This example shows a zoomable choropleth map of world countries, where each country’s fill color encodes its population estimate on a scale from light to dark red. The visualization is built with D3 v5, using `d3.geoMercator` for projection, `d3.geoPath` to render country outlines from TopoJSON data sourced from the world-atlas package, and `d3.scaleLinear` for the color mapping. A `d3.zoom` handler applies transforms to all country paths, and hovering a country displays its name as a tooltip. Population data comes from a TSV file loaded via `d3.tsv`.