function Back() {
  this.lib = library;

  this.back = null;
}

Back.of = function () {
  const instance = new Back();
  instance.init();
  return instance;
};

Back.prototype.init = function () {
  const target = new this.lib.btnBack();
  target.x = 40;
  target.y = 80;
  target.scaleX = 1.3;
  target.scaleY = 1.3;
  target.addEventListener('click', this.goHome, false);
  this.back = target;
  stage.addChild(target);
};

// 返回主菜单 TODO:
Back.prototype.goHome = function () {
  console.log('goHome');
};