def update_path(self, board, color, path):
        """ update win/loss count along path """
        wins = board.score(BLACK) >= board.score(WHITE)
        for node in path:
            if color == BLACK:
                color = WHITE
            else:
                color = BLACK
            if wins == (color == BLACK):
                node.wins += 1
            else:
                node.losses += 1
            if node.parent:
                node.parent.bestchild = node.parent.best_child()