An electronic amusement device and a method for operating the device are disclosed. In accordance with one embodiment, a slot machine identifies a tracked symbol and initializes a running count representing active occurrences of the tracked symbol generated during a play session. During the session, the slot machine generates at least one outcome represented by a set of symbols and determines whether the outcome includes an occurrence of a tracked symbol. The slot machine adjusts the running count, increasing the running count to reflect occurrences of the tracked symbol and decreasing the running count to reflect expiration of occurrences of the tracked symbol. Once the running count reaches a predetermined level, the slot machine determines a bonus payout based on the running count.