Gabriela Nav Structure

menu.html

<nav>
<div class="top">
  <ul>
    <li data-bottom="one" class="current">One</li>
    <li data-bottom="two">Two</li>
    <li data-bottom="three">Three</li>
  </ul>
</div>

<div class="bottom">
  <ul data-top="one" class="showing">
    <li>Thing 1</li>
    <li>Thing 2</li>
    <li>Thing 3</li>
  </ul>
    <ul data-top="two">
    <li></li>
    <li></li>
    <li></li>
  </ul>
    <ul data-top="three">
    <li></li>
    <li></li>
    <li></li>
  </ul>
</div>
</nav>

style.css

.top .current {
  font-weight: bold;
}
.bottom ul {
  display: none;
}
.bottom ul.showing {
  display: block;
}