F-Stop, the Portal prequel Valve canceled in 2007, is now playable after the community stitched it together from several leaks. Most of its assets were already sitting in the 12 TB Steam2 archive that leaked in August, but that dump didn't include the game's source code or its mapsrc data. Those two missing pieces showed up on the Valve Cut Content project's Discord server over the past few days, where the team verified the map files before merging everything into one build.
It isn't fully complete, as some textures and dialogue are still missing, but YouTube playthroughs suggest it's largely stable, and the campaign wraps up in under an hour. Getting a copy yourself is another matter, since the Discord server apparently went invite-only after all the attention. F-Stop came out of what Gabe Newell later called the Directed Design Experiments, a three-month stretch where Valve split into five teams, each building its own prototype.
Its central idea is an Aperture Science camera that photographs an object so you can place it elsewhere to solve puzzles, a concept the 2023 game Viewfinder later explored. Valve staff apparently liked it, but playtesters were less impressed. It was shelved, and some of its dialogue, characters, and mechanics were reworked into Portal 2. The playthroughs show an early Cave Johnson talking to the player (without J.K. Simmons' voice), along with personality cores acting as puzzle companions. Valve hasn't commented on this project, and there's no indication of an official release.
Source: TechPowerUp News · Summarized by HeadlinesBriefing