It seems like a crossplatform GUI toolkit built atop of Raylib, where the primary languages you're working in are Ruby and CSS.

Yeah! That's pretty accurate, although it's not quite css/html.

It also integrates some helpful libraries, like libuv for cpu intensive tasks and I'm currently working on adding networking/HTTP and builds for android (it already runs on a pinephone).

The thing I think that is cool is that you don't need to compile your apps, you can just run them with the binary.