Anyone with mac issues:
How to run the game / The application can't be opened
In the terminal, write "sudo chmod -R a+x " without the quotation marks, (don't press enter yet, and notice the space at the end after 'a+x', make sure it's there) then drag Game.app into the terminal and press enter. It will likely ask for your password for security reasons. When you type it in, it may not show anything. Just type it like normal and press enter. You should now be able to launch it via Game.app.
"Demon Deals" cannot be opened because the developer cannot be verified (macOS cannot verify that this app is free from malware)
Option 1. In the Finder, locate Game.app. Do not use Launchpad for this, as it won't work. Control-click Game.app in the Finder, then "Open". You may need to click "Open" again. After having opened the game in this way, it should be saved as an exception, and you should be able to open it normally from now on. Option 2. In the terminal, write "sudo spctl --master-disable" without the quotation marks, then hit enter. It will likely ask for your password for security reasons. When you type it in, it may not show anything. Just type it like normal and press enter. If it still doesn't launch, at this point, go ahead and follow the instructions above on "How to run the game". If you wish to re-enable the macOS developer verification check again, do the same in the terminal as before, except write "sudo spctl --master enable" without the quotation marks, then hit enter.