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F-Stop, the secret mechanic of Valve's unreleased Portal prequel, has finally been revealed

About effing time

Just after Portal 2 was released, Valve and Geoff Keighley also released The Final Hours of Portal 2, an interactive book about the making of 2011’s best potato-based puzzle game. The most revealing story in the book was about how Valve had spent some time making a game that was Portal’s follow-up in name only. It was set in the past, without Chell or the GlaDOS that we know, and had a new mechanic called “F-Stop”. It was essentially a different game and was never released.

Valve remained coy about what F-Stop was in the hope of eventually using it, but they never did. In an unlikely twist, a developer using the Source Engine for their own game were given permission to show off F-Stop’s secrets. It was based around the “Aperture Camera”, which could copy, paste, and rescale items in the world.

LunchHouse Software have been working with Valve's official code in their own Portalish puzzler Punt, but have released a small documentary about F-Stop on their own site. Here, peep at it.

This is just a glimpse. Part one of Exposure, a deep-dive exploration of the mechanics, according to LunchHouse: “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. We've reached out to Valve, who've given us explicit permission to continue with our project using their original code.”

Explicit permission? I hope that means Gabe swore at them. We've seen the sort of scaling that Aperture Camera can create in last year's Superliminal, which might be why Valve are finally happy to let it escape their vault. If that's the case, I hope that Arkane accidentally makes Half-Life 3 and that Valve just sighs and lets it happen.

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Craig Pearson avatar

Craig Pearson


I love square sausage, cats, and climbing pretend rocks.

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