Fix gravity reset and add spawn cap for swirl arena

src/scenes/scene-swirl-arena.js

@@ -0,0 +1,88 @@
+(() => {
+  const { Bodies } = Matter;
+  const scenes = (window.PhysilinksSceneDefs =
+    window.PhysilinksSceneDefs || []);
+
+  scenes.push({
+    id: "swirl-arena",
+    name: "Swirl Arena",
+    config: {
+      gravity: 0,
+      gravityScale: 0.0007,
+      timeScale: 0.9,
+      spawnIntervalMs: 520,
+      initialSpawnCount: 90,
+      spawnLimit: 500,
+      autoSpawn: true,
+      minChain: 3,
+      palette: ["#f472b6", "#22c55e"],
+      ballRadius: 20,
+      spawnOrigin: "center",
+      spawnJitter: 120,
+      blobBalls: false,
+      noGameOver: true,
+      winCondition: {
+        type: "colorClear",
+        targets: [{ color: "#22c55e", count: 100 }],
+      },
+      negativeScoreColors: ["#f472b6"],
+      negativeProgressColors: ["#f472b6"],
+      link: {
+        stiffness: 0.82,
+        lengthScale: 1.08,
+        damping: 0.06,
+        lineWidth: 3,
+        rope: true,
+        renderType: "line",
+        maxLengthMultiplier: 3.6,
+      },
+      onBeforeUpdate: ({ engine }) => {
+        const t = (engine.timing?.timestamp || 0) * 0.0005;
+        engine.gravity.x = Math.cos(t);
+        engine.gravity.y = Math.sin(t);
+      },
+    },
+    createBodies: (w, h) => {
+      const wallThickness = Math.max(36, Math.min(w, h) * 0.05);
+      const innerW = w - wallThickness * 2;
+      const innerH = h - wallThickness * 2;
+      const cx = w / 2;
+      const cy = h / 2;
+      const wallOptions = {
+        isStatic: true,
+        restitution: 0.3,
+        render: { fillStyle: "#0b1222", strokeStyle: "#0b1222" },
+      };
+      return [
+        Bodies.rectangle(
+          cx,
+          cy - innerH / 2 - wallThickness / 2,
+          innerW + wallThickness * 2,
+          wallThickness,
+          wallOptions,
+        ),
+        Bodies.rectangle(
+          cx,
+          cy + innerH / 2 + wallThickness / 2,
+          innerW + wallThickness * 2,
+          wallThickness,
+          wallOptions,
+        ),
+        Bodies.rectangle(
+          cx - innerW / 2 - wallThickness / 2,
+          cy,
+          wallThickness,
+          innerH + wallThickness * 2,
+          wallOptions,
+        ),
+        Bodies.rectangle(
+          cx + innerW / 2 + wallThickness / 2,
+          cy,
+          wallThickness,
+          innerH + wallThickness * 2,
+          wallOptions,
+        ),
+      ];
+    },
+  });
+})();