Practical shooting, also known as dynamic shooting or action shooting, is a set of shooting sports where the competitors are trying to unite the three principles of precision, power and speed, by using a firearm of a certain minimum power factor to score as many points as possible during the shortest amount of time (or sometimes within a set maximum time). While scoring systems vary between organizations, each measures the time of which the course is completed, with penalties for inaccurate shooting. The courses are called "stages", and are shot individually by the shooters. Usually the shooter must move and shoot from several positions, fire under or over obstacles and in other unfamiliar positions. There are no standard exercises or set arrangement of the targets, and the courses are often designed so that the shooter must be inventive, and therefore the solutions of exercises sometimes varies between shooters.