Headshot Ratio
Headshot Ratio is one of the soldier's skills that can be upgraded with experience killing zombies. When he scores a headshot, a random event players cannot control, it instantly kills the zombie he shoots. By increasing this skill, players greatly increase their chances of shooting the approaching zombies in the head.
Gun Skills
The pistol the soldier carries has two separate skills associated with it: Gun Damage and Gun Power. Gun Damage determines how much damage each individual bullet does to an oncoming zombie. Every time the soldier shoots a zombie, they are knocked backwards, giving the solider more opportunity to shoot them. How far they are knocked back is determined by the Gun Power skill.
Knife Skills
Just like with the gun, the soldier's knife fighting has two skills associated with it. These skills are Knife Damage and Knife Power. They function the same as their gun counter parts. The higher your knife damage skill, the more your knife hurts a zombie, while the higher the power, the farther the zombie is knocked back.
Cheat Code
"Zombie Survival: Special Mission" has exactly one cheat code. To use it, on the main menu, press the "Cheats" option. In the box that appears, type in the word "stagger," then press the "Proceed" button. When you start the game, your soldier will have the highest level in every skill he has, as well as being much faster as normal. This makes the game's difficulty closer to a playable level, but it also prevents you from sending your score to the leader boards.