For the last three years, 2K Marin's take on the XCOM universe has been surrounded by all the mystery, fear and excitement of a UFO sighting. We last saw it back in 2010, coming back wide-eyed with wonder rather than filled with dread that the strategy of the '90s original was being lost in the first-person reboot. Despite the worries of the hardcore, and despite some of the skepticism from fans of the original, there's always been a spine running through 2K Marin's game that's indebted to X-Com creator Julian Gollop's original vision.

Now, with a shift from first to third person, that's more pronounced than ever before. You're guiding crosshairs over alien skulls, there are rechargeable health slots and the loud moments outnumber those trademark periods of eerie silence, but in every other way The Bureau is as much an XCOM game as Firaxis' brilliant Enemy Unknown. It's all about choices and consequences, and about how well laid plans can rapidly fall apart under a hellstorm of alien laser fire.

It helps that 2K Marin has taken so much from the game Firaxis made in the void created by The Bureau's protracted development. You head up a team of three agents, plucked from four recognizable class-types who come complete with their own perks, and who can be kitted out with bespoke loadouts. They're mortal souls, too - if one of them falls on the field and isn't revived in time, they're gone for good. It wouldn't be an XCOM game without permadeath, of course, which makes it all the stranger that it seems this was a feature only added after Firaxis proved there was an appetite for it in Enemy Unknown.

In the heat of battle, the appropriating's a little more explicit, the visual language taken wholesale from Enemy Unknown. There's a command wheel that's available at a button press, instantly pausing the action and offering a range of options. They're told in a familiar fashion: hover the cursor over cover and a blue holographic shield will pop up if you're sending them into cover that's effective, a red shield appearing if you're exposing them to danger.

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It's been borrowed, though, because it works - the quickfire strategy of The Bureau instantly snaps into place, its mix of cover-based gunplay and real-time tactics making sense soon after the first skirmish commences. Gunfights are snappily paced, with plans often needing to be conjured and executed on the fly, but play it all back to yourself and it's got all you'd expect from an XCOM encounter - taking the high ground will lend you an advantage, as will funneling two AI partners through the centre of a map while you quietly flank an encampment.

With a range of special abilities available (the commander's able to send aliens spinning up in the air with a Pulse Wave, while elsewhere an agent can summon enemies into the centre of the battlefield) there's a link that can be made to Mass Effect's combat, but really The Bureau feels like the breakneck strategy of Ghost Recon: Advanced Warfighter and Brothers in Arms engineered to run that little bit deeper. What's most important, though, is that it feels exactly like XCOM should, a winning formula thoughtfully transposed to a third person action game that's a little smarter than most.

There's a lot that lends The Bureau an identity of its own, though, and that's where it gets really interesting. Some of the alien design's been lifted from Firaxis game, true - there are sectoids and mutons here, all under the control of mysterious new race the outsiders - but the world is entirely 2K Marin's, and it's a fascinating, beautiful construction worthy of the team who breathed new life into Rapture with BioShock 2.

The timeline's been shifted from the '50s of the first pass at XCOM to the '60s, allowing for a slightly darker tint to the vision. You're William Carter, one of the very first XCOM agents who wears a permanent weary snarl, and who with his snappy dress sense proves that waistcoats really are this year's bow and arrow in the fast-changing world of video game fashion.

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The Bureau's take on '60s Americana is one full of fedoras and fear, where Cold War paranoia cuts as sharp as the lines on Carter's neatly pressed suit. There's a clear debt to Hollywood science fiction cinema of the time, Don Siegel's Invasion of the Body Snatchers clearly referenced in the mobs of infected sleepwalkers who stumble about the town of New Pima where the demo takes place.

Beyond that grander vision of an America that's all about coffee and pie served and with a side order of suspicion there's something else going on too. The Bureau's world feels exquisitely realised on a more minute level, with some smart writing working its way into the cracks between the action - which isn't exactly surprising, when you consider that Spec Ops: The Line's writer Walt Williams is helping call the shots here.

There are little notes left around the scenery, and little details dropped around the environment that are a delight to track down. "You may be able to take a sick day, but your sales figures can't," says one small slip of paper acknowledging the outbreak of illness in the sales office of a car dealership, suggesting that The Bureau's going to some interesting places, and that it's got a savvy sense of time and place.

How Williams engages with the sense of choice and consequence that's central to the XCOM brand remains to be seen, but it's a safe bet that they'll be tackled with the same brand of intelligence that helped elevate Spec Ops: The Line to something more than just another shooter. Right now thought, it's clear that this is very much the XCOM you love and know taken from a different perspective - and that should be more than enough to abate any residual fears.

UPDATE: Walt Williams has been in touch to clarify his position on The Bureau, and while he did work on the game for a short period in 2012 his input was minor as he helped 2K Marin's main team of writers.