A donut chart displays sales values by day, with each slice labeled by its corresponding day number and a legend mapping colors to days. Built with D3 v6, the visualization uses `d3.pie` and `d3.arc` to generate slices, `d3.scaleOrdinal` with `schemeCategory10` for coloring, and SVG `path` elements for rendering. Data is loaded from a CSV via `d3.csv`, with values parsed as numbers. A separate, reusable `scatterPlot` module using `scaleLinear`, `extent`, `axisLeft`, and `axisBottom` is also included, though not instantiated in the main script.