At the main menu screen that reads, "Game Start", Time Attack", and "Options", enter L button, up on D-pad, R button, and down on D-pad. This will give you access to "another world" full of new puzzles. After entering this code, a tiny character will appear in the lower right portion of the screen. Select "game start" and when you select "Puzzle Game", it will say "Another World" underneath it. Press A and you'll go to another world!

For more puzzles, press A, Up, B, Down at the Title Screen.

Start a new Puzzle game, and at the screen where you choose your path, press Left, Left, Up, Down, L, R, L, R, L + R. If you do it it right, a Character Select screen will appear.