/**** 
* Plugins
****/ 
var tween = LK.import("@upit/tween.v1");

/**** 
* Classes
****/ 
var Ball = Container.expand(function (value) {
	var self = Container.call(this);
	self.value = value || 2;
	self.velocityX = 0;
	self.velocityY = 0;
	self.gravity = 0.8;
	self.bounce = 0.4;
	self.friction = 0.98;
	self.radius = 60;
	self.isStatic = false;
	self.mergeTimer = 0;
	self.hasBeenMerged = false;
	var ballAsset = self.attachAsset('ball' + self.value, {
		anchorX: 0.5,
		anchorY: 0.5
	});
	var valueText = new Text2(self.value.toString(), {
		size: 42,
		fill: 0xFFFFFF
	});
	valueText.anchor.set(0.5, 0.5);
	self.addChild(valueText);
	self.update = function () {
		if (self.hasBeenMerged) return;
		if (self.mergeTimer > 0) {
			self.mergeTimer--;
			return;
		}
		// Apply physics only if not static
		if (!self.isStatic) {
			// Store previous position for continuous collision detection
			var prevX = self.x;
			var prevY = self.y;
			// Apply gravity
			self.velocityY += self.gravity;
			// Calculate intended new position
			var newX = self.x + self.velocityX;
			var newY = self.y + self.velocityY;
			// Continuous collision detection - check path from current to intended position
			var stepCount = Math.max(1, Math.ceil(Math.abs(self.velocityX) + Math.abs(self.velocityY)) / (self.radius * 0.5));
			var stepX = (newX - self.x) / stepCount;
			var stepY = (newY - self.y) / stepCount;
			var collisionOccurred = false;
			// Check each step along the movement path
			for (var step = 1; step <= stepCount && !collisionOccurred; step++) {
				var testX = self.x + stepX * step;
				var testY = self.y + stepY * step;
				// Test collision with other balls for stacking support
				for (var i = 0; i < balls.length; i++) {
					var otherBall = balls[i];
					if (otherBall === self || otherBall.hasBeenMerged || otherBall.mergeTimer > 0) continue;
					var dx = otherBall.x - testX;
					var dy = otherBall.y - testY;
					var distance = Math.sqrt(dx * dx + dy * dy);
					var minDistance = self.radius + otherBall.radius;
					if (distance < minDistance) {
						// Check for merge first - increased sensitivity for same-numbered balls
						var mergeDistance = self.value === otherBall.value ? minDistance * 1.2 : minDistance;
						if (self.value === otherBall.value && self.mergeTimer === 0 && otherBall.mergeTimer === 0 && distance < mergeDistance) {
							var newValue = self.value * 2;
							if (newValue <= 2048) {
								var newBall = new Ball(newValue);
								newBall.x = (self.x + otherBall.x) / 2;
								newBall.y = (self.y + otherBall.y) / 2;
								newBall.velocityX = (self.velocityX + otherBall.velocityX) / 2;
								newBall.velocityY = (self.velocityY + otherBall.velocityY) / 2;
								newBall.mergeTimer = 10;
								balls.push(newBall);
								gameArea.addChild(newBall);
								// Mark for removal
								self.hasBeenMerged = true;
								otherBall.hasBeenMerged = true;
								LK.getSound('merge').play();
								LK.setScore(LK.getScore() + newValue);
								scoreText.setText(LK.getScore());
								// Check win condition
								if (newValue === 2048) {
									LK.showYouWin();
								}
								return;
							}
						}
						// Allow stacking - only prevent collision if ball is falling onto another ball from above
						if (self.velocityY > 0 && testY > otherBall.y - otherBall.radius) {
							// Stop at the top of the other ball to allow stacking
							self.y = otherBall.y - otherBall.radius - self.radius;
							self.velocityY = 0;
							self.isStatic = true;
							collisionOccurred = true;
							break;
						}
					}
				}
			}
			// If no collision occurred, move to intended position
			if (!collisionOccurred) {
				self.x = newX;
				self.y = newY;
			}
			// Boundary collisions after position update
			var localWidth = gameAreaRight - gameAreaLeft;
			var localBottom = gameAreaHeight - 20; // gameAreaHeight minus bottom wall height
			// Ground collision
			if (self.y + self.radius > localBottom) {
				self.y = localBottom - self.radius;
				self.velocityY *= -self.bounce;
				self.velocityX *= self.friction;
				if (Math.abs(self.velocityY) < 1) {
					self.velocityY = 0;
					self.isStatic = true;
				}
			}
			// Side walls collision
