Since the numbers on enemies keep changing every playthrough, is every fight winnable? Does it calculate the enemy numbers or is it random and sometimes there is no way to win?
Because this is a roguelike, you have to be careful about your card choices every time you get one, or indeed you may end up in an unwinnable position.
the way math works, it should be statistically likely that you are able to win each fight, especially if you know how to use the sword to essentially get free add/subtract operations.
