In accordance with some embodiments, an online game server provides a reel-type slot machine game interface that is modified over a course of a game and wherein the game includes a bonus feature that is triggered once a sufficient number of special symbols (e.g., scatter symbols) are accumulated by a player. In accordance with some embodiments, in order to qualify for the bonus feature, the special symbols need to be accumulated as a result of a single wager and original spin and any cascades that are triggered by an outcome of the original spin.