X-Mercs: Invasion is a sci-fi strategy game. It involves taking control of a military squad whom you must lead into battle against alien invaders. You are dropped into scuffles by a snazzy looking airship, and the ensuing combat plays out in turn-based fashion on a virtual grid.

Once you've completed a fight, you can return to your base to upgrade squad members, research new weaponry, and monitor the global situation from your command room.

If this is all sounding weirdly familiar, then you've probably played X-Com: Enemy Unknown, a game to which X-Mercs undoubtedly owes a sizeable creative debt.

There does appear to be some subtle deviations from the X-Com formula, however.

For example, you can choose your allegiances, and even buddy-up with the aliens if you feel like humanity needs to be taught a hard lesson in interspecies relations.

You'll be able to download X-Mercs: Invasion from the App Store soon. In the meantime, check out the trailer about to experience an intense bout of déjà vu.