oncerules

Oncerules refers to a flexible concept used in hobbyist game design, puzzles, and some informal discussions about rules. It denotes rules or constraints that apply only once within a defined scope, such as a single game session, a round, or a particular puzzle instance. The term is informal and lacks a formal standard, with different communities adopting varying definitions and mechanisms.

In practice, oncerules are used to introduce temporary effects, exceptions, or strategic choices that add novelty without permanently altering the game's core rules. Examples include a one-time power that a player can use during a game, a clue that can be skipped once, or a conditional rule that applies only during the first round. In software or data processing analogies, an oncerule might describe a rule that is applied to the first input or iteration and then discarded.

Design considerations for oncerules include ensuring that usage is clearly tracked, balanced in relation to other mechanics, and easy for players to understand. Potential downsides include added complexity or ambiguity if the scope or triggering conditions are unclear.

See also: one-shot mechanics, single-use items, limited-use abilities, rule variants.