def walkable(grid_array: list) -> list:
    """Get a list of all the coordinates that are walkable

    Args:
        grid_array (list): map of the terrain

    Returns:
        list: all coordinates that are walkable
    """
    walkable = []
    for i, row in enumerate(grid_array):
        for j, cell in enumerate(row):
            if cell == 0:
                walkable.append((i, j))
    return walkable