This area chart displays the average fuel mileage (MPG) of cars grouped by model year, using a dataset of 30 vehicles parsed from a CSV file. The visualization aggregates individual car records by year, then draws a steel-blue filled area with a darkblue boundary line, red circular data points, and numeric value labels. Built with D3 v7, the code uses `d3.csvParseRows` to clean the data, `d3.rollup` with `d3.mean` for aggregation, and `d3.area()` along with `d3.line()` generators to render the SVG paths.