anchor.diff:      demo.value = input.value;
     });
   
  -  demo.updated.listen((args) {
  +  demo.output.listen((data) {
       input.style.background = '';
  -  });
  -
  -  demo.error.listen((args) {
  +  }, onError: (error) {
       input.style.background = 'red';
     });
   }
  
positive.code:   static final String _errorLevelIdKey = 'error-value';
    final BungeeNum _scale;
    final CanvasElement _canvas;
    final _QrCalc _qrMapper;
    final CanvasRenderingContext2D _ctx;
  
    String _value = '';
  
negative.code:   void _update() {
      final t = [_typeNumber, _errorCorrectLevel, _value];
  
      _qrMapper.source = t;
    }
  
    void _onFrame(double highResTime){
  