Bulma class: .tabs.is-toggle.is-toggle-rounded

<div class="tabs is-toggle is-toggle-rounded">
  <ul>
    <li class="is-active"><a>Pictures</a></li>
    <li><a>Music</a></li>
    <li><a>Videos</a></li>
    <li><a>Documents</a></li>
  </ul>
</div>

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