End a shot's topspin dip at the bounce, so a kicking ball kicks up

A shot's extra gravity is its dive in flight, but it was carried through
the bounce: heavy topspin skidded away low and Oliver met nearly every
ball 0-25 cm off the grass. After its bounce a ball now falls under plain
gravity (tennis modes only), and every planner that rolls a bounce
forward switches at the same moment. The higher bounces pushed the
auto-run into volleys, so it now takes a kicking ball at the top of its
bounce, up to chest height. Median contact rises from 0.42 to 1.13 m at
the bottom of the ladder. v369.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

PROJECT.md

@@ -5485,6 +5485,23 @@ there when the window opened) or `early 40ms`. That was the question his first l
   kicks UP. Resetting `ball.g` at the bounce would fix the picture but moves every timing in the
   rally (all four planners), so it is a decision to put to him.
 
+### The dip ends at the bounce: topspin kicks UP (2026-10-14, v369, Oliver: "ja, bau den topspin-fix")
+A shot's extra gravity (quality topspin `spinFactor`, the serve's `serveSpin`) is its DIVE IN FLIGHT,
+and it used to be carried THROUGH the bounce: a "heavy topspin" ball skidded away low and nearly every
+contact in his logs was 0-25 cm off the grass. `gAfter()` hands a ball plain gravity at its bounce
+(tennis modes; gore's balls keep theirs). The kick itself was already `bY`/`bXZ`'s spin factor. Every
+planner that rolls a bounce forward switches at the same moment (physics, `intercept`, `bounceContact`,
+`ringCue`, `matchOutOfReachFlight`); one left on the old gravity would predict a ball that is not there.
+- **Side effect, caught by the probe:** higher bounces fell outside the auto-run's 0.45-1.3 m comfort
+  band, so it found no point behind the line and ran forward to VOLLEY (38-42% volleys). The player
+  now takes a kicking bounce at its top, up to `rallyTop` 1.7 m. Volleys are back to 8-18%.
+- **Measured** (probe, median player contact): rung 1 0.42 -> 1.13 m, rung 6 0.53 m, and against the
+  big hitter still 0.35 m. The cause there is no longer the bounce. A contact fires on the FIRST frame
+  the ball is in reach, so against hard pace it is met as it enters reach, just off the bounce. Waist
+  high contact against pace would need the contact model itself changed: contact at the closest
+  approach, quality by distance from the sweet spot. That is a separate decision. The timed ring still
+  returns 92-98%. 162 tests, nine seeds.
+
 # OPEN — leftovers, in rough priority order
 
 Nothing here is broken; these are known gaps and unverified risks.

index.html

@@ -1140,6 +1140,6 @@ if (location.hostname !== 'splatter-tennis.wuwi.one' && !window.Capacitor?.isNat
   </div>
 </div>
 <span id="recLamp" hidden>REC</span>
-<script type="module" src="src/main.js?v=368"></script>
+<script type="module" src="src/main.js?v=369"></script>
 </body>
 </html>

src/config.js

@@ -91,6 +91,7 @@ export const TUNE = {
   rallyBack: 0.6,          // m behind the baseline a baseliner recovers to
   rallyBehind: 2.2,        // m behind the baseline he will drop back to let a deep ball come down
   rallyHit: 1.0,           // m: a baseliner meets the ball falling through this height
+  rallyTop: 1.7,           // m: ...and the player's auto-run accepts a kicking bounce up to here (chest high)
   lowVolleyQ: 0.3,         // quality cap on a volley struck below the tape: you can only block it up
   scoopY: 0.45,            // m: a ball met lower than this after its bounce is dug out, same cap
   // THE SOFT BALL (step 3): the down-flick, its length = how far. Drop at one end, lob at the other.

