StepMania

StepMania is a cross-platform rhythm video game and engine. It was originally developed as a simulator of Konami's arcade game series Dance Dance Revolution, and has since evolved into an extensible rhythm game engine capable of supporting a variety of rhythm-based game types.
The primary game type features the following game play:
as arrows scroll upwards on the screen, they meet a normally stationary set of target arrows. When they do, the player presses the corresponding arrows on their keyboard or dance mat. The moving arrows meet the targets based on the beat of the song. The game is scored based upon how accurately the player can trigger the arrows in time to the beat of the song.
StepMania allows for several input options. Specialized adapters that connect console peripherals like PS2 and Xbox controllers or dance pads to one's computer can be used. Alternatively, the keyboard can be used to tap out the rhythms using arrow or other keys.