US Patent 7841937 Slot machine

When a start condition of a payout variable game is fulfilled during a base game, depending on number of award-not-accompanied occurrence times of a specific symbol combination selected by a player at the beginning payout variable game to be executed a predetermined number of times at maximum, a number of credits to be paid out to an award-accompanied occurrence of the specific symbol combination during the payout variable game is varied depending on number of award-not-accompanied occurrence times of the specific symbol combination. Alternatively, a number of credits to be paid out at a termination of the payout variable game is varied depending on number of award-accompanied occurrence times of the specific symbol combination.