I tryed building a MacOS version here and the "Console.WindowWidth" was throwing an error also. I didn't have to add "usingSystem", at least to run here in my Mac.
I've built a Linux (for some releases) and a Mac versions, I'm just waiting for ne0hash to reply the thread to see if I can upload the game's page with new files.
But, if you (@KevinCross) would like to give it another chance, @quibar 's solution seem to work ;)