The fifth rule of the Codex makes a distinction most people never bother to make: the difference between a law and a habit. Reality is full of rules. A small number of them are physics — gravity, the speed of light, the impossibility of being in two places. Break those and reality breaks you. The rest are cultural, historical, imposed by people who are mostly dead and were mostly guessing. They feel just as solid. They are not.

The NPC obeys both kinds equally, because the NPC does not test. A rule is a rule. The way things are done is the way things are done. The constraint that came from physics and the constraint that came from someone's preference decades ago are treated with the same automatic deference, because checking which is which never occurs to anyone running on default.

A player tests. Before obeying a rule that costs something, the player asks one question: is this an actual constraint, or a convention dressed as one? Most of the rules that hem in a life turn out to be the second kind. The career path that "isn't done". The timeline you are "supposed" to follow. The permission you are waiting for from no one in particular.

The ones that bend are usually the most interesting, because everyone else mistook them for walls and stopped. Reality is more negotiable than you think. Not infinitely — the physics is real. But the line between the fixed and the merely accepted sits much further out than the default arc lets you believe. Find it by pushing.