Press X(2), Y(2), click Left Analog-stick(2), Right Analog-stick(2), press L(2), R(2) at the main menu. There is no confirmation message. Start a game then pause and enter the options screen. The "Cheats" option will be unlocked at the options menu, with "Trooper Level", "Enemy AI", and "Mission List" selections. Note: Do not set the "Trooper Level" option to "Full", as one bullet hit will take half of your life away.