Frustrating, but good.
Altogether, the game works pretty well. I hated Naaij's levels though, due to how close you have to be on quite a few of the areas. The last level in particular has a nearly impossible jump right after the beginning of the level. I understand adding difficulty, but I'd rather have a killswitch for areas like that and more difficulty in other areas.
Even so, it's not impossible to beat the game by any means, which brings me to some of the reviewers. Every badge is doable. If you need proof of this, look at my account. I've got every badge fom this game, and it didn't take me very long.