A gaming system (10, 100) implementing a base game and a feature game. A game controller (101) controls play of the game. The gaming system has at least one display (14, 106) and a player interface (107). The feature game comprises at least one series of game events, in which a plurality of symbols from at least one predetermined symbol set that includes at least first and second symbols, are randomly selected and displayed on the at least one display (14, 106). The feature game is a challenge feature and during play of the feature game, the game controller (101) maintains in computer memory (103) counters for said at least first and second symbols, varies the value of said counters on the occurrence of the at least first and second symbols and causes the at least one display to show a value of the counters. The values of the counters are evaluated against predetermined competitive criteria to determine the outcome of the series of game events.