turtle可移动向后滚动背景_turtle scroll background

本程序让海龟变身隧道图，让它们不断地向后移动，从而形成滚动效果背景。
下面是部分代码预览：

"""
  可移动向后滚动背景,。
"""
from turtle import *

screen = Screen()
screen.setup(480,360)
screen.title("向后滚动的背景")
screen.bgcolor("blue")
screen.delay(0)
screen.bgpic("隧道.png")

backgrounds =["隧道1.gif","隧道2.gif","隧道3.gif"]
[screen.addshape(bg) for bg in backgrounds]
    
costuems = ['造型1.gif','造型2.gif']
[screen.addshape(c) for c in costuems]
    
bg_index = 0                # 全局背景索引号
currentbg = backgrounds[bg_index]
bg1 = Turtle(shape=currentbg)
bg1.speed(0)
bg1.penup()
 
bg2 = bg1.clone()
alt = 1
 
screen.mainloop()

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