HKD is a circular, water-based science which encompasses strikes, kicks, pressure points, joint-breaks, throws, ground work and finishing techs. It is also a very internal style. It covers Ki in-depth, healing, etc.
HKD and TKD are not similar in any way. One is circular, the other linear. HKD is soft, TKD strong. HKD low circular whipping kicks, TKD high straight muscular kicks. Foot work is not the same. The science behind them are different. HKD generates its power much differently than most.
HKD does not have any kata. They do not exist. If you are doing HKD kata, it was made up, or most likely, you are in a TKD school which claims HKD. Don't get me wrong, there are such valid schools out there where the teacher has trained in both, and he will 95% of the time be Korean. TKD is a national sport of theirs, and HKD schools are plenty there.
HKD is combat orientated. Its goal is to shut down the body as quickly as possible, thus we only have 3 targets, Breath, Mobility and Sight. Shut down one of these and the fight is over.
Any specific questions, glad to be of assistance
