from typing import Union


def game_of_life_rule(cell: bool, neighbors: int) -> Union[bool, None]:
    """Classic rule of John Conway's Game of Life.\n
    Common notation: `B3/S23`.
    """
    # A low cell switches to high state if is has 3 neighbors
    if not cell and neighbors == 3:
        return True
    # A high cell switches to low state if does not have 2 or 3 neighbors
    elif cell and not neighbors in (2, 3):
        return False