利用python如何实现猫捉老鼠小游戏

import turtle
import time
import random

def up():
 jerry.setheading(90)
 jerry.forward(20)
def down():
 jerry.setheading(270)
 jerry.forward(20)
def left():
 jerry.setheading(180)
 jerry.forward(20)
def right():
 jerry.setheading(0)
 jerry.forward(20)
playground=turtle.Screen()
playground.register_shape('tom.gif')
playground.register_shape('jerry.gif')
playground.onkey(up,'Up')
playground.onkey(down,'Down')
playground.onkey(left,'Left')
playground.onkey(right,'Right')

#监听
playground.listen()

writer=turtle.Turtle()
writer.color('brown')
writer.hideturtle()
writer.penup()
writer.home()
writer.write("Tom & JERRY",align='center',font=("Comic sans MS",50,"bold"))
writer.goto(0,-50)
writer.write("READY?3,2,1,GO",align='center',font=("Comic sans MS",20,"bold"))
time.sleep(3)

writer.clear()

tom=turtle.Turtle()
tom.shape('tom.gif')
tom.penup()
tom.goto(random.randint(-200,200),random.randint(-200,200))
tom.pendown()
tom.pensize(3)
tom.color('blue')

jerry=turtle.Turtle()
jerry.shape('jerry.gif')
jerry.speed(0)
jerry.penup()
jerry.goto(random.randint(-200,200),random.randint(-200,200))
jerry.color('brown')

start=time.time()
while True:
 tom.setheading(tom.towards(jerry))
 tom.forward(5)
 if tom.distance(jerry)<10:
  end=time.time()
  playground.clear()
  jerry.goto(0,0)
  jerry.write("GAME OVER",align='center',font=("Comic sans MS",50,"bold"))
  jerry.goto(0,-50)
  jerry.write("YOU SURVIVED {:.1f} SECONDS".format(end-start),align='center',font=("Comic sans MS",20,"bold"))
  tom.pu()
  tom.goto(-50,-70)
  tom.stamp()
  jerry.pu()
  jerry.goto(50,-70)
  jerry.stamp()
  break