A gaming system includes a gaming machine and game-logic circuitry. The gaming machine includes a display device configured to display (i) a symbol array comprising a plurality of symbols and (ii) a modifier array comprising a plurality of modifiers. The game-logic circuitry is configured to select, for a plurality of rounds of populating the symbol array with symbols, a subarray of the modifier array. The selected subarray is displayed by the display device. The game-logic circuitry is further configured to generate, using a random-number generator, one or more random numbers to determine an outcome of a round of the plurality of rounds, modify the subarray in response to the outcome of the round including a selection symbol, and apply, in response to a trigger round of the plurality of rounds, the modifiers of the subarray to an outcome associated with the trigger round.