Post by the author Sam Rose about it: https://bsky.app/profile/samwho.dev/post/3ltpdkr3bmk2o
If you're going to use fancy fonts at least make them webfonts.
I picked fonts that are present on a wide variety of systems without having to be downloaded on page load. I just forgot some CSS to make sure numbers looked distinct.
Fortunately someone sent me a PR with the right CSS.