Some of these CSS frameworks are great. If you’re viewing this on a desktop browser, there is a table of contents in the right sidebar.
NES.css
https://nostalgic-css.github.io/NES.css/
PS1
https://github.com/micah5/PSone.css
DOS
http://kristopolous.github.io/BOOTSTRA.386/
BIOS
https://github.com/vinibiavatti1/TuiCss
Terminal
https://github.com/andersevenrud/retro-css-shell-demo
Windows 98
https://jdan.github.io/98.css/
React components:
Windows XP
https://botoxparty.github.io/XP.css/
Windows 7
https://khang-nd.github.io/7.css/
Windows 10
https://github.com/jianzhongli/csswin10
C64
http://pixelambacht.nl/2013/css3-c64/
Classic Mac
https://github.com/npjg/classic.css
Amiga
https://github.com/renkman/Renkbench
“Retro”
https://github.com/ritenv/retro-desktop
Paper
I like this one, though I’m not sure if it’s responsive.
Brutalist
HTML
https://secretgeek.github.io/html_wysiwyg/html.html
Markdown
https://mrcoles.com/demo/markdown-css/
LaTeX
Longer List
There’s a longer list here:
https://github.com/sw-yx/spark-joy/blob/master/README.md#fun-css-frameworks