This is a very strange place for sure! I like the theme of the different areas and how it feels you're progressing deeper into the stomach. The combat is fun but difficult, I had to retry multiple times to get to level 3. Great music too, it really adds to the intense combat!
I did encounter some bugs: The grenade launcher pucks didn't explode or damage enemies at all, and in level 3 after the moving platform section there was one rotten tooth I couldn't drill and got stuck there.
I would suggest improving the air manoeuvrability while jumping, I found it hard to control especially for the platform section. I also think adding a rapid fire weapon would be cool as your game is very movement based, and it's hard to fire the ray gun while moving.
Nice work!