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

/**** 
* Classes
****/ 
var Bullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.attachAsset('bullet', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 5;
	self.update = function () {
		self.x += self.speed;
		if (self.x < 0) {
			self.destroy();
		}
	};
});
var Enemy = Container.expand(function () {
	var self = Container.call(this);
	var enemyGraphics = self.attachAsset('enemy', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = -3;
	self.update = function () {
		self.x += self.speed;
		if (self.x < 0 || self.x > 2048) {
			self.destroy();
		}
	};
});
var Ground = Container.expand(function () {
	var self = Container.call(this);
	var groundGraphics = self.attachAsset('ground', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.update = function () {
		// Ground does not move
	};
});
var Player = Container.expand(function () {
	var self = Container.call(this);
	var playerGraphics = self.attachAsset('player', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 5;
	self.update = function () {
		if (self.x < 0) {
			self.x = 0;
		}
		if (self.x > 2048) {
			self.x = 2048;
		}
		// Player only moves horizontally
	};
});

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

/**** 
* Game Code
****/ 
var ground = game.addChild(new Ground());
ground.x = 1024;
ground.y = 2732 - 50;
var player = game.addChild(new Player());
player.x = 1024;
player.y = ground.y - 150;
var enemies = [];
var bullets = [];
game.update = function () {
	if (LK.ticks % 60 == 0) {
		var enemy = game.addChild(new Enemy());
		enemy.x = 2048;
		enemy.y = Math.random() * 2732;
		enemies.push(enemy);
	}
	for (var i = bullets.length - 1; i >= 0; i--) {
		var bullet = bullets[i];
		for (var j = enemies.length - 1; j >= 0; j--) {
			var enemy = enemies[j];
			if (bullet.intersects(enemy)) {
				bullet.destroy();
				bullets.splice(i, 1);
				enemy.destroy();
				enemies.splice(j, 1);
				break;
			}
		}
	}
};
game.down = function (x, y, obj) {
	var bullet = game.addChild(new Bullet());
	bullet.x = player.x;
	bullet.y = player.y;
	bullets.push(bullet);
};
game.move = function (x, y, obj) {
	player.x = x;
	tween(player, {
		y: Math.sin(x / 100) * 200 + 2732 / 2
	}, {
		duration: 1000
	});
};

===================================================================
--- original.js
+++ change.js
@@ -1,5 +1,10 @@
 /**** 
+* Plugins
+****/ 
+var tween = LK.import("@upit/tween.v1");
+
+/**** 
 * Classes
 ****/ 
 var Bullet = Container.expand(function () {
 	var self = Container.call(this);
@@ -103,6 +108,10 @@
 	bullets.push(bullet);
 };
 game.move = function (x, y, obj) {
 	player.x = x;
-	// Player only moves horizontally
+	tween(player, {
+		y: Math.sin(x / 100) * 200 + 2732 / 2
+	}, {
+		duration: 1000
+	});
 };
\ No newline at end of file