This visualization presents the hierarchical structure of world countries, organized by continent and subregion. The tree diagram lays out nodes horizontally, with continents as the top level and individual countries as the final leaves. The code uses `d3.tree` for layout, `d3.hierarchy` to parse the JSON data, and `d3.linkHorizontal` to generate the curved connecting paths. Text size scales based on the node’s depth, and the SVG rendering supports pan-and-zoom interaction through the `d3.zoom` event handler. The data is loaded from `data.json` and styled with Playfair Display typography.