Choropleth Map
An interactive choropleth map shades countries by the average number of Olympic medals won, with a dropdown menu to switch between gold, silver, and bronze. D3 v6 drives the visualization, using `d3.geoMercator` and `d3.geoPath` to project GeoJSON country boundaries, while `d3.scaleThreshold` maps medal counts to color scales like `d3.schemeOranges`. Hovering highlights a country and displays a tooltip with its name and medal total. Data comes from a CSV of Olympic medal summaries, rendered as SVG with animated opacity transitions.