Really loved the idea of this game, it made it so unique, and it was fun to spam my keyboard and have a purpose for it. I'm a fan of puzzle games, riddles and all that, but even for me some of the puzzles were hard to guess, mainly the references of specific things, like the films or the IQ ones (I also don't get the horse one, I guessed the answer, but it took me a while).
About the secret levels, yeah.. I got them, but I almost threw my pc out my window. I didn't get the first and for the second I had to do a bunch of stuff to get the audio reversed, no complains for the third tho, loved that one haha.
Overall, it was fun, a little bit hard, but fun. Even playing with more people, I don't think they'd had get some references either. Maybe a way to see more hints could help or make less specific references.
Thanks for making a game like this. My favorite level was the patience one, clever hahaha