anchor.diff:      }
       return true;
     }
  +
  +  // Scoring and HUD
  +  void addScore(int score) {
  +    _hud.score += score;
  +  }
   }
   
   // Game objects
  
positive.code: 
    set score(int score) {
      _score = score;
      _updateHud();
    }
  
    Hud(this.spriteSheetUI) {
      pivot = Point.origin;
  
      sprtBgScore = new Sprite(spriteSheetUI["scoreboard.png"]);
      sprtBgScore.pivot = Point.origin;
      sprtBgScore.scale = 0.6;
      addChild(sprtBgScore);
  
      sprtBgShield = new Sprite(spriteSheetUI["bar_shield.png"]);
      sprtBgShield.pivot = new Point(1.0, 0.0);
      sprtBgShield.scale = 0.6;
      addChild(sprtBgShield);
    }
  
    void spriteBoxPerformedLayout() {
  
negative.code:     // Move objects to center camera and warp objects around the edges
      centerCamera();
      warpObjects();
  
      // Check for level up
      if (_asteroids.length == 0) {
        _currentLevel++;
        setupLevel(_currentLevel);
      }
  
      // Update shield
      if (_numFrames > _numFramesShieldActive) _shield.visible = false;
  