code: function distanceTo(e) {
           var a = this.getBounds();
           var b = e.getBounds(); // the me.Vector2d object also implements the same function, but
           // we have to use here the center of both entities
  
           var dx = a.pos.x + a.width / 2 - (b.pos.x + b.width / 2);
           var dy = a.pos.y + a.height / 2 - (b.pos.y + b.height / 2);
           return Math.sqrt(dx * dx + dy * dy);
         }
docs: return the distance to the specified entity
  @name distanceTo
  @memberOf me.Entity
  @function
  @param {me.Entity} entity Entity
  @return {Number} distance