World Countries Tree
This example displays the hierarchical structure of world countries organized by continent and subregion, with country names rendered as nodes in a tree layout. The visualization uses D3 v5’s `tree` and `hierarchy` functions to compute node positions, `linkHorizontal` to draw curved connector paths, and SVG elements for rendering. Text size scales with node depth, and the entire graphic supports zooming via the `d3.zoom` API. Data comes from `data.json`, which nests countries under regional groupings.