I like the concept and the art is fantastic. I wish we could just hit "enter" to submit the calculation instead of having to type and then click. I also initially found it confusing that negative values need to be rounded to zero and that it would flip which side of the screen the heroes and enemies stats were being displayed on. I also had an instance in the second level where I got an enemy attack calculation wrong, and that ended the fight as a hero win. That made me think I was supposed to intentionally get enemy attacks wrong.
Despite those issues, I think you did a great job and this is among the best looking games from the jam I've played.