Holy shit man, some of those levels were really god damn hard. I managed to get to level 16 (the chimney one), and that was just too much for me. It's very impressive that you managed to get that many good levels though, and have the game engaging enough to be playable for that long. I think the sound design was a huge part of that, as has been mentioned by other commenters. Overall, it felt really well polished. The only thing that was off was when the guy in the blue shirt didn't get impaled when I accidentally shot him.