From the introduction: Threshold 3d6 is intended to be a simple and fast roleplaying game that uses three six-sided dice (3d6) for most checks and for determining the result of random effects. It also has a focus around the number 3. Many things come in 3’s, including degrees of success or failure. It is intended to be a very straight-forward system that requires very little knowledge of existing game systems or system mastery to enjoy the game.