The listing, Antichamber (Steam Key) has ended.
Antichamber is a single-player first-person puzzle-platform video game
http://store.steampowered.com/app/219890/
About the Game
Antichamber is a mind-bending psychological exploration game where nothing can be taken for granted. Discover an Escher-like world where hallways wrap around upon each other, spaces reconfigure themselves, and accomplishing the impossible may just be the only way forward.
Several years in the making, Antichamber received over 25 awards and honors throughout its development, in major competitions including the Independent Games Festival, the PAX10, IndieCade and Make Something Unreal. Antichamber was also supported by the Indie Fund.