This treemap visualizes U.S. steel scrap trade values by partner country, with radio buttons to switch between Import and Export data. Each rectangle represents a country, sized and colored by total trade value, and clicking a cell drills down to show individual commodities. The visualization uses D3.js v7 with `d3.hierarchy`, `d3.treemap`, and `d3.scaleSequential` for color encoding, rendering SVG elements with interactive click handlers and animated updates. Data comes from a CSV file containing import/export records.