Gone Home was prototyped as a custom campaign for Amnesia: The Dark Descent, and now you can play that early build for yourself.
A lot goes into the process of making a game, but one of the earliest decisions is choosing what game engine to use. When Fullbright started working on its indie hit Gone Home, they thought it would work well with the same engine that powered Frictional Games' Amnesia: The Dark Descent. Trouble was, Frictional created that engine itself, and did so without planning on releasing it to other developers. The Amnesia team rejected Fullbright's request to utilize their proprietary engine, but that didn't stop Fullbright from creating a proof-of-concept Amnesia mod anyway - a mod that's now free to the public.
"From time to time we get requests from people who want to license our HPL2 engine in order to make a commercial game," says Frictional's Thomas Grip. "Our reply is to simply state that there is no documentation, we do not have time for support and they are better off using Unity or UDK anyway."
It seems that Fullbright listened, since the commercial version of Gone Home is powered by Unity. After the game became a success, Fullbright sent Grip a copy of the old prototype Amnesia mod that inspired the full version of Gone Home. That mod is available to everyone on the internet, by the way, so if you liked Gone Home you can see what it was like in the early days. Check out the mod (installable as a Custom Story) right here.
Source: Frictional Games