The Boost Gauge (ブーストゲージ,Būsuto Gēji?), also called the Tension Gauge (テンションゲージ,Tenshon Gēji?) or the Ring Energy Gauge, is a reoccurring game mechanic in the Sonic the Hedgehog series. It allows the player to charge energy for the Boost and Fire Boost.
The Boost Gauge is presented as an energy gauge of varying design which appears on the heads-up-display in the games. For as long as there is energy remaining in the Boost Gauge, the player can perform the Boost/Super Sonic Boost/Fire Boost. Using these techniques drains the Boost Gauge though, and should it run out, the player can no longer perform them. The means of charging the Boost Gauge vary between games.
The Sonic Rush series introduced a specific reoccurring mechanic for the Boost Gauge, where it is dubbed the "Tension Gauge." When the Boost Gauge is charged to maximum capacity, it gains unlimited energy for a short time, allowing limitless usage of the Boost/Fire Boost during that time.
Sonic Rush series
In Sonic Rush and its sequel, Sonic Rush Adventure, the Boost Gauge is referred to as the Tension Gauge. It also uses the Tension Gauge mechanics, allowing unlimited energy for a brief time when overcharged. In these games, the Boost Gauge is presented as a gauge on the left side of the screen and is made of several stabled segments with a star icon on top. Their designs differ between games though: In Sonic Rush its segments are flat, and in Sonic Rush Adventure the segments are arrow-shaped while the gauge has more elegant details.
The Tension Gauge can be charged to a maximum of 300%. The gauge's color turns from blue to orange, and then red in accordance to the amount of energy in it. When at maximum capacity, the Boost Gauge will flash and its star icon spins.
In Sonic Unleashed, the Boost Gauge is referred to as the Ring Energy Gauge on the Xbox 360/PlayStation 3 version and the Boost Gauge on the Wii/PlayStation 2 version. All versions display the gauge in the lower left corner of the screen. On the Xbox 360/PlayStation version, the Boost Gauge is a dark gauge with a red-yellow bar within it, a Ring icon and counter on the left, and an overarching multicolored bar for measuring speed. On the Wii/PlayStation 2 version, the Boost Gauge is merely a Ring icon and counter with horizontally-stacked bar units next to it.
In these games, the player starts the Stages with no energy in the Boost Gauge. The player can fill the Boost Gauge by collecting Rings, using the Sonic Drift, or by performing Action Chains (Wii/PlayStaion 2 version only). Taking any damage depletes the gauge though. On the Wii/PlayStation 2 in particular, using the Sonic Boost costs one unit from the Boost Gauge.
On the Xbox 360/PlayStation 3 version, the player can increase Sonic's Ring Energy parameter to enlarge the gauge permanently up to six times.
On the Wii/PlayStation 2 version, the Boost Gauge can be increased temporarily by one unit for every thirtieth Ring (up to six units). Conversely, the maximum number of units will decrease by one when the player takes damage (down to three units).
In Sonic Colors, the Boost Gauge is merged with the Wisp Gauge as the Boost is classified as a Color Power in this game. Nevertheless, it is still referred to as the Boost Gauge. On the Wii version, the Boost 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 Icon.
In the Nintendo DS, the Boost Gauge is positioned on the left side of the screen and looks like it did in Sonic Rush Adventure, but with a blue bar on the left side and the Wisp Icon on top. This Boost Gauge is similar to the Boost Gauge in the Sonic Rush series; it capable of being charged to a maximum of 300% and the color of the gauge will change from blue to orange, and then red to indicate the amount of energy in it. However, it lacks the Tension Gauge mechanic.
When beginning an Act on the Wii version, the Boost Gauge will be empty from the start. On the DS version however, it will be filled at 100% capacity when starting an Act. The player can replenish the Boost Gauge by collecting White Wisps or defeating enemies holding White Wisps.
In the Nintendo DS version, after collecting all Special Rings, the player is awarded with an option that grants the Boost Gauge unlimited energy. Similarly, in the Wii version, when transforming into Super Sonic, the Boost Gauge will have unlimited energy for as long as Sonic stays transformed.
In Sonic Generations, the Boost Gauge is back to its original form and singular function. On the console/PC version, the Boost Gauge is blue with a green energy bar, a thick left end, and a stylized white and yellow frame. On the Nintendo 3DS, the Boost Gauge is similar to the console/PC version's, except that its shape is mirrored, its color is cyan, and it lacks a frame.
The Boost Gauge only appears in Act 2 of all the Stages as it is only there the Boost is usable. On the Nintendo 3DS version, it possesses the Tension Gauge mechanic, allowing for brief infinite energy when overcharged (which is signified by its energy bar turning from yellow to blue).
The player can replenish the Boost Gauge by collecting Rings, defeating enemies and performing Freestyle Tricks. Should the Boost Gauge be full on the console/PC version, performing Freestyle Tricks will charge the Boost Gauge with extra energy, which is showcased by the energy bar extending outside its frame. If the player loses a life in the console/PC version, they will be revived with an empty Boost Gauge, while in the Nintendo 3DS version, they will restart with the same amount of energy they get in the gauge when they enter a stage.
On the console/PC version of the game, there are various Skills that allows manipulation of the Boost Gauge, including the Auto-Gauge, Endless Boost, Gauge Rebooter, and Boost Gauge Up. Also, when Modern Sonic transforms into Super Sonic, his Boost Gauge will have unlimited energy for as long as Modern Sonic stays transformed.
In Sonic Forces, this game mechanic is once again referred to as the Boost Gauge. In this game, the Boost Gauge is a simple black rectangle with a blue (red when playing as Shadow and yellow with lightning effects when playing as Super Sonic) energy bar inside it and a few black blocks underneath it on the left side. It also has the word "BOOST" underneath it on its right side.
The Boost Gauge only appears in the Sonic Stages and Tag Stages as it is only there the Boost is usable. The player can replenish the Boost Gauge in this game by collecting White Wisps or defeating enemies. If the player attempts to Boost while the Boost Gauge is empty, the gauge will shake briefly.