Get the community patch which upgrades graphics, enables quicker keys to save, breakable lights fixtures and more! Takes the game from good to great! STALKER is my favorite gaming style!
Sneak around and attempt to take out any force with stealth attacks. The more silent you are, the more deadly you become. When you kill an enemy, pick their body up and hide it. Enemies see only whats in their vision, and while an enemy is in-sight they appear on your mini-map. If you don't crouch, they will hear you even easier! Turn on night vision and pull out your silenced weapon to become the ultimate STALKER! (still challenging!)
Each NPC has a unique name, and they will remember if they like you. They can die from enemies too, though. The killed NPCs are replaced with half as many fresh new NPCs, most of the time, which helps the game still feel alive, and progresses. If you shoot your friend once, they will forgive you. If you shoot them twice, then its war...
There are different groups/factions. Military, Bandits, Loners, Duty, Freedom, etc. Everything is at war. If you pis-off the Military, they will attack your base. If you don't ball-up, they will all die. Game changing! Although, you can save anytime you want. Which makes winning a serious battle, actually possible. Making you the most badass in the zone! Although, no one truly knows how cool you are, due to saves! ;D (I wish there was a video replay, where it shows you how [through saving] your character is elite.)
Mutated animals run around constantly. Sometimes you can take a souvenier from them. The types of mutated creatures become really sneaky and different than you can imagine. They will solo attack armed soldier squads too. Sometimes wiping them out. You get no rewards for helping NPC communities survive, but it is rewarding to know you just saved a friendly base.
Better equipment comes much faster from helping NPCs with a task. But you will probably gain access to much of the same guns much later on, from fallen enemies, except armor never drops from enemies. Bullets fall with gravity. You can watch a bullet fall towards a distant target. If you choose to use a sniper weapon, you will have to adjust your manual aim to compensate for this new thing called gravity. Also, the distance between you and your target feels real!
What else... there are... artifacts, which give bonuses. They are supposed to be found in anomalies, which are dangerous ghost like traps. If you hear your radiation meter going off, throw a metal bolt by pressing 6, to see if you are about to get zapped by stepping on a trap. Also, if you hear radiation, you are probably getting pummeled with radiation poisoning. Might want to step back. Suit up to get less exposure! (This seems bigger in the game Pripyat.)
Lastly, the atmosphere is really in depth. Everyone speaks with a Russian accent, and when the wind blows the bushes wave. Day/Night cycles and eating let you feel like you are really camping in the zone. Its cold and a loner's friend.