private static boolean isGameOver(int[][] board) {
		for (int row = 0; row < 4; row++) {
			for (int col = 0; col < 3; col++) {
				if (board[row][col] == board[row][col + 1]) {
					return false;
				}
			}
		}

		for (int col = 0; col < 4; col++) {
			for (int row = 0; row < 3; row++) {
				if (board[row][col] == board[row + 1][col]) {
					return false;
				}
			}
		}
		return true;
	}