Secret level
Press [Up]x2, [Down]x2, [Left], [Right],
[Left], [Right], [A], [B], [A] when the
"Press Start" text appears at the title screen.
Expert mode
Press [Up]x2, [Down]x2, [B], [A]
when the "Press Start" text appears at the title screen.
Enter the options screen and choose the new "S" difficulty
level under the "Rules/Difficulty" selection.