A bonus game controller is disclosed for use with a plurality of gaming machines in networked relationship with the bonus game controller. The bonus game controller comprises a trigger determiner arranged to determine whether a bonus trigger signal has occurred at a gaming device. The bonus game controller is arranged to implement a first bonus game when a bonus trigger signal occurs at a gaming device, and also comprises a bonus prize allocator arranged to allocate a bonus prize to the gaming device based on an outcome of the first bonus game and based on one or more respective outcomes of at least one other subsequent bonus game implemented within a qualification period. A gaming system including a plurality of gaming devices and a game controller is also disclosed. A corresponding method is also disclosed.