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