public Actor(Sprite ss){
		this.ss = ss;
		/**
		 * Sprite indexes are column-major.
		 */
		down = new Animation(ss, 0,0,2,0, true, duration, false);
		down.setPingPong(true);
		left = new Animation(ss, 0,1,2,1, true, duration, false);
		left.setPingPong(true);
		right = new Animation(ss, 0, 2, 2, 2, true, duration, false);
		right.setPingPong(true);
		up = new Animation(ss, 0, 3, 2, 3, true, duration, false);
		up.setPingPong(true);
	}