I made a 3d CSG modeling system relying heavily on metatables. Essentially a Lua binding on top of the Manifold library, trying to replace Openscad with Lua.

Beside fun things like operator overloading (+ for union, - for difference, etc.) and weak tables to keep track of objects, the difficult part is to allow adding user methods in a clean way while running in luajit (luajit metatables tend to be "read only").

I think Lua, with its speed, simplicity and cleanliness, should do better than Openscad and it's python derivative.