			if (self.x - self.radius < 0) {
				self.x = self.radius;
				self.velocityX *= -self.bounce;
			}
			if (self.x + self.radius > localWidth) {
				self.x = localWidth - self.radius;
				self.velocityX *= -self.bounce;
			}
		}
		// Enhanced merge detection pass - check for nearby same-numbered balls
		for (var i = 0; i < balls.length; i++) {
			var otherBall = balls[i];
			if (otherBall === self || otherBall.hasBeenMerged || otherBall.mergeTimer > 0 || self.mergeTimer > 0) continue;
			var dx = otherBall.x - self.x;
			var dy = otherBall.y - self.y;
			var distance = Math.sqrt(dx * dx + dy * dy);
			var minDistance = self.radius + otherBall.radius;
			// Enhanced merge sensitivity for same-numbered balls
			if (self.value === otherBall.value) {
				var mergeTriggerDistance = minDistance * 1.15; // 15% more sensitive
				if (distance < mergeTriggerDistance) {
					var newValue = self.value * 2;
					if (newValue <= 2048) {
						var newBall = new Ball(newValue);
						newBall.x = (self.x + otherBall.x) / 2;
						newBall.y = (self.y + otherBall.y) / 2;
						newBall.velocityX = (self.velocityX + otherBall.velocityX) / 2;
						newBall.velocityY = (self.velocityY + otherBall.velocityY) / 2;
						newBall.mergeTimer = 10;
						balls.push(newBall);
						gameArea.addChild(newBall);
						// Mark for removal
						self.hasBeenMerged = true;
						otherBall.hasBeenMerged = true;
						LK.getSound('merge').play();
						LK.setScore(LK.getScore() + newValue);
						scoreText.setText(LK.getScore());
						// Check win condition
						if (newValue === 2048) {
							LK.showYouWin();
						}
						return;
					}
				}
			}
			// Allow overlapping for stacking - only separate horizontally if needed
			if (distance < minDistance && distance > 0) {
				var overlap = minDistance - distance;
				var normalX = dx / distance;
				var normalY = dy / distance;
				// Only separate horizontally to maintain stacking ability
				if (Math.abs(normalX) > 0.7) {
					// Only if collision is more horizontal than vertical
					var separationX = normalX * overlap * 0.51;
					self.x -= separationX;
					// Ensure balls stay within bounds after separation
					var localWidth = gameAreaRight - gameAreaLeft;
					self.x = Math.max(self.radius, Math.min(localWidth - self.radius, self.x));
				}
			}
		}
	};
	return self;
});

/**** 
* Initialize Game
****/ 
var game = new LK.Game({
	backgroundColor: 0x34495e
});

/**** 
* Game Code
****/ 
var balls = [];
var nextBallValue = 2;
var gameAreaLeft = 224;
var gameAreaRight = 1824;
var gameAreaTop = 400;
var gameAreaBottom = 2600;
var dropCooldown = 0;
var gameAreaHeight = gameAreaBottom - gameAreaTop;
// Create game area background
var gameAreaBg = game.addChild(LK.getAsset('gameArea', {
	anchorX: 0.5,
	anchorY: 0,
	x: 1024,
	y: gameAreaTop
}));
// Create game area container for balls
var gameArea = new Container();
gameArea.x = gameAreaLeft;
gameArea.y = gameAreaTop;
game.addChild(gameArea);
// Create visible walls
var leftWall = game.addChild(LK.getAsset('leftWall', {
	anchorX: 1,
	anchorY: 0,
	x: gameAreaLeft,
	y: gameAreaTop
}));
var rightWall = game.addChild(LK.getAsset('rightWall', {
	anchorX: 0,
	anchorY: 0,
	x: gameAreaRight,
	y: gameAreaTop
}));
var bottomWall = game.addChild(LK.getAsset('bottomWall', {
	anchorX: 0.5,
	anchorY: 0,
	x: 1024,
	y: gameAreaBottom
}));
// Create danger zone indicator
var dangerZone = game.addChild(LK.getAsset('dangerZone', {
	anchorX: 0.5,
	anchorY: 0,
	x: 1024,
	y: gameAreaTop,
	alpha: 0
}));
// Create game over line (invisible)
var gameOverLine = game.addChild(LK.getAsset('gameOverLine', {
	anchorX: 0.5,
	anchorY: 0.5,
	x: 1024,
	y: gameAreaTop + 100,
	alpha: 0,
	visible: false
}));
// Create score display
var scoreText = new Text2('0', {
	size: 80,
	fill: 0xFFFFFF
});
scoreText.anchor.set(0.5, 0);
LK.gui.top.addChild(scoreText);
scoreText.y = 100;
// Create next ball preview
var nextBallPreview = LK.getAsset('ball' + nextBallValue, {
	anchorX: 0.5,
	anchorY: 0.5,
	x: 1024,
	y: 300,
	scaleX: 0.75,
	scaleY: 0.75
});
game.addChild(nextBallPreview);
// Create next ball value text
var nextBallText = new Text2(nextBallValue.toString(), {
	size: 24,
	fill: 0xFFFFFF
});
nextBallText.anchor.set(0.5, 0.5);
nextBallText.x = 1024;
