Hello,

We're not exactly sure what's going on, but it might be some specific hardware configuration issue. Try playing the game on a small resolution in window mode, or in fullscreen (not windowed fullscreen!), and make sure to lower the settings in the "Advanced" menu as well. If you have a Bootcamp/Windows setup, that might also help you to play with better performance, as reported by some Mac players.
If that doesn't work, we would suggest that you get a refund.