As mentioned the X3100 is a GMA card. The fact is we will not offer any support for people trying to play using the GMA card. I do know the game does run on the X3100 (I have played on a MacBook) although during battles etc near the end of the game it slows down quite a lot making the game play less fun.
As such we officially don't support the game on this card. We decided it is better to not support it than get lots of people in forums and reviews complaining that the performance on the MacBooks is not perfect (because trust me they will!). Instead we don't officially support the cards but we don't block the game from running on them. Remember although I said it runs on a MacBook it is your choice to play under the specifications so if you buy the game don't expect to be able to get refunds and/or detailed support if you hit trouble.
As an aside when people say it plays on PC GMA which I have seen before for lots of Mac games recently I would point out almost no PC game supports the GMA cards officially. If you get lucky the game will run but you might experience slowdown.