As is typically the case with any new puzzle game I play, it took me an unreasonable amount of time to grasp the mechanics (or rather the logical ideas resulting from them). I took just as long on the later levels as I did the first 10 or so. Pretty thankful for the comprehensive introduction section! I'll hold back on praising the rest of the puzzles; to do so would be to spoil some truly remarkable ideas.
I would comment on aspects of the game not pertaining to my own experience, but it looks like HuskyManiac beat me to it. Ditto all he mentioned, couldn't have said it better myself. This game is the epitome of hidden gems, highly recommend to all puzzle enthusiasts.