From d69896ddb8261c08ca516fe22d5fa33ba2a1e362 Mon Sep 17 00:00:00 2001
From: Oliver Rieger <or@4morgen.de>
Date: Sat, 11 Jul 2026 10:45:36 +0200
Subject: [PATCH] Assist predicts the interception point instead of chasing the
 ball

Same predictive brain as the CPU: simulate the trajectory, run to where the
ball will be hittable (x and z), and drift back to home position after your
own shot. Full speed while chasing, 55% while recovering.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 game.js | 37 ++++++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/game.js b/game.js
index d0b64e9..d1e1c07 100644
--- a/game.js
+++ b/game.js
@@ -321,21 +321,24 @@ function onBounce() {
 let phaseWasServe = false;
 
 // ---------------------------------------------------------------- update ----
-// Where should the AI run to? Simulate the ball forward and take the first point
-// in its half where the ball is at comfortable hitting height.
-function aiIntercept() {
+// Where should a player run to? Simulate the ball forward and take the first point
+// in their half where the ball is at comfortable hitting height.
+function intercept(side) {
   let { x, y, z, vx, vy, vz } = ball;
   const g = TUNE.gravity, dt = 0.01;
+  const inZone = side === 'O' ? zz => zz <= 9.5 : zz => zz >= COURT.L - 9.5;
+  const home = side === 'O' ? { x: 0, z: 2.5 } : { x: 0, z: 22.8 };
   let fallback = null;
   for (let i = 0; i < 240; i++) {
     vy -= g * dt; x += vx * dt; y += vy * dt; z += vz * dt;
     if (y <= 0 && vy < 0) { y = 0; vy = -vy * TUNE.bounceY; vx *= TUNE.bounceXZ; vz *= TUNE.bounceXZ; }
-    if (i > 5 && z <= 9.5 && y < 1.6) {
-      if (y > 0.7) return { x, z: Math.max(0.8, z) };            // waist-high contact preferred
-      if (y > 0.3 && !fallback) fallback = { x, z: Math.max(0.8, z) };
+    if (i > 5 && inZone(z) && y < 1.6) {
+      const pt = { x, z: side === 'O' ? Math.max(0.8, z) : Math.min(24.5, z) };
+      if (y > 0.7) return pt;                                    // waist-high contact preferred
+      if (y > 0.3 && !fallback) fallback = pt;
     }
   }
-  return fallback || { x: 0, z: 2.5 };
+  return fallback || home;
 }
 
 function trySwing(ch, isAI) {
@@ -397,15 +400,15 @@ function update(dt) {
       P.x += mx * TUNE.playerSpeed * slow * dt;
       P.z += mz * TUNE.playerSpeed * slow * dt;
       let assist = 0;
-      if (!mx && !mz && TUNE.autoAssist > 0 && ball.active && ball.lastHit === 'O') {
-        const rate = TUNE.playerSpeed * TUNE.autoAssist * slow * dt;
-        const dx = ball.x - P.x; // run toward the incoming ball so one thumb suffices
-        assist = Math.sign(dx) * Math.min(Math.abs(dx), rate);
-        P.x += assist;
-        if (ball.bounces > 0) { // ball on our side: also close the depth gap
-          const dz = Math.max(COURT.netZ + 1.5, Math.min(24.5, ball.z)) - P.z;
-          P.z += Math.sign(dz) * Math.min(Math.abs(dz), rate);
-          if (!assist) assist = dz;
+      if (!mx && !mz && TUNE.autoAssist > 0 && ball.active) {
+        const chasing = ball.lastHit === 'O';
+        const rate = TUNE.playerSpeed * TUNE.autoAssist * slow * dt * (chasing ? 1 : 0.55);
+        const tgt = chasing ? intercept('P') : { x: 0, z: 22.8 }; // run to the ball, then recover home
+        const dx = tgt.x - P.x, dz = tgt.z - P.z, d = Math.hypot(dx, dz);
+        if (d > 0.05) {
+          P.x += dx / d * Math.min(rate, d);
+          P.z += dz / d * Math.min(rate, d);
+          assist = dx || 0.01;
         }
       }
       P.x = Math.max(-6.5, Math.min(6.5, P.x));
@@ -428,7 +431,7 @@ function update(dt) {
   }
   if (phase === 'rally') {
     const incoming = ball.active && ball.lastHit === 'P';
-    const tgt = incoming ? aiIntercept() : { x: 0, z: 2.5 };
+    const tgt = incoming ? intercept('O') : { x: 0, z: 2.5 };
     const dx = tgt.x - O.x, dz = tgt.z - O.z, d = Math.hypot(dx, dz);
     if (d > 0.1) {
       O.x += dx / d * Math.min(TUNE.aiSpeed * dt, d);