The common app.css I put in each project. Constantly changing over time, but sick of digging through to find my most recent project to copy it over from. It uses a two-tone monochrome-esque aesthetic, but it's easy to extend since it's just css variables.
Intended for use with modern-normalize. E.g.
import 'modern-normalize.css';
import 'app.css';
It also uses IBM Plex Serif, which is available from Google fonts (or Bunny, etc.)