This was a lot of fun to play. The aesthetics and artwork were fantastic, and the SFX/music were satisfying and fit nicely. The level of polish for a 9-day jam game is really impressive. The only real issue I had was that it could be hard to tell which status effects were applied to the opponent and what they were even doing (I never did figure out what "vulnerability" did, exactly).
I managed to beat the boss on my second attempt (though it was close). I'd love to see an extended version with more cards, synergies, and strategy.