alien.py

@@ -26,4 +26,19 @@ class Alien(Sprite):
             elif self.rect.left <= 0:
                 return True
 
-        
+            def update(self):
+                """向左或向右移动外星人"""
+                self.x += (self.ai_settings.alien_speed_factor * self.ai_settings.fleet_direction)
+                self.rect.x = self.x
+
+        class BoosAlien(Sprite):
+            """BOOS外星人"""
+
+            def __init__(self, ai_settings, screen, health=500):
+                """初始化外星人并设置其初始位置"""
+                self.screen = screen
+                self.ai_settings = ai_settings
+                self.health = health
+                # 加载外星人图像，并设置其rect属性
+                self.image = pygame.image.load('images/boosalien.png')
+                self.rect = self.image.get_rect()