The art style looks good! the character is charming. hitting the nail felt really fun, I loved the sound and the impact.
A common problem I faced was that the game spawns the nail sometimes in an impossible to reach area like this:
and then I have to restart and lose a life for something out of my control. another issue is that the first hammer hit every stage goes through the block without propelling you upwards, which can feel frustrating.
I love the idea, and when the stars align and the generation creates an interesting level it really shines.