General Information

1st Style Arcade Version Songs

To unlock the hidden songs (mostly just the 1st style songs), play in Arcade mode. One new song will be unlocked for every five songs you play in Arcade mode.
To unlock Original Course Setting, either unlock all hidden Expert Courses or accumulate 573 minutes of play time in Arcade and/or Free Mode. Game time is accrued only while actually playing a song.
To unlock everything immediately, achieve at least a 573 combo on any song in either Arcade Mode or Free Mode, and then finish (clear?) the song.

The game does not recognize the difference between SP and DP scores when saving; this means doubles data will often overwrite singles data. Doubles players are recommended to use two memory cards.
Various songs have incorrect timing; some songs have timing windows that are too tight, some songs have sections where the timing is off by a beat or so, and some songs are just messed up beyond description. Timing issues also vary by difficulty level. The songs with perhaps the most notoriously bad timing are GAMBOL, e-motion, OVERDOSER, and SOFT LANDING ON THE BODY.
Song sorting in Free Mode (sorting by name) and in the Records is off in some places.
Not all songs have L7 notes. Selecing L7 will play their respective 7K note charts instead.
When you achieve a new high EX Score, the game will record that new EX Score and all other new attributes that go with that most recent play session, even if the ancillary scores were better in your previous record. I.E., it will overwrite any previous combo counts, judgment counts, and your clear status if they differ between your previous record and your new record. This will change Perfect Combos to simply Cleared status if you did not achieve a Perfect Combo with your new higher EX Score, even if you had previously achieved a Perfect Combo on that song. It will also change Cleared status to "Played" (shown simply as a blank) if you achieve a higher EX Score but fail to clear the song, even if you had previously cleared it.