This example visualizes global population estimates for 2018 using semi-transparent circles positioned over a natural Earth projection map. Countries with missing data appear in a different shade, while hover effects highlight individual nations. The visualization loads UN population data from a CSV file and country boundaries from a TopoJSON world atlas, then renders the map using `d3.geoPath` and `d3.geoNaturalEarth1`. Circle sizes are scaled with `d3.scaleSqrt`, positioned via `d3.geoCentroid` and `projection`, and the map supports zooming through `d3.zoom`. A custom legend is drawn using SVG circles and text.