World Countries Tree
This visualization shows a hierarchical tree of world countries, organized by continent and subregion. It maps the geographic hierarchy of nations into a horizontal icicle-style layout. The D3.js v5 code uses the `tree` layout, `hierarchy`, and `linkHorizontal` functions to position nodes and draw connecting paths. Text labels are rendered with variable font sizes based on depth, and the SVG supports pan and zoom through a `zoom` event. The data is loaded from a local JSON file containing the full country and regional structure.