This network graph maps the conceptual relationships between calculus topics, such as derivatives, integrals, and function properties. The visualization employs a force-directed layout, using D3's `forceSimulation`, `forceManyBody`, `forceLink`, and `forceCenter` APIs to position nodes. The graph is rendered as SVG circles and connecting lines, with node sizes and colors indicating hierarchy, from main concepts to child topics and leaf details. The data structure, defined in `data.js`, establishes a network where the largest node represents the core topic of "平均变化率" (average rate of change).