code: function(e) {
          if (!e) return;
  
          //use current position
          var dx = this._x - e._x,
              dy = this._y - e._y,
              dw = this._w - e._w,
              dh = this._h - e._h;
  
          this._cascadeInner(dx, dy, dw, dh);
      }
docs: @
  #._cascade
  @comp 2D
  @kind Method
  @private
  
  @sign public void ._cascade(e)
  @param e - An object describing the motion
  
  Move the entity's children according to a certain motion.
  This method is part of a function bound to "Move": It is used
  internally for ensuring that when a parent moves, the child also
  moves in the same way.