Hold LB + RB + click Left Analog-stick + Right Analog-stick while viewing the map.
Press X, Left Analog-stick Down, Left Analog-stick Up, Y, Left Analog-stick Left, Left Analog-stick Right, X Y at the title screen. The "objective completed" melody will confirm correct code entry. Press Start to play the game in Easy mode.
Press Left Analog-stick Left, Left Analog-stick Right, Left Analog-stick Down, X, Left Analog-stick Right, Left Analog-stick Left, Left Analog-stick Up, Y while viewing the map.