程序代码：

import sys
import pygame
from pygame.sprite import Group
from setting import Setting
from ship import Ship
from bullet import Bullet
from allien import Allien


class AlienInvasion:
    #管理游戏资源和行为的类
    def __init__(self):
        pygame.init()
        self.setting = Setting()
        self.screen = pygame.display.set_mode((self.setting.screen_width,self.setting.screen_height))
        #设置背景色
        # 创建飞3
        self.ship = Ship(self)
        # 创建子弹的编组
        self.bullets =pygame.sprite.Group()
        self.bulelts_allowed = 5
        # 创建外星人的编组
        self.alliens = pygame.sprite.Group()
        pygame.display.set_caption("Alien Invasion")


    #开始游戏的主循环
    def run_game(self):
        while True:
            
            #监视键盘和鼠标的辅助方法
            self._check_event()
            # 创建外星人
            self.ship.update()
            # 控制子弹移动方法检查子弹是否达到最上面
            self.update_bullet()
            self.creat_fleet()
            #让最近绘制的屏幕可见的方法
            self.update_alliens()
            #让最近绘制的屏幕可见的方
            self._update_screen()
        
    def update_alliens(self):
        self._check_fleet_edges()
        self.alliens.update()

    def update_bullet(self):
        self.bullets.update( )
        for bullet in self.bullets.copy():
            if bullet.rect.bottom < 0:
                self.bullets.remove(bullet)
    

    # 创建外星人组
    def creat_fleet(self):
        # 创造一个外星人并计算一行可以容纳多少外星人
        # 外星人间距等于外星人宽度
        allien = Allien(self)
        allien_width = allien.rect.width
        available_space_x = self.setting.screen_width - (2 * allien_width)
        number_allien_x = available_space_x // (2 * allien_width)
        # 计算屏幕可以容纳多少行外星人
        allien_hegiht = allien.rect.height
        available_space_y = self.setting.screen_height - (3 * allien_hegiht)
        row_number = available_space_y // (2 * allien_hegiht)
        self.creat_allien(row_number,number_allien_x)

    def creat_allien(self,row_number,number_allien_x):
        for number_row in range(row_number - 1):
            for number_x in range(number_allien_x):
                allien = Allien(self)
                allien_width = allien.rect.width
                allien_height = allien.rect.height
                allien_width, allien_hegiht = allien.rect.size
                allien.x  = allien_width + (2 * allien_width * number_x)
                allien.y =  allien_height + (2 * allien_height * number_row)
                allien.rect.x = allien.x 
                allien.rect.y = allien.y
                self.alliens.add(allien)
    def _check_fleet_edges(self):
        for alien in self.alliens.sprites():
            if alien.check_edges():
                self._change_fleet_direction()
                break
    def _change_fleet_direction(self):
        for alien in self.aliens.sprites():
            allien.rect.y += self.setting.fleet_drop_speed
        self.setting.fleet_direction *= -1


    def _fire_bullet(self):
        if len(self.bullets) <=  self.bulelts_allowed:
            new_bullet = Bullet(self)
            self.bullets.add(new_bullet)

        # 响应事件的辅助方法 
    def _check_event(self):
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                sys.exit()
            # 按下按键的操作
            elif event.type == pygame.KEYDOWN:
                self._check_event_keydown(event)
            # 松开按键的操作
            elif event.type == pygame.KEYUP:
                self._check_event_keyup(event)
                # 按下按键的操作
            elif event.type == pygame.KEYDOWN:
                self._check_event_keydown(event)
        
    def _check_event_keydown(self,event):
            if event.key == pygame.K_RIGHT:
                self.ship.moving_right = True
            elif event.key == pygame.K_LEFT:
                self.ship.moving_left = True
            elif event.key == pygame.K_SPACE:
                self._fire_bullet()
            elif event.key == pygame.K_q:
                sys.exit()
    
    def _check_event_keyup(self,event):    
            if event.key == pygame.K_RIGHT:
                self.ship.moving_right = False
            elif event.key == pygame.K_LEFT:
                self.ship.moving_left = False


        # 屏幕刷新的辅助方法
    def _update_screen(self):
        self.screen.fill(self.setting.bg_color)
        self.ship.blitme()
        for bullet in self.bullets.sprites():
            bullet.draw_bullet()
        self.alliens.draw(self.screen)
        pygame.display.flip()

    #创建游戏实例并开始游戏
if __name__ == '__main__':
    ai_game = AlienInvasion()
    ai_game.run_game()
import pygame
from pygame.sprite import Sprite
class Allien(Sprite):
    def __init__(self,ai_game):
        super().__init__()
        self.screen = ai_game.screen
        self.setting = ai_game.setting
        # 创建图像和其矩形
        self.image = pygame.image.load("image/alien.bmp")
        self.rect = self.image.get_rect()
    
        # 每个外星人都在左上角附件
        self.rect.x = self.rect.width
        self.rect.y = self.rect.height
        # 储存x的精确位置
        self.x  = float(self.rect.x)

    def update(self):
        self.x += (self.setting.allien_speed * self.setting.fleet_direction)
        self.rect = self.x 

    def check_edges(self):
        screen_rect = self.screen.get_rect()
        if self.rect.right >= screen_rect.right or self.rect.left <=  screen_rect.left:
            return True

#储存游戏中所有设置的类
class Setting:
    def __init__(self):
        #屏幕设置
        self.screen_width = 1200
        self.screen_height = 800
        self.bg_color = (230,230,230)
        # 飞船速度设置
        self.ship_speed = 1.5
        # 子弹设置
        self.bullet_speed = 1
        self.bullet_width = 3
        self.bullet_height = 15
        self.bullet_color = (60,60,60)
        # 外星人设置
        self.allien_speed = 1.0
        self.fleet_drop_speed = 10
        # fleet_direction = 1 为1 表示右移，为-1表示左移
        self.fleet_direction = 1
    
    
        import pygame
from pygame.sprite import Sprite

class Bullet(Sprite):
    # 子弹的类
    def __init__(self,ai_game):
        super().__init__()
        self.screen = ai_game.screen

        # 在（0,0）处先创建一个矩形，再移动到飞船
        self.rect = pygame.Rect(0,0,ai_game.setting.bullet_width,ai_game.setting.bullet_height)
        self.rect.centerx = ai_game.ship.rect.centerx
        self.rect.top = ai_game.ship.rect.top

        # 储存用小数表达的子弹的y
        self.y = float(self.rect.y)

        self.color = ai_game.setting.bullet_color
        self.speed = ai_game.setting.bullet_speed


    # 子弹的移动
    def update(self):
        #更新表示子弹位置的小数值
        self.y -= self.speed
        # 更新表示矩形y位置???
        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)