def in_board(game_board, y, x):
	"""
	check the position is in board or out of board, when finding the neighbors.

	:param game_board: (lst) game-board
	:param y: neighbor's y position
	:param x: neighbor's x position
	:return: (bool)
	"""
	return 0 <= y < len(game_board) and 0 <= x < len(game_board[y])