complement superscript shows squares on Android

[bsdz]

When I play levels with the complement superscript character on Android Chromium browsers the characters are rendered as boxes. The same happens to other characters like union / intersection symbols. I.e.

Curiously, the union / intersection symbols aren't affected on levels without the complement "c" superscript. I.e.

This happens on Android Chrome, Edge and Kiwi browsers.

I wasn't able to upload my saved state to a Firefox browser so can't say anything about those.

This doesn't affect Firefox on Android although there's a slightly annoying Firefox issue where the keyboard won't automatically open when editing a tactic :-(

The fonts render correctly on my desktop Chrome browser (running on Linux).