US Patent 7195559 Slot machine with dynamic wild symbol feature

A slot machine conducts a wagering game in which a plurality of arrays of symbols are successively displayed. Each array may, for example, result from a free spin of a plurality of symbol-bearing reels. In each free spin, the reels are rotated and stopped to place the symbols on the reels in visual association with a display area. One or more of the symbols of each array are designated as wild. Payouts for the successive arrays are awarded according to a pay table. In one embodiment, the plurality of arrays are successively displayed during a bonus game triggered by a start-bonus outcome in a basic game.