.md

@@ -3732,6 +3732,17 @@ scaled so the BODY matches the standing frame (98% of sprite height) and the rac
 this on any new pose with a raised prop.
 
 ## Gotchas learned the hard way
+
+- **MODULE-LEVEL STATE CLOCKED OFF `G.idleT` MUST SURVIVE THE CLOCK GOING BACK TO ZERO.**
+  `resetState()` rewinds `G.idleT` for every new run; anything living in a module's own closure does
+  not rewind with it. The camera flashes had both halves of that bug at once (2026-08-21): a
+  `flashNext` inherited from the previous run meant NO photographs until the new run's clock climbed
+  past it, and any flash still in flight was left with a `t0` in its own future, which makes
+  `1 - (now - t0)/life` permanently greater than 1 — a shutter frozen at full brightness in the
+  stand for the rest of the session. Oliver: "at a random place in the crowd some frozen midflash
+  circle is visible. after a few points the flashes unfreeze." `tickFlashes` now clears and re-arms
+  whenever the clock moves backwards. **If you add anything else with a remembered `t0` or a "next
+  at" in render.js, give it the same guard** — the reset path will not do it for you.
 - **Nothing outside the four slot accessors may know how many slots there are.** `endBurst` had
   `[0, 1, 2, 3, 4].find(i => slotId(i) === id)`, which was correct for exactly as long as the rack
   held five. `RACK_MAX` 4 → 9 and a burst weapon in slot 5..9 was suddenly unfindable, so it was