编写一个游戏（编号为12−3, 12和4）：开始时，在屏幕上中央有一个火箭；玩家可通过上/下/左/右四个方向键移动该火箭；请确保该火箭不离开屏幕。

    #a_rocket.py
    import pygame
    from rocket_setting import Settings
    from a_rocket_ship import Ship
    import rocket_game_functions as gf
    
    def run_game():
    pygame.init()
    ai_settings = Settings()
    screen = pygame.display.set_mode(
        (ai_settings.screen_width, ai_settings.screen_height))
    pygame.display.set_caption("Alien Invasion")
    
    ship = Ship(ai_settings, screen)
    
    while True:
        gf.check_events(ship)
        ship.update()
        gf.update_screen(ai_