This is a 2D planetary orbit simulator. You can place planets and watch them orbit each other (or fly away from each other, or collide). The controls and more info are in the README in the download.

This is an early prototype. It's missing a lot of features and the UI isn't done yet (most controls use keyboard shortcuts).

This should work on any desktop OS, but I've only tested it on Windows. Please contact me if it doesn't work for whatever reason.