This example displays a map of Japan using a Mercator projection, rendered as an SVG path with a violet fill that transitions to light blue on hover. It loads geographic data from the world-atlas TopoJSON dataset, extracts Japan’s geometry via `topojson.feature`, and fits the projection to the country’s bounds using `d3.geoMercator().fitSize`. The visualization applies `d3.zoom` for interactive pan and zoom, and uses `d3.json` to fetch the data asynchronously.