Interestingly, the tab completion tripped me up, it makes it with capitals as "TopoJSON", but it will tab-complete as the lowercase module (library? what's the correct term?)

Cool so this doesn't work because I'm not passing geographic data to the geo mark. Needed to look at what I was copying from the docs and "merge" with the topojson. That function is kinda magical, keep an eye on that ✨