There's a subtle difference between a good game and a great game, and you managed to perfectly hit that. The writing is superb, the art is amazing, the levels are well balanced, gameplay is interesting and the mechanics start easy and go really deep. I played the game the entire way through, and thoroughly enjoyed doing so.
I try to always find a point of improvement for a games to make my feedback as useful as possible, but frankly there is nothing worth mentioning. Great job.