We talk a lot about value when it comes to video games. Is Mirror's Edge worth £40 when its single-player campaign can be completed in about seven hours? Is Call of Duty: World at War? Is the PS3 exclusive downloadable Challenge Rooms game pack for BioShock, and free premium theme 2K Games has thrown in to sweeten the deal, worth £6.29?

The question is both yes and no. Yes if you absolutely loved 2K Games' BioShock. And we mean absolutely loved, because this is fan service in the extreme. When you first access one of the three challenge rooms a disclaimer of sorts presents itself. The game tells you that what you're about to play has nothing to do with BioShock's famed story, and isn't an extension in any way to that. It doesn't open up new areas of underwater city Rapture, seen through the bubbly waters that surround the dystopia but not visited in the main game, nor does it reveal the background to one of Rapture's demented citizens merely touched upon previously, perhaps through an extra campaign chapter. Rather disappointingly, it does none of these things, and the game almost apologises for that fact before you even begin.

Instead, the three challenge rooms should be taken for what they are - something on the side, a different dish cooked with the same ingredients - and nothing more. There are no well-placed audio logs to pick up, no striking scrawl on the walls detailing the trials and tribulations of a paradise gone mad. This is BioShock's gameplay stripped down to its essentials, displayed naked for all to see and prod.

The emphasis then, is on what most players eschewed with the original game - puzzles. One of the reasons BioShock was for so many the best FPS of 2007, trumping CoD4 and Halo 3, was because it required you to use your little grey cells almost as much as your trigger finger. Plasmids allowed you to manipulate your enemies, the brilliantly designed Splicers and Big Daddies and the environment itself, but you were never forced to play the game this way. Indeed, one of BioShock's main flaws was that it could be played, and beaten, fairly easily simply by pumping stat bonuses into the wrench attack. That won't work with the challenge rooms.

You'll need to rescue a Little Sister in every challenge room

Take The 'I' in Team, one of the challenge rooms, for example. Here, you need to defeat a single Big Daddy in order to rescue its Little Sister. In BioShock you'd probably hit it with a few electro bucks from your shotgun, or freeze it with a plasmid before pelting it with armour-piercing bullets. You begin this challenge room with nothing. Absolutely nothing. We're desperately trying to avoid spoiling the experience, since merely mentioning what plasmids, weapons and enemies you come across will detract from the fun of discovering it all for yourself, but we will say that the various mini-puzzles in this challenge room force you to play BioShock in a very different way to what many will be used to.

A Shocking Turn of Events is another puzzle-heavy challenge room. Here you need to activate a switch six times with electricity in order to get a Little Sister down from a broken Ferris wheel. The trick is that you only have a finite amount of resources, and so simply blasting the switch with repeated hits of plasmid Electrobolt isn't an option. The opening puzzle sets the tone perfectly - you're stuck in a room with no way out. Through a window you can see a Vita-Chamber. The only thing you can interact with is a broken switch. How do you progress? We'll let you work it out.

If The 'I' in Team and A Shocking Turn of Events focus the mind on solving puzzles, the third and final challenge room, Worlds of Hurt, is a return to the more action-oriented gameplay experienced in the main game. Here, a Little Sister is trapped in a room surrounded by eight doors, each leading to a self-contained challenge that pits the player against different opponents of varied difficulty. All BioShock's vending machines are available, and you're granted all of the game's weapons after completing the opening challenge, but cash is scarce, as is Adam. Your skill at managing resources is tested here, as much as your knowledge of what works best against Rapture's many enemies.

Returning to the point posed at the top of the review, is the DLC worth £6.29? While A Shocking Turn of events and The 'I' in Team won't take you much more than an hour to complete on the normal difficulty, Worlds of Hurt should keep you going for a couple of hours at least. For many, there won't be much gameplay left to eek out the DLC once you've rescued the Little Sister for the first time in each of the three challenge rooms, but for others the fun won't stop there.

Trophy hunters will be pleased - they're rock hard.

Trophy hunters will be pleased to discover that the DLC brings with it a new set of Trophies - four for each challenge room. You'll get one for finding all of the well hidden roses dotted about each challenge room, as well as completing each of the challenge rooms on any difficulty, as you'd expect, but the unique Trophies specific to each challenge room have us most interested. The 'I' in Team, for example, awards a bronze Trophy for rescuing the Little Sister without blowing up any machine gun turrets, which on face value looks ridiculous difficult. Charging up the Ferris wheel nine times in A Shocking Turn of Events is equally bemusing, and rescuing the Little Sister in Worlds of Hurt in under 15 minutes (a timer displays on the HUD) on medium or higher difficulty seems at this point an impossibility. If you like this kind of thing, getting all of the Trophies is going to take some serious time, skill and brains.

The DLC also brings with it a change to the main BioShock game hardcore fans are sure to appreciate: the new game plus feature. It lets you start a new game with your character data, including weapons and plasmids, carried over from your last completed game, which should make the PS3-exclusive Survivor difficulty much more manageable. But this addition is really only for the hardcore BioShock fans.

Which sums up the DLC well, really. For those of you not bothered about Trophies it will feel short. And for those of you looking for more story or weapons to play with, or even an alternative to the main game's disappointing final quarter, you'll be left wanting. But for those of you who absolutely loved BioShock, who, more specifically, simply loved how it worked, so much so that you took the time to explore every plasmid, every weapon and every gene tonic to its fullest, preferring to defeat enemies with Rapture itself than with bullets, then the £6.29 is unquestionably justified.