def game_of_life(board):
    rows = len(board)
    cols = len(board[0]) if rows else 0
    for r in range(rows):
        for c in range(cols):
            neighbors = 0
            for dr in (-1, 0, 1):
                for dc in (-1, 0, 1):
                    nr, nc = r + dr, c + dc
                    if (dr or dc) and 0 <= nr < rows and 0 <= nc < cols:
                        neighbors += board[nr][nc] & 1
            old = board[r][c] & 1
            if neighbors == 3 or (old == 1 and neighbors == 2):
                board[r][c] |= 2
    for r in range(rows):
        for c in range(cols):
            board[r][c] >>= 1
    return board