Circles on a Map
This visualization uses a natural Earth projection to display global population data for 2018, with each country represented by a circle whose area is proportional to its population. The map supports pan and zoom interactions, and hovering over a country reveals its population through a tooltip. Built with D3.js, it uses `d3.geoPath` for map rendering, `d3.scaleSqrt` for the size scaling, and custom legends to explain both the color scheme and circle sizes. Population data comes from a CSV file joined to a TopoJSON world atlas.