This example displays U.S. state population data as a choropleth map, with darker blue representing higher population. Ten states are mapped to population values, while all other states appear gray. The tooltip reveals the state name and population in millions upon mouseover. The map draws state boundaries as SVG paths using `d3.geoPath` with a `geoAlbersUsa` projection. Data is loaded from the `us-atlas` TopoJSON file, transformed with topojson-client, and colored through a sequential blue scale from `d3.scaleSequential`. Boundary strokes are added using `topojson.mesh`.