I eat garbage.
THOUGH, it might have been helpful to have something at the end of the demo that alerts you: "Hey! You can't go on without paying $$ suckah!"
Thanks to everyone for your help. I didn't see an option to buy the full version for MAC on STEAM, but I must have been having vision problems,...
I am playing the Mac demo in STEAM.
I passed Mission 3: it says "Well done, agent. You have successfully completed this mission."
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