It is a solid basis for a game with more depth!
However, I got kind of bored after the first fights, because it became really too easy and the animations made the pace extremely slow. I only played Jasper and Velrach, but as others have pointed out, Jasper seems pretty op with a few powerups that weren't even particularly rare if I remember correctly. Maybe other characters are op as well, but I didn't have the courage to start all over again.
Here are my suggestions :
- Balance the game. Some abilities are way too strong/too cheap. One obvious example for me was the "get 3 mana when you steal a 1-mana enemy" (I thought "Well, I will just be able to keep attacking all game and never end my turn ?", and yes that was it.). I know you talked about "breaking the game", which is kind of fun, but it happened way too early to be enjoyable for me.
- Make the animations trigger faster the more powerups you have. Having to wait for all these +x damage (even as overkill) killed the pace of the game and made it really painful to get to the end.
- Make the enemies more unique. I would actually like it more if there were only like 5 enemies, but with very different behaviors/abilities. When I played, they all looked like plain numbers to me (even if the art is kinda cool).
- Make the gold loots move or disappear. Currently, the amount of gold you get seems purely random and you don't have any influence over it. If the coins were to move to other cards or disappear after the first turn, you would really have interesting choices to make (prioritize winning or earning money).
That's it! It was pretty good though and upgrading to a more interesting game seems like it might not be that difficult now that you've done the hard work.