title: Combine CSS psuedo classes on transition
body: <p>I'm trying to transition a child element when the parent element is focused.</p>
  
  <p>I want to do something like:</p>
  
  <pre><code>parent:focus{
  //do something to first-child
  } 
  </code></pre>
  
  <p>Is this possible, or does this require JS?</p>