This is really really cool! There’s a lot of clever ideas here, like the reversed coins, bullets and life counter. It’s a great touch that the music itself is in reverse as well.
I did encounter some frustrations with the unforgiving coin paradox mechanic, which while I think is conceptually very cool, does punish the player quite harshly for a small mistake. Jaco van Hemert suggested a paradox meter, and I agree with that solution!