anchor.diff:      querySelector(spaceCenter).onMouseDown.listen((mouseEvent) {
         _startMovingCenterPosition = mouseEvent ;
         _movingCenter = true ;
  +      _toggleMenu();
         querySelector(spaceCenter + " a img").attributes["src"] = "assets/img/compass_275_red.png";
       });
   
  
positive.code:     
      
      querySelector(spaceMenu)
      ..style.zIndex = "99"
      ..style.position = 'absolute'
      ..style.right = (centerRight  - centerSize /2 +2   ).toString() + "px"
      ..style.top =  centerTop < window.innerHeight/2  ? (centerTop+1  + centerSize /6 ).toString()+ "px" : (centerTop+1  - centerSize *8/6 ).toString()+ "px"
  
negative.code:       }
      });
  
    }
    
    void _toggleMenu(){
      var menu = querySelector(spaceMenu);
      if ( menu.style.zIndex == "99" ){
        menu.style.zIndex = "102" ;
        menu.classes.add("open") ;
      }else{
        menu.style.zIndex = "99" ;
        menu.classes.remove("open") ;
      }
    }
    
    
    void _moveCenter(Point start, Point end){
      double centerRightComputed =   -end.x + start.x  + centerRight ;
  