Abstract: Gaming apparatus (100) including (a) a symbol display area (224), which displays a plurality of symbols; (b) a symbol selection component (300), which selects symbols from amongst a predefined set of symbols, and arranges for them to be displayed on the symbol display area; (c) a win-indicating component (302), which indicates a win when the symbol display area displays a pattern of symbols which includes a winning combination according to preselected rules; (d) a bonus-indicating component (304), which indicates a bonus substitute period when the symbol display area displays a pattern of symbols which includes a bonus-triggering combination according to preselected rules; (e) a substitute symbol insertion component (306), which arranges for insertion of one or more substitute symbols into the symbol display area when a bonus substitute period is indicated; wherein the insertion of substitute symbols into the symbol display area improves the probability of a win.