[sigmaisaletter]

-counter strike 1.6: https://cs16.samke.me/?

[sigmaisaletter]

Went searching and found a few more:

-PlayStation: https://github.com/micah5/PSone.css

-Gameboy: https://github.com/luttje/css-pokemon-gameboy

-Windows7: https://github.com/khang-nd/7.css

-Win95: https://github.com/AlexBSoft/win95.css

-Oldschool RPG: http://ronenness.github.io/RPGUI/

-MacOS 8: https://github.com/npjg/classic.css

-MacOS 6: https://github.com/sakofchit/system.css

And some that are more than just CSS:

-386 DOS: https://github.com/kristopolous/BOOTSTRA.386 (Bootstrap Theme)

-Terminal: https://github.com/xtermjs/xterm.js

-another Terminal: https://github.com/andersevenrud/retro-css-shell-demo

-90s website: http://code.divshot.com/geo-bootstrap/ (Bootstrap)

[al_borland]

I had the 386 bootstrap theme as an option on a site I had several years ago. I did not like modals at the time. Make sure to test. Every other Bootstrap theme I tried at the time could simply drop in and work.

[throwaway148773]

This is also featured in other Valve games. It's called vgui or something like that