/**** 
* Classes
****/
var Dot = Container.expand(function () {
	var self = Container.call(this);
	var dotGraphics = self.attachAsset('dot', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.velocityY = 0;
	self.gravity = 0.5;
	self.bounce = -15;
	self.update = function () {
		self.velocityY += self.gravity;
		self.y += self.velocityY;
		if (self.y > 2732 - self.height / 2) {
			self.velocityY = self.bounce;
		}
		for (var i = 0; i < obstacles.length; i++) {
			if (self.intersectsTop(obstacles[i])) {
				self.velocityY = 0;
				self.y = obstacles[i].y - self.height / 2;
			}
		}
	};
	self.intersectsTop = function (obstacle) {
		var dotBottom = self.y + self.height / 2;
		var obstacleTop = obstacle.y - obstacle.height / 2;
		var withinXBounds = self.x > obstacle.x - obstacle.width / 2 && self.x < obstacle.x + obstacle.width / 2;
		return dotBottom >= obstacleTop && dotBottom < obstacleTop + self.gravity && withinXBounds;
	};
	self.bounceUp = function () {
		self.velocityY = self.bounce;
	};
});
var Obstacle = Container.expand(function () {
	var self = Container.call(this);
	var obstacleGraphics = self.attachAsset('obstacle', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = -5;
	self.move = function (offsetY) {
		self.x += self.speed;
		if (self.x < -self.width / 2) {
			self.x = 2048 + self.width / 2;
			self.y = Math.random() * (2732 - self.height) + self.height / 2;
			if (obstacles.indexOf(self) === obstacles.length - 1) {
				var newObstacle = game.addChild(new Obstacle());
				newObstacle.x = 2048 + self.width / 2;
				newObstacle.y = Math.random() * (2732 - newObstacle.height) + newObstacle.height / 2;
				obstacles.push(newObstacle);
			}
		}
		if (offsetY) {
			self.y += offsetY;
		}
	};
});

/**** 
* Initialize Game
****/
var game = new LK.Game({
	backgroundColor: 0x000000
});

/**** 
* Game Code
****/
var dot = game.addChild(new Dot());
dot.x = 2048 / 2;
dot.y = 2732 / 2;
var obstacles = [];
var obstacle = game.addChild(new Obstacle());
obstacle.x = 2048 / 2;
obstacle.y = 2732 - obstacle.height / 2;
obstacles.push(obstacle);
var scoreTxt = new Text2('0', {
	size: 150,
	fill: "#ffffff"
});
scoreTxt.anchor.set(0.5, 0);
scoreTxt.x = 2048 / 2;
scoreTxt.y = 50;
LK.gui.top.addChild(scoreTxt);
game.on('down', function (obj) {
	dot.bounceUp();
});
LK.on('tick', function () {
	var previousY = dot.y;
	dot.update();
	var offsetY = previousY - dot.y;
	for (var i = 0; i < obstacles.length; i++) {
		obstacles[i].move(dot.y < 1400 && offsetY > 0 ? offsetY : 0);
		if (dot.intersects(obstacles[i])) {
			LK.effects.flashScreen(0xff0000, 1000);
			LK.showGameOver();
		}
	}
	// Update score based on the dot's survival time
	var currentScore = Math.floor(LK.ticks / 60);
	LK.setScore(currentScore);
	scoreTxt.setText(LK.getScore().toString());
});

===================================================================
--- original.js
+++ change.js
@@ -15,9 +15,21 @@
 		self.y += self.velocityY;
 		if (self.y > 2732 - self.height / 2) {
 			self.velocityY = self.bounce;
 		}
+		for (var i = 0; i < obstacles.length; i++) {
+			if (self.intersectsTop(obstacles[i])) {
+				self.velocityY = 0;
+				self.y = obstacles[i].y - self.height / 2;
+			}
+		}
 	};
+	self.intersectsTop = function (obstacle) {
+		var dotBottom = self.y + self.height / 2;
+		var obstacleTop = obstacle.y - obstacle.height / 2;
+		var withinXBounds = self.x > obstacle.x - obstacle.width / 2 && self.x < obstacle.x + obstacle.width / 2;
+		return dotBottom >= obstacleTop && dotBottom < obstacleTop + self.gravity && withinXBounds;
+	};
 	self.bounceUp = function () {
 		self.velocityY = self.bounce;
 	};
 });