That was cute! A nice interpretation of the theme.
I liked the character's moveset. The hammer was quite fun to use. The coins piercing through enemies is a great touch; it makes the coins that much more useful.
The only time I was worried was when I got stuck in a pit of spikes on Level 3 and never died. Luckily, I soon discovered the restart key 'R'.
The layered text-to-speech effect for the antagonist is really good!! They're nicely designed, too.
My only concern is that a lot of the sound effects are quite loud, especially the coin pickup sound. The audio often peaks at +0.0 dB, and even reached +1.1 dB at the boss.
All in all, Great work!