Shifting side reels into reel area for electronic gaming device

Innovations in user interface ("UI") features of an electronic gaming device, and in features of backend processing to implement the UI features, are presented. For example, control logic selects active reels, which include side reels and main reels. Compared to the main reels, the side reels typically include symbols of greater interest to a user. The control logic also selects a subset of the active reels. The control logic spins at least some of the active reels on a display screen of the device. The control logic shifts some active reels into a reel area while shifting other active reels out of the reel area, before stopping at the subset of the active reels. Reel shifting can increase game volatility while maintaining a designated level of return to player. At the same time, by selecting side reels and reels within the reel area when shifting stops, outcomes can satisfy regulations.