title: Changing sprite images with for loop
body: <p>I've got a sprite of two images, one position is 0 0, another 0 -150 px. I'd like to make them change every 10 seconds. I'm vaguely familiar with JavaScript, so far I've got 
  this:</p>
  
  <pre><code>function changeBackground () {
  // some for loop? //
  
  }
  setInterval(function(){changeBackground()},10000);
  </code></pre>
  
  <p>I'm sorry this is realy just a few lines but I'm really lost. A little hint would be appreciated.</p>