World Countries Tree
This D3.js visualization shows the hierarchical structure of world countries, organized by continent and subregion, using an indented tree layout. The SVG rendering displays country names as text nodes connected by curved paths, with font size decreasing at each depth level to emphasize the hierarchy. The code uses `d3.json` to load the country data, `d3.tree` for layout, `d3.hierarchy` for nesting, and `d3.linkHorizontal` for the link paths. A custom `d3.zoom` event handler enables interactive pan and zoom of the entire visualization.