A bonus game that operates in combination with a slot machine base game is provided. The bonus game includes a series of free spins or free evaluations in which symbols of a set of symbols are set to be wild symbols. Free spins occur for each symbol acting as a wild symbol until the symbol appears on the reels in a winning format, either alone or in combination with other symbols. Then, the next symbol of the set is used in the wild symbols and so on until all symbols for the set are used. If free spins remain after all symbols of the set are used, the free spin sequence is repeated until the free spins are exhausted.