模块一：外星人管理与碰撞系统

目标：生成动态外星人群，处理移动、触边检测与子弹碰撞。

# alien.py（基础外星人类）
class Alien(Sprite):
    def __init__(self, game):
        super().__init__()
        self.screen = game.screen
        self.image = pygame.image.load('alien.bmp')
        self.rect = self.image.get_rect()
        self.rect.x = self.rect.width  # 初始位置
        self.rect.y = self.rect.height
        self.x = float(self.rect.x)    # 精确水平位置（浮点数）

    def update(self):
        """水平移动外星人"""
        self.x += self.settings.alien_speed * self.settings.fleet_direction
        self.rect.x = self.x

    def check_edges(self):
        """检测是否触边"""
        screen_rect = self.screen.get_rect()
        return self.rect.right >= screen_rect.right or self.rect.left <= 0

# alien_invasion.py（外星人群管理）
class AlienInvasion:
    def _create_fleet(self):
        """生成多行多列外星人"""
        alien = Alien(self)
        alien_width, alien_height = alien.rect.size
        available_space_x = self.settings.screen_width - 2 * alien_width
        number_aliens_x = available_space_x // (2 * alien_width)
        available_space_y = self.settings.screen_height - 3 * alien_height
        number_rows = available_space_y // (2 * alien_height)

        for row_number in range(number_rows):
            for alien_number in range(number_aliens_x):
                self._create_alien(alien_number, row_number)

    def _check_fleet_edges(self):
        """触边后下移并反向"""
        for alien in self.aliens.sprites():
            if alien.check_edges():
                self._change_fleet_direction()
                break

    def _change_fleet_direction(self):
        """下移并反转方向"""
        for alien in self.aliens.sprites():
            alien.rect.y += self.settings.fleet_drop_speed
        self.settings.fleet_direction *= -1

    def _check_collisions(self):
        """子弹与外星人碰撞检测"""
        collisions = pygame.sprite.groupcollide(
            self.bullets, self.aliens, True, True
        )
        if collisions:
            self.stats.score += self.settings.alien_points * sum(len(v) for v in collisions.values())
            self.sb.prep_score()
            self._check_high_score()

模块二：计分系统与游戏统计

目标：实时跟踪得分、最高分、剩余生命与关卡进度。

# game_stats.py
class GameStats:
    def __init__(self, game):
        self.settings = game.settings
        self.reset_stats()
        self.high_score = 0
        self._load_high_score()  # 从文件加载历史最高分

    def reset_stats(self):
        self.ships_left = self.settings.ship_limit
        self.score = 0
        self.level = 1

    def _load_high_score(self):
        try:
            with open("high_score.txt", "r") as f:
                self.high_score = int(f.read())
        except FileNotFoundError:
            pass  # 首次运行无文件则保持0

# scoreboard.py（UI渲染）
class Scoreboard:
    def __init__(self, game):
        self.screen = game.screen
        self.stats = game.stats
        self.text_color = (255, 255, 255)
        self.font = pygame.font.SysFont("Consolas", 32)
        self.prep_score()
        self.prep_high_score()
        self.prep_level()
        self.prep_ships()

    def prep_score(self):
        """格式化得分并渲染图像"""
        rounded_score = round(self.stats.score, -1)
        score_str = f"Score: {rounded_score:,}"
        self.score_image = self.font.render(score_str, True, self.text_color)
        self.score_rect = self.score_image.get_rect(right=self.screen_rect.right - 20, top=20)

    def prep_high_score(self):
        """渲染最高分"""
        high_score_str = f"High Score: {self.stats.high_score:,}"
        self.high_score_image = self.font.render(high_score_str, True, self.text_color)
        self.high_score_rect = self.high_score_image.get_rect(centerx=self.screen_rect.centerx, top=20)

    def prep_ships(self):
        """显示剩余生命图标"""
        self.ships = pygame.sprite.Group()
        for ship_number in range(self.stats.ships_left):
            ship = Ship(self.game)
            ship.rect.x = 10 + ship_number * (ship.rect.width + 5)
            ship.rect.y = 10
            self.ships.add(ship)

模块三：菜单、音效与暂停功能

目标：实现主菜单界面、音效播放和游戏暂停逻辑。

# button.py（菜单按钮）
class Button:
    def __init__(self, game, msg, y_offset=0):
        self.screen = game.screen
        self.rect = pygame.Rect(0, 0, 200, 50)
        self.rect.center = game.screen_rect.center
        self.rect.y += y_offset
        self._prep_msg(msg)

    def _prep_msg(self, msg):
        """渲染按钮文字"""
        self.msg_image = pygame.font.SysFont("Consolas", 36).render(msg, True, (255, 255, 255))
        self.msg_image_rect = self.msg_image.get_rect(center=self.rect.center)

    def draw(self):
        """绘制按钮"""
        self.screen.fill((0, 135, 0), self.rect)  # 绿色背景
        self.screen.blit(self.msg_image, self.msg_image_rect)

