downloaded the Mac version, tried to open the game but it just says it can't be opened
Interesting, people on my other game suddenly started getting that error too.
Could you try opening the terminal and typing: xattr -cr
Then dragging the app to the line after the -cr? It should work after that.
Let me know if that helps.
I think mac hit both of my games with a gatekeep error recently.
Here's a vid (@0:52) showing where to put it just in case.