def join_matrixes(matrix_1, matrix_2, matrix_2_offset):
    """ Copy matrix 2 onto matrix 1 based on the passed in x, y offset coordinate """
    offset_x, offset_y = matrix_2_offset
    for cy, row in enumerate(matrix_2):
        for cx, val in enumerate(row):
            matrix_1[cy + offset_y - 1][cx + offset_x] += val
    return matrix_1