In order to run SteemitGame.exe on Mac or Linux, you'll need to install Wine. On a Mac, I recommend WineSkin, which is an application that will wrap Wine as a .app file.

You will also need XQuartz.

Once WineSkin is installed, the goal here is to create a wrapper called SteemitGame.app to kick off the app.

1. After installing WineSkin, just launch it, and you'll see:
   
2. Install an engine by clicking on the + symbol.
   
3. Let that install, then click Create New Blank Wrapper and name it SteemitGame.
   
4. Once it's created, click on View wrapper in Finder:
   
5. This will take you to the finder. Just double-click on the new SteemitGame.app wrapper.
   
6. Click on Install Software.
   
7. Then click on Choose Setup Executable and pick SteemitGame.exe:
   
8. I suggest just installing to C: ...
   
9. Pick Game.exe after the install (this will be automatically filled in), and click OK:
   
10. This will do the install and eventually bring you back to the Wineskin app. Quit from that and double-click on SteemitGame.app once again.
    

Enjoy!