为什么 python turtle 图形不断崩溃停止响应

每当我try 运行我的程序时，它都会画出两只乌龟，然后窗口停止响应.

我所期待的是，直到其中一块接触到另一块基于我拖动它靠近另一块的基础上，我将能够自己拖动它们两个.然而，每当我运行程序时，在绘制了两只乌龟之后，窗口停止响应.我没有收到任何错误，它只是在冻结后关闭，直到我单击关闭按钮.我看过其他人的帖子，他们有这个问题，但他们最后没有creen.mainloop()，而我有.

import turtle

captured_pieces = []

blue = turtle.Turtle()
black = turtle.Turtle()
screen = turtle.Screen()

blue.penup()
black.penup()

blue.shape('square')
black.shape('triangle')

blue.setpos(100,100)
black.setpos(-100,-100)

blue.color('blue')
black.color('black')

def bmove():
    black.ondrag(black.goto)
    if black.distance(blue) < 30:
            captured_pieces.append("BlC")
            print(captured_pieces)
            check()

def blmove():
    blue.ondrag(blue.goto)
    if blue.distance(black) < 30:
            captured_pieces.append("BC")
            print(captured_pieces)
            check()

def check():
      if "BlC" in captured_pieces:
            print("blue captured")

def check():
      if "BC" in captured_pieces:
            print("black captured")

while "BlC" not in captured_pieces and "BC" not in captured_pieces:
      bmove()
      blmove()

screen.mainloop()