def flatten_list(complex_list):
    """Flatten a multi-dimensional list to 1D list"""
    if not complex_list:
        return []
    flattened_list = []
    for level1 in complex_list:
        if isinstance(level1, (list, tuple)):
            flattened_list.extend(flatten_list(level1))
        else:
            flattened_list.append(level1)
    return flattened_list