This interactive pie chart displays the distribution of electric-vehicle charging stations across cities, with a dropdown menu to switch between metrics: charging ports, daily users, monthly energy, and average charge time. Built with D3 v7, it loads data from a text file, aggregates values by city using `d3.rollup`, and renders SVG slices with `d3.arc`. Hovering reveals a tooltip with percentages, while labels show city names and shares. Animated transitions update the chart when the metric changes.