text: #统计信息
  
  class GameStats():
      '''跟踪游戏统计信息'''
      def __init__(self, ai_settings):
          '''统计初始化信息'''
          self.ai_settings = ai_settings
          self.reset_stats()
          #游戏刚启时处于活动状态
          self.game_active = False
  
          #高分不被重置
          self.high_score = 0
  
      def reset_stats(self):
          '''初始化在游戏运行期间可能变化的统计信息'''
          self.ships_left = self.ai_settings.ship_limit
          self.score = 0
          self.level = 1
  