How to create a shortcode to let the user add the ID of a YouTube video?

add_shortcode('youtube', 'youtube_shortcode'); 

function youtube_shortcode($atts){  

  if(!isset($atts[0])) return;
  $id = strip_tags($atts[0]);
  ob_start();
  ?>

<div><a class="fancybox" href="#video_<?php echo $id; ?>">
<img src="http://img.youtube.com/vi/<?php echo $id; ?>/0.jpg" alt="Welcome To High Output" width="220px" height="120px" /></a></div>


<div id="video_<?php echo $id; ?>" style="display: none;">
<iframe title="YouTube video player" class="youtube-player" type="text/html" width="480" height="390" src="http://www.youtube.com/embed/<?php echo $id; ?>" frameborder="0" 
allowFullScreen></iframe></div>

  <?php
  return ob_get_clean();
}

use it like: [youtube "dm36W5NTPag"]