Complexity Trees and Pruning: Control How Quickly Possibilities Branch
Technical terms: Complexity tree, Bushiness, Pruning
A complexity tree represents possible choices and their consequences as branches. Bushiness describes how many plausible branches appear at each point. Pruning is the process by which players or rules discard branches that are illegal, obviously weak, irrelevant, or inconsistent with a plan.
An activity can have simple rules and enormous bushiness. Expertise often looks less like calculating farther and more like recognizing which branches do not deserve attention.
See it in word construction
From one letter, thousands of words may be linguistically possible, but endpoints, available space, theme, crossings, dictionary setting, and the maker's emerging composition prune most of them.
What you can do with it
Give players useful filters. Too little bushiness makes decisions automatic; too much unstructured bushiness makes every move feel like searching a dictionary without direction.
Ask a player
What helped you narrow the possibilities without making the choice for you?
Nearby ideas
- Perceived action space — distinguish legal possibilities from considered ones.
- Cognitive load — limit what must be processed at once.
- convention — prune through a practical rule.
- Enabling constraint — create direction within abundant possibility.
Richard Garfield, Skaff Elias, and Robert Gutschera, Characteristics of Games (2012), discussion of complexity trees, bushiness, and pruning. ---