For starters, when I say you run to the right, I mean it. You run at a constant pace constantly. You cannot stop, turn back, go slower or go faster. This give the impression you are fixed and the obstacles in your path come at you. Each of these obstacles must be avoided by a series of finely timed jumps, blocks, kicks, slides and leaps and there is really not much of an option on how you get past a particular series of obstacles. If you fail to avoid anything attempting to block your steady trip right--even once--you go all the way back to the beginning of the level, which can be quite a ways in some cases.
On the surface, this makes Bit.Trip Runner sound terribly difficult but in reality most levels can be beat in a half-dozen or a dozen tries once you get the hang of the controls. Now, having to try levels so many times would be obnoxious in many games but here you get to restart almost immediately, which lessens the frustration at repeatedly losing immeasurable. Furthermore, typically some of the most difficult obstacles of each level are presented right at the beginning so you don't have to go through a bunch of boring easy stuff to get to the hardest parts so once you've mastered the beginning of a level, the rest of it is a breeze. There are a few unpleasant difficulty spikes here and there but overall Bit.Trip Runner feels pretty much fair.
In addition to the quick restart upon death, this is a game that also draws you in w/ its music. They soundtrack is nice enough but the really engaging this is how your play affects what you are hearing. Each obstacle you avoid or each item you pick up plays a note and these notes sting together to form something of a melody. Additionally, players can pick up crosses that cause the level of the music to rise in intensity and complexity if they are collected (but seem to have no effect on gameplay). When the tune gets really jumping it's because you've been playing well and are avoiding lots of obstacles. It's a real thrill to have the music going full blast at the end of some of the tougher levels.
There is something about this that reminds me quite a lot of Guitar Hero and other rhythm games. The game sets the pace and really there's only one way to perfectly execute each level. Like Guitar Hero, you can play w/ just the visual cues but you're really missing out on the whole experience. Overall, it works very well and Bit.Trip Runner is a wonderful take usual platforming experience.