一、子弹方法
增添：\bullet.py:

    def update(self):
        """向上移动子弹"""
        self.y -= self.speed_factor
        self.rect.y = self.y

    def draw_bullet(self):
        """在屏幕上绘制子弹"""
        pygame.draw.rect(self.screen, self.color, self.rect)

二、子弹编组
更新：\FatChickenWars.py:

...
from pygame.sprite import Group
...
	    # 创建一只肥鸡
    chicken = Chicken(screen, fcw_settings)
    # 创建子弹编组
    bullets = Group()
...
	        # 更新肥鸡状态
        chicken.update()
        # 更新子弹状态
        bullets.update()
...

2021.1.21