US Patent 7815504 Slot machine and playing method thereof

When a start condition of a special game is established during a base game, payout amount of credits for occurrence of an award accompanied by payout of credits due to a specific symbol during a predetermined number of times of a special game is varied in accordance with the number of rearranged specific player-selected symbols at the start of the special game. Alternatively, payout amount of credits when the predetermined number of times of the special game terminate is varied in accordance with the number of times of occurrence of the award accompanied by payout of credits due to the specific symbol.