docs: 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;
  }