Interesting, this seems more resource efficient than even fltk, which is the lightest usable cross-platform GUI library. And it's pure C unlike fltk.

It's great to see such projects in an era of unabashed resource consumption.

https://github.com/rxi/microui

Just around 1100 lines of C code.

You need to bring your own renderer, but that's the same for Nuklear or Dear ImGui.

I wrote a WASM wrapper for the microui demo too:

https://floooh.github.io/sokol-html5/sgl-microui-sapp.html