第 14 步：我们到了！现在我们的足球正在移动，我们需要让它从玩家的头部反弹。
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microbit = codesters.Microbit()
microbit.show_string("hello")
stage.set_background("soccerfield")
sprite = codesters.Sprite("athlete2")
sprite.move_down(150)
def button_a():
sprite.move_left(50)
microbit.event_button_a(button_a)
def button_b():
sprite.move_right(50)
microbit.event_button_b(button_b)
ball = codesters.Sprite("soccerball")
ball.set_x_speed(5)
ball.set_y_speed(5)
