This example visualizes the total number of hotel bookings per state using a pie chart, with each slice colored by a categorical scale and accompanied by a legend. Hovering over a slice reveals a tooltip showing the state and its booking total. The implementation uses D3.js v6, including `d3.rollup` to aggregate data from a CSV file, `d3.pie` for layout, and `d3.arc` for rendering SVG paths. The chart is built within a React-free HTML page, with smooth opacity transitions for the tooltip on mouse events.