Hello!
I would like to ask, that if I purchase the GSB full edition through Steam (75% discount on this weekend!!) can I install and play it on my mac? Since I just downloaded the mac demo and this game is so awesome and this chance of saving money and getting this seems to be unmissable 
After that I’ll purchase any forthcoming DLC at full price I promise!
Thanks your response in advance!
Not at the moment, unless the mac version shows up on steam, which wouldn’t surprise me, but it has not been discussed yet.
Stay tuned etc.
understand
So if I buy the game through steam now, and then GSB mac version shows up there, i will be able to download and play that too. Correct me if I wrong, but if this is the way, i’m right on it.
That’s how it was with every other game where Steam picked up a mac port.
Here’s my recommendation (and what I did): by a copy as a gift, and send it to yourself. Then wait and see if the Mac version shows up. If it does, bam, you can claim it. If not, you can re-send the game as a gift to another friend. For the gratuitously huge sale that it’s on, that’s a damned cheep gift that you can give to someone.
I actually bought 3 copies today - two for friends and one for me just in case it comes out on Mac through Steam. I already have the main game for Mac, but for this price I’ll happily take the risk to be able to get the DLC through Steam too. And if not, well, I’ve got another version to give to a friend! For $6 a pop for the special edition, I almost felt bad buying them - hopefully I can make up for it in quantity, haha.