title: Differentiate between :focus via tab-key and :focus via click in CSS
body: <p>Although I am quite certain that the answer to my question will be "Can't be done" I'd like to be sure and ask you guys here.</p>
  
  <p>I have a rather typical scenario in which I want to enable tabbing through my website (i.e. using tab key on keyboard). The item the user has just tabbed upon should be marked visually via CSS. So far, so good. This, obviously, demands the focus-pseudo class:</p>
  
  <pre><code>a {
      color: #000;
  
      &amp;:hover {
          color: lighten(#000, 10%); // discreet change
      }
  
      &amp;:focus {
          background-color: green; // extreme change
      }
  }
  </code></pre>
  
  <p>But I want to apply this style solely when the user tabs through the page. When the user hovers or clicks an element the style should be something different.</p>
  
  <p>Example: A user hovers or clicks an anchor. Then the visual aid can be discreet because the user already knows which element he has interacted upon. But when he tabs through the page he can not be so sure and thus the styling should be more drastic.</p>
  
  <p>The problem I am having is: An element gets the focus-styles applied on on both tabbing the page and clicking on it.</p>
  
  <p>Is there a CSS-only way to apply styles solely when an element got focused via tabbing?</p>
  
  <p>Again, I am pretty sure that this is not possible, but just to be sure I have asked the question.</p>