I think this is a great game (I think) with a lot of hard but fair puzzles. The four set of levels ups the ante considerably, but I found solving it rewarding.
But is the fifth set (in complete darkness) meant to be solvable? I recognized the first levels and I feel like I can get some distance in it, but it stops being fun when you are feeling around for each jumps that have become nigh-impossible. If it just how the game ends, that is a real letdown.