src/gameplay.js

@@ -39,6 +39,14 @@ const strikeKick = () => {
 const bXZ = () => TUNE.bounceXZ * (ball.spin || 1);
 // ...and backspin keeps it LOW as well: the vertical rebound gives up part of what the pace does
 const bY = () => TUNE.bounceY * (1 - TUNE.spinLow * (1 - (ball.spin || 1)));
+// THE DIP ENDS AT THE BOUNCE (2026-10-14, Oliver's pick). A shot's extra gravity (quality topspin,
+// the serve's spin) is its DIVE IN FLIGHT — it was carried through the bounce, so a "heavy topspin"
+// ball skidded away LOW afterwards and nearly every contact in his logs was 0-25 cm off the grass.
+// Real topspin kicks UP. After the bounce a ball falls under plain gravity; the kick itself is
+// bY/bXZ's spin factor. Tennis modes only — gore's balls keep theirs. Every planner rolling a bounce
+// forward switches here too (intercept, bounceContact, ringCue, matchOutOfReachFlight) or it would
+// predict the old low ball.
+const gAfter = g => (rallyFeel() || G.mode === 'tennis' ? TUNE.gravity : g);
 
 export function solveShot(x0, y0, z0, tx, tz, s, g = TUNE.gravity, ty = 0.08) {
   const dx = tx - x0, dz = tz - z0, dist = Math.hypot(dx, dz), T = dist / s;
@@ -1295,7 +1303,7 @@ function matchOutOfReachFlight(rz, pred) {
   const g = ball.g || TUNE.gravity;
   const spd = rzChaseSpeed(rz);
   const vyl = ball.vy - g * pred.t;                  // vertical speed at touchdown
-  const t2 = Math.max(0.05, 2 * (-vyl * bY()) / g);
+  const t2 = Math.max(0.05, 2 * (-vyl * bY()) / gAfter(g));
   const vx2 = ball.vx * bXZ(), vz2 = ball.vz * bXZ();
   const T = pred.t + t2;
   for (let i = 0; i <= 10; i++) {
@@ -1450,12 +1458,13 @@ const rallyHome = ch => ({ x: 0, z: Math.abs(ch.z - COURT.netZ) < TUNE.netFrom |
 // bounce that never gets that high. A SHORT ball is met on the RISE instead, moving in. Closed form
 // off predictLanding, for racketAI (intercept walks the flight for itself).
 function bounceContact(short) {
-  const g = ball.g || TUNE.gravity;
+  let g = ball.g || TUNE.gravity;
   let { x, y, z, vx, vy, vz } = ball;
   if (ball.bounces === 0) {
     const p = predictLanding(); if (!p) return null;
     x = p.x; z = p.z; y = 0;
     vy = -(vy - g * p.t) * bY(); vx *= bXZ(); vz *= bXZ();
+    g = gAfter(g); // the dip ends at the bounce
   }
   const apex = y + Math.max(0, vy) ** 2 / (2 * g), h = Math.min(TUNE.rallyHit, apex);
   const r = Math.sqrt(Math.max(0, vy * vy - 2 * g * (h - y)));
@@ -1472,7 +1481,7 @@ function intercept(side) {
   // classic CPU speeds up or slows down. Same guard on every dial it scales.
   const spd = side === 'O' ? TUNE.aiSpeed * (G.diff ? G.diff.speed : 1) : TUNE.playerSpeed * assistK();
   let { x, y, z, vx, vy, vz } = ball;
-  const g = ball.g || TUNE.gravity, dt = 0.01;
+  let g = ball.g || TUNE.gravity; const dt = 0.01; // g switches to plain gravity at the simulated bounce (gAfter)
   const inZone = side === 'O' ? zz => zz <= ZONE_DEPTH : zz => zz >= COURT.L - ZONE_DEPTH;
   const home = rallyFeel() ? rallyHome(ch) : HOME[side];
   const plan = rallyFeel() ? rxPlan(ch) : null;
@@ -1485,11 +1494,13 @@ function intercept(side) {
