Very cool! I loaded it up and played around with it a bit.
Huh, I didn't know about that GEOS book back when I was a kid trying to figure out how to make GEOS programs. I wrote a letter to Berkeley Softworks asking for information about how one could develop GEOS programs, and I guess someone felt sorry for me because they sent me a huge binder with a printed version of the Hitchhiker's Guide to GEOS:
https://www.lyonlabs.org/commodore/onrequest/geos/geos-manua...
I still have it today. Needless to say, as a kid, I had a great time reading it, making programs, and learning lots of new things. :)
https://www.computinghistory.org.uk/det/32184/Commodore%2064.../
Trying things out without any preconceptions of how programming should work was quite an adventure.