Disagree with the premise. The purpose of Demeter isn't to prevent one class from mucking up the internal state of another, that's a side-effect. Its purpose

Disagree with the premise. The purpose of Demeter isn't to prevent one class from mucking up the internal state of another, that's a side-effect. Its purpose is to prevent one class from being coupled to the internal structure of another so that if you change one, you don't have to change the other. It stops code updates, not state updates, from rippling out. This is why the original formulation of the LoD didn't talk about instances, it talked about classes. You were only allowed to know about the surface-level structure of your neighbours, but anything else of the same class as your neighbours was fair game. So in the `player.Position.X` example, we actually don't have enough information to know if it's a violation or not: we don't know what class `player.Position` is, and we don't know whether it's a legitimate neighbour class. If there's another `Position` field somewhere in scope that's legit, `player.Position.X` is allowed, because we're already coupled to that structure, and getting to it via the `player` object doesn't add any coupling that wasn't there already.