Don't know where to start as most of what I want to say has already been said before... It feels more like a prototype, I like the level design and animations though.
My suggestions -
1) Add a looping BGM, the game is too bland without it.
2) Add a rules panel/ in game controls list. A new player doesn't know what to do.
3) The 'Collect coins to unlock a secret door' should be visible as the game starts as someone might just miss it (like I did at first)
4) The movement need some work, as other people already mentioned
5) I noticed a bug where if you keep dying and keep collecting 1 coin each time, the coins keep spawning but the coin counter disappears.
I read you had less time to work on the project, I have been in such situations in the past :D. It's okay if this project wasn't grand or how you envisioned, keep learning and improving that's all!