INVINCIBLE: Pause the game and press up,up,up,left,down,down,down,left,up,up,up,left,right.
NOTE: This code can only work in singel player mode
INFINITE AMMO: Pause the game and press up,down,left,down,down,left,down,down,left,down,down,
down,left,right.
NOTE: This code can only wor in singel player mode