JSFiddle - React, Tailwind, and code Playground

HTML

<input type="checkbox" id="last">
<div id="header">
  <nav>
    <ul>
      <li>1</li>
      <li>2</li>
      <li><label for="last">3</label></li>
    </ul>
  </nav>
</div>

CSS

#last{
  display:none;
}
#header{
  background:#bbb;
}
#last:checked + #header{
  width:100px;
}