关于pygame的一些事情：我怎样才能停止游戏？

Question

我做了一个名为＆＃34; Alien Invasion＆＃34;在python中。当游戏结束时，它就无法停止。它无法显示按钮＆＃34; Play＆＃34;，它会重新开始！我不知道发生了什么。这里有一些关于game_functions和game_stats的代码：

def ship_hit(ai_settings,stats,screen,ship,aliens,bullets):
    if stats.ships_left>0:
        stats.ships_left-=1
        aliens.empty()
        bullets.empty()
        create_fleet(ai_settings,screen,ship,aliens)
        ship.center_ship()
        sleep(0.5)
    else:
        stats.game_active=False
        pygame.mouse.set_visible()

def update_screen(ai_settings,screen,stats,ship,aliens,bullets,play_button):
    screen.fill(ai_settings.bg_color)
    for bullet in bullets.sprites():
        bullet.draw_bullet()
    ship.blitme()
    aliens.draw(screen)
    if not stats.game_active:
        play_button.draw_button()
    pygame.display.flip()

def check_play_button(ai_settings,screen,stats,play_button,ship,aliens,bullets,mouse_x,mouse_y):
    button_clicked=play_button.rect.collidepoint(mouse_x,mouse_y)
    if button_clicked and not stats.game_active:
        pygame.mouse.set_visible(False)
        stats.reset_stats()
        stats.game_active=True
        aliens.empty()
        bullets.empty()
        create_fleet(ai_settings,screen,ship,aliens)
        ship.center_ship()

class GameStats():
    def __init__(self,ai_settings):
        self.ai_settings=ai_settings
        self.reset_stats()
        self.game_active=False