I love the art and music but the gameplay feels a bit off. The speed of the enemies coupled with the slowness of attack charging and inability to move while attacking makes it feel like the only viable option is to kite them around the room then sit in one of the bottom corners letting them run into your attack. And because the attack hits above but not below, being at the top of the screen feels like a straight up misplay. I saw in the other comments you mentioning that it gets better after a few upgrades but I think you'll turn a lot of people off before they get that far. I'd suggest either tweaking the current attack (speed it up or allow some movement) or adding other attack options that fill in the gaps and make combat a bit less one note.
Outside of the combat I do like the structure of the game, the progression and risk/reward of choosing to go deeper or start over are great ideas!