Systemic depth is the quality of a game system that supports multiple tiers of strategic operation: beginners engage at one level while experts play a different, richer game using the same rules. A game has depth when mastering one layer reveals the next. Sellers frames depth as hierarchical levels of play — a hallmark of systems that generate lasting engagement (Sellers 2018, see source-advanced-game-design).
Distinct from complexity: a complicated game can have many rules with little depth; an elegant game (few rules, many interactions) can have great depth. Bushnell’s Law captures the ideal: easy to learn, difficult to master. See systemic-depth-elegance.
Related: systemic-depth-elegance, emergence, game-balance, elegance, systems-thinking