This example visualizes the hierarchical structure of world countries, organized by continent and subregion, using a static tree layout with horizontal links. The SVG rendering uses D3 v5’s `hierarchy` and `tree` layouts, with `linkHorizontal` for the connecting paths. Node labels are sized proportionally to their depth in the hierarchy, and circles mark each country or region. The visualization supports zooming and panning through D3’s `zoom` behavior. Data is loaded from a local `data.json` file containing the nested geographic classification.