I’ve been building a small 3D game engine using mruby: https://github.com/carlosdanielpohlod/redgem The engine is written in C++, but I wanted Ruby to be the main way to build games with it. It has physics, a 3D editor, Blender level import, and a few other things. It’s still a work in progress, and I used AI quite a lot to help build it. There’s definitely room for improvement, but I thought it would be interesting to share it with the mruby community.

Website, demo and downloads: https://carlosdanielpohlod.github.io/redgem-site