public void mouseMoved(MouseEvent e) {
      MyWorldView.SPACE_INVERSE_TRANSFORM.transform(e.getPoint(),p);// Change mouse coordenates from
      if (currentElement !=null)                                    // pixels to meters.
        if (currentElement.contains(p.getX(), p.getY())) 
           return;
        
      PhysicsElement newElement = world.find(p.getX(), p.getY()); 
      if (newElement == currentElement) return;
      if (currentElement != null) {
         currentElement.setReleased();
         currentElement = null;
      }
      if (newElement != null) { 
         currentElement = newElement;
         currentElement.setSelected();
      }
      world.repaintView();
   }