This example renders a pie chart of fictional car brand values using D3 v4 and React. The chart displays ten slices in a circular SVG layout, with each slice colored via d3.scaleOrdinal and d3.schemeCategory10. Hovering over a slice triggers mouseover and mousemove events that show a tooltip with the brand name and value, while reducing the opacity of other slices. A separate legend div is built alongside the SVG, and the chart uses d3.arc and d3.pie for geometry and data binding.