Well, I've just finished the single player campaign. The story is top-notch, with a couple of memorable characters. Yet, there are some flaws in the gameplay mechanics. Moreover, you cannot save your progress, unless the game lets you between main missions. Some missions are long and tough to survive through, and saving after checkpoints would be superb for the players.
By the way, this is NOT an easy game, even if you change the difficulty level to Survivor (Easy) on the options menu. Thus, if you're new to shooters, you may want to start with an easier game.
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