This visualization displays a hierarchical course structure as a node-link tree, with circles representing topics and connecting lines showing parent-child relationships. The tree layout is computed using d3.hierarchy and d3.tree, which positions nodes based on the nested JSON data loaded from hierarchy.json. The SVG rendering uses D3’s data join pattern, binding circle and line elements to descendant and link data respectively, with coordinates mapped to the tree’s computed x and y positions. The visualization fills the entire viewport by dynamically setting the SVG dimensions to the window size.