This was super ambitious to try to make a full deck builder in a week, mad props for that - I'm impressed you managed it!
I think the mechanics need to be explained to the player better, though - I saw that below the enemy's health there's an attack number, but they don't seem to attack every turn, so I was a bit confused about how the enemy attacking worked? I don't know if that's a glitch or if I'm misunderstanding something, but I think copying Slay the Spire and just having the enemy's next attack value for that turn displayed there would be a good solution. I think some screen shake when the player takes damage would be helpful too (and perhaps a red overlay or something?) - there is screen shake when you do a big attack on the enemy but I found it hard to notice when I was taking damage.
Anyway, super impressive game and I think it has lots of potential if you polish it some more!