groove radar

A system of displaying the difficulty of a song in Dance Dance Revolution, first used in DDR 6th Mix (DDR MAX). It is represented as a circle with a star shape in the middle that stretches to show the values of five points on it. It was created to give players a better idea of what to expect when going into a song, instead of just an arbitrary number for difficulty, the foot rating (although this was later put back in under the groove radar in DDR 7th Mix aka DDR MAX 2.)

AIR represents the frequency of "jumps" (two-arrow hits) in a song.
FREEZE represents the frequency of hold arrows.
STREAM is the overall density of steps in the song.
VOLTAGE is the maximum density of steps.
CHAOS is still somewhat unknown. A DDR simulator called Stepmania represents Chaos as the number of off-beat steps (as in, not 4th or 8th notes), but in actual DDR games, it seems to be the overall "irregularity" of steps.