Unlock the following Game Modifiers by completing Campaign mode on the corresponding difficulties:
GAME MODIFIER – HOW TO UNLOCK
Double-Physics (Doubles force of explosions) – Complete Campaign mode on Medium difficulty.
Hollywood Mode (Enemies have big heads) – Complete Campaign mode on Easy difficulty.
Tough Guys (Enemies have more health) – Complete Campaign mode on Hard difficulty.
Private – Complete the game on Easy Difficulty.
Kaboom – Destroy the gas station.
Poll and Dive – Survive the pool attack.
Droppin Bombs – Call in the airstrike to defeat the Command Center.
Seen Your Video – Watch an unlocked video.
Staff Sergeant – Complete the game on Normal Difficulty.
Long Range – Kill 20 enemies with a sniper rifle.
Color Me Impressed – Complete a mission on Normal without dying, failing, restarting, or continuing campaign.
Hummer – Kill 15 enemies on the HMV turret.
Rocketman – Kill 2 aliens with one Rocket.
Sergeant Major – Complete the game on Hard Difficulty.
One Hundo – Unlock all the unlockables.