Level select:
At the selection screen, press Up, Left, Down, Right, Up, Right, Up, Down, Left, Up, L1 + R1, L2 + R2 to unlock all levels

View credits:
At the mission briefing screen, press Left, Right, Up, Down Five times

Cheat mode:
Press Up, Left, Down, Right, Up, Right, Up, Down, Left, Up, L1 + R1, L2 + R2 at the mission selection screen to enable cheat mode and unlock all missions. The screen will flash to confirm correct code entry. Pause game play and select the Cheat Screen option to enable : All Weapons, One Hit Kills, and Player Can't Die.

Secret mission 1A:
Successfully complete mission 1 under five minutes with more than 40% accuracy.

Secret mission 4A:
Successfully complete mission 4 under 6 minutes 44 seconds with more than 40% accuracy.

Secret mission 5A:
Destroy more than half of the Energy Plough and use your tractor beam on the second half in mission 5.

Secret mission 5B:
Search for the Info unit in mission 5 and use the tractor beam to acquire it.