Thank you for your feedback! Glad you enjoyed it!
The coins were directly inspired by the need for a shop to avoid death. I made sure to put them in the places I wanted you to go, minus a few. And also the fact that prices rise after purchasing, so you're always risking a jump for more coins.
The difficulty might be because every time you die, it speeds up. And it gets a bit unmanageable at time, I agree.
The point in the 3D level is that the camera has a wall that pushed you off, so you want to stay way ahead of it, but that also means that you don't see much (even less with the resolution). I think a lot of people agree that the 3D levels are a bit hard to play because of that. So I'd definitely try something different in the future