Add scene selection with multiple level configs

main.js

@@ -12,13 +12,113 @@
   } = Matter;
 
   const config = {
-    gravity: 0.78,
-    spawnIntervalMs: 720,
+    gravity: 1,
+    spawnIntervalMs: 520,
     minChain: 3,
     palette: ["#ff595e", "#ffca3a", "#8ac926", "#1982c4", "#6a4c93"],
-    ballRadius: 48,
+    ballRadius: 18,
   };
 
+  const scenes = [
+    {
+      id: "scene1",
+      name: "Balanced (default)",
+      config: {
+        gravity: 1,
+        spawnIntervalMs: 520,
+        minChain: 3,
+        palette: ["#ff595e", "#ffca3a", "#8ac926", "#1982c4", "#6a4c93"],
+        ballRadius: 18,
+      },
+      createBodies: (w, h) => [
+        Bodies.rectangle(w / 2, h + 40, w, 80, {
+          isStatic: true,
+          restitution: 0.8,
+        }),
+        Bodies.rectangle(-40, h / 2, 80, h * 2, { isStatic: true }),
+        Bodies.rectangle(w + 40, h / 2, 80, h * 2, { isStatic: true }),
+        Bodies.rectangle(w * 0.25, h * 0.55, 160, 20, {
+          isStatic: true,
+          angle: -0.3,
+        }),
+        Bodies.rectangle(w * 0.7, h * 0.4, 220, 24, {
+          isStatic: true,
+          angle: 0.26,
+        }),
+      ],
+    },
+    {
+      id: "scene2",
+      name: "Low-G terraces",
+      config: {
+        gravity: 0.65,
+        spawnIntervalMs: 600,
+        minChain: 3,
+        palette: ["#fb7185", "#fbbf24", "#34d399", "#38bdf8"],
+        ballRadius: 22,
+      },
+      createBodies: (w, h) => [
+        Bodies.rectangle(w / 2, h + 50, w, 100, {
+          isStatic: true,
+          restitution: 0.9,
+        }),
+        Bodies.rectangle(-50, h / 2, 100, h * 2, { isStatic: true }),
+        Bodies.rectangle(w + 50, h / 2, 100, h * 2, { isStatic: true }),
+        Bodies.rectangle(w * 0.2, h * 0.45, 200, 18, {
+          isStatic: true,
+          angle: 0.08,
+        }),
+        Bodies.rectangle(w * 0.5, h * 0.6, 260, 18, {
+          isStatic: true,
+          angle: -0.04,
+        }),
+        Bodies.rectangle(w * 0.8, h * 0.42, 180, 18, {
+          isStatic: true,
+          angle: 0.14,
+        }),
+      ],
+    },
+    {
+      id: "scene3",
+      name: "Fast drop maze",
+      config: {
+        gravity: 1.25,
+        spawnIntervalMs: 420,
+        minChain: 3,
+        palette: ["#e879f9", "#38bdf8", "#f97316", "#22c55e"],
+        ballRadius: 16,
+      },
+      createBodies: (w, h) => {
+        const bodies = [
+          Bodies.rectangle(w / 2, h + 40, w, 80, {
+            isStatic: true,
+            restitution: 0.75,
+          }),
+          Bodies.rectangle(-40, h / 2, 80, h * 2, { isStatic: true }),
+          Bodies.rectangle(w + 40, h / 2, 80, h * 2, { isStatic: true }),
+        ];
+        for (let i = 0; i < 5; i += 1) {
+          const x = (w * (i + 1)) / 6;
+          const y = h * 0.35 + (i % 2 === 0 ? 40 : -30);
+          bodies.push(
+            Bodies.circle(x, y, 18, { isStatic: true, restitution: 0.9 }),
+          );
+        }
+        bodies.push(
+          Bodies.rectangle(w * 0.3, h * 0.55, 140, 16, {
+            isStatic: true,
+            angle: -0.3,
+          }),
+          Bodies.rectangle(w * 0.7, h * 0.58, 160, 16, {
+            isStatic: true,
+            angle: 0.28,
+          }),
+        );
+        return bodies;
+      },
+    },
+  ];
+
   const sceneEl = document.getElementById("scene-wrapper");
   const activeColorEl = document.getElementById("active-color");
   const chainLenEl = document.getElementById("chain-length");
@@ -57,33 +157,16 @@
   const runner = Runner.create();
   Runner.run(runner, engine);
 
-  // Static boundaries and some obstacles to bounce around.
+  // Static boundaries and scene-specific obstacles.
   let boundaries = [];
-  const createBounds = () => {
+  let currentScene = scenes[0];
+
+  const rebuildSceneBodies = () => {
     boundaries.forEach((b) => World.remove(world, b));
-    boundaries = [
-      Bodies.rectangle(width / 2, height + 40, width, 80, {
-        isStatic: true,
-        restitution: 0.8,
-      }),
-      Bodies.rectangle(-40, height / 2, 80, height * 2, { isStatic: true }),
-      Bodies.rectangle(width + 40, height / 2, 80, height * 2, {
-        isStatic: true,
-      }),
-    ];
-    boundaries.push(
-      Bodies.rectangle(width * 0.25, height * 0.55, 160, 20, {
-        isStatic: true,
-        angle: -0.3,
-      }),
-      Bodies.rectangle(width * 0.7, height * 0.4, 220, 24, {
-        isStatic: true,
-        angle: 0.26,
-      }),
-    );
+    boundaries = currentScene.createBodies(width, height);
     World.add(world, boundaries);
   };
-  createBounds();
+  rebuildSceneBodies();
 
   const balls = [];
   let spawnTimer = null;
@@ -112,6 +195,28 @@
     }
   };
 
+  const populateSceneSelect = () => {
+    sceneSelectEl.innerHTML = "";
+    scenes.forEach((scene) => {
+      const opt = document.createElement("option");
+      opt.value = scene.id;
+      opt.textContent = scene.name;
+      sceneSelectEl.appendChild(opt);
+    });
+  };
+
+  const applyScene = (sceneId) => {
+    const next = scenes.find((s) => s.id === sceneId) || scenes[0];
+    currentScene = next;
+    sceneSelectEl.value = next.id;
+    Object.assign(config, next.config);
+    engine.gravity.y = config.gravity;
+    rebuildSceneBodies();
+    buildLegend();
+    restartGame();
+    updateHud();
+  };
+
   const chain = {
     active: false,
     color: null,
@@ -426,7 +531,7 @@
       min: { x: 0, y: 0 },
       max: { x: width, y: height },
     });
-    createBounds();
+    rebuildSceneBodies();
   };
 
   Events.on(engine, "afterUpdate", () => {
@@ -474,6 +579,9 @@
       setPaused(!isPaused);
     }
   });
+  sceneSelectEl.addEventListener("change", (e) => applyScene(e.target.value));
+  populateSceneSelect();
+  sceneSelectEl.value = currentScene.id;
   highScore = loadHighScore();
   buildLegend();
   updateHud();