OKAY, I'm reasonably happy with the current version. I now have a "progress map" on AlphabeticalZürich, available at https://www.alphabeticalzurich.ch/map.html
The base tiles are @protomaps, with an extra dash of Leaflet (https://leafletjs.com/), an export of my progress spreadsheet as CSV, and some "let's throw some Zürich opendata at the geometry problem".
And a non-zero amount of work to integrate it as I wanted (including "how do I avoid trivially leaking my API key"), but I *think* it's reasonably clean. It would probably warrant a proper blog post, if only to document things for myself, but now I need a break (... since at least few hours if I'm being honest with myself.)
But there, I'm happy - now I need to update the spreadsheet and the real-world data below it :D
