Complete all 16 practice rounds. Enter the Options screen and there will be a new option called Floor. You can now choose different floor sets and backgrounds.
Score a rating of Expert in all game modes (Excluding Practice)
Master Set
Score a rating of Master in any game mode (Excluding Practice)
Set 1
Score a rating of OK in all game modes (Excluding Practice)
Set 3
Score a rating of Super in all game modes (Excluding Practice)
4/30/2002
Waves
Once you have the green background at the main menu, hold the C-up button to make a watersprout or C-down to make a vortex that can be controlled with the joystick.