Having a blast with this (pun intended). Only picked it up last week and after a few days I'm finally getting the hang of it, so far I've managed to launch 3 satellites/probes, crashed into the moon twice and landed on there once, and now just started to build a space station (first successful rendevous and docking). $23 on Steam or from https://kerbalspaceprogram.com/ and well worth it. Plenty of mods for it too.