   let fallback = null, deepest = null, anyHit = null, rise = null, nb = ball.bounces;
   for (let i = 0; i < 300; i++) {
     vy -= g * dt; x += vx * dt; y += vy * dt; z += vz * dt;
-    if (y <= 0 && vy < 0) { y = 0; vy = -vy * bY(); vx *= bXZ(); vz *= bXZ(); nb++; }
+    if (y <= 0 && vy < 0) { y = 0; vy = -vy * bY(); vx *= bXZ(); vz *= bXZ(); nb++; g = gAfter(g); }
     // FROM THE BACK: meet it between its bounce and the next one — at the top or falling through
     // rallyHit+0.3, from as far as rallyBehind behind the line; a short ball the first moment it is
     // up off the grass. Only if nothing like that is reachable do the old candidates below apply.
-    if (back && nb === 1 && i > 5 && y > 0.45 && y < TUNE.rallyHit + (plan.short ? 0.6 : 0.3)) {
+    // (up to rallyTop since the dip ends at the bounce: a kicking ball is taken at the top of its
+    // bounce, chest high, rather than chased forward and volleyed — 40% volleys was the first cut)
+    if (back && nb === 1 && i > 5 && y > 0.45 && y < (plan.short ? TUNE.rallyHit + 0.6 : TUNE.rallyTop)) {
       const inB = side === 'P' ? z <= COURT.L + TUNE.rallyBehind : z >= -TUNE.rallyBehind;
       if (inB && Math.hypot(x - ch.x, z - ch.z) / spd <= i * dt) {
         if (plan.short || vy < 1) return { x, z };
@@ -1525,7 +1536,8 @@ function intercept(side) {
 // that moment in the swing window — whatever the pace. TUNE.ringTime 0 restores the distance ring.
 export function ringCue() {
   if (!ball.active || ball.lastHit !== 'O' || ball.vz <= 0) return null;
-  const g = ball.g || TUNE.gravity, dt = 1 / 120;
+  let g = ball.g || TUNE.gravity;
+  const dt = 1 / 120;
   let { x, y, z, vx, vy, vz } = ball, b = ball.bounces;
   // ...against where the player WILL be: the auto-run is still carrying him to its target at the pace
   // he is running now, and measuring against where he stands made the cue jump 50-180 ms a frame
@@ -1544,7 +1556,7 @@ export function ringCue() {
       return { eta: t, sweet, band, gold: Math.abs(t - sweet) < band };
     }
     vy -= g * dt; x += vx * dt; y += vy * dt; z += vz * dt;
-    if (y <= 0 && vy < 0) { y = 0; vy = -vy * bY(); vx *= bXZ(); vz *= bXZ(); b++; if (b > 1) return null; }
+    if (y <= 0 && vy < 0) { y = 0; vy = -vy * bY(); vx *= bXZ(); vz *= bXZ(); g = gAfter(g); b++; if (b > 1) return null; }
   }
   return null;
 }
@@ -2492,6 +2504,7 @@ export function update(dt) {
       }
       ball.y = 0; ball.vy = -ball.vy * bY();
       ball.vx *= bXZ(); ball.vz *= bXZ();
+      ball.g = gAfter(ball.g); // the dip ends at the bounce: a topspin ball kicks UP now (gAfter)
       if (Math.abs(ball.vy) > 1.0) dustPuff(ball.x, ball.z, 3, 0.7); // a real bounce kicks up the court
       onBounce();
       if (ball.active && Math.abs(ball.vy) < 0.8) { // rolled out — dead ball

tools/rally-sim.mjs

@@ -152,6 +152,7 @@ for (const rung of RUNGS) {
       '<3.5m(net)%': pct(h, x => x.fromNet < 3.5),
       'volley%': pct(h, x => !x.bounced),
       'medTimeToHit_s': +med(h.filter(x => x.dt).map(x => x.dt)).toFixed(2),
+      'medContactY': +med(h.map(x => x.y)).toFixed(2),
     });
   }
   for (const side of ['P', 'O']) {