Sum is a set of roleplaying rules suitable for any genre or setting of game. Roleplaying games are often confused with their rules. In fact any roleplaying game can be played with any number of different rules. Rules should exist for two purposes: to help players roleplay, and to simulate the world in which the story takes place. This set of rules is designed to help players do both. It has similarities to a number of other rule systems, but emphasizes the fact that different characters in the game need to be roleplayed, and simulated, to different levels of detail.