# alien_invasion.py（音效与状态管理）
class AlienInvasion:
    def _load_sounds(self):
        """加载所有音效资源"""
        self.bg_music = pygame.mixer.Sound('sounds/bg_music.mp3')
        self.shoot_sound = pygame.mixer.Sound('sounds/shoot.wav')
        self.explosion_sound = pygame.mixer.Sound('sounds/explosion.wav')
        self.bg_music.set_volume(0.3)
        self.bg_music.play(-1)  # 循环播放背景音乐

    def _check_events(self):
        """处理菜单事件"""
        for event in pygame.event.get():
            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_p:  # 按P键暂停
                    self.paused = not self.paused
            elif event.type == pygame.MOUSEBUTTONDOWN:
                mouse_pos = pygame.mouse.get_pos()
                self._check_play_button(mouse_pos)  # 点击Play按钮

    def _update_screen(self):
        """动态绘制界面"""
        self.screen.fill(self.settings.bg_color)
        if self.game_active:
            self.ship.blitme()
            self.bullets.draw(self.screen)
            self.aliens.draw(self.screen)
            self.sb.show_score()
        else:
            self.play_button.draw()  # 显示主菜单
        pygame.display.flip()

模块四：多样化敌人与技能系统

目标：扩展敌人类型，实现护盾、炸弹等特殊技能。

# alien.py（扩展敌人）
class ShieldAlien(Alien):
    def __init__(self, game):
        super().__init__(game)
        self.image = pygame.image.load('images/shield_alien.bmp')
        self.shield = 2  # 护盾层数

    def hit(self):
        """被击中时减少护盾"""
        self.shield -= 1
        if self.shield <= 0:
            self.kill()

class ShootingAlien(Alien):
    def __init__(self, game):
        super().__init__(game)
        self.shoot_cooldown = 2000  # 射击间隔（毫秒）
        self.last_shot = pygame.time.get_ticks()

    def try_shoot(self):
        """尝试发射子弹"""
        current_time = pygame.time.get_ticks()
        if current_time - self.last_shot > self.shoot_cooldown:
            self.last_shot = current_time
            return AlienBullet(self.rect.center)  # 返回子弹对象

# ship.py（技能实现）
class Ship:
    def __init__(self, game):
        # ...原有代码...
        self.shield_active = False
        self.shield_start_time = 0
        self.bomb_count = 3  # 初始炸弹数量

    def activate_shield(self):
        """激活护盾（持续5秒）"""
        if not self.shield_active:
            self.shield_active = True
            self.shield_start_time = pygame.time.get_ticks()

    def use_bomb(self):
        """使用炸弹清屏"""
        if self.bomb_count > 0:
            self.bomb_count -= 1
            self.game.aliens.empty()
            self.game.bullets.empty()

系统整合与交互逻辑

1. 初始化流程：

class AlienInvasion:
       def __init__(self):
           pygame.init()
           self.settings = Settings()
           self.stats = GameStats(self)
           self.sb = Scoreboard(self)
           self.ship = Ship(self)
           self.aliens = pygame.sprite.Group()
           self.bullets = pygame.sprite.Group()
           self._create_fleet()  # 生成初始外星人群
           self._load_sounds()
           self.play_button = Button(self, "Play", y_offset=-50)
           self.quit_button = Button(self, "Quit", y_offset=50)

2. 主游戏循环：

def run_game(self):
       while True:
           self._check_events()
           if self.game_active and not self.paused:
               self.ship.update()
               self._update_bullets()
               self._update_aliens()
               self._check_collisions()
               self._check_aliens_bottom()  # 检测外星人触底
           self._update_screen()

关键设计总结

1. 模块化架构：各功能（外星人、计分、菜单、技能）独立实现，通过主类协调。

2. 事件驱动：统一事件循环处理输入、状态切换与资源更新。

3. 资源管理：集中加载图像、音效，支持动态替换（如护盾外星人图片）。

4. 可扩展性：通过继承（ShieldAlien）和组合（Scoreboard）灵活扩展功能。

调试与优化策略

1. 性能监控：使用 pygame.time.Clock() 控制帧率，避免CPU过载。

2. 碰撞优化：利用 pygame.sprite.Group 的批量检测代替逐元素遍历。

3. 内存管理：及时销毁越界子弹和死亡外星人，减少资源占用。

4. 平衡性调整：在 Settings 类中集中定义速度、生命值等参数，便于快速迭代。