This example displays a natural Earth projection world map with country boundaries, graticule lines, and a bold outline. It uses `d3.geoNaturalEarth1` and `d3.geoPath` to render geographic features, with `d3.geoGraticule` for the grid. Country shapes come from a TopoJSON file fetched from a GitHub gist, converted via `topojson-client`, while the React-based `viz` function manages asynchronous data loading and SVG rendering.