World Countries Tree
A world countries tree visualizes hierarchical geographic organization by rendering the United Nations subregion classification as a dendrogram. The visualization shows continents linking to subregions like Southern Asia, which then branch into individual countries such as Afghanistan and India. Built with D3.js v5, the SVG-based layout uses the `d3.tree` and `d3.hierarchy` APIs to compute node positions, while `d3.linkHorizontal` generates the curved paths. Pan and zoom interactions are enabled through `d3.zoom`, with text size decreasing at each depth level to reflect the tree structure.