nextBallText.y = 300;
game.addChild(nextBallText);
// Create instruction text
var instructionText = new Text2('Tap to drop ball', {
	size: 40,
	fill: 0xFFFFFF
});
instructionText.anchor.set(0.5, 0);
instructionText.x = 1024;
instructionText.y = 150;
game.addChild(instructionText);
function getRandomNextBallValue() {
	var values = [2, 4, 8];
	return values[Math.floor(Math.random() * values.length)];
}
function updateNextBallPreview() {
	game.removeChild(nextBallPreview);
	game.removeChild(nextBallText);
	nextBallPreview = LK.getAsset('ball' + nextBallValue, {
		anchorX: 0.5,
		anchorY: 0.5,
		x: 1024,
		y: 300,
		scaleX: 0.75,
		scaleY: 0.75
	});
	game.addChild(nextBallPreview);
	nextBallText = new Text2(nextBallValue.toString(), {
		size: 24,
		fill: 0xFFFFFF
	});
	nextBallText.anchor.set(0.5, 0.5);
	nextBallText.x = 1024;
	nextBallText.y = 300;
	game.addChild(nextBallText);
}
function checkGameOver() {
	for (var i = 0; i < balls.length; i++) {
		// Check if ball touches the danger zone (first 100 pixels of game area)
		// Since balls are in gameArea container, we use local coordinates
		// Only trigger game over if ball is static (not actively falling) and in danger zone
		if (balls[i].y - balls[i].radius <= 100 && balls[i].isStatic) {
			LK.showGameOver();
			return;
		}
	}
}
function cleanupMergedBalls() {
	for (var i = balls.length - 1; i >= 0; i--) {
		if (balls[i].hasBeenMerged) {
			gameArea.removeChild(balls[i]);
			balls[i].destroy();
			balls.splice(i, 1);
		}
	}
}
game.down = function (x, y, obj) {
	if (dropCooldown > 0) return;
	// Constrain drop position to game area (convert to local coordinates)
	var localWidth = gameAreaRight - gameAreaLeft;
	var localX = x - gameAreaLeft;
	var dropX = Math.max(60, Math.min(localWidth - 60, localX));
	var newBall = new Ball(nextBallValue);
	newBall.x = dropX;
	newBall.y = 170; // Start below the danger zone (100px) plus ball radius (60px) plus buffer
	newBall.velocityX = 0;
	newBall.velocityY = 0;
	balls.push(newBall);
	gameArea.addChild(newBall);
	LK.getSound('drop').play();
	// Update next ball
	nextBallValue = getRandomNextBallValue();
	updateNextBallPreview();
	dropCooldown = 30; // 0.5 seconds at 60fps
};
game.update = function () {
	if (dropCooldown > 0) {
		dropCooldown--;
	}
	cleanupMergedBalls();
	checkGameOver();
	// Update score display
	scoreText.setText(LK.getScore());
};

===================================================================
--- original.js
+++ change.js
@@ -52,69 +52,52 @@
 			// Check each step along the movement path
 			for (var step = 1; step <= stepCount && !collisionOccurred; step++) {
 				var testX = self.x + stepX * step;
 				var testY = self.y + stepY * step;
-				// Test collision with other balls
+				// Test collision with other balls for stacking support
 				for (var i = 0; i < balls.length; i++) {
 					var otherBall = balls[i];
 					if (otherBall === self || otherBall.hasBeenMerged || otherBall.mergeTimer > 0) continue;
 					var dx = otherBall.x - testX;
 					var dy = otherBall.y - testY;
 					var distance = Math.sqrt(dx * dx + dy * dy);
 					var minDistance = self.radius + otherBall.radius;
 					if (distance < minDistance) {
-						// Collision detected - stop at safe position
-						var safeDistance = minDistance + 2; // Add small buffer
-						if (distance > 0) {
-							var normalX = dx / distance;
-							var normalY = dy / distance;
-							self.x = otherBall.x - normalX * safeDistance;
-							self.y = otherBall.y - normalY * safeDistance;
-							// Check for merge first - increased sensitivity for same-numbered balls
-							var mergeDistance = self.value === otherBall.value ? minDistance * 1.2 : minDistance;
-							if (self.value === otherBall.value && self.mergeTimer === 0 && otherBall.mergeTimer === 0 && distance < mergeDistance) {
-								var newValue = self.value * 2;
-								if (newValue <= 2048) {
-									var newBall = new Ball(newValue);
-									newBall.x = (self.x + otherBall.x) / 2;
-									newBall.y = (self.y + otherBall.y) / 2;
-									newBall.velocityX = (self.velocityX + otherBall.velocityX) / 2;
-									newBall.velocityY = (self.velocityY + otherBall.velocityY) / 2;
-									newBall.mergeTimer = 10;
