tops become two columns on mobile devices.
          </p>
          <pre class="grid-frow-code visible-md visible-lg">
<!--     --><span class="fake-comment">// Shrink your browser window to see the four quarters snap into two rows of halves</span>
<!--   --></pre>
          <pre class="grid-frow-code visible-xs visible-sm">
<!--     --><span class="fake-comment">// Expand your browser window to see the two rows of halves snap into four quarters</span>
<!--   --></pre>
          <div class="grid-example">
 