At the title screen, first press and hold Up and then hold A; then release Up and then A. Then press and hold Right and then hold A; then release Right and then A. Press and hold Down and then hold A; then release Down and then A. Press and hold Left and then hold A; then release Left and then A.Finally press and hold Left and press B. If done right, a sound should be heard. Now press up or down to select levels and while playing, pause the game and press Select to change weapons.