The particle effects and lighting are pretty flat, and they really need to do something about the animations of players running backwards and make it look more natural, if you're holding the gun pointing in one direction and running backwards, the legs should be pointing in the other direction (the direction you're running) while the shoulder should be pointing in the direction of motion, it might not matter in a single player campaign but during multiplayer campaign looking at another player running around like that just seems... unnatural.
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