单击格子填充随机颜色正方形演示的练习题

请同学们完成如图所示功能，把下面代码完善即可：

import random
import turtle

def fill_square(x,y):
    """x,y是小正方形内随机的一个坐标,如果刚好在左边上,则填充右边的小正方形,如果刚好在下边上,则填充上边的小正方形,填充颜色随机"""
        
turtle.speed(0)
turtle.delay(0)
turtle.dot(10,'red')
turtle.penup()
turtle.goto(-250,250)

for i in range(11):
    turtle.pd()
    turtle.fd(500)
    turtle.bk(500)
    turtle.pu()
    turtle.right(90)
    turtle.fd(50)
    turtle.left(90)

turtle.penup()
turtle.goto(-250,250)
turtle.right(90)
for i in range(11):
    turtle.pd()
    turtle.fd(500)
    turtle.bk(500)
    turtle.pu()
    turtle.left(90)
    turtle.fd(50)
    turtle.rt(90)
turtle.penup()
turtle.home()
turtle.ht()

screen = turtle.Screen()
screen.onclick(lambda x,y:fill_square(x,y))  # 单击会调用fill_square函数在x,y处进行填充
screen.mainloop()