Hold [Option] and select "New Game". Release the key after the weapon
level increases to 999999 in the tool box.
Nuclear difficulty level:
Hold [Option] and select "Difficulty Level".
Locate a plane and shoot it down. Completely destroy the plane just
before it reaches the ground. A prompt offering nuclear missiles will
appear. To fire a nuclear missile, hold [Option] while firing a
Enable the "Nuclear missiles" code, then fire all missiles as nuclear.
Obtain another set of missiles, and fire them as nuclear. A UFO will
appear while the second set of missiles are being fired.
Select the machine gun and shoot the parachutist twice. Then, shoot
him once more just before he reaches the ground.
Select the laser and fire the weapon a few times in the lower middle
section of the field. When the correct location is hit, an earthquake
will that destroy everything on the ground.