Due to the setting of the game, designer Hideo Kojima has introduced three major elements to the MGS formula.
The first change is the injury system, whereby Snake must extract bullets, stitch cuts and mend bones to continue. The second system ties into the injury and that is the introduction of stamina. Without fixing Snake's injuries Snake's stamina can only replenish so far and when Snake runs out of stamina from walk, running, etc he can only move very slowly. To replenish stamina, Snake must eat food, either from rations that he finds or from eating the wild life in the jungle that he can catch.
Lastly, comes the introduction of the camouflage system that determines how visible Snake is to enemy soldiers. Snake can find and wear different camouflage outfits to blend into the surroundings better and make himself less visible.
