def find_empty(board):
    """Function to find empty cells in game board.

    Args:
        board (list): the current game board.

    Returns:
        (i, j) (tuple): empty position (row, column) if found, otherwise None.
    """
    for i in range(len(board)):
        for j in range(len(board[0])):
            if board[i][j] == 0:
                return (i, j)  # row, col

    return None