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Most video game fans are Watch Fast & Furious 6 Onlinefamiliar with Portaland it's numbered sequel, but developer Valve originally had a different idea for following up its unexpected 2007 hit.

F-Stop, as the canceled game was reportedly called, would have ditched the original game's portal gun for the Aperture Camera. (Aperture is a reference to the fictional corporation behind the portal gun, among other things.) Players would have used the camera to snap photos that would let them re-position objects in the world and tackle perspective-based puzzles.

The previously unreported Valve project is the subject of a new YouTube series called Exposure, from the indie studio Lunch House Software. The first episode, which released just before Christmas, takes a look at what would have been F-Stop's "base mechanics," with more episodes to come.

The fine folks at Eurogamer first spotted and reported on the series on Saturday.

Nothing in the first episode points to exactly how F-Stopwould have functioned as a Portalsequel (beyond the basic Aperture connection). But if you're familiar with that earlier game, the core focus on using perspective and spatial awareness to solve puzzles stands as the most obvious throughline. Hopefully future episodes will dig into more of how the story might have worked.

Lunch House is apparently prepping the series with Valve's blessing. The indie studio licensed Valve's Source Engine – the game development tools that power Half-Life, Counter-Strike, and others – and somewhere in that process learned of F-Stop's existence.

The specifics of how that happened aren't clear, but Lunch House's Tristan Halcomb, who also narrates the first episode of Exposure, noted on Twitter that Valve knows this is happening.

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In-development projects get canceled all the time in video games, and for various reasons. Often they're either never spoken of again or they transform into something different that still carries some of the original core design concepts. So to get details on F-Stop, and from the notoriously leak-averse Valve no less, is a rare and wondrous gift to fans of video games.

Portal, for anyone who doesn't remember, first surfaced in Valve's release of The Orange Box. The big source of hype in that 2007 release was the inclusion of Half-Life 2and its two add-on "Episodes," none of which had ever been released on consoles before. The collection also contained Valve's Team Fortress 2, an early precursor to a style of game that may now be best embodied in Overwatch.

But Portalwas the big surprise of The Orange Box. It's a short game compared to the rest, with a play time that hovers around 3-5 hours for most players. But Portal's inventive puzzle mechanics, defined by the "portal gun" that let players create a door between any two points, amounted to a fresh and eye-opening take on how a first-person shooter-style experience could be twisted into something decidedly different.

Portal, the first game, won all sorts of accolades following The Orange Box's release, and it eventually spawned a sequel. That sequel, Portal 2, sticks to a more traditional path of building directly on the original game's core ideas. It's a longer game, for one. It also builds in some new mechanics and introduces the option for two players to solve a set of puzzles in a separate co-op story mode.

F-Stopwould have obviously taken those ideas in a bit of a different direction, what with the camera and its unique capabilities. It's not quite the same thing, but the recently released puzzle game Superliminalfeatures some funky perspective play that's not too far off from what F-Stopwould have offered.

I actually played Superliminal(which is from developer Pillow Castle) during the recent holiday break and really enjoyed it. The game is short by modern standards, probably coming in at the lower end of the original Portal's 3-5 hour playtime. It shares some similar qualities as well, including the basic story premise of you being caught in a mysterious corporation's testing program.

The puzzles are what matters, though, and Superliminalis a fundamentally different kind of game. If watching Exposureand reading all about the early days of Portal's success has you in the mood to play something similar, Superliminalhas relatively low hardware requirements for a modern PC game and is more than worth your time.