Role-playing game system

A role-playing game system is a set of game mechanics used in a role-playing game (RPG). A game system is roughly analogous to a game engine in the video game industry.

The system can take any of several forms. Generic role-playing game systems, such as the "d20 System" and "GURPS", are not tied to a specific storytelling genre or campaign setting and can be used as a framework to play many different types of RPG. Others, such as "Dungeons & Dragons", are designed to depict a specific genre or style of play, and others, such as the first and second editions of "RuneQuest", are not only genre-specific but come bundled with a specific campaign setting to which the game mechanics are inseparably tied. Some systems, such as the "D6 System", are refinements of those used in earlier games.

Most role-playing game systems involve rolling dice in order to introduce a random element into the process by which success or failure in an action is determined. Usually, the total of the numbers on the dice is added to an attribute which is then compared to a difficulty rating, or (as in World of Darkness games) the attribute is used to determine the number of dice rolled, and the number of successes (die rolls above the difficulty rating) determines the degree of success. Some games use a different randomising element, such as Castle Falkenstein, which uses playing cards.

However, some games such as the "Amber Diceless Role-playing Game" use no randomising element at all. These instead use direct comparison on character ability scores to difficulty values (which may themselves be derived from the ability scores of other characters), often supplemented with either resource pools from which points may be "spent" and "regained", thereby allowing characters to use more or less effort (as in "Nobilis"), or choice mechanisms of a rock-paper-scissors variety (as in the "Lost Worlds" gamebooks).