Valve's cancelled Portal prequel F-Stop is playable, rebuilt from three leaks

F-Stop, the Portal prequel Valve shelved in 2007, can now be played start to finish. Valve had nothing to do with it. Fans from the Valve Cut Content project stitched the game together from three separate leaks: the August Steam2 dump held nearly all of its assets but none of its source code or map sources, and those two missing pieces turned up on the project's Discord last week. After the map files were checked, everything went into one build. The campaign takes under an hour.

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Three leaks, one playable build

Piece one is the Steam2 archive that leaked in late August. Outlets disagree on its size (TechPowerUp says 12 TB, Kotaku roughly 13 TB), but either way it covered Valve builds from 2003 to 2013, and F-Stop was in there almost whole. What it lacked was the code and the mapsrc folder, where Valve keeps the source files for its maps.

Those were pieces two and three. According to Valve Cut Content's Discord moderators, quoted by Kotaku, whoever had the maps first wanted $1,000 for them and then handed them over for free. The team verified the map files (the maps specifically, not the entire package) and put the game together. People who have finished it put it at around 99 percent complete. Some textures and lines of dialogue are missing, yet the build holds up.

Getting a copy is another story. Once the attention arrived, the Discord server went invite-only. We are not linking to any files either: this is leaked Valve code, not a release.

A camera instead of a portal gun

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F-Stop came out of what Gabe Newell later called the Directed Design Experiments: for three months Valve split into five teams, and each built its own prototype. This one was about an experimental Aperture Science camera. You photograph an object, put it somewhere else, and that is how the puzzle gets solved. If that sounds familiar, the 2023 indie game Viewfinder took a similar idea all the way to release.

The playthrough above (from the Meme Man? channel, the full campaign plus extra maps in 46 minutes) shows plenty that later landed in Portal 2. Cave Johnson talks to the player, though not in J.K. Simmons' voice, and personality cores tag along through the test chambers as puzzle partners. Valve staff reportedly liked the concept more than playtesters did. It was shelved, and some of its dialogue, characters and mechanics were reworked for Portal 2.

Valve hasn't said a word about any of this, and nothing suggests an official release. I wouldn't hold my breath. What we do get is a much clearer picture of where some of Portal 2's oddly familiar moments came from.

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