I imagine about 80% of this film was entirely on green screens. I'm not entirely sure I followed the plot in any great detail.
It's intense, it's bloody, it's raw; it asks you to pay attention, it asks you to care, it asks for more and it doesn't hold back. Not your standard X-men movie by a long shot, and all the better for it. I'm intrigued by the little hints dropped here and there, but that part of the story is yet to be told, evidently...