This pie chart visualizes monthly expenditures by department, using proportional slices and a color-coded legend. The chart is rendered in SVG on an HTML page. The code loads CSV data from a GitHub gist, processes it with `d3.csv`, and builds arcs using the `d3.pie` and `d3.arc` APIs. Section colors are assigned via `scaleOrdinal`, and labels and legend values are formatted with `d3.format`.