diff --git a/index.html b/index.html
index 69bdee6..3255d03 100644
--- a/index.html
+++ b/index.html
@@ -102,6 +102,7 @@
         <script src="./src/scenes/scene-lavalamp.js"></script>
         <script src="./src/scenes/scene-relax.js"></script>
         <script src="./src/scenes/scene-swirl-arena.js"></script>
+        <script src="./src/scenes/scene-stack-blocks.js"></script>
         <script src="./src/scenes/index.js"></script>
         <script src="./src/ui.js"></script>
         <script src="./src/main.js"></script>
diff --git a/src/main.js b/src/main.js
index a6fdd0f..d697930 100644
--- a/src/main.js
+++ b/src/main.js
@@ -52,6 +52,7 @@
     minChain: 3,
     palette: ["#ff595e", "#ffca3a", "#8ac926", "#1982c4", "#6a4c93"],
     ballRadius: 18,
+    ballShape: "circle",
     link: {
       stiffness: 0.85,
       lengthScale: 1.05, // max stretch factor; slack below this
@@ -320,12 +321,18 @@
               (Math.random() - 0.5) * Math.max(spawnJitter, config.ballRadius),
           }
         : null;
-    const x =
+    const columnCount = currentScene?.config?.spawnColumns;
+    let x =
       centerSpawn?.x ??
       Math.max(
         config.ballRadius + 10,
         Math.min(width - config.ballRadius - 10, Math.random() * width),
       );
+    if (Number.isFinite(columnCount) && columnCount > 0) {
+      const columnWidth = width / columnCount;
+      const colIndex = Math.floor(Math.random() * columnCount);
+      x = columnWidth * (colIndex + 0.5);
+    }
     const spawnFromBottom = currentScene?.config?.spawnFrom === "bottom";
     const y =
       centerSpawn?.y ??
@@ -342,21 +349,30 @@
             Math.floor(Math.random() * (batchMax - batchMin + 1)) + batchMin,
           );
     for (let i = 0; i < batchCount; i += 1) {
-      const blob = createBallBodies(
-        Math.min(
-          Math.max(
-            config.ballRadius + 10,
-            x + (i - batchCount / 2) * config.ballRadius * 1.5,
-          ),
-          width - config.ballRadius - 10,
+      const targetX = Math.min(
+        Math.max(
+          config.ballRadius + 10,
+          x + (i - batchCount / 2) * config.ballRadius * 1.5,
         ),
-        y +
-          i *
-            (spawnFromBottom
-              ? -config.ballRadius * 0.5
-              : config.ballRadius * 0.5),
-        color,
+        width - config.ballRadius - 10,
       );
+      const targetY =
+        y +
+        i *
+          (spawnFromBottom
+            ? -config.ballRadius * 0.5
+            : config.ballRadius * 0.5);
+      const halfSize = config.ballRadius * 1.05;
+      const region = {
+        min: { x: targetX - halfSize, y: targetY - halfSize },
+        max: { x: targetX + halfSize, y: targetY + halfSize },
+      };
+      const hits = Query.region(balls, region);
+      if (hits && hits.length > 0) {
+        triggerGameOver();
+        return;
+      }
+      const blob = createBallBodies(targetX, targetY, color);
       if (blob.constraints.length > 0 && blob.blobId) {
         blobConstraints.set(blob.blobId, blob.constraints);
       }
@@ -402,6 +418,39 @@
     }
   };
 
+  const spawnInitialColumns = () => {
+    const rows = currentScene?.config?.initialRows;
+    const columns = currentScene?.config?.spawnColumns;
+    if (!Number.isFinite(rows) || rows <= 0) return false;
+    if (!Number.isFinite(columns) || columns <= 0) return false;
+    const columnWidth = width / columns;
+    const side = config.ballRadius * 2;
+    const rowGap = side * 1.05;
+    for (let r = 0; r < rows; r += 1) {
+      const y = config.ballRadius * 1.5 + r * rowGap;
+      for (let c = 0; c < columns; c += 1) {
+        const x = columnWidth * (c + 0.5);
+        const color =
+          config.palette[Math.floor(Math.random() * config.palette.length)];
+        const blob = createBallBodies(x, y, color);
+        blob.bodies.forEach((body) => {
+          body.plugin = body.plugin || {};
+          body.plugin.hasEntered = true;
+          balls.push(body);
+          World.add(world, body);
+        });
+        if (blob.constraints.length > 0) {
+          World.add(world, blob.constraints);
+        }
+        if (blob.constraints.length > 0 && blob.blobId) {
+          blobConstraints.set(blob.blobId, blob.constraints);
+        }
+      }
+    }
+    spawnCount += rows * columns;
+    return true;
+  };
+
   const cleanupBall = (ball) => {
     if (ball.plugin && ball.plugin.entryCheckId) {
       clearTimeout(ball.plugin.entryCheckId);
@@ -517,7 +566,10 @@
     if (isGridScene()) {
       spawnGridBalls();
     } else {
-      spawnInitialBurst();
+      const spawnedGrid = spawnInitialColumns();
+      if (!spawnedGrid) {
+        spawnInitialBurst();
+      }
       startSpawner();
     }
     showGoalIntro();
@@ -1000,6 +1052,15 @@
       body.plugin = { color, hasEntered: false, entryCheckId: null };
       return { bodies: [body], constraints: [], blobId: null };
     }
+    if (currentScene?.config?.ballShape === "rect") {
+      const side = config.ballRadius * 2;
+      const body = Bodies.rectangle(x, y, side, side, {
+        ...commonOpts,
+        chamfer: 4,
+      });
+      body.plugin = { color, hasEntered: false, entryCheckId: null };
+      return { bodies: [body], constraints: [], blobId: null };
+    }
     const body = Bodies.circle(x, y, config.ballRadius, commonOpts);
     body.plugin = { color, hasEntered: false, entryCheckId: null };
     return { bodies: [body], constraints: [], blobId: null };
diff --git a/src/scenes/index.js b/src/scenes/index.js
index aba2356..f9c004a 100644
--- a/src/scenes/index.js
+++ b/src/scenes/index.js
@@ -8,6 +8,7 @@
     "scene-lava",
     "swirl-arena",
     "relax",
+    "stack-blocks",
   ];
   const orderedScenes = desiredOrder
     .map((id) => scenes.find((s) => s.id === id))