This interactive map displays Japan’s country boundaries, rendered as SVG paths with animated simplification controls. The visualization uses a slider to adjust a topological simplification threshold, dynamically redrawing the map to show varying levels of geographic detail. Built with D3 v4, the code loads TopoJSON data, applies topojson.presimplify, and projects features using d3.geoMercator with d3.geoPath and a custom d3.geoTransform filter. Hovering highlights regions in orange and shows tooltips with area names, while the map resizes responsively with the window.