Alright...you MUST finnish the game before you can use these cheats...otherwise they won't work.

To Enter Code

1.) start mission
2.) press ESC to pause
3.) press and hold LCtrl, LShift, LAlt
4.) put in code with number keys.

Code

7755 - restore health
5964 - perfect mode
6869 - always devastating
8967 - all upgrades
7795 - infinite missiles
7578 - invulnerable
9587 - targeting indicator mode