It's been a lot longer than I was hoping since my last update.
I've done some fairly major rearchitecting that will allow for some cool new features, including layers and infinite undo histories that persist beyond the application closing.
I had just about finished the changes and the latter feature a few days before Christmas when I hit an obscure memory bug. It seems to be originating from some code written months ago, showing up around my hot reloading code or when that's removed, my XInput handling.
I went back to my parent's house for the holiday before I was able to track the bug down. Armed only with my work MacBook Pro, I was unable to do any more work directly on Geometer (which is currently Windows-only).
Instead, as I've only been using asserts for validating behaviour so far, I spent some time working on a single header file test suite.
Take a look at sweet.h's GitHub repo if you want to use it for yourself.
Hopefully I'll have a more geometry-related update for you soon.