Maybe it turns into impossibly hard later on, but the first couple of screens are just a series of surprise traps that kill you on the first time but are reasonably easy to avoid once you've learned them properly (compared to this type of impossibly hard: http://www.youtube.com/watch?v=nscP9QpXoFM). If you look at this with Raph Koster's Theory of Fun (http://en.wikipedia.org/wiki/A_Theory_of_Fun_for_Game_Design), it's basically brain candy constantly telling you you've gained valuable skills by learning about new trap patterns in the environment, so I can see why it's compelling.
