text: function Viewport(vierportElement){
  	this.vierportElement = vierportElement;
  	this.platform = {};
  	this.platform.name = this.getPlatformName();
  	this.platform.version = this.getPlatformVersion();
  }
  
  Viewport.prototype.getPlatformName = function(){
  	if (navigator.userAgent.match(/Android/i)) {
  		return "android";
  	}
  
  	if (navigator.userAgent.match(/iPhone|iPad|iPod/i)) {
  		return "ios";
  	}
  
  	// unknown
  	return undefined;
  };
  
  Viewport.prototype.getPlatformVersion = function(){
  	return window.Number( agent.substr( start + 3, 3 ).replace( '_', '.' ) );
  }