anchor.diff:  
     double _emitCounter;
     int _numEmittedParticles = 0;
  +
  +  double opacity = 1.0;
   
     static Paint _paint = new Paint()
       ..filterQuality = ui.FilterQuality.low
  
positive.code:   }
  
    void paint(Canvas canvas) {
  
      List<ui.RSTransform> transforms = <ui.RSTransform>[];
      List<Rect> rects = <Rect>[];
  
negative.code:       // Color
        if (particle.simpleColorSequence != null) {
          Color particleColor = new Color.fromARGB(
            (particle.simpleColorSequence[0] * opacity).toInt().clamp(0, 255),
            particle.simpleColorSequence[1].toInt().clamp(0, 255),
            particle.simpleColorSequence[2].toInt().clamp(0, 255),
            particle.simpleColorSequence[3].toInt().clamp(0, 255));
  