Hello, it's compatible with systems before Catalina.
The download for mac might have been offline. If you want we can reupload the Mac version (pre-Catalina unfortunately)
For the record, the download page contains only one link, to:
FULL GAME Version 1.60 909 MB May 09, 2022
Inside the zip file, there are Windows executables and libraries, and web content (which I assume is the bulk of the game, with the binaries only for packaging). I tried serving the index.html page directly, but that didn’t work for me, and is certainly not how you intended customers to engage. I didn’t see any macOS content though, but please let me know if I missed something.
Thank you very much for your help!