Add a purely-visual, transient juice layer over a committed move — score
popups + a tinted particle/flash burst at the clears — with no change to the
model, score, moves, or settled board.
- assets/fx/particle.png: key the painted transparency checkerboard out of the
provided particle art to real alpha (8-connected border flood fill +
smooth luminance falloff that preserves the soft glow), downscaled to a
256x256 RGBA white sparkle. tools/key_particle.sx is the reproducible tool.
- board_fx.sx: BoardFx (live particle bursts + one "+points" popup) and
BoardFxAssets. The engine image path samples texture*white (no draw-time
tint), so the white sprite is tinted per gem colour at LOAD time into one
texture per colour; a burst animates by scale (grow -> shrink) and the soft
texture edges carry the fade. Combos (cascade depth > 1) burst bigger and the
popup is larger + gold. All driven by delta_time and self-pruning.
- board_anim.sx: AnimMove carries the model's cascade.awarded so the popup
shows the real payout without re-deriving any scoring in the view.
- board_view.sx / main.sx: wire BoardFx + the tinted assets, tick each frame,
spawn on a legal commit, and render bursts (clipped to the grid) under the
popups (drawn on top). Input-lock (BoardAnim.active) is untouched; FX never
gate input and may outlast the move slightly before vanishing.
Goldens (iPhone-17-class sim, iOS 26): p6_fx.png (combo: gold "+480" + bursts
mid-cascade), p6_fx_match.png (single match: "+30" + red burst), p6_fx_after.png
(settled board, FX fully gone). Gate: ios-sim build links, 15/15 logic tests
green (scoring/cascade goldens unchanged).
A swipe that began while a move animation was playing could still commit:
mouse_down latched the drag unconditionally and the animation-active check
sat at mouse_up, so a press made mid-animation committed once the timeline
finished before release — against a board mid-transition.
Gate input at gesture START instead. Add a pure `accepts_input(anim)`
predicate (false while a timeline is active) and check it at mouse_down: a
press begun mid-animation is dropped and never latches a drag, so it cannot
commit when the animation later settles. The now-dead mouse_up gate is
removed. Animation visuals and the logical model are unchanged.
Extend tests/anim_plan.sx to assert accepts_input rejects for the whole
window (idle accept / busy reject / settled accept) and that press-gating
drops the exact failure gesture a release-gate would let through.
Add a purely-visual animation timeline so the board no longer snaps on a
move. board_anim.sx records, on a value-copy of the pre-move board, the
swap and each cascade round's matched cells + per-column fall provenance,
then BoardView plays it over delta_time: the two swapped gems SLIDE between
cells (and ping out-and-back on an illegal swap), matched gems SCALE OUT,
and survivors FALL into place while refills drop in from above the grid.
The model stays authoritative: plan_and_commit still calls commit_swap on
the real board exactly as before, and the recording replays the identical
primitives from the identical cells + RNG state, so the timeline ends ON
the model's settled board. tests/anim_plan.sx is the determinism guard —
it asserts the committed board, score, moves, and the timeline's final
state all equal an independent commit_swap of the same move, that the
rounds are contiguous, and that an illegal swap records nothing and leaves
the board untouched. All pre-existing logic/cascade goldens stay green.
Evidence (sx-test-metal, iOS 26.0, time-sampled with temporarily-lengthened
durations; committed durations are the short production values):
goldens/p6_anim_swap.png gems sliding between (5,4)/(6,4)
goldens/p6_anim_clear.png matched reds scaling out in row 4
goldens/p6_anim_fall.png gems mid-fall with gaps + refill dropping in
goldens/p6_anim_after.png settled board == model (SCORE 30, MOVES 29/30)
