This visualization displays 2011 EV stock values as a hierarchical tree chart, with countries (China, India, UK, USA) branching into vehicle categories (buses, cars) and then into BEV and PHEV types with labeled numeric values. The code uses d3.hierarchy and d3.tree to compute the layout, then draws cubic Bezier curves as links. Node and link colors are encoded directly in the JSON data structure, with SVG rendering and a linear-gradient CSS background.