title: Border thickness transition
body: <p>Is there a way to ease-in-out between 2 border thicknesses?</p>
  
  <p>My code:</p>
  
  <pre><code>nav a {
  border-bottom: 1px solid #AADA4B;
  }
  
  
  nav a:hover {
  border-bottom: 3px solid #AADA4B;
  }
  </code></pre>
  
  <p>Thanks very much for the help.
  Sam.</p>