NotanOS is an operating system on Alpha state that has caught my attention and reminded me to EyeOS.
Imagine install an app based on Node.JS and make available in any web browser a front-end with a entire graphic desktop...
As mentioned, the requirements are minimal: any operating system (not Raspbian necessarily), node.JS and userserv. Then run the following and access from a web browser to https://ip-raspberrypi:
wget http://fingswotidun.com/cruft/notanos.tar.gz tar -xzf notanos.tar.gz ln -sr notanos ~/Notanos
It don't have a demo where you can "play", but the idea is very close to EyeOS with a demo ready for you in this link.
Link: github.com > notanos