Wherever you go in a Valve game, you can bet it’s seen a few changes. Portal 2 was once supposed to start in an Aperture Science incubation ward, a vast battery of coldly machined cots full of anesthetised test subjects. I’m guessing Valve thought that was too much like the chapter thumbnail of a Matrix DVD, which would partly explain why the game now has you waking up in a dimly-lit motel room instead. This, you realise instantly, is just a different coldly machined cot with kitsch wallpaper and a telly, and is a dozen times more sinister.

Valve’s attitude to such movie and TV tropes has thawed considerably since The Orange Box. The idea of the motel, synonymous in fiction with voyeurism and threat, as an actual prison is a shameless lift from Chan-wook Park’s Oldboy. The way it’s then ripped apart to reveal the colossal ‘cell block’ around it is almost as cinematic as the intro to Left 4 Dead 2, bigger and louder than Valve’s other famous monorail sequences. And when you crash down into the ruined test chambers of Aperture post-GLaDOS, now under the watch of mother nature, the music cue comes straight from Lost.

Portal 2’s debt to that time-shifting mystery show is surprising, really, evident in its environment, tone, and themes of dark industrial secrets rooted in analogue times. It’s big enough, certainly, that when you discover the weird ‘interactive trailer’ for JJ Abrams’ Super 8 in the PC version of Portal 2 (an entire Source-powered map with its own textures and concept), it feels a bit like payback.

Aperture doesn’t stay dead for long once you’re up and about, the supreme idiocy of Wheatley, the architect of your escape, reviving a particularly vengeful GLaDOS as well. The bulk of Portal 2 then sees this living laboratory dust itself off and pull itself together in a sheer masterclass of texturing and animation. A game of near-solitude does, you discover, have a huge supporting cast of panels and servos that channel Pixar’s seminal Luxo Jr; Aperture is, in fact, very much the child of those frolicking Anglepoise lamps.

Valve’s texturing has been second-to-none since Half-Life 2 (and, let’s not forget, Vampire: The Masquerade – Bloodlines) introduced us to Source, an engine that places ‘surface’ on a pedestal. It’s a canvas that craves detail and has amply rewarded games like NeoTokyo, Rob Briscoe’s remake of Dear Esther, and Valve’s own firstperson shooters. What you’ll notice in this collection are the incredible mosaics that comprise Aperture’s walls, dilapidated at first but falling gradually into line with GLaDOS’s hardcoded austerity before… well, a lot of neat little spoilers.

The attention to detail continues to Chell, the player character only ever seen through the odd perpendicular portal. Her evolution is well documented, Valve’s mission being to strip her of the sexuality most games shove in your face. She’s attractive, athletic, and tailored solely for the eyes of a security-conscious machine – which of course invokes its own kind of fashion. The women of George Lucas’s THX 1138, the Pan Am girls of 2001: A Space Odyssey: both are obvious templates, but the edges have been softened and sharpened respectively, the shaved heads and test pilot hats phased out. As such, Matt Charlesworth’s final design is the perfect pair of hands and feet for the iconic getup of portal gun and heel springs.

There’s the small issue of her ethnicity, though, and its curious shift between games, which I don’t really have time for here. Also, the two not-so-small issues of ATLAS and P-body, the cutely anthropomorphised stars of the game’s co-op mode. And there are, of course, the flourishes and themes that make this oblique trip through the Half-Life 2 fiction seem vitally familiar: those human elements that bugger up the plans of vast alien intellects, making their dastardly methods seem risible and flawed.

About the screenshots. They weren’t really possible until Valve finally patched in custom FOV to coincide with its release of the Portal 2 SDK. I’d tried this thing with combining timescale modification with the game’s zoom function (an FOV slide, effectively) but it was a pain in the butt. There’s also a quirk in recent versions of Source that makes 2160p unavailable when using triple buffering, and let me tell you it took ages to figure that one out. Finally, there are the extraordinary gymnastics required to get Chell in shot through the thirdperson camera. And the thing with her eyes… I don’t even want to talk about that.

What I hope the shots illustrate is Valve’s impeccable process for simply building a modern videogame. Here is a company that cuts corners like it’s sculpting a masterpiece – or so it seems when you marvel at the result. There’s no magic to Source, and actually, when you look at the Portal maps in the Unreal-powered Killing Floor, you realise there isn’t that much separating it, either. The difference is having the time, diligence and fortune to know what you want and how to get it, even if it isn’t obvious at the start.