def check_game_over(cards):
    """
    Check if the game is over by checking if all cards are hidden or not

    >>> check_game_over(create_cards_list())
    True
    >>> cards = create_cards_list()
    >>> cards[0].hidden = True
    >>> check_game_over(cards)
    False
    """
    for card in cards:
        if card.hidden:
            return False

    return True