A gaming machine having a display to display symbols at a plurality of display positions and a plurality of prize identifiers. The gaming machine also includes a game controller to cause a display to display a plurality of symbols at the display positions and visually moves a number of a plurality of prize identifiers at a first speed. If a trigger condition occurs with the displayed symbols, the game controller selects a prize identifier of the prize identifiers to be upgraded while visually moving the selected prize identifier being upgraded at a second speed onto the display. The game controller completes the upgrading on the display while the selected prize identifier is being displayed.