anchor.diff:  
     updateView() {
       updateRoot(vRoot()([
  -      vElement('button', type: 'MoveButton')('Move'),
         vComponent($Box, data: new BoxData(_anchor, position == 0)),
         vComponent($Box, data: new BoxData(_anchor, position == 1)),
         vComponent($Box, data: new BoxData(_anchor, position == 2))
  
positive.code:   }
  
    updateView() {
      updateRoot(vRoot(type: 'Counter')(elapsedSeconds));
    }
  }
  
  
negative.code:   Anchor _anchor = new Anchor();
  
    init() {
      new Timer.periodic(new Duration(seconds: 1), (t) {
        position = (position + 1) % 3;
        invalidate();
      });
  