code: function (target) {
              var a = this.getBounds();
              var dx, dy;
  
              if (target instanceof me.Renderable) {
                  var b = target.getBounds();
                  dx = a.centerX - b.centerX;
                  dy = a.centerY - b.centerY;
              } else { // vector object
                  dx = a.centerX - target.x;
                  dy = a.centerY - target.y;
              }
  
              return Math.sqrt(dx * dx + dy * dy);
          }
docs: return the distance to the specified target
  @name distanceTo
  @memberOf me.Renderable
  @function
  @param {me.Renderable|me.Vector2d|me.Vector3d} target
  @return {Number} distance