First time I heard of this: it's a "N-Body Integrator". I'm not sure I need this for anything, but I kind of wish I did. Just the thing for doing real-physics simulation of a solar system or protoplanetary disk.
Serious astrophysics software, and under the GPL v3:
https://rebound.readthedocs.io/en/latest/
[Thanks to npub1uw8g8f3g29gw8uxfcj5863rnc783xyk0alqm9mcsx3leut98dausxy88kr (npub1uw8…88kr) for this link]
#Astronomy #FreeSoftware #OpenSource