var monster = new Sprite(32, 32);
	monster.image = game.assets[monster_image];
    monster.x = randomX;
    monster.y = randomY;
    monster.tl.moveBy(288, 0, 90)
            .scaleTo(-1, 1, 10)
            .moveBy(-288, 0, 90)
            .scaleTo(1, 1, 10)
            .loop();
    game.rootScene.addChild(monster);