Complete a level.
Discover a secret room.
Finish a level without killing any enemies.
Kill 20 or more enemies on any level.
Complete any level in less than 20 seconds.
Complete any level without setting off any alarms.
Complete the game. (32 levels)
Answer 3 trivia questions correctly.
Answer 10 trivia questions correctly.
Answer 20 trivia questions correctly.
Destroy all the fuel in the fuel depot. (Level 21)
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