Area 51

Secret Room: X Marks the Spot (Level 4)

    Make sure every yellow box is shot while you are riding on the STAAR jeep

Bad Ending (Level 8)

    If Mothership escapes without having all panels shot off

Good Ending (Level 8)

    Make sure that all panels are shot off the Mothership before it escapes

Kronomorph Code

    At the beginning of the game (Level 1), ONLY shoot the first three STAAR team members you see, and you'll get infrared vision

Secret Room: Chow Palace (Level 2)

    Shoot out all of the upper windows of the far back wall in the Hangar

Secret Room: Chow Palace (Level 7)

    Shoot all the yellow barrels at the first area where the four purple zombies are throwing barrels on the hill

Secret Room: Egg-Cellent (Level 2)

    Make sure all of the yellow barrels are shot when you are riding on the forklift up until you get to the parked trucks

Secret Room: Headquarters (Level 5)

    Shoot the doorplate of the second door marked General Weatherby as the door is opening