I'm very sorry about that!
So based on some research, it sounds like MacOS Catalina introduced some new security features for applications that aren't on the Apple Store which is why you're running into that.
I'm primarily a Windows user, so I wasn't aware of this update until now; sorry about that! I'll get working on a fix, and hopefully get it out this week.
In the mean time, if you really want to play the game there does appear to be a work around... but you'll have to follow this guide:
https://www.imore.com/how-open-apps-anywhere-macos-catalina-and-mojave
Thanks for letting me know about this issue.