Usually with Renpy games it's better to just unzip in a new location and not overwrite. The saves are in two spots and one is not the game folder. In the main game directory there should be a .sh(linux), .exe (pc) and a .app (Mac).
Yeah, that's what I always do, unzip to the main directory I keep such games in. I then delete the temp file once I give the game a go and see it functions properly, but with this particular demo, it asked if I wanted to overwrite the files, which was weird in its own right because I had just started having the files written. I should have known then, but I never ran into such a situation. It was like the download processed the windows portion and then overwrote it with the Mac if I gave it permission to overwrite. No worries, it downloaded fine once I did not say overwrite. I am still evaluating the demo to see if I will buy the full version.