Super well-polished game! I'm surprised to see you were just a solo developer on this one, well done!
I think the concept is really cool, it's quite innovative to combine deckbuilding and dice throwing - it feels like something that should have existed for ages but this is the first time I've seen that mechanic. It's a double dose of randomness but never felt unfair.
There was a bit of confusion at first. I wasn't sure what to do when clicking on cards and clicking on dice didn't do anything, then read the description to see that dice need to be dragged onto compatible cards to play. An in-game instruction there would've been great. It also wasn't clear at first whose health/stats were whose, as there's no visual distinction between the opponent's health and mine. Last critique: my fight with the Leech felt a bit too long, I think they got lucky with high d20 rolls that took me a while to chip away at their health.
Overall, though, this really impressed me! Very nice work!