S.T.A.L.K.E.R. Anomaly is a free single-player survival FPS (first person shooter) game or “standalone mod” based on 2010 hit game S.T.A.L.K.E.R. Call of Pripyat. It is powered by the Monolith 64-bit engine, a custom fork of the X-Ray engine. Players can choose from a variety of ways to play the mod. Play story mode with 4 chapters of interesting quests, sandbox mode if you prefer to make up your own story, or the combat intense warfare mode where factions fight for influence and control over different areas of the zone.
Anomaly is also highly customizable, play it the way you like and have the most fun. There are hundreds of settings that can be tweaked in the options menus and for more advanced changes, there are over 1000 addons for Anomaly that were created by other players to change the experience in more advanced ways.

GAMMA Mode

Users of STALKER Anomaly also add Grok’s GAMMA automated modpack to the game, which aims at providing a balanced survival, scavenging, cooking, crafting and repairing focused experience with a long progression and smooth gameplay.
In order to get the complete GAMMA client (heavy, rarely modified files) you need to download it from the associated discord server where a team of people is ready to help you with your questions and potential issues related to this project: https://discord.gg/stalker-gamma