So as it says on the store page at the bottom:
The demo only has a single map and layout, but is otherwise the same experience. There's also a free Mac build, since I know some people play my games on Macs but since the Catalina update I can't guarantee it works on those operating systems.
The Mac build there isn't a demo, it's the full game. I just can't guarantee that it works on all Mac computers, and as it's an issue with the engine compatibility that I have no control over, I'm not going to charge people for a game build that I can't be sure will work for them.