The run cycles anchor on their feet, and stride at a real cadence

Oliver: 'the motion seems very flashy and unnatural'. Two causes, both
measured: drawChar centres a frame by its total width while the racket's
reach varies across the cycle, so the BODY teleported sideways up to 28
source px on a frame swap (the female player was worst) — every frame is now
padded until its lower-third centroid sits at the frame centre (residuals
±0.2 px, the normalisation lives in _runroll.py's cut). And the hardcoded
4.5 cycles/s was tuned on 2-4 near-duplicate frames; on eight real phases it
was a strobe — rolled sets stride at TUNE.runHz (2.4), old art keeps 4.5.

In-pane: body wobble down from ~36 device px per swap to 3.2.

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

src/config.js

@@ -41,6 +41,8 @@ export const TUNE = {
                     // the dive is what buys the pace its net clearance
   serveHardErr: 1.6,// how much a hard serve multiplies the timing scatter: pace is paid for in
                     // faults, which is what makes tap = safe second serve a real decision
+  runHz: 2.4,       // stride cycles/s for the rolled 6/8-frame run sets. The old hardcoded 4.5 was
+                    // tuned on 2-4 near-duplicate frames; on eight real phases it strobed
   serveSpin: 1.3,   // extra gravity a full-power serve carries (was a fixed 0.35). Without it the
                     // net-clearance loop ate the whole smash: a flat fast ball can't get over the
                     // tape AND come down on a target, so it got throttled back to walking pace.

src/render.js

@@ -221,7 +221,7 @@ function farB(z) {
 // Asset cache-buster — bump with main.js?v=N (see the img.src note below). EXPORTED because the
 // menu screens hang <img> tags on the same files, and two copies of this number is one copy too
 // many: the one that does not get bumped is the one that serves a cached 404.
-export const SPRV = 109;
+export const SPRV = 110;
 // The boot bar in main.js watches this. Nothing here CHANGES when things load — every sprite was
 // already requested at import — it just makes the wait visible and holds the menu back until the
 // last sheet has landed. See the onerror note below for the other half of "sometimes missing".
@@ -1445,10 +1445,12 @@ function drawChar(ch) {
     name = 'p_pull';
   // The run cycle at whatever count the character's sheet carries: the _runroll.py cycles are 6
   // (one call, one row, one character — see assets/_runroll.py for why the old per-frame art
-  // flickered); un-rolled characters fall back to 4 or 2. Same CYCLE rate at every count — more
-  // frames subdivide the stride, they do not speed it up, exactly as ZFRAMES does for the shamblers.
+  // flickered); un-rolled characters fall back to 4 or 2.
   const runN = SPR[pre + 'run8'] ? 8 : SPR[pre + 'run6'] ? 6 : SPR[pre + 'run4'] ? 4 : 2;
-  if (ch.pose === 'run') name = pre + 'run' + (Math.floor(ch.runT * 4.5 * runN) % runN + 1);
+  // The rolled 6/8-frame cycles run at their own STRIDE RATE (TUNE.runHz, cycles/s). The old 4.5
+  // was tuned on 2-4 near-duplicate frames, where it read as vigour — on eight real phases it was
+  // a strobe ("very flashy and unnatural"), most of a full stride every display frame.
+  if (ch.pose === 'run') name = pre + 'run' + (Math.floor(ch.runT * (runN >= 6 ? TUNE.runHz : 4.5) * runN) % runN + 1);
   // (the receiver used to flip to run1/run2 here as a "split-step" — it read as a man sprinting on
   //  the spot, because the run frames are a full leaning stride, not a ready-hop. He idles now.)
   if (ch.pose === 'swing') name = pre + (ch.poseT < 0.15 ? 'swing1' : 'swing2');