Been interesting to see the technique development over the release. People discovering jammed pipes and item combinations with some pretty clear progression of ideas among designs. One halfpipe, and then a bunch of loopdy-loops.
If Munroe, Goodhart, davean et. al. read this, one cool addition would be object hard points on other objects for attachments. Like a steering wheel with rotating repulsors. Fan speed adjustment would also be nice like the repulsor strength.
Rapier, alongside https://nalgebra.org/ (which it uses underneath) has seriously good documentation and some advanced features like cross-platform determinism (something made hard by the way floating point differs between platforms)