What is Two dee ecks?

Stands for beatmaniaIIDX, a famous rhythm game arcade style that has been made by Konami. beatmaniaIIDX got 20 version of games, from the 1th style to the 10th style, then we got IIDX Red, Happy Sky, DistorteD, Gold, DJ Troopers, Empress, Sirius, Resort Anthem, Lincle, and the most recent one, Tricoro. You can find a lot of cabinets in arcades and somewhere in the internet even HDD rips for PC.