Intentionally lose the game by dying repeatedly to increase the number of lives per credit between four to six.
Additional Time
Intentionally lose the game by allowing the timer to run out repeatedly to increase the time limit between seventy and eighty.
Disable enemy markers
Press Right(4), Left, Down, Up, Right at the mode selection screen.
Double Hit Bonus
To get a "Double Hit Bonus" just fire right when a moving tagets walks behind a stationary one or when two moving targets pass each other and they line up in one in front of the other (relative to you).
Get Four Continues
If you continue more than 30 times, you'll be given four continues to complete the level.
Get Three Continues
If you continue more than 15 times, you'll be given three continues to complete the level.
Infinite Continues
If you continue more than 100 times during gameplay, you will be given infinite continues to complete the game with.
Survival Boss Mode
After you defeat the big Boss by shooting him three times, he will hang from the tower. If you shoot him or the girl, they will both fall. You will complete the game and unlock survival boss mode.
Time Attack Boss Mode
After you defeat the big Boss by shooting him three times, he will hang from the tower. Shoot the chain and complete the game that way to unlock time attack boss mode.
Trade Health For Time
To trade half of one health pack to gain five seconds, pause the game and press UP, UP, DOWN, DOWN, LEFT, RIGHT, LEFT, RIGHT, X, CIRCLE.
Trade Time For Health
To trade five seconds of time for one half of a health pack, pause the game and press CIRCLE, X, RIGHT, LEFT, RIGHT, LEFT, DOWN, DOWN, UP, UP.