public int compare(Sprite s0, Sprite s1) {
			if (s0.y + s0.x < s1.y + s1.x) return -1;
			if (s0.y + s0.x > s1.y + s1.x) return 1;
			if (s0.x < s1.x) return -1;
			if (s0.x > s1.x) return 1;
			if (s0.y < s1.y) return -1;
			if (s0.y > s1.y) return 1;
			if (s0.z < s1.z) return -1;
			if (s0.z > s1.z) return 1;
			return 0;
		}