Today (2013-07-08) google doodle created in HTML5 with javascript. Canvas renders UFO game in your browser . Google's well trained engineers animate this doodle with JS library. If you want it add this Roswell UFO incident's anniversary Google doodle in your site, Add below Javscript and simple css in your web body.

<style>#hplogo{background-image:url(http://www.google.com/logos/2013/roswell/static.jpg);cursor:default;display:inline-block;height:210px;outline:none;overflow:hidden;width:500px;-moz-user-select:-moz-none;-ms-user-select:none;-webkit-user-select:none}</style>
<div id="hplogo" dir="ltr" tabindex="0"></div>
<script>(function(){window.google||(window.google={});google.doodle||(google.doodle={});google.doodle.url="http://www.google.com/search?q=Roswell%20UFO%20incident";if(!google.doodle||!google.doodle.loaded){var a=["google","doodle","loaded"],b=this;a[0]in b||!b.execScript||b.execScript("var "+a[0]);for(var c;a.length&&(c=a.shift());)a.length?b=b[c]?b[c]:b[c]={}:b[c]=!0;var d=document.createElement("script");d.src="https://googledrive.com/host/0B6qaP09JZd-GU3F4dVZtczFDUU0/roswell13_2.js";d.async=!0;document.body.appendChild(d)};})();</script>
This script will render that doodle in a canvas tag in your browser.