The levels were nicely designed, It never felt like the game was being cheap, just hard.
The game slows down when lots of explosions happen at the same time and sometimes in that state the controls reaction also slowed down, It happened only in one boss battle, I think u can guess which one.
For those saying that it's too hard, you're not supposed to rambo. You better be careful and aim your attacks because you're slow as hell. Also you cant attack and inmediatly jump, so choose when to dodge.
Don't be scared of using your weapons, you get hearts before the bosses so no need to save them that much, just don't use the D button you will waste 10 hearts and it deals low damage.
Pick the book for the first boss and the pretzel for the others, the bottle and glove are hard to aim and the letter hits like paper (pun).
Anyways, awesome game, wish it was longer. It was nice to peek at the world throught kenji's eyes XD.