What's nice about this is that it allows for programmatic CAD, enabling things like web applications that can download an .stl file based on user input. I hope I can find a weekend or two to play with it.
BTW: I spent a few weekends playing with Microcad (https://microcad.xyz/). It was cool, and had a similar rust feel. I just, for the life of me, couldn't figure out how to do 3d ellipses.
Here's an ellipsoid in build123d using geometric transformation of a sphere:
Also, FYI build123d now runs in the browser thanks to OCP.wasm. Example playground here https://jojain.github.io/build123d-sandbox/