Gun Kata is a fictional gun-fighting martial art discipline that is a significant part of the film.
It is based upon the premise that, given the positions of the participants in a gun battle, the trajectories of fire are statistically predictable. By pure memorization of the positions, one can fire at the most likely location of an enemy without aiming at him in the traditional sense of pointing a gun at a specific target.
By the same token, the trajectories of incoming fire are also statistically predictable, so by assuming the appropriate stance, one can keep one's body clear of the most likely way of enemy bullets.
Video: Equlibrium gun kata
Gun fu, a portmanteau of gun and kung fu, is the style of sophisticated close-quarters gunplay seen in Hong Kong action cinema and in Western films influenced by it. It often resembles a martial arts battle played out with firearms instead of traditional weapons. It may also be described by other terms such as bullet ballet, Gun Kata, or gymnastic gunplay.
The focus of gun fu is both style and the usage of firearms in ways that they were not designed to be used. Shooting a gun from each hand (usually paired with jumping to the side at the same time), shots from behind the back, as well as the use of guns as melee weapons are all common. Other moves can involve shotguns, submachine guns, rocket launchers, and just about anything else that can be worked into a cinematic shot. It is often mixed with hand-to-hand combat maneuvers.
"Gun fu" has become a staple factor in modern action films due to its visually appealing nature (regardless of its actual practicality in a real-life combat situation). This is a contrast to American action movies of the 1980s which focused more on heavy weaponry and outright brute-force in firearm-based combat.