So begins the brief front story introducing the setup for Metroid Complex. That's not a typo really. In lieu of there being a proper 2D sequel coming from Nintendo's loins, and Konami's repeated attempts to mutate their Castlevania franchise in similar directions, it is left to developers Chair (through Epic) to endow Microsoft's current console finally with a game of familiar design. It's akin to slipping on a favourite T-shirt again after discovering it at the bottom of your drawer; you always loved it, but you had rather forgotten it was ever there to begin with.

Thankfully, the old mantra of not fixing something if it wasn't broken has been heeded here, and all the factors that make Metroid such a beguiling template to duplicate are present and correct. Opening sequence that shows all the weapons off before they are lost? Check. Free-form, explorable locations with off-the-track tunnels to clamber through? Check. Areas you can't reach until you find the appropriate weapon? Check. Occasional boss battles? Check. Ability to sequence break (to a degree)? Check. You can't fault Chair for not wanting to stray too far from what has proven to be popular in the past.

There are some new ideas brought to the table, however. Performing or completing various tasks earns experience points and, like an RPG, your character can level up and improve his stats throughout the game; these are carried forward to new games started a la Dead Rising, making the prospect of taking on the Insane difficulty level a little less daunting. Certain actions such as meleeing the guards instead of shooting them earn experience multipliers, meaning you can level up quicker, giving some depth to working out sequences of takedowns to maximise accrual. Reaching particular levels also imbues you with permanent characteristics, something especially important to note when considering a speed run.

Going in all guns blazing is often not the best option and the ability to sneak about, take down guards silently and avoid potentially large fire-fights by crawling in air vents (the scene in the canteen is somewhat amusing) gives variety to the strategic decisions you will make. Unlike Metroid, every enemy you face will be out to kill you. Although Shadow Complex works on a two-dimensional plane, some of the guard attacks come from in and out of the screen; the controls to return fire can be a little fiddly at times, but only really when your level is low. With sufficient experience behind you it becomes much easier to target them efficiently.

While the staple power-ups of missiles, double jump, turbo-speed, wall bouncing et al are included, there are also some new weapons to play around with, the most notable being the foam gun. Aim, fire, and a mass of gloopy, white gunge shoots forth and sticks to whatever it hits. Fire more at the same spot and it continues to build up. Aside from its most obvious use in assisting the navigation of the base, there are many more applications just waiting to be discovered. Chair has been quite clever in just what you can do with the gun, and it can be immense fun playing around with it and seeing what its possibilities are. Especially when linked to other weapons you might be carrying...

Shadow Complex offers four difficulty levels that are well balanced in their differences, allowing both novice and experienced Metroid players a good challenge. One secret that can be unlocked certainly helps when going through on Insane, but even then it's still a tough prospect. The map also doesn't show any of the items you can collect. With a small hark to Epic's major IP Gears of War, taking cover, picking your shots and targets wisely, and being patient are good tactics to remember. Save rooms are also well placed, meaning that, should you die, you won't have to replay too much of the game to get back to where you have been before.

The accuracy of the homage would be for nout if the game was all mouth and no trousers, but that isn't the case here. Shadow Complex induces the same compulsion to explore, to investigate, to just reach the next save room over before quitting. Then you change your mind, carry on and find you're still playing two hours later. Some of the item power-ups are hidden in quite ingenuous locations and there will be occasional fist-clenching moments when you figure out how to access them. Although not overly long, a first play through going for 100% will probably last eight to ten hours; you still get an awful lot of value for your money.

When first announced, there was some scepticism whether another development team could in any way pull off a Metroid-style game to rival the original. Now that it has been delivered, even the most die-hard, staunch Nintendo fan cannot grumble that Chair has achieved the almost impossible; a game that comes damn near to matching the pinnacle of that series, Super Metroid. Almost that is. Maybe it is just as well, the apocalypse may have occurred in other circumstances. Put simply this is one of the best games of 2009 and arguably the best game yet released on XBLA.