def ij_to_dxdy(start_idx, end_idx, _row_size=14):
    """
    Helper function to calculate _x, _y, _dx, _dy given two indexes from the board
    Determine the row, change in column, and change in row
    # of the start/end point pair
    :param start_idx: starting index
    :param end_idx: ending index
    :param _row_size
    :return: _x, _y, _dx, _dy
    """
    #  for move validation
    _x = start_idx % _row_size
    _y = _row_size - start_idx // _row_size
    _dx = (end_idx % _row_size) - (start_idx % _row_size)
    _dy = (_row_size - end_idx // _row_size) - _y
    return _x, _y, _dx, _dy