private Score AddNextFrameBonus()
 {
     if (_nextFrame == null)
     {
         return(BonusBallScore());
     }
     return(_nextFrame.GetBonusScore(this));
 }
 public Score TotalScore()
 {
     return(_ball1.TotalScore() + _ball2.TotalScore() + _nextFrame.GetBonusScore(this));
 }