This example displays a world map with circles positioned at the centroids of countries, sized to reflect their 2018 population estimates. The map uses a natural Earth projection via `d3.geoNaturalEarth1` and renders geographic boundaries with `d3.geoPath`, while circle radii are scaled with `d3.scaleSqrt`. Populated countries appear with teal circles, and gray or pink fills indicate data availability. The visualization loads population data from a CSV and country geometries from TopoJSON, and supports zooming through `d3.zoom`. Hovering reveals a tooltip with the region name and population count.