On the title screen, type any of the following:
"ITSEASYWHENYOUKNOWHOW" --- Infinite continues
"BLUEDAY" -------------- Turns everything blue
"IAMAFREINDOFIANS" ------------------- Message
"VERSION" ----------------------- Version date
"CREDITS" ----------------------- Game credits
"HELLOS" ---------- Greeting to various people
"SIAMESE" - unlimited lives and following keys
'F1' - Normal rifle
'F2' ---- Full auto
'F3' ---- Three way
'F4' ----- Shot gun