Free game Super Sanctum TD!
I wouldn’t like to keep this from you guys, but Super Sactum TD (worth 3,99) is temporarly for free when creating an account on greenman gaming. Sanctum is predecessor of Sanctum 2, which is also native for the Mac. So my advise, create an account the, get the steam key, activate it in Steam and trash the greenman gaming account again! If you are not familier to the game, then check the trailer below.
The game is for Mac and Windows, so you can play the game normally using the Mac Steam client. Enjoy!