FAB

The FAB (.fab) is a circular, elevated primary-action button, typically anchored to a fixed position in a corner of the viewport (positioning is left to the consuming page rather than baked into the component). It renders on a <button> and is meant to hold a single icon. Unlike .btn, a FAB has no outline/text style variants — it is always a solid, shadowed circle.

<button type="button" class="fab" aria-label="Compose">
  <span class="fab-icon" aria-hidden="true">＋</span>
</button>