World Countries Tree
This visualization displays a hierarchical tree of world countries organized by continent and subregion, using a left-to-right layout with curved links and text labels sized by depth. The data is loaded from a JSON file and processed with `d3.hierarchy` and `d3.tree`, while `d3.linkHorizontal` generates the paths and `d3.zoom` enables panning and zooming on the SVG. Text styling relies on CSS `text-shadow` for readability, and the layout adapts to the full browser viewport.