"""
   左右键移动火箭飞行交互动画。
   本程序会生成一枚火箭,用左右键可以改变它的方向。
   按空格键来切换它是否要移动。
"""

import turtle

screen = turtle.getscreen()
screen.setup(400,500)
 
screen.title("左右键移动火箭飞行交互动画")
screen.bgcolor("black")
rocket = turtle.Turtle()
rocket.color('cyan')
  
should_move = False

def move_control():
    global should_move
    should_move = not should_move

def move_rocket():
    global should_move
    if should_move:       
        rocket.pendown()
        rocket.forward(2)
    else:     
        rocket.penup()
    screen.ontimer(move_rocket, 25)

def close_window():
    screen.bye()

screen.onkey(move_control, "space")
screen.onkey(close_window, "q")
screen.onkey(lambda:rocket.left(90), "Left")
screen.onkey(lambda:rocket.right(90), "Right")

screen.listen()                      
move_rocket()

screen.mainloop()