A reel-type secondary game is played simultaneously with a conventional reel-type main game on a gaming machine. The secondary game is initiated only after the player meets certain criteria, such as betting additional credits. Once the secondary game is initiated, one or more special symbols are added to the leftmost reel and the rightmost reel used in the main game, but not the reels in-between. The added special symbols do not affect the symbols used in the main game. All the reels containing the symbols used in the main game and the one or more special symbols are rotated and randomly stopped. Awards are granted for winning symbol combinations obtained in the main game. If the special symbols align with a certain stop position, a special bonus game is played or the player wins a progressive jackpot.