diff --git a/game_functions.py b/game_functions.py
index 4dc62b8..9f3fc6f 100644
--- a/game_functions.py
+++ b/game_functions.py
@@ -134,4 +134,28 @@ def check_bullet_collisions(ai_settings, screen, stats, sb, ship, aliens, bossal
             if stats.level != stats.bosslevel - 1:
                 create_fleet(ai_settings, screen, ship, aliens)
             else:
-                pass
\ No newline at end of file
+                pass
+    # 增加：只有在BOSS关才启用
+    elif stats.level == stats.bosslevel:
+
+        # 子弹击中BOSS外星人，BOSS外星人失去一定血量
+        for bullet in bullets:
+            if pygame.Rect.colliderect(bullet.rect, bossalien.rect):
+                bossalien.health -= 100
+                bullets.remove(bullet)
+
+        # 生命值为0时删除该BOSS
+        if bossalien.health <= 0:
+            # 提高等级，加分
+            stats.level += 1
+            sb.prep_level()
+            stats.score += ai_settings.bossalien_points
+            sb.prep_score()
+            check_high_score(stats, sb)
+
+            create_fleet(ai_settings, screen, ship, aliens)
+
+        # BOSS发射子弹和船碰撞
+
+        if pygame.Rect.colliderect(bossbullet.rect, ship.rect):
+            ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets, bossalien, bossbullet)