Gravity Simulator is a very cool sandbox game that lets you experiment with gravity and the orbit of objects around a sun.
You can select various celestial objects and throw them into orbit around a central star. By tweaking how your ‘throw’ them and even adjusting the gravity you can create some startling and informative effects.
Use the Mouse to setup your own planetary system and see what happens.
Whether you are looking for something education to mess about with or just want to create some trippy patterns, Gravity Simulator is well worth a go.