var GrayHeart = Container.expand(function () {
	var self = Container.call(this);
	var grayHeartGraphics = self.createAsset('grayHeart', 'Gray Heart icon', 0, 0);
});
var Heart = Container.expand(function () {
	var self = Container.call(this);
	var heartGraphics = self.createAsset('heart', 'Heart icon', 0, 0);
});
var Santa = Container.expand(function () {
	var self = Container.call(this);
	var santaGraphics = self.createAsset('santa', 'Santa character', .5, .5);
	self.lastX = self.x;
	self.move = function (newX) {
		var halfWidth = this.width / 2;
		var oldX = this.x;
		this.x = Math.max(halfWidth, Math.min(2048 - halfWidth, newX));
		if (oldX > this.x) {
			this.scale.x = 1;
		} else if (oldX < this.x) {
			this.scale.x = -1;
		}
		self.lastX = this.x;
	};
	self.collect = function () {};
});
var Gift = Container.expand(function () {
	var self = Container.call(this);
	var giftGraphics = self.createAsset('gift', 'Gift item', .5, .5);
	self.drop = function () {
		self.y += 5;
		var deltaX = (Math.random() - 0.5) * 4;
		self.x = Math.max(self.width / 2, Math.min(2048 - self.width / 2, self.x + deltaX));
	};
});
var Game = Container.expand(function () {
	var self = Container.call(this);
	var score = 0;
	var scoreTxt = new Text2(score.toString(), {
		size: 150,
		fill: "#ffffff"
	});
	scoreTxt.anchor.set(.5, 0);
	LK.gui.topCenter.addChild(scoreTxt);
	var lives = 3;
	var hearts = [];
	for (var i = 0; i < lives; i++) {
		var heart = new Heart();
		heart.x = i * (heart.width + 10);
		heart.y = 10;
		hearts.push(heart);
		LK.gui.topLeft.addChild(heart);
	}
	var santa = self.addChild(new Santa());
	var gifts = [];
	santa.x = LK.stageContainer.width / 2;
	santa.y = 2732 - santa.height;
	var giftCreationInterval = LK.setInterval(function () {
		var gift = new Gift();
		gift.x = Math.random() * 2048;
		gift.y = 0;
		gifts.push(gift);
		self.addChild(gift);
	}, 2000);
	LK.on('tick', function () {
		santa.move();
		for (var i = 0; i < gifts.length; i++) {
			gifts[i].drop();
			if (santa.intersects(gifts[i])) {
				santa.collect(gifts[i]);
				score++;
				scoreTxt.setText(score.toString());
				gifts[i].destroy();
				gifts.splice(i, 1);
				i--;
				if (hearts.length > 0) {
					var lostHeart = hearts[hearts.length - 1];
				}
			} else if (gifts[i].y > 2732) {
				gifts[i].destroy();
				gifts.splice(i, 1);
				i--;
				if (--lives <= 0) {
					if (hearts.length > 0) {
						var lostHeart = hearts.pop();
						lostHeart.destroy();
						var grayHeart = new GrayHeart();
						grayHeart.x = lostHeart.x;
						grayHeart.y = lostHeart.y;
						LK.gui.topLeft.addChild(grayHeart);
					}
					LK.showGameOver();
				} else if (hearts.length > 0) {
					var lostHeart = hearts.pop();
					lostHeart.destroy();
					var grayHeart = new GrayHeart();
					grayHeart.x = lostHeart.x;
					grayHeart.y = lostHeart.y;
					LK.gui.topLeft.addChild(grayHeart);
				}
			}
		}
	});
	stage.on('down', function (obj) {
		var pos = obj.event.getLocalPosition(self);
		santa.move(pos.x);
	});
	stage.on('move', function (obj) {
		var pos = obj.event.getLocalPosition(self);
		santa.move(pos.x);
	});
});

===================================================================
--- original.js
+++ change.js
@@ -27,9 +27,10 @@
 	var self = Container.call(this);
 	var giftGraphics = self.createAsset('gift', 'Gift item', .5, .5);
 	self.drop = function () {
 		self.y += 5;
-		self.x += (Math.random() - 0.5) * 4;
+		var deltaX = (Math.random() - 0.5) * 4;
+		self.x = Math.max(self.width / 2, Math.min(2048 - self.width / 2, self.x + deltaX));
 	};
 });
 var Game = Container.expand(function () {
 	var self = Container.call(this);