Writing the Geostationary Orbit 'autopilot' was an interesting challenge... Sure needed a refresher about orbital mechanics. But I'm almost there, now it is only a matter of refining the precision. And I learned a lot in the process.
Currently, you can input a target longitude, and the satellite will 'drift there' (it can take some time, as it does with real-life satellites). Then it will make sure that the Eccentricity is very very low and the Period is 1 sidereal day.
The final objective is to be able to deploy a small fleet of these satellites and have each one autonomously travel to a preset longitude, then stay there.
Oh and to simulate data relay between two out-of-sight locations on Earth (but it should be the fun part lol).