更新 'alien_invasion,py'

alien_invasion,py

@@ -12,4 +12,7 @@ import game_functions as gf
 def run_game():
     # 初始化pygame、设置和屏幕对象
     pygame.init()
-    ai_settings = Settings()
+    ai_settings = Settings()
+    screen = pygame.display.set_mode(
+        (ai_settings.screen_width, ai_settings.screen_height))
+    pygame.display.set_caption("Alien Invasion")