Sometime after last year's E3 demonstration of the XCOM reboot - a re-envisioning of a title many consider to be the best PC game ever made - the game disappeared. Martin Slater had resigned as studio head of 2K Marin, helping to fuel rumours of massive changes to the project, and the studio themselves offered a response akin to saying, "Changes? What changes?".

But the game reared its head at long last at E3, and as we sat down to a presentation in a room adorned with some impressively 1960s-related décor, we were finally told that - yes - there has been a change in direction. And yes, don't worry, while we're still looking at an FPS reboot of a classic turn-based title, the game is edging back to its roots and turning its focus to the strategic elements of the original.

You play the role of Agent William Carter, a member of the XCOM Division who has been put in charge of stopping an alien invasion that has hit Earth during the Kennedy era. Along with that responsibility, you are in charge of choosing which particular members make up your team, with each potential candidate having a skillset specific to their character class.

Players are given the ability to pick and choose which missions they take; missions that variously include reconnaissance, search and rescue and defense, alongside assignments that directly affect the overarching invasion story. You can undertake your tasks in any order you like, but leaving a job to undertake later may have a significant effect on the way it plays out. Ignore a rescue mission, for example, and you may show up to find a town under alien control.

The E3 hands-off demonstration took Carter and two of his agents to Georgia, USA, in a bid to track down a doctor who plays a key role in understanding alien technology. The aliens themselves - the Outsiders, they're called - are faintly odd-looking characters. Imagine something shaped like a humanoid but made largely out of shards of glass like a disco ball, and you get close. Some can mimic the look of other humans and take on their identity. Others are squid-like and fly through the air, grabbing hold of the unlucky.

Fighting against the Outsiders on the field takes a more tactical slant than originally expected. Carter can direct his team using Tactical View, essentially a way of slowing down time and choosing how your agents should react in combat, based on their particular abilities.

Using a power costs Time Units, which limits how many abilities can be used at any given moment - something that should ring familiar to anyone who played the original title. These powers include the ability to actually seize control of the alien tech you find. The right agent can access alien technology and use it to your team's advantage, either by bringing it back to your base hub to research it further, or to use it immediately against the enemy as a weapon. The latter tactic offers a potent way to turn the tide of a battle, but at the cost of long-term benefits.

The Outsiders themselves can also use powers, drawing upon their living technology. At one point the aliens protected themselves with a sizeable, bullet-absorbing barrier - a shield that was smart enough to adapt when Carter attempted a flanking manoeuvre. Certain agents have the ability to disrupt such problems, but your men will need careful protection if they're to work efficiently. Your agents powers have been designed in such a way that they can be chained together for maximum effect. One neat combo finds you shielding an agent, and then getting them to draw all enemy fire, allowing you to freely move to a more useful position. The need for solid teamwork was particularly obvious during the demo's climax, a dramatic set-piece battle against a Sentinel - the UFO-like craft that featured in last year's demo.

The project's narrative director, Jordan Thomas, hinted at a meatier subtext hidden behind the invasion plot - referencing the political nature of the era that mirrors the invasion, at a time when outsider movements were themselves first breaking into the mainstream of America. Whether this implies the game will be particularly heavy on narrative is still to be seen, but regardless, fans should breathe a sigh of relief that XCOM now seems a little more respectful to its turn-based roots.

XCOM is due for release on Xbox 360, PS3 and PC on March 9, 2012.