This example shows an interactive pie chart visualizing transaction data grouped by card method (VISA, MASTERCARD, VISAELECTRON) and status, with data loaded from a remote API. The chart renders as SVG paths using `d3.pie` and `d3.arc`, with a donut layout and labels connected via polylines. The code uses `d3.rollup` and `d3.group` to aggregate transaction counts, and transitions animate arc updates and label repositioning via `transition.attr`. A spectral color scale maps categories, and clickable labels are appended for potential interactivity.