code: function Circle(x, y, radius)
  {
      /**
       * @property x
       * @type Number
       * @default 0
       */
      this.x = x || 0;
  
      /**
       * @property y
       * @type Number
       * @default 0
       */
      this.y = y || 0;
  
      /**
       * @property radius
       * @type Number
       * @default 0
       */
      this.radius = radius || 0;
  }
docs: The Circle object can be used to specify a hit area for displayobjects
  
  @class Circle
  @constructor
  @param x {Number} The X coord of the upper-left corner of the framing rectangle of this circle
  @param y {Number} The Y coord of the upper-left corner of the framing rectangle of this circle
  @param radius {Number} The radius of the circle