Game was a lot of fun to play. It fits the theme really well, the controls felt good after a while.
I think the pace leads to a lot of button mashing. If you slowed the enemies down and made the map more spaced out, it'd give the player more opportunity to manoeuvre instead of staying still and spamming attack. There were times when I lost hearts, but didn't know how.
You should definitely add some music.
A very minor recommendation is that instead of throwing a hammer, it'd made more sense if the player was shooting projectiles like arrows at the enemies.