Play is shaped by what everyone expects everyone else to do, so the strategic environment is a moving object the rules do not describe.
The rules are fixed and the correct play is not, because the correct play is a response to the current distribution of opponents' choices. A strategy strong against the popular one becomes popular and is then countered, which produces cycles that no reading of the rulebook would predict.
In practice
- A deck that wins a tournament is beaten the following month by decks built to beat it.
- An interview technique that works becomes known, is prepared for, and stops working.
- Further reading
- Wikipedia
- Subject
- Play & Game Design
- Essay
- Small worlds with visible rules