Exhausting all of them for the Master Electrician Trophy is the most satisfying pure puzzle in Challenge Rooms, and the choice of tactics and open design make saving time for the Expert Trophy a more cerebral exercise too. It's still a shame that some of the solutions are a simple matter of combing every corner of the level for items, or using the one genetic mutation available to you in a rather obvious manner.
The third Challenge Room, Worlds of Hurt, is a very different proposition, and closer to our expectations. Here the focus turns to combat, and carefully measured doses of the genetic experimentation and player resourcefulness that made BioShock's name.
In Worlds of Hurt, you have to free a Little Sister from a circular prison by besting the enemies in the eight chambers that surround it. You're given a large range of weapons after the first, but aside from that, you're drip-fed Adam (BioShock's genetic currency) and money to buy plasmids, ammunition and supplies, as well as picking up weapon upgrades and invention supplies as you go.
The rooms themselves - teasingly and usefully revealed under glass before you drop into them - have surprising variation and scale, pitting you against enemies of one kind or many, or in automated mazes of turrets and drones. On Easy level the enemies are a pushover, but you'll still have to be frugal with your ammunition and other resources.
On higher difficulty levels both brain and reflexes will be comfortably stretched by this brilliant, bare exposition of BioShock's multiple mechanics. Worlds of Hurt gives you the maximum amount of choice possible and forces you to exercise it with imagination and care. Unlike the puzzle levels, it's highly replayable, as you'll want to try out multiple strategies, possibly aiming for the Tough Guy Trophy which only allows you to use Plasmids, Tonics, the Wrench and the Research Camera - but possibly just for the sake of it.
Challenge Rooms is a short experience, but for the relatively small price-tag, it's intriguing, unusual and handsomely crafted. The signposting in particular is done with humour, flair and great sleight-of-hand, as you'd expect from the creators of the original game. You'd also expect it to be gorgeous, and it is - the new settings have all the wrecked glamour and unsettling Deco doom of the main game, with superb, cinematic use of lighting in particular.
But Challenge Rooms doesn't quite live up to its potential. With the Plasmids and Tonics, 2K Boston created a vast, unique and immensely powerful toolset for this kind of condensed, thinking-man's-shooter - but it hasn't figured out how to fully exploit them yet. The puzzle rooms are a drop in the ocean, featuring only a couple of basic, prescribed examples. On the other hand, Worlds of Hurt doesn't have the focus to force players to think laterally and dig the most out of them.
By contrast, Valve's Portal took one tool and extrapolated its potential with devastating and sustained brilliance - leaving just enough room for players to come up with multiple solutions along the way. In its two puzzles especially, Challenge Rooms feels like no more than the first, hesitant step to evolving something similar for the BioShock universe - something we still believe is entirely possible. We hope this isn't the last we see of the concept.
7 / 10