Flash Kick

The Flash Kick (サマーソルトキック, Samaasoruto Kikku, "Somersault Kick") is one of Guile's special attacks, introduced with him in Street Fighter II. His friend Charlie has a similar version called Somersault Shell.

Description
Executed by charging downward then pressing upward and kick, Guile/Charlie performs a backflip, kicking his opponent harshly as he does. The attack is so quick as to be almost instantaneous, and the arc of the kick leaves, as the name would suggest, a flash in its wake.

The size of the flash (and, thus, the chance of it hitting the opponent) and the height achieved as performed are usually determined by the strength of the kick used, as well as the damage, stun, recovery: light kick has the least damage, height, stun, and recovery; heavy kick grants the most damage and stun with the greatest height, but longest recovery; and medium is a balance of the two.

The EX Special version introduced in Street Fighter IV hits twice, does even more damage and stun than heavy punch, breaks armor and has longer invincibility.

Two upgraded versions of the Flash Kick exist.

In crossovers
A non-charge variation (simply downward then upward without charging the former) of this move exists in Marvel vs. Capcom 2, which can executed only in mid-air. In X-Men vs. Street Fighter, the Flash Kick sends out an arc of energy upwards.

Differences
There are visual differences in how Guile and Charlie execute the move. Guile simply leaps up and executes the overhead kick with one leg while performing a moonsault, rather than a somersault. Charlie turns to face away from the opponent and performs an overhead kick with one leg before finishing it off with another overhead kick from the other leg, all while somersaulting.

Tactics
The kick's speed means it is useful as a nigh-impenetrable anti-air counter. It is also good for zoning, ending combos, punishing, and preventing certain cross-up attempts. The EX Flash Kick is the best anti-air variant (with light kick coming second), and heavy kick can set up juggles.

The highest priority of the move is during the deepest point of impact: i.e., if the move is performed at the last possible moment. If used at this point, the Flash Kick will beat almost any other normal attack, short of a Shoryuken. In the original Street Fighter II, the move had no recovery time on landing, having been designed as analogous to a normal jump attack. This meant Guile could often beat an opponent to a throw, even if the Flash Kick is whiffed. This feature was removed in subsequent games, and the recovery time on landing was changed to match that of the Shoryuken.

In the Street Fighter IV series, the move has Armor Break, and grants split-second invulnerability during start-up.

Trivia

 * In Street Fighter Alpha 3, the color of flash changes based on the color swap of the character using it. For example, if the player uses Charlie's red costume, the flash will be red instead of teal. In addition, Charlie's version, when performed with heavy kick, will always hit twice.

Other games

 * In Final Fight Streetwise, Kyle has a counterattack that bears a striking resemblance to the Flash Kick.
 * In Asura's Wrath, the titular character uses an uppercut followed with a Flash Kick-like move as a heavy attack while fighting Akuma.
 * In Resident Evil 5 and Resident Evil 6, both Sheva Alomar and Jake Muller use Flash Kick as one of their melee attacks.
 * In Project X Zone, Frank West from the Dead Rising series uses a Somersault kick in two of his special moves.
 * In The King of Fighters '94, Korea Team (Kim Kaphwan, Chang Koehan, and Choi Bounge) each have a Flash Kick-style move called the Hien Zan.
 * In Double Dragon Neon, a boss called Mecha Biker, designed as a reference to Mega Man, sometimes performs a Flash Kick-like attack after his sliding kick.
 * In Final Fight Revenge, Cody's special move is a Flash Kick.
 * In Remember Me, the protagonist Nilin can use a Flash Kick-like attack as one of her Chain attacks.
 * In X-Men: Next Dimension, Cyclops has a move called power flash kick, which involves him kneeing the opponent and then performing the flash kick. There are three variations of this move.