This example uses the D3.js library to create a zoomable tree diagram that visualizes hierarchical data from a JSON file, depicting confirmed cases, deaths, and recoveries across hospital departments. The visualization uses an animated, interactive collapsible tree layout where nodes represent locations like clinics and centers, with edge thickness scaled to data values. The code implements custom D3 scales for color and width, and uses SVG rendering with transitions to animate the expanding and collapsing of nodes. Tooltip styling and node colors are defined through CSS and D3's scaleLinear function.