First off, THIS GAME IS SO GODDAMN AMAZING. Unfathomable amounts of content and level space for something that's free, and all the secrets and jokes in the game are fantastic. I've played through a majority of the entire game and I've finished it, I've gotten to Omphalos and gotten the infinite piss mask.
I do have some complaints though, my biggest one being that it is WAY TOO EASY TO GET SENT OUT OF BOUNDS. I'm chilling in the arcade level and this hat-wearing worm thing throws some bombs at me AND I IMMEDIATELY GO FUCKIN FLYING OUT INTO SPACE, which of course, is mildly frustrating at best, but with the way the game works, it's worse than it should be. In short, I don't entirely mind getting thrown out of the map, but the consequences are massive. First off, your progress in that level is forfeit. Unless you can somehow use the trampoline and the boost to put yourself back within the level bounds at a speed low enough that you don't just go through the floor, you will have to be transported to a different level. Secondly, and most frustratingly, your momentum gets saved when you transfer levels, SO EVEN IF YOU GO TO ANOTHER LEVEL, YOU'RE JUST GONNA GET SENT RIGHT BACK OUT OF BOUNDS AGAIN, which is extremely frustrating. This can really fuck with you when you're transported to the 'Below Water' level, since the water plane that covers the level is so thin that it's extremely easy to fall right through it. This has happened to me on numerous occasions, and while it's not a complete softlock, it's really frustrating to deal with. If you could fix this, I PROMISE YOU I WILL PLAY THE ENTIRE GAME AGAIN, BECAUSE I LOVE THIS GAME.
Side note: It fuckin hurt to read that "you won the game" sign cause I haven't found everything yet! The infinite piss mask is a giant reward though, that's so awesome.