Omg thanks for reply! I think its already as much fun to play with as Universe Sandbox, I assume you've seen that. It has huge potential! Can you share what language its in or any of the code for drawing a circle? It already draws a bigger circle for larger masses, but only slightly. Does the hitbox expand with it, or is that why the effect is so minimal? The Solar System preset has coloured circles.. another idea is to have masses above 10^x draw in colour c... where x=8, c=1.. x=9, x=2, etc.. also the trails is nice, but maybe you can optimise the code by omitting it, not having to store.. 300,000 coords? but maybe have the option to draw little vector arrows for velocity as the F3 thing.. but otherwise have less code to execute and faster simulation? I would love to see some option for objects to bounce in some situation, like low speed low angle glancing blows, but merge in head on higher speed ones etc. But more urgently, and much easier - have some very very tiny "drag" factor so orbits very gradually decay.. that would help systems evolve and not remain static forever, and I think matches real life.. orbits decay over very long timescales, not just from interstellar dust but also from other effects. Any info you can share would be great, would be amazing if it could be Open Source someday, even though I suck at coding. Thanks for making and sharing it!