This example displays a world population choropleth map, coloring selected countries from a custom dataset by population using a blue color scale. The visualization is built with D3 v7 and TopoJSON, projecting geographic data with `d3.geoNaturalEarth1()`. Country polygons are rendered using `d3.geoPath()`, and a hover tooltip shows the country name and population. A quantized legend created with `d3.scaleQuantize()` and `d3.axisBottom()` maps the color range to population values.