So this recently came out, it’s free and amazingly fun for something so unfinished. Go to http://kerbalspaceprogram.com/ and download it. Now.
You build a rocket and launch it. You control the staging order and when they go off as well as having the ability to control direction. The world is also procedurally generated, orbits work, and there are massive plans for other planets and many, many more items. Half the fun is the horrible failures too, since your brave little Kerbalian astronauts start freaking the fuck out.
It also has Jeb, and Jeb gives no fucks.
Well, usually doesn’t at least.