Yeah, the collisions were probably the hardest part to figure out and fine tune. I've had to go back and forth quite a bit with my artist, whom I had only told to "draw a level," and that "I'll figure the rest out." Probably not the best idea in hindsight, but I think it was the only way we could've finished this game on time. All the art in the game took about 80% of the dev time, so I couldn't really add much more.
Thanks for playing!
Quick edit: the collisions in the last level are actually fully 2D, while in the rest of the game every scene is three-dimensional, everything is mapped out with 3D colliders and rotated at a 45° angle.