The Wisp Gauge, also called the Boost Gauge, is a game mechanic that first appeared in Sonic Colors. It is a variant of the standard Boost Gauge which measures the remaining time for a Color Power.
The Wisp Gauge is a bar that appears on the heads-up-display in the respective games that will be instantly filled when utilizing a Color Power. For as long as the Color Power is active, the Wisp Gauge will deplete and when it is empties, the Color Power ends. However, not all Color Powers drain the Wisp Gauge at the same rate: the Cyan Laser and Orange Rocket drain it almost immediately while the Yellow Drill, Pink Wisp and Blue Cube drain it much slower.
When a Color Power is in effect, the player can collect Wisps of the same type that is currently used to replenish the Wisp Gauge and extend the Color Power's duration, though certain Color Power's lets the player replenish it in other ways. Certain elements for different Color Powers can also freeze the Wisp Gauge completely, like destroying enemies or gimmicks such as the Underground Pipes, Optical Cable, Cannons and Ring Dash.
In both versions of Sonic Colors, the Wisp Gauge doubles as both itself and the Boost Gauge since the Boost is considered a Color Power too. However, its design differs between the versions of the game.
In the Wii version of the game, the Wisp Gauge is a horizontal blue bar in the lower left corner of the screen with a stylized circulator on the left that displays the Wisp in the player's possession. In the Nintendo DS version, the Wisp Gauge look like the Tension Gauge, resembling a vertical stack of arrows on the left side of the screen with a blue bar on the left side and the "Wisp Icon" on top.
In this game, the Wisp Gauge looks like it did in the Wii version of Sonic Colors, except its blue bar is thicker and its stylized circulator is smaller.
Sonic Lost World
In both versions of Sonic Lost World, like in Sonic Generations, the Wisp Gauge appears whenever the player uses a Color Power and disappears once it wears off. Once again though, it is given a different design for each version.
In the Wii U version of the game, the Wisp Gauge is a round circle in the upper right corner of the screen with a yellow bar inside it that occupy most of it, except in the center. In the Nintendo 3DS version, the Wisp Gauge is very similar to the one in the Wii version except that it is located in the lower left corner of the screen, has a icon in the middle for displaying the Wisp in the player's possession, and its bar is segmented.
In Sonic Runners, the Wisp Gauge looks exactly as it did in the Wii U version of Sonic Lost World. The Wisp Gauge appears next to the playable character on the screen when using a Color Power and will disappear once it wears off.
↑Sonic Colors (Wii) European instruction booklet, p. 18.
↑Sonic Colors (Wii) United States instruction booklet, p. 14.
↑ 3.03.1Sonic Colors (Nintendo DS) European instruction booklet, p. 8.