I tried downloading the game and after the download, and after I tried to open the app, I receive this message: "Cultris" is damaged and can't be open. You should move it to Trash." I am on the most current OS and do not see an option in the settings to "allow any" downloads to open.
Google "How to open apps from unidentified developers on macOS", one option is to move the downloaded file to your application folder and use right click > open. There is also other ways in doing it but you will find it.