The DK2 is incredibly resource intensive, especially on your video card. I'm no Mac expert, but I believe the video card that Mr. Cook has decreed is all Mac users really need might (no, will absolutely, definitely without question) scream in infernal agony before quickly expiring were a Mac user to get it working with their computer.
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I would think it would be borderline unplayable on most if not all Mac's. Sorry to put a damper on things but there is a reason why PC gaming is... well, aimed predominantly at PC's.