title: CSS select every other pair element
body: <p>I have a simple unordered list.</p>
  
  <pre><code>&lt;ul&gt;
    &lt;li&gt;First item&lt;/li&gt;
    &lt;li&gt;Second item&lt;/li&gt;
    &lt;li&gt;Third item&lt;/li&gt;
    &lt;li&gt;Forth item&lt;/li&gt;
    &lt;li&gt;Fifth item&lt;/li&gt;
    &lt;li&gt;Sixth item&lt;/li&gt;
  &lt;/ul&gt;
  </code></pre>
  
  <p>I need to be abel to select every other element in pairs. So basically, I need the first + second, fifth + sixth, and so on as the pattern will repeat indefinitely. </p>
  
  <p>I want to avoid using javascript as this will be an angular app, so I don't to do any DOM manipulation.</p>
  
  <p>I've tried messing with <code>nth-child()</code> equations but can't figure out what equation will give me what I need. Any ideas? Any help is appreciated!</p>