Nice demo. I liked the sound effects and animations. The scenery looked good.
Recommendations:
- Fix the camera, as it goes behind walls.
- It's best not to make 3D platformer controls so slippery, as it increases the difficulty and some of your platforms are tiny.
- Wasn't sure how I died. This should be more obvious.
- Coins reset, but the tally doesn't.
- Timer is a bit harsh.
- Music.
- Moving clouds were distracting, I'd remove them.
It's a great start, but needs some work. Good luck!