public static byte[][] createAndValidateSkyMap(int w, int h) {
		int attempt = 0;
		do {
			byte[][] result = createSkyMap(w, h);

			int[] count = new int[256];

			for (int i = 0; i < w * h; i++) {
				count[result[0][i] & 0xff]++;
			}
			if (count[Tile.cloud.id & 0xff] < 2000) continue;
			if (count[Tile.stairsDown.id & 0xff] < 2) continue;

			return result;

		} while (true);
	}