Abstract: In one aspect, an electronic gaming machine includes a game controller that executes instructions that cause the game controller to: (i) display a plurality of reels to form a matrix of symbol positions; (ii) simulate spinning the plurality of reels; (iii) display a plurality of player-populated symbol positions within the matrix; (iv) display a first player-selectable symbol of a sequence of player-selectable symbols; (v) receive, during the spinning, an add gesture associated with the first player-selectable symbol representing a request for addition of the first player-selectable symbol to the matrix; (vi) add the first player-selectable symbol to a first player-populated symbol position in response to the add gesture; (vii) simulate stopping each reel of the plurality of reels, the first player-selectable symbol overlaying a reel symbol at the first player-populated symbol positions; and (viii) evaluate the symbols displayed within the matrix to determine a game outcome.