Ahhh really?! I know switching between worlds is a very popular mechanic even in big game titles too. It's such a neat concept. I am obsessed with the aesthetics for Paper Mario so if it was anything like that, I would have been sold :P I wanted to keep my character 2D so I could do the animations and drawings for it since I'm not a 3D artist, but I know I have seen some games mix in 3D environment with 2D characters!
I really wish I had more time to make more levels! I prioritized getting the controls UI since I didn't have time to do a tutorial level (the first one was supposed to be that with a walkthrough).