For how cheap it is, this is a very good coop game. Especially the concept that you don't have to 100% every room to beat the game is quite interesting and provides replay incentive for achievement hunters. Some of the prequels certainly have better puzzles and it (intentionally) feels quite arcady at times, but it's a great journey nonetheless. Sure, it could have been a bit longer, but I just don't think that's what they were going for with this game.