Light and noise also play a role in combat. As you move through an area, an indicator makes note of how visible you are at the time. Sneaking through the shadows can be difficult, though the ammo you save by avoiding a fight in the early part of a mission may be your saving grace in the latter half.

This style of balancing act reappears throughout the game, always giving you options but never handing you everything. For example, at one point you will take on a mission from a group of scientists that are researching a particularly dangerous part of the Zone. Anyone who enters the area goes mad within a short amount of time. If you retrieve an artifact for the scientists, they'll reward you with a piece of protective gear that allows you to enter that section of the Zone without risking insanity.

It would seem like a necessary task, but like anything else in the game, it's a choice. If you fail the mission (or turn it down outright) you won't get the protective gear, however it doesn't block your progress. You can still accept the next mission in the insanity zone, only now it's a bit more challenging. Without the protective gear you have to dart in, complete the objective and dart out. Stay to fight, or lollygag looking at the sights, and you'll lose your mind. Layering choice upon choice, STALKER certainly has the potential to score high in the replay department.

If the voyeur in you wants to know more about the gritty details behind STALKER's unsettling realism, click here for our up-close look at the real exclusion zone. You can also learn more about what makes the NPCs tick as we plunge through the ins and outs of STALKER's A-Life system by clicking here. Be sure to check back tomorrow as we continue our obsessive coverage on this haunting title.