Neat concept. The most obvious complaints I had (no card preview in deck builder, lack of feedback) are almost certainly things that you didn't have time to do. Each of the three times I tried it, I got stuck at a stalemate (I guess I think about at the same level as your AI). Some sort of mechanic where you lose one HP if you attack and do no damage might be an easy way to fix the issue, or just some way to forfeit a match.
Certainly an ambitiously-scoped game. I'm impressed by how much you managed to get done in the time.