pydance is a dancing simulator, in which you must step on particular arrows
on the floor in time with music playing in the background. pydance supports
multiple difficulty levels for each song, background images and movies,
lyrics, freeze arrows, BPM changes and stops, and many common modifiers like
2x, drop, stealth, and so on.

pydance is interoperable with other dancing games, and can play the
popular DWI, SM, and KSF formats. It is capable of playing games similar
to Dance Dance Revolution, Pump It Up, ParaParaParadise, Dance ManiaX,
and Technomotion. It also implements several unique modes. You can also
make your own steps for songs in the .dance format.

WWW: http://icculus.org/pyddr/