This example visualizes the hierarchical structure of countries grouped by continent and subregion, using a horizontal tree layout from a JSON dataset. Parent nodes are labeled with larger text, and each leaf represents a country. The visualization is built with D3.js v5, using `d3.tree`, `d3.hierarchy`, and `d3.linkHorizontal` for rendering SVG paths and text. Pan and zoom interactions are enabled via `d3.zoom`, with the tree rendered in an SVG container.