===================================================================
--- original.js
+++ change.js
@@ -1,77 +1,87 @@
-/****
+/**** 
 * Classes
 ****/
 // Ball class to represent the game balls
 var Ball = Container.expand(function (type) {
-  var self = Container.call(this);
-  var assetId = 'ball_' + type;
-  var ballGraphics = self.attachAsset(assetId, {
-    anchorX: 0.5,
-    anchorY: 0.5
-  });
-  self.type = type;
-  self.upgrade = function () {
-    var nextType;
-    switch (self.type) {
-      case 'small':
-        nextType = 'medium';
-        break;
-      case 'medium':
-        nextType = 'large';
-        break;
-      case 'large':
-        // Already at largest size, no upgrade
-        return;
-    }
-    // Replace current asset with the next upgrade
-    self.removeChild(ballGraphics);
-    assetId = 'ball_' + nextType;
-    ballGraphics = self.attachAsset(assetId, {
-      anchorX: 0.5,
-      anchorY: 0.5
-    });
-    self.type = nextType;
-  };
+	var self = Container.call(this);
+	var assetId = 'ball_' + type;
+	var ballGraphics = self.attachAsset(assetId, {
+		anchorX: 0.5,
+		anchorY: 0.5
+	});
+	self.type = type;
+	// Initialize velocity property for gravity effect
+	self.velocity = {
+		x: 0,
+		y: 0
+	};
+	self.upgrade = function () {
+		var nextType;
+		switch (self.type) {
+			case 'small':
+				nextType = 'medium';
+				break;
+			case 'medium':
+				nextType = 'large';
+				break;
+			case 'large':
+				// Already at largest size, no upgrade
+				return;
+		}
+		// Replace current asset with the next upgrade
+		self.removeChild(ballGraphics);
+		assetId = 'ball_' + nextType;
+		ballGraphics = self.attachAsset(assetId, {
+			anchorX: 0.5,
+			anchorY: 0.5
+		});
+		self.type = nextType;
+	};
 });
 
-/****
+/**** 
 * Initialize Game
 ****/
 var game = new LK.Game({
-  backgroundColor: 0x000000 // Init game with black background
+	backgroundColor: 0x000000 // Init game with black background
 });
 
-/****
+/**** 
 * Game Code
 ****/
-// Initialize an array to keep track of all balls
 // Define ball assets with increasing sizes and colors for each upgrade level
+// Initialize an array to keep track of all balls
 var balls = [];
 // Function to check for collisions and upgrade balls
 function checkCollisions() {
-  for (var i = 0; i < balls.length; i++) {
-    for (var j = i + 1; j < balls.length; j++) {
-      if (balls[i].intersects(balls[j]) && balls[i].type === balls[j].type) {
-        balls[i].upgrade();
-        balls[j].destroy();
-        balls.splice(j, 1);
-        // Adjust index to continue checking without skipping a ball
-        j--;
-      }
-    }
-  }
+	for (var i = 0; i < balls.length; i++) {
+		for (var j = i + 1; j < balls.length; j++) {
+			if (balls[i].intersects(balls[j]) && balls[i].type === balls[j].type) {
+				balls[i].upgrade();
+				balls[j].destroy();
+				balls.splice(j, 1);
+				// Adjust index to continue checking without skipping a ball
+				j--;
+			}
+		}
+	}
 }
 // Event listener for spawning balls on touch
 game.on('down', function (obj) {
-  var event = obj.event;
-  var pos = event.getLocalPosition(game);
-  var newBall = new Ball('small');
-  newBall.x = pos.x;
-  newBall.y = pos.y;
-  balls.push(newBall);
-  game.addChild(newBall);
+	var event = obj.event;
+	var pos = event.getLocalPosition(game);
+	var newBall = new Ball('small');
+	newBall.x = pos.x;
+	newBall.y = pos.y;
+	balls.push(newBall);
+	game.addChild(newBall);
 });
 // Main game update loop
 LK.on('tick', function () {
-  checkCollisions();
+	// Apply gravity to each ball
+	for (var i = 0; i < balls.length; i++) {
+		balls[i].velocity.y += 0.5; // Gravity acceleration
+		balls[i].y += balls[i].velocity.y;
+	}
+	checkCollisions();
 });
\ No newline at end of file