Hi, I don't have a Mac but according to some other people this gets around it:
A regular reminder for fellow Catalina users: if having trouble running the game, you need to execute the following on the command line:
cd [to the directory where AFirmHandshake.app is located] cd AFirmHandshake.app/Contents/MacOS chmod +x "A Firm Handshake"
After this, you need to hold control + right-click on the application, and select Open.