On the main menu, hold C-Down or C-Up to shift the whirlpool on the screen, and hold the button while moving the STICK to move the whirlpool across the screen.
Activate the "Floor" option, then complete all the modes except for practice and multiplayer to gain the "OK" rating, and the background will turn green. Select any game mode but practice, choose the man that represents the pieces to change him into a duck, and begin the game with triangular, rectangular, and square pieces.
Complete all 16 practice rounds and the background will become red. Go to the options screen and choose the "Floor" option.