This example shows a world population map where individual countries are shaded with a blue sequential color scale, and hovering over a country reveals its name and population in millions via a tooltip. It renders a Natural Earth projection using `d3.geoPath` and `d3.geoNaturalEarth1`, with geographic data loaded from TopoJSON via `topojson.feature` and country names from a TSV file. The code uses `d3.scaleSequential` with `d3.interpolateBlues` to map population values to fill colors, and SVG paths for country boundaries.