Something something visual identity.
This isn't a stylesheet, it's a bunch of PostCSS modules.
They're supposed to be extended and bundled on a case-by-case basis.
You'll need define your own postcss entrypoint and import ditto.css (using postcss-import):
/* styles.css */
@import "ditto.css";
/*
...any additions here
*/Copy this repo's postcss.config if you want.
The styles also depend on Fira Code and Material Symbols, which you'll need to include yourself.