This is easily the zaniest of the games on offer here. In Kerbal Space Program, you must build a spacecraft that is capable of sending its crew into space without getting them killed. There is a huge collection of ship parts at your disposal, each with their own functionalities.
There is a total of three modes to play. Sandbox allows you to create anything freely. In Science mode, you must perform research to advance the knowledge of Kerbalkind and further available technology. Finally, there's Career mode, where you must oversee every aspect of the program.
With three different play modes, plus various activities like mining resources, constructing bases and space stations along with building all kinds of ships, the fun is never-ending. Not to mention that the outcome of building crazy spaceships at times is hilarious.