anchor.diff:    }
   
     // replacement method for Star.prototype.draw in JS version
  -  void _drawSceneStar(Star star) {
  +  void _drawStar(Star star) {
       _mvPushMatrix();
   
       // Move to the star's position
  
positive.code: 
      // transform/draw each star
      for (Star s in _stars) {
        _drawSceneStar(s);
        _spin += 0.1;
      }
  
  
negative.code:     if (_elmTwinkle.checked) {
        // Draw a non-rotating star in the alternate "twinkling" color
        _gl.uniform3f(_uColor, star.twinkleR, star.twinkleG, star.twinkleB);
        _renderStar();
      }
  
      // All stars spin around the Z axis at the same rate
  