I'm wondering if there are only 4 thresholds of resistance:
immune
resistant
neutral
vulnerable

Or, is it like a number? The reason I ask, is I ultimately want to know what happens when someone who is vuln fire, gets an item or prep which gives resist_fire. What happens when someone with resist_fire gets a resist_fire prep? What about resist_fire and resist_magic against a fireball spell? Do these things stack/accumulate?

Thanks!