title: jquery animate only opacity left to right
body: <p>Is it possible to animate only the opacity, and have it move in a direction across a div? Let's say from left to right?</p>
  
  <p>Here is my code so far: just missing something that says Left, if it's even feasible:</p>
  
  <pre><code>$(document).ready(function() {
      $('#box').mouseenter(function() {
          $(this).animate({opacity: ".5"}, 500);
      });
  });
  </code></pre>