I really really really like the sounds and the art. One thing I hope you could implement after the jam is more visual feedback for each thing you do. (maybe card tweens a bit when picked up, some effects on hit, etc). Right now it just lacks that oomph, in each action you take. I'm a really big fan of slay the spire, and the mechanic you introduced was a great spin! I'm so glad you made the back side quite op, and not just -5 instead of +5 and anything like that.
I also think more weaker fodder enemies would be great. If expand upon this, maybe add some weaker enemies that are easy to defeat, but incentivizes the player to use some of their backsides before you face the elite.
Will definitely play the game again if it pops up on NewGrounds or something.
I enjoyed my time playing the game!