In game design, difficulty is the measure of time, resources or fortune required for a character to succeed at an action. Whilst a roleplaying game's core resolution mechanic covers the resolution of a typical action, games with difficulty rules can modify that base mechanic, to account for increased likelihood of success or failure in non-typical situations.
Roleplaying games use a variety of methods to increase or decrease the difficulty of actions, including:
- Increasing or decreasing the target number that characters must compare their results to;
- Adjusting the values of dice or cards with a modifier (commonly known as a "difficulty modifier");
- Manipulating the act of rolling dice or drawing cards - rolling more or less dice in a dice pool, optional or forced re-rolls, drawing extra cards etc. (see advantage);
- Altering the scope of what can and cannot be achieved within the fiction as part of an action;
- Applying increased or discounted costs of player resources (both fictional resources and metacurrency).
Some games only use one method to adjust difficulty, whilst others might use multiple methods, to distinguish between different kinds of difficulty factors.
The occasions that warrant the use of difficulty rules vary from game to game - some games include tables listing a great number of complicating factors and their effects, whilst other games leave such matters entirely to the GM's judgement, or only track the impact of difficulty in special circumstances.
For games in which combat is an expected part of play, typical difficulty factors for combat actions include the range of weapons used, an opponent's use of cover, and environmental conditions that limit movement or visibility. Social interaction tests often incorporate difficulty to reflect the disposition of a conversational partner, and the GM's judgement of how the player chose to roleplay. It is also common for games to increase difficulty if a character wants to accomplish multiple actions in a limited space of time (e.g. acting more than once in a round), or undertake an especially impressive action that will have a big impact on the narrative (e.g. attacking multiple targets). Many characters have special abilities that decrease the difficulty of specific types of action.
Whilst difficulty typically tracks the nuances of fictional situations, the term is also sometimes used to monitor the impact of meta-concerns upon action resolution. For example, difficulty can be modified based on a player's spotlight in that session, or how long it has been since their last successful action.