I liked the art. I think the bosses felt more or less the same, as they just dealt damage and not much else. Its pretty clear the focus was put more on what the player can do. However, I found the card mechanics quite fun to play with, and the variance in cards helps add to that. I think if you want to continue this, my advice would be to make the player be able to save cards across turns, so you could do things like save good cards for another turn, and also have enemies interact with the cards (ex. poison apple guy poisoning some of your cards so they cost health to use) which I think could help expand the system even further. But still, the game is awesome! Great job.