thanks for featuring the graph! since 2014 or so it's gapminder.org/tools

is r scale implicitly sqrt? this is correct, but would be helpful to make it clear somehow so that a user won't put another sqrt calculation on top. maybe have "r" default to linear scale and "s" for size or "a" for area default to sqrt

Yes, the r scale is sqrt by default. https://observablehq.com/plot/features/scales#other-scales

Adding in Plot.dot fill: "last" fills the dots like in the original (or D3 historical [1] ;-) animation, but generates _millions_ of entries for the legend...any hint at how to avoid that? Also IMHO the data preparation in [1] was less frightening than here ;-) [1] https://observablehq.com/@mbostock/the-wealth-health-of-nations

you need to add fill: "region" in the input options too (the second argument to groupZ), otherwise each country gets a different color (and a place in the legend, serialized to string as [Object object]).