The game, called Kerbal Space Program, puts the you in charge of building and launching rockets capable of putting little, green "Kermen" into space. You begin by assembling your rocket from various parts in the game's Vehicle Assembly Building. Then you head out to the launch pad to fire it off and see what happens.
The game does not currently have specific missions, but you can set your own goals from completing a successful sub-orbital hop, to reaching orbit, to landing on the Mün. KSP features solidly realistic orbital mechanics which equates to a very high learning curve. After playing for several hours, I have had a couple sub-orbital launches, but still haven't managed to reach orbit. I suspect that I will need to do some number crunching, or at least jotting down in order to achieve that next milestone.
Having spent the past year and a half developing a space exhibit for the museum where I work, I am very pleased to see a game like this. Though the physics are difficult to master, the simple process of tinkering with virtual rockets and blasting them to space or smithereens is a lot of fun.
The game is currently in an open beta test ala Minecraft. There is a free demo version available for download with limited features. If my description sounds intriguing, I encourage you to check it out. If you get sucked in like I did, it is currently just $15 to pick up the latest test version, which will continue to yield updates as the game progresses.
Let's light this candle!