- Level can increase or decrease, but XP never decreases. Total XP indicates maximum level you can advance to.
- You can only advance a level when you return from an expedition to town or home base.
- You can only advance one level per expedition, even if your XP total indicates you could advance more.
- You can advance a level after any expedition, no matter how trivial, as long as you earn at least 1 XP and your total XP indicates you should be a higher level.
I might add one or two rules, but they cover some other ideas I haven't even addressed yet.