<!DOCTYPE html>
<p>There should be a centered blue rectangle at the top of the yellow rectangle.</p>
<div style="position:relative; border:1px solid; width:20em; background:yellow;">
    <div style="columns:3; column-gap:0; column-fill:auto; height:6em; margin-top:10em; padding:0 1em;">
        <div style="height:9em;"></div>
        <div style="position:absolute; top:0; width:6em; height:3em; background:blue;"></div>
    </div>
</div>