Systems.css, design system for building retro Apple interfaces
System.css is a CSS library for building interfaces that resemble Apple's System OS which ran from 1984-1991
As mentioned on the page, there's also 98.css, which inspired this project.
I like some elements, especially the scrollbars and title bars. I can imagine a few design details added to this site in the future and taking the overall look into a more retro direction.