Interactive Visualisation
A treemap visualizes hierarchical sales data from a UK sales CSV, with regions and towns nested by country. Users hover over rectangles to see a breadcrumb showing the region, town, and total sales value. Built with React and D3 v7, the chart uses `d3.stratify`, `d3.treemap`, and `d3.scaleOrdinal` to structure and color the hierarchy, while SVG rendering and `mouseenter` events drive the interactive labels and layout.