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The Fullbright Company recently released its interactive-story game Gone Home to praise from critics. The developer built the title on the popular Unity software kit, but that’s not what it started on.

When Gone Home designer Steve Gaynor first began development on the mystery adventure, he originally built it on the HPL2 engine from developer Frictional Games. That’s the same engine used on first-person horror game Amnesia: The Dark Descent. Gaynor intended to see through the creation of Gone Home on that SDK, but it was not meant to be.

Now, Gaynor and Frictional are releasing the original test build. You can download it here. To play it, extract the file in the “custom_stories” folder in Amnesia: The Dark Descent. Then boot up the game, select “Custom Story”, and start the “Test Game.”

“From time to time, we get requests from people who want to license our HPL2 engine in order to make a commercial game,” Frictional Games head Thomas Grip wrote in a blog post. “This is quite flattering, but the answer is always ‘no.'”

Grip explains that the studio doesn’t have the resources to create documentation or give support to studios working with its software. The company usually tells interested developers to use Unity or Epic Games’ Unreal Development Kit.

That’s how it went down with Gaynor and Gone Home.

Early in development, Gaynor e-mailed Grip to ask if he could release a commercial game using the engine. That game was Gone Home. It already existed as a proof-of-concept in the HPL2 engine, but — as usual — Grip said no to licensing its SDK. Frictional pointed Gaynor in the direction of Unity, and that was that.

Gaynor took the advice and released Gone Home built on Unity in August. Around that time, Grip remembered that the original version of the title was an HPL2 game, so he asked Gaynor and his team, The Fullbright Company, to dig up the old files.

Grip released a few comparison shots. Check ’em out below:

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