Thanks to the FAQ https://trac.wildfiregames.com/wiki/FAQ#Gameplay and to the very length discussion here:  I finally have an idea about what the nebulous resistance levels do. Which raises the question: Why is it so complicated in the first place ? I don't think that many people know what those values mean. How about dropping the resistance levels and the obscure exponential calculation and just use percentages that everybody understand? E.g. 10 hack attack on a unit with 5