This pie chart visualizes monthly expense categories from a CSV file, displaying each category's proportion with a colored slice and an outer label. Each slice is rendered with the `d3.arc` path generator, while labels are placed using `d3.arc` centroid calculations. A legend lists categories and values, using `d3.scaleOrdinal` with `d3.schemeCategory10` for colors. The chart is built with D3 v7, rendering to SVG, with the `d3.pie` layout function computing slice angles from the data.