Hi. I downloaded the game from the main link and it seems to work so far. I unzipped with The Unarchiver. Running 10.15.5 on 2017 13" MBP on 2560x1440 setting on an external monitor.
I could not find the Catalina-specific download you mentioned.
The art consists of "coarse" (as opposed to fine) lines, no smoothing. Is that the intended effect? Switching resolutions doesn't seem to do much until I get closer to very low resolutions where things start to look fuzzy.
Thanks! looks like a beautiful game, can't wait to check it out more.