This visualization shows the hierarchical structure of world countries, organized by continent and subregion, with all branches originating from a single "World" root node. The tree layout uses vertical curved links to connect parent and child nodes, with country names displayed at varying font sizes based on their depth in the hierarchy. Built with D3 v5, the code employs `d3.tree()`, `d3.hierarchy()`, and `d3.linkVertical()` to compute and render the layout, while `d3.zoom()` enables interactive panning and scaling of the SVG graphic. The data comes from a local JSON file containing the nested geographic classification.