Fun at first, but between level 7 or something and at least level 15, it's the same problem over and over (sure, positions change a little bit, but the method is exactly same). I wonder if it changes a bit later, but even if it does, it would be cool if some of these redundant levels were removed so people don't get bored.

Edit: level 17 is a little bit more interesting (albeit being the same thing) but level 18 and 19 aren't… Level 20 is the first one with 3 moves, so it starts becoming interesting again. Level 10 to 19 should really be summarized in just two or 3 levels.

Edit2: level 51 still has three moves. Three moves are more interesting than two, and most of those aren't too straightforward and repetitive (many aren't too hard, but some are a little bit tricky, which is cool), yet it causes a little sense of stagnation… I'm done.