Coverst-ux/space-sim ? reverse-engineered prompt

Build me a Python space simulation app that shows both a solar system mode and a bigger galaxy style N body mode.

I want it to simulate gravity in 3D, animate planets and stars smoothly, and leave nice orbit trails behind them. It should be able to run with a small number of bodies for a simple solar system, or scale up to lots of bodies for galaxy type chaos, and it should stay fast enough to feel real time. Please use a stable physics update so the orbits do not drift apart too badly over time, and include body collisions that merge objects when they hit. I also want zoom and camera controls so I can explore the simulation, plus config based loading so I can tweak body settings without editing code.

If it makes sense, add a simple way to compare performance between a basic approach and a faster one for bigger simulations. Keep the visuals clean and make it easy to run from one main entry point. Look up current docs online if you need to.