Cute design. Well done with the level generation! Few things indeed to address.
All the money you have is only from the last run. It was frustrating to discover that you lose that money. When I had 4 skulls and 800 gold i had to go for another run so I had 5 skulls. That just felt weird
The corridors between rooms are too narrow. I don't know if that was the intended but this way there was no strategy with fighting. Which is shame because the charging mechanism is really nice
Lastly what were those things you can buy in level 7 and 8. I didn't felt difference