Enter the options screen and select "Cheat Codes". Then, enter one of the following codes to activate the corresponding cheat function.

Effect - Code

Master code - big fat cheater
Unlimited ammunition for any power-up you buy - endless supply
More firepower, fast auto-fire for every weapon - triggerhappy
Display accuracy - bullseye
Power-ups cost nothing - credit check
Start with 99 ships - starfleet
Level select - jump to level
Practice bonus rounds - target practice
All enemies are snipers, extra hard mode - sitting duck
Space Invaders style, stick to one level - back to the roots
No cash, invaders do not drop coins - keep the change