anchor.diff:      loading.value = item;
     }
   
  -  arrowLeftRightMouseDown(ev,isLeft) {
  +  scroll({toLeft: true}) {
       var _itemSpan = ref(items[0].toString());
       var _scrollListDiv = ref('round-list');
       var _visibleItemsWindowSize = scrollStep * _itemSpan.marginEdge.width;
  
positive.code:     _scrollStep = _scrollStep.replaceAll('px','');
      _scrollStep = num.parse(_scrollStep).round();
  
      if (isLeft) {
        _scrollStep += _visibleItemsWindowSize;
      }
      else {
  
negative.code:   render() {
      var _items = [];
      for (var item in items) {
        var className = '';
        if (selected.value == item) {
          className = 'selected';
        } else if (active.value == item) {
          className = 'active';
        } else if (loading.value == item) {
          className = 'loading';
        }
        _items.add(span({'ref' : '$item', 'key': item,
          'onMouseDown': (ev) => mouseDown(ev, item),
          'className' : '$className'}, item));
      }
  
      var leftArrowButton = div({'key': 'leftArrowButton', 'onMouseDown': (ev) =>
          scroll(toLeft: true)}, '<');
      var rightArrowButton = div({'key': 'rightArrowButton', 'onMouseDown': (ev) =>
          scroll(toLeft: false)}, '>');
  
      var textSpan = span({'key': selectorText,
        'className' : 'round-selector-text'}, selectorText);
  