<section units>
  <h2>Units</h2>
  <div length="100"></div>
  <div length="3"></div>
  <div length="50"></div>
</section>

<section types>
  <h2>Types</h2>
  <div length="100px"></div>
  <div length="3rem"></div>
  <div length="50%"></div>
</section>