Wowwww, this felt like a professional release, so much polish and smooth gameplay. Great art and music. I found it really difficult (only ever managed to beat 1 boss before getting clobbered in the next round), but in a good "boss fight" way that felt like a proper challenge (nothing felt fiddly -- every death was my fault). Although maybe ramping the challenge over time might make it a bit easier for noobs like me :P
Dragging cards from the bottom is a super cool idea, having to quickly look back and forth to see what you have vs where the boss is on screen is a very unique experience that isn't something I've ever seen before. It injects a sense of urgency into your traditional deckbuilder. Very very fun, I'll be following you guys to see what else you come up with because this is *awesome*.