Division is a mode that only appears in Rebirth and Premiere 2.
In this mode, you have access to all the songs available in Rebirth (or the new ones (no revivals like Beethoven, Another Truth or etc) in Rebirth 2). When you start a song, you'll randomly see some letters passing by (G and W). Stepping on such letters will change the stepchart in the following ways:
G = Groove. Steps increase difficult level to Hard-like patterns.
W = Wild. Same thing as above, but with Crazy-like patterns. Not sure about this, but the more W's you get during the song, the harder the patterns become.
If you don't step on any letter, you'll play a very easy stepchart.
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