<!DOCTYPE HTML>
<style>
div { font-family: monospace; font-size: 12px; width: 450px; }
rt { font-size: 50%; }
</style>
<!--
In a 450px container, the minimum font size at 15em per line is 30px.
This means we map 0px-45px into 30px-45px, so 12px gets mapped to 34px.
-->
<div><ruby><rb>base<rt>rubytext</ruby></div>