I enjoyed the art quite a bit, but there's so much more to explore here mechanically. Things to explore include new abilities, multiple dice, loaded dice (biasing certain values), or having low rolls be useful too.
As for playability, my main feedback is that the heal/superdice buttons should be "disabled" if you don't have enough juice to use them. And the defend button should be rebranded to imply it grants you juice. I had to learn about this by reading the instructions outside of the game :O
I'd be curious to see this concept extended to a larger scope with some of the richer mechanics.