The listing, [Steam] Space Engineers (Early Access) has ended.
Space Engineers is a sandbox game about engineering, construction, exploration and survival in space and on planets. Players build space ships, space stations, planetary outposts of various sizes and uses, pilot ships and travel through space to explore planets and gather resources to survive.
What the developers have to say:
“Space Engineers is an Early Access game, which means that it is still under development but already in a very playable state and contains a vast amount of new features that have been added since its first release (e.g. Multiplayer, Survival mode). The game is being improved on a regular basis through updates that add and polish features and content, optimizations and bug fixes.
We invite you to give us your feedback and suggestions to help us create the best game possible.
Buy now, play on Steam and receive all future updates for free.
Please be sure to read the list of current features before you buy the game. It will give you an insight on what is or isn't actually working: http://www.SpaceEngineersGame.com/features.html
Everything in the game is subject to change”