I think the only thing blocking us now from terraforming Mars (apart from getting there in the first place) is its lack of magnetic field. We can pump however many gasses we want in an attempt to build an atmosphere but without a spinning liquid core Mars just won't be able to hold onto an atmosphere. Solar winds will strip it away again. In the game Surviving Mars, you can build magnetic field generators but they are costly and require tremendous power. I imagine, if we had the technology, that would be accurate. Is there some other way?