Invulnerability
Enter the password "XBABYX", then start a game. Your energy will decrease, but you won't die.
Level Select
To start on any level, enter the password "ZZZCYX".
Rapid Fire
For rapid fire, enter the password "YAYAYA".
Hidden Level
In mission 1, phase 2, go south after you complete your objectives. Here you'll find a dead-end canyon with an alternate exit. Take it to enter a bonus underwater mission.
