This is really good! Overall the gameplay and design is great! I think if you keep working on this after the jam and give it that full game polish it could make a really great card game. Surprisingly well balanced for a jam game! My only issues were fairly minor for a jam game:
No real instructions inside the game
When selecting cards, the cards underneath are selected first. That means when trying to target a creature you have to click in the top/bottom portion which doesn't overlap with cards attached to it, which was confusing. I thought I couldn't target certain creatures until I worked that out!
I didn't know I could right-click the cards to see them so I was playing a bit blind for a while
Options menu button doesn't work