Invincibility
Click on the word "PATROL" at the title screen in the order R, L, A, O, T, and P to enable cheat mode. Click on the "Invincibility" button, then type brokenbombs. Bombs will now have no effect on the buildings. Note: This cannot be used simultaneously with the "Unlimited ammunition" code.
Unlilited ammunition
Click on the word "PATROL" at the title screen in the order R, L, A, O, T, and P to enable cheat mode. Click on the "Infinite Ammo" button, then type tonsofgunsforyou. Note: This cannot be used simultaneously with the "Invincibility" code.
Bonus level
Play a perfect game with no buildings bombed without enabling the cheats. The Sunset City, USA bonus level, with stealth bombers and helicopters will be unlocked.