That's not great. It really puts me off buying the game as I can't play on my laptop (OSX) and desktop (Windows), depending on if I want to laze around on the couch or not.

You should really offer something equivalent to Steam Play - one purchase, access to the game on all platforms.

It seems that a purchase will only buy the game for one platform.

I use Windows, Linux and OSX regularly and I'd like to play it on whichever device I'm using. Do I have to buy the game three times in order to be able to do this?