Beatmania IIDX (ビートマニア ツーディーエックス Bītomania Tsūdiekkusu) (alternately Beatmania IIDX or just IIDX, pronounced "two dee-ecks" or "two deluxe") was first introduced by Konami in Japan on February 26, 1999. This game spawned over 19 arcade releases and over 13 console releases on the Sony PlayStation 2. It is the sequel to the beatmania game series that is part of the Bemani line of music games.
Players recreate the musical score of songs available to them through the use of a DJ simulating controller. The player must coordinate their hands in order to hit the correct keyboard buttons, spin the turntable, or a combination of both in correspondence to color coded notes that approach the judgement bar displayed on screen. Notes are divided on screen by columns which separate them accordingly to match the seven buttons and the turntable on the DJ simulating controller. As a result of hitting notes, different sounds are then produced throughout a songs duration. Correctly hitting notes will produce an accurate musical score, while incorrectly hitting notes will produce inaccuracies and mistakes in the music.
Source: Wikipedia, "Beatmania IIDX", available under the CC-BY-SA License.