函数check_events()越来越长，是时候遏制一下这种势头了。
更新：\game_functions.py:

...
def check_keydown_events(event, chicken):
    """响应键盘按键按下事件"""
    if event.key == pygame.K_RIGHT:
        chicken.moving_right = True
    elif event.key == pygame.K_LEFT:
        chicken.moving_left = True


def check_keyup_events(event, chicken):
    """响应键盘按键松开事件"""
    if event.key == pygame.K_RIGHT:
        chicken.moving_right = False
    elif event.key == pygame.K_LEFT:
        chicken.moving_left = False


def check_events(chicken):
    """响应按键和鼠标事件"""
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()

        elif event.type == pygame.KEYDOWN:
            check_keydown_events(event, chicken)

        elif event.type == pygame.KEYUP:
            check_keyup_events(event, chicken)
            
...

调试无误。

2021.1.21