递归绘制Koch雪花曲线

import turtle
def koch(size, n):
    if n == 0:
        turtle.fd(size)
    else:
        for angle in [0, 60, -120, 60]:
            turtle.left(angle)
            koch(size/3, n-1)
def main():
    turtle.setup(1200, 1000)
    turtle.speed(11)
    turtle.penup()
    turtle.goto(-300, 200)
    turtle.pendown()
    turtle.pensize(2)
    level = 4
    koch(600, level)  # 3阶科赫曲线
    turtle.right(120)
    koch(600, level)
    turtle.right(120)
    koch(600, level)
    turtle.hideturtle()
    turtle.done()
main()