A slot machine type wagering game having a bonus feature that is activated by a start-bonus outcome in the basic game. For example, one start-bonus game outcome may be the occurrence of a winning pay line in the base game array. Certain symbols on the winning pay line are replaced to create a bonus array; all other symbols in the bonus array remain the same, and in the same position, as in the original base array. The replacement symbols are randomly determined. Once the symbols are replaced, the bonus array is checked for winning symbol combinations on active pay lines. If the bonus array forms winning symbol combinations (i.e., a winning pay line), a second start-bonus game outcome may be triggered and the process continues until an array is created that does not form any winning pay lines.