There's also Wily http://www.cs.yorku.ca/~oz/wily/

there’s something so beautiful about the plan9 aesthetic https://plan9.io/plan9/img/screenshot-small.png

Wonder if it’s possible to recreate on any mainstream operating system…

I use Rio, Acme, and occasionally Sam from plan9port [1].

The only major problems are X.org dependency, lack of mouse warping in XWayland (essential for Acme), and slow text rendering on Raspberry Pi 5.

[1]: https://9fans.github.io/plan9port/

Turns out googling for "8½ window system" gives no results (although Google's KI has this to say 'Based on the search results, "8½" refers to the Windows 8.1 update, which was released in 2013 to address critical user feedback regarding the original Windows 8')

However googling for "8 1/2 window system" leads to a proper page about the 8½ window system https://9p.io/sys/doc/8%C2%BD/8%C2%BD.html

It shouldn't be too hard to reproduce it with a tiling window manager and some quirky colors.