I previously posted on the Kerbal Space Program, a game which has a whimsical interface but uses realistic physics for its rockets and orbital mechanics: Kerbal Space Program – a game to create your own space program – Space-for-All.

This article describes the game and why it “is getting more and more attention recently from the space geek community”, including places like JPL and SpaceX:  Kerbal Space Program: The Spaceflight Simulator that Conquered JPL:  Program is Praised for its Orbital Mechanics and Newtonian Dynamics – Moonandback

Here’s a video tutorial on the game: