public void overlay(Screen screen2, int xa, int ya) {
		int[] oPixels = screen2.pixels;
		int i = 0;
		for (int y = 0; y < h; y++) {
			for (int x = 0; x < w; x++) {
				if (oPixels[i] / 10 <= dither[((x + xa) & 3) + ((y + ya) & 3) * 4]) pixels[i] = 0;
				i++;
			}

		}
	}