What you are seeing is called artifacting. Your GPU, Graphics Processing Unit, can\'t handle the load of the game visuals/physics. No offense to you, or to anyone else, but you shouldn\'t be playing video games on a Mac, they just aren\'t made for them. Try turning your graphics settings down all the way, and if they already are, then you might want to invest in a PC (If you are that interested in still playing the game, that is, I\'m not pushing you to buy a PC)