Platformer showcase polish: longer levels, JOINT mechanics, crusher alleys

CHANGELOG.md

@@ -66,14 +66,46 @@ The native shim's ABI is tracked separately by `b2Version()` (currently `4`).
     (spike-type — hurts from every side). L4's PIRANHA row is now twice as
     long (four burrows on staggered timers).
   - **Longer, re-spaced levels** (the layout law: widen before squeezing
-    a beat in), grown across two passes to L1 5568, L2 4032, L3 4800,
-    L4 4864. Existing verified beats are preserved in place; each level's
-    walled-door / steps finale shifts as a whole. New classic acts: a L1
-    "meadow gauntlet" (a one-way cloud over two slimes + a darting fly); a
-    L2 second machine bay (a third chained crusher + an always-on sweeping
-    saw); a L3 second snow cloud + a final glacier slime; a L4 "bowling
-    lane" (a second snail to shell-and-kick + a slime to bowl over). More
-    decor and a live `awake N/M` body count on the HUD.
+    a beat in), grown across several passes to L1 7552, L2 5952, L3 6592,
+    L4 6656. Existing verified beats are preserved in place; each level's
+    walled-door / steps finale shifts as a whole. Classic acts stacked on:
+    L1 a "meadow gauntlet" + a "homeward run" (chained thwomp + snail under
+    a cloud); L2 second and third machine bays (chained crushers + an
+    always-on saw + a snail); L3 a second snow cloud + a glacier slime,
+    snail and thwomp; L4 a "bowling lane" plus a snail-heavy finale.
+    **Snails are now used liberally** (L4 carries four), the **classic
+    chained-weight thwomps are back** in every level alongside L4's faced
+    crushers, and there are more clouds, coins, and decor throughout. A
+    live `awake N/M` body count on the HUD.
+  - **A marquee CRUSHER ALLEY + cloud hop closes every level** (the latest
+    pass: "show off the engine with as much pizzazz as possible"). Each
+    level's homeward stretch is now a row of FOUR tile-block thwomps the
+    hero times a dash BENEATH, biome-matched so the mechanic reads at a
+    glance — **green** blocks (L1, L2 grass), **blue** (L3 ice), **red**
+    (L4 haunted) — followed by a two-cloud HOP to the flag with coins up
+    top. Powered by a new `pTileFace` parameter on `pfMakeThwomp` (a plain
+    tile sprite, no mood-face swaps; the same drop/rest/rise/re-arm cycle,
+    so the alley never blocks the path for good). The four levels each grew
+    ~1280px for the new gauntlets; the walled-door/steps finales shifted as
+    whole units; coins and their totals self-count as the level builds.
+  - **A per-frame optimization pass** against the kit's performance
+    playbook (FFI round-trips are the second-biggest per-frame cost). The
+    new crusher rows exposed that `pfTickThwomps` read each block's
+    position over the FFI *every frame even while ARMED* — a static body
+    resting at a fixed perch that cannot move until triggered — so it now
+    caches each perch x (`gBlockX`) and gates the armed→falling trigger on
+    that + the shared hero snapshot, paying `b2kPosition` only for the 0–1
+    blocks actually in motion (≈8 → ≈1 FFI/frame, identical trigger). Plus
+    the sliding-shell tick reads its velocity once (not twice) and the HUD
+    reuses the snapshotted player state and a single camera-scroll read. An
+    Opus audit confirmed every other per-frame tick was already at the
+    playbook's standard (O(1) idle gates, hoisted clocks, shared snapshot,
+    change-gated writes, sleep-friendly).
+  - **The L3 ice boulder slides ALL THE WAY** in its direction now (per
+    the user: "it is an ice block/boulder") - lower friction so it coasts
+    far, and its reset line moved off-screen-left (past the run, below the
+    camera edge) so a fresh one comes from the source rather than the old
+    one teleporting back in place.
   - **User review fixes:** the SNAIL faced backwards relative to travel
     (gotcha 26 — its sheet art is mirrored vs the slimes'); a per-row
     `gSlimeFlip` polarity column inverts only its flip. The barrel's