Ignore all the people whining about SOC being unplayable without mods. I bought it on Steam, sure, but I've played a good few quests/missions and explored the world with nary an issue. The steep difficulty is due to the design of the game, but if you swear by your quicksave key then nothing can stop you. Even with my shitty PC only being able to run the game at almost the lowest settings, the atmosphere of the S.T.A.L.K.E.R series is unmatched.