-									balls.push(newBall);
-									gameArea.addChild(newBall);
-									// Mark for removal
-									self.hasBeenMerged = true;
-									otherBall.hasBeenMerged = true;
-									LK.getSound('merge').play();
-									LK.setScore(LK.getScore() + newValue);
-									scoreText.setText(LK.getScore());
-									// Check win condition
-									if (newValue === 2048) {
-										LK.showYouWin();
-									}
-									return;
+						// Check for merge first - increased sensitivity for same-numbered balls
+						var mergeDistance = self.value === otherBall.value ? minDistance * 1.2 : minDistance;
+						if (self.value === otherBall.value && self.mergeTimer === 0 && otherBall.mergeTimer === 0 && distance < mergeDistance) {
+							var newValue = self.value * 2;
+							if (newValue <= 2048) {
+								var newBall = new Ball(newValue);
+								newBall.x = (self.x + otherBall.x) / 2;
+								newBall.y = (self.y + otherBall.y) / 2;
+								newBall.velocityX = (self.velocityX + otherBall.velocityX) / 2;
+								newBall.velocityY = (self.velocityY + otherBall.velocityY) / 2;
+								newBall.mergeTimer = 10;
+								balls.push(newBall);
+								gameArea.addChild(newBall);
+								// Mark for removal
+								self.hasBeenMerged = true;
+								otherBall.hasBeenMerged = true;
+								LK.getSound('merge').play();
+								LK.setScore(LK.getScore() + newValue);
+								scoreText.setText(LK.getScore());
+								// Check win condition
+								if (newValue === 2048) {
+									LK.showYouWin();
 								}
+								return;
 							}
-							// Collision response - calculate new velocities
-							var relativeVelX = self.velocityX - otherBall.velocityX;
-							var relativeVelY = self.velocityY - otherBall.velocityY;
-							var relativeSpeed = relativeVelX * normalX + relativeVelY * normalY;
-							if (relativeSpeed > 0) {
-								var impulse = relativeSpeed * 0.9; // Damping factor
-								self.velocityX -= impulse * normalX;
-								self.velocityY -= impulse * normalY;
-								otherBall.velocityX += impulse * normalX;
-								otherBall.velocityY += impulse * normalY;
-								// Apply friction
-								self.velocityX *= self.friction;
-								self.velocityY *= self.friction;
-								otherBall.velocityX *= otherBall.friction;
-								otherBall.velocityY *= otherBall.friction;
-							}
 						}
-						collisionOccurred = true;
-						break;
+						// Allow stacking - only prevent collision if ball is falling onto another ball from above
+						if (self.velocityY > 0 && testY > otherBall.y - otherBall.radius) {
+							// Stop at the top of the other ball to allow stacking
+							self.y = otherBall.y - otherBall.radius - self.radius;
+							self.velocityY = 0;
+							self.isStatic = true;
+							collisionOccurred = true;
+							break;
+						}
 					}
 				}
 			}
 			// If no collision occurred, move to intended position
@@ -180,22 +163,22 @@
 						return;
 					}
 				}
 			}
-			// Standard separation for overlapping balls
+			// Allow overlapping for stacking - only separate horizontally if needed
 			if (distance < minDistance && distance > 0) {
 				var overlap = minDistance - distance;
 				var normalX = dx / distance;
 				var normalY = dy / distance;
-				var separationX = normalX * overlap * 0.51; // Slightly more than half
-				var separationY = normalY * overlap * 0.51;
-				self.x -= separationX;
-				self.y -= separationY;
-				// Ensure balls stay within bounds after separation
-				var localWidth = gameAreaRight - gameAreaLeft;
-				var localBottom = gameAreaHeight - 20; // gameAreaHeight minus bottom wall height
-				self.x = Math.max(self.radius, Math.min(localWidth - self.radius, self.x));
-				self.y = Math.max(self.radius, Math.min(localBottom - self.radius, self.y));
+				// Only separate horizontally to maintain stacking ability
+				if (Math.abs(normalX) > 0.7) {
+					// Only if collision is more horizontal than vertical
+					var separationX = normalX * overlap * 0.51;
+					self.x -= separationX;
+					// Ensure balls stay within bounds after separation
+					var localWidth = gameAreaRight - gameAreaLeft;
+					self.x = Math.max(self.radius, Math.min(localWidth - self.radius, self.x));
+				}
 			}
 		}
 	};
 	return self;