A few suggestions, besides the bugs and the problems with hitboxes:
-Make it clearer where the player has to go, so he doesn't feel lost;
-Playtest a lot your game. There's a level where you can't go further because the platforms are too hgih to jump on them, and the controls are still inverted from the upside down section;
-Focus a little bit more on the presentation. A game can have a wonderful gameplay, but it it doesn't look good, many won't even play it. So spend some time to have a better menu and clearer fonts