I would love to see this developed more! The combat system was interesting. I had a bit of a hard time figuring out the controls at first but once I got it I had fun. The music at the beginning is a little jarring but otherwise the sounds are awesome. The fireball card defiantly is super satisfying to use and I would love to see more offensive spells. And if you did expand on this maybe a way to build your deck before the level? A little enemy variety and maybe a boss.
I did encounter a few bugs. There's a card that lets you remove one from your deck but if that was your last card you're in a soft lock. The AI navigation tried to go through walls instead of around. And very occasionally the fireball would fire in the opposite direct that I put it down.
I also thought it was a little abrupt that the whole game stops when you hover over your cards. Maybe if the game slows down a little and the longer you hover the slower it gets. That way you can maintain the fast pacing of the game which was my favorite part.