Overlay

<div class="tng-backdrop"></div>
<button
  class="tng-icon-button on-contrast is-neutral | p-absolute at-top-right inset-md"
>
  <i class="tng-icon icon-close" aria-hidden="true"></i>
  <span class="sr-only">Close</span>
</button>
<div class="tng-overlay at-pretty-center">
  <div class="tng-surface pb-xl pi-2xl">
    <p>Hello World!</p>
  </div>
</div>

Hello World!