Emergent Complexity
Complex interactions that arise naturally from a simple ruleset.
The opposite of innate complexity (in which complex rules need to be learned in order to play) and a desired property of a game. Arises when you have a simple ruleset from which complex interactions can arise.
Related to the idea of Emergent Gameplay in the context of strategy, another desired property of a game. See Emergence for the general idea.
References:
- The Art of Game Design - A Book Of Lenses (2nd Edition) by Jesse Schell (Chapter 13. Game Mechanics Must Be In Balance)