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>

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