This interactive map of Japan visualizes geographic regions as SVG paths, rendered with the Mercator projection. Users can adjust a range slider to simplify the map topology in real time, controlling the level of detail through a custom geoTransform filter that removes small areas. The visualization is built with d3.js v4, the topojson library for converting TopoJSON to GeoJSON, and d3.geoPath for generating path data. Hovering over a region displays its name in a tooltip and highlights it in light green.