This interactive Sankey diagram visualizes the flow of values between API endpoints in a Swagger-defined pet store, grouping operations like GET, POST, PUT, and DELETE toward response codes. Built with D3.js v3 and the custom `d3.sankey` layout, nodes are draggable via `d3.behavior.drag`, triggering `sankey.relayout()` to recompute link paths. The SVG rendering uses `sankey.link()` for curved, stroke-width-scaled flows and colors nodes by category. Input data comes from a JSON file mapping resource operations to HTTP methods and status codes.