<!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>