def base2p15_decode(base2p15: str) -> str:
    """
    Encode/decode given base2p15 string as binary string

    :param base2p15: A base2p15 string, generated by base2p15_encode
    :type base2p15: str
    :returns: A binary string e.g. 00001001
    :rtype: str
    """
    bit_string = ""
    offset = 0xa1
    padding = int(base2p15[0], 16)
    for character in base2p15[1:-1]:
        character = ord(character) - offset
        bits = bin(character)[2:].zfill(15)
        bit_string += bits

    character = ord(base2p15[-1]) - offset
    bits = bin(character)[2:].zfill(15)[:15 - padding]
    bit_string += bits
    return bit_string