If you've never played it, cancel your plans. If you have, you'll be glad to know it's just as engrossing and exhilarating as the versions that preceded it on consoles, PC, and Mac. Best of all, it's priced at just $4.99, half what you'll pay for it on Steam and one-third the Xbox price.
It's not quite apt to describe Limbo as a side-scrolling adventure, though that's precisely what is. The game's gorgeous black-silhouette visuals may look reminiscent of Contre Jour, Vector, and World of Goo (all gems in their own right), but this is as much about atmosphere, story, and, believe it or not, emotion as it is about solving puzzles.
I'm hesitant to reveal much about how Limbo operates or what your goal is, as I think discovery is part of the fun. I will tell you that the mechanics are about as simple as they can be, requiring little more than strategic dragging of your finger.
The developer summarizes the entire game thusly: "Uncertain of his sister's fate, a boy enters Limbo." That's it; you know nothing else at the outset, when you awake in a nightmarish woods and must figure out what to do next.
Note that word "nightmarish." Limbo definitely has a creepy quality to it, feeling less like film noir and more like a haunted dream. And my feeling is that once you enter it, you won't want to awaken.
That's where I'll leave it. If you want to know more, or at least make sure this is five dollars well spent, I invite you to read "Happily getting stuck in Limbo," in which CNET authors Dan Ackerman, Jeff Bakalar, and Scott Stein dissect (and positively gush over) the Xbox version of the game.
I will say that although Limbo does feel a little claustrophobic on an iPhone or iPod, it's no less enthralling. Do yourself a favor and don't miss this gem of a game, which I suspect will quickly earn a spot on many a "Top iOS games" list.