I do really like the videos when dying and switching levels, did you make them yourself? (I don't see any credits for assets used so congratz on that).
I did find that the game was a bit too simple/tedious for my taste, I'd have liked a bit more challenge and less just moving sideways for thousands of pixels.
Also something that you could look into is improved character movement scripts, for a platformer that's really what people are doing 90% of the time: moving. I love how mario handles it: going up normally, like you do, then possibly have some hang time where if you keep up pressed, you stay at the same height, and afterwards going down with double the gravity, feels way more reactive.