An electronic gaming machine includes a processor configured to control a display device to display a matrix of symbol positions and a bonus meter, where the bonus meter displays a bonus prize. In response to a bonus game trigger condition being satisfied, the processor is configured to control the display device to display a plurality of volatility options, each being player selectable and associated with a number of free spins and a multiple or another percentage of the bonus prize. A player selection of one volatility option is received, and a plurality of free spins are initiated. During each free spin, the processor is configured to control the display device to display a symbol in each symbol position of the matrix, evaluate the matrix to determine whether the matrix includes at least one free game scatter symbol, and if at least one free game scatter symbol is included, to add the multiple or percentage of the bonus prize to a credit balance of the player, whereby the multiple or percentage of the bonus prize is capable of being repeatedly added to the credit balance of the player during the first plurality of free spins.