A choropleth map of COVID-19 cases by country, with each nation colored on a spectral scale via `d3.scaleOrdinal` and `d3.schemeSpectral`. Hovering highlights a country in red, and a click-drag zoom uses `d3.zoom` with a Natural Earth projection (`d3.geoNaturalEarth1`) and `d3.geoPath`. Data loads from a CSV and TopoJSON using `d3.csv`, `d3.json`, and `topojson.feature`; a custom color legend renders SVG circles and text.