Installation instructions can be found here:
Elevator: Source is a single or co-op elevator experience that is different each time you play. What floor will you stop on next? What will happen? Who knows! We don't even know! And we made the game. It's THAT EXCITING.
Elevator: Source brings you:
Up to 28 randomized floors to stop on (with DLC packs possible in the future!)
A thrilling co-op experience
Realistic elevator physics
Cunning, state of the art AI that REALLY GOES INTO THE ELEVATOR AND WAITS!
Real moral choices! What floor do you get off at? Do you ever get off? Only you are able to craft your elevator story.