Indicator whether or not it is for Mac

I don't use mac, but I think this would be really great!

Not really...

You really just have to know if it's there.

I have a Mac, so I see what you're coming from, but I don't think it's necessary.

What's the game in question? What format is it in-a physical box? A serial key?

On Steam there's the Steamplay icon and icons for the supported platforms.

Right above add to cart it says steamplay and on the right of steamplay it shows what platforms the game's for.

Eh, it might be an ok idea, but even steam is off on if it runs on a mac. For example Shank 2, Penny Arcade 1&2, and intrusion 2 all say that they run on mac but I have yet to get them to actually run on my Mac partition. You just got to know what games you can run and which you can't.