It has also been influenced by boxing and, more heavily, by Shōtōkan, including the kyū/dan ranking system, which comprises white, yellow, green, purple, and brown belts followed by ten degrees of black belt.
It has also been influenced by Muay Thai and, more heavily, by Shōtōkan, from which it derives the use of kata and the kyū/dan ranking system. The ranking system comprises white, yellow, green, purple, and brown belts followed by ten degrees of black belt.