We're finally learning more about Valve's long-secret Portal prequel

Shortly after the release of the famed Orange Box, Valve embarked upon a series of "Directed Design Experiments" that Gabe Newell hoped would spark a new wave of creativity at the studio. One of them, as explained by the Half-Life Wiki, was called F-Stop, and it was enough of an internal hit that it was tapped for full development as a prequel to Portal. For reasons unknown, that prequel never came to be, and the whole thing sunk into obscurity—another Valve mystery, to be occasionally whispered about in Reddit threads.

One of the reasons so little is known about F-Stop is that Valve simply refused to talk about it, apparently out of hope that it would actually turn it into a proper game someday [Half-Life: Alyx stares directly into the camera]. Valve seems to have had a recent change of heart, however, as an upcoming YouTube series called Exposure, being made by indie studio LunchHouse Software, will not just explain how F-Stop was intended to work, but actually show it in action.

"The mechanics are not based on speculation or hearsay. Instead, Exposure uses the original, official code from Valve's own F-STOP, or as it was properly named, Aperture Camera," the video description states. It also notes that Valve has given the studio "explicit permission to continue with our project using their original code."

The "gameplay" in the clip bears more than a passing resemblance to Superliminal, a perception-bending first-person puzzler released in November—a similarity that didn't go unnoticed on Twitter. That may be why Valve is suddenly willing to let this cat out of the bag: There's not much point in keeping your special mechanic a secret if someone else has already turned it into a game, after all. 

And while an unused game mechanic might seem like a thin basis for a multipart video series, LunchHouse's Tristan Halcomb told USgamer that there's enough to it to make more than a dozen videos, although they're aiming to keep it to five or six.

A full release schedule hasn't been set yet: Halcomb said LunchHouse wants to "discuss the future of the project a bit more with Valve to see what opportunities we may have going forward before committing to a follow up, so we're working based on their schedule to some extent." For now, you can follow along with the project at exposure.lunchhouse.software.

Andy Chalk

Andy has been gaming on PCs from the very beginning, starting as a youngster with text adventures and primitive action games on a cassette-based TRS80. From there he graduated to the glory days of Sierra Online adventures and Microprose sims, ran a local BBS, learned how to build PCs, and developed a longstanding love of RPGs, immersive sims, and shooters. He began writing videogame news in 2007 for The Escapist and somehow managed to avoid getting fired until 2014, when he joined the storied ranks of PC Gamer. He covers all aspects of the industry, from new game announcements and patch notes to legal disputes, Twitch beefs, esports, and Henry Cavill. Lots of Henry Cavill.