As someone with like 500 hours on Slay the Spire, that was a really fun experience. I really like all the processes and card's names, really creative! I also really liked the fact there were multiple upgrades possible for cards.
I encountered a bug I think that would show my hand as being unplayable if I had no energy, even if I could still play 0-cost cards, but that was just visual. Another time I couldn't because of a time-eater effect on the boss, and I did not notice it until too late, so I'd say some stuff could be a little clearer, but damn that's a very impressive game for just one person in a week!
Thanks for your submission and good luck with the jam!