World Countries Tree
This visualization displays a hierarchical tree of world countries, organized by continent and subregion, using a horizontal icicle layout. The interactive SVG graphic uses D3 v5's `tree()` layout, `hierarchy()`, and `linkHorizontal()` to draw the branching structure, with country names plotted as text nodes. Font size decreases with tree depth, and the entire view supports zooming via the `zoom()` event handler. Data comes from a JSON file containing the nested geographic groupings.