Splatter: chevrons in perspective, and a smash that actually flies

The chevrons were stepped along the SCREEN line at a fixed size, so they read as
a flat sticker over a 3D court. They now step through world space and take their
size from their own projection scale — near ones roughly twice the far ones —
and they fade IN toward the target so the eye is walked up the lane instead of
being handed a uniform stripe. The arrowhead scales with the target's own depth
too. (proj is a true projective map, so the screen direction stays constant
along the line; only size and alpha needed to vary.)

Hard shots now fly hard: serve pace is weighted onto quality (19 base + 22×q,
so 21 -> 41 m/s) instead of 21 -> 28. Two things had to give way for it.

Serve topspin was a fixed 1 + 0.35q, which meant a fast flat ball could not
both clear the tape and land on a target, so the net-loft loop throttled every
smash back to walking pace — measured 21.8 m/s whether you drew 60px or 95px.
TUNE.serveSpin 1.3 lets it leave flat and DIVE, which is what a smash is.

And the loft loop's margin was doHit's quality cushion, which taxed exactly the
shots meant to hurt. It's now sized to the real error it exists to cover: the
sim samples the net plane once a frame, so a diving ball can test below the tape
when the closed form clears it. Margin = descent rate × the dt clamp. A flat
drive pays almost nothing, a lob pays what it must.

Measured, target 20m out: 24.7 / 32.2 / 41 m/s for weak / mid / full draw. At
the net it's 9.6 / 11.2 / 11.6 — still the slow floaty lob, as it should be.

Ball-vs-shambler contact gets a crude sweep (radius + half a frame's travel),
because a 41 m/s ball steps 0.7m per frame at 60fps and 1.6m at main.js's dt
clamp, both wider than a shambler. Verified the full smash connects at both.

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

config.js

@@ -11,7 +11,14 @@ export const TUNE = {
   swingWindup: 0.06,       // s before contact window opens
   swingWindow: 0.16,       // s contact window length
   baseShotSpeed: 16, qualityShotSpeed: 12,  // horizontal m/s = base + q*quality; perfect timing = real pace
-  serveSpeed: 21, serveQualitySpeed: 7,
+  // the slingshot's pace range. Weighted hard toward QUALITY so a full draw is a smash you can
+  // see: 21 m/s floppy at the minimum pull, 41 m/s at full. (baseShotSpeed above is the rally
+  // volley and stays put — it's shared with tennis mode and the CPU.)
+  serveSpeed: 19, serveQualitySpeed: 22,
+  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.
+                    // Heavy topspin lets it leave flat and DIVE, which is what a smash actually is.
   aimError: 2.4,           // m of scatter at quality 0
   perfectMs: 45,           // |offset from window center| for PERFECT
   aiQualityMin: 0.45, aiQualityMax: 0.85, aiFlub: 0.09,