One or more non-transitory computer-readable media storing computer-executable instructions which, when executed by one or more processors of an electronic gaming machine, cause the one or more processors to:
- cause one or more displays of the electronic gaming machine to display a first set of N first symbol positions and a second set of N second symbol positions, each second symbol position adjacent to one of the first symbol positions;
- conduct a defined number of reel spins in respect of the second symbol positions using a first set of index reel strips, the first set of index reel strips comprising (a) a plurality of regular index reel strips, each of which comprises an index symbol at least one reel strip position of the respective regular index reel strip, and (b) a plurality of prize increment index reel strips, each of which includes a prize increment symbol at least one reel strip position of the respective prize increment index reel strip, wherein, in a first reel spin of the defined number of reel spins, a reel strip position is selected for each second symbol position from a corresponding index reel strip in the first set of index reel strips, and in each subsequent reel spin of the defined number of reel spins after the first reel spin of the defined number of reel spins, a reel strip position is selected from the corresponding index reel strip for each second symbol position where the reel strip position selected for that second symbol position in any previous reel spin of the defined number of reel spins did not have the index symbol or the prize increment symbol, wherein:
- each reel strip position selected in each subsequent reel spin of the defined number of reel spins is selected from one of the index reel strips in the first set of index reel strips, and
- each index reel strip from which the reel strip position that is selected for one of the reel spins in the defined number of reel spins has the index symbol or the prize increment symbol is removed from the first set of index reel strips for any remaining reel spins of the defined number of reel spins;
- determine, at the conclusion of the defined number of reel spins, a composition of a prize wheel based on the number of the reel strip positions that are selected during the defined number of reel spins and that have the prize increment symbol, wherein each of the reel strip positions that are selected that have the prize increment symbol results in an increment of at least one prize of the prize wheel relative to a corresponding prize of a base prize wheel;
- spin and stop the determined prize wheel so that prizes of the prize wheel are displayed on the one or more displays of the electronic gaming machine at respective ones of the first symbol positions;
- conduct a prize evaluation based on each prize displayed at any of the first symbol positions that is adjacent to any of the second symbol positions for which the reel strip position that was selected during any of the reel spins of the defined number of reel spins has the prize increment symbol or the index symbol;
- and
- make a prize award based on the prize evaluation.