Neat game. Very addicting. My best run is 6. I wish there was a way to get rid of cards, like throw away one card every level, since those +1 health basic cards don't help much later on when the enemy is doing 12 damage per turn, but not sure how it would be balanced because if you end up with only draw card effects in your deck, you could keep drawing forever until the enemy dies in one turn.
Good and fun game overall. I really enjoyed playing it. Well done!