All levels
Go to the codes screen in the options menu and press Down, Left, Left, Down, Left, Down, Right, Down, Left, Down
More Special Features
Go to the codes screen in the options menu and press Left, Down, Up, Left, Right, Up, Down, Left, Right, Down
More Items
Go to the codes screen in the options menu and press Right(5x), Left (3x), Up, Up.
Get Difficult Mode
Go to the codes screen in the options menu and press Down, Up(8x), Down.
Get Normal Mode
Go to the codes screen in the options menu and press Up, Down, Up, Down, Up, Down, Up, Down, Up, Down.
Get Easy Mode
Go to the codes screen in the options menu and press Up, Down(8x), Up.
Get Old Soul Super Weapons
Go to the codes screen in the options menu and press Right, Up, Down, Down, Up, Right, Right, Up, Down, Down.