This example displays a choropleth map of the United States, where state fill darkness corresponds to population values from a small inline dataset. It uses D3 v7 and topojson-client to load and convert US Atlas TopoJSON into GeoJSON features, then renders them as SVG paths via `d3.geoPath` and a `d3.geoAlbersUsa` projection. A `d3.scaleLinear` maps population extents to a blue color range, with unlisted states shown in gray. Hovering reveals a tooltip with each state's name and population via an appended `<title>` element.