Method of gaming, a gaming system and a game controller

An electronic method of playing of a game using a gaming machine, the method comprising:

• establishing a credit balance in response to a credit input of the gaming machine receiving a physical item associated with a monetary value;
• increasing and decreasing the credit balance based at least on a wagering activity;
• in accord with the wagering activity, selecting, via a game controller of the gaming machine, a plurality of symbols;
• displaying, via a display of the gaming machine, each symbol of the plurality of symbols at a display position of a plurality of sets of display positions;
• selecting, via the game controller, at least one modification condition from a plurality of modification conditions;
• in response to the plurality of symbols forming a winning outcome, determining, via the game controller, whether the at least one modification condition has been met;
• in response to said determining that the at least one modification condition has been met, selecting, via the game controller, a symbol set modification from a plurality of symbol set modifications, and modifying, via said game controller, the plurality of the symbols displayed at the plurality of sets of display positions, including interchanging the symbols displayed at a first set of the plurality of sets of display positions with the symbols displayed at a second set of the plurality of sets of display positions based on the symbol set modification selected from the plurality of symbol set modifications;
• awarding a first award based on the winning outcome;
• and
• determining whether to make a second award based on the symbols displayed at the plurality of sets of the display positions as modified.