A dark-themed SVG line chart displays the average revenue of various sports teams by their founding year. The visualization uses D3 v7 to aggregate data from a CSV file, calculating the mean revenue for each sport per year. Lines are drawn using `d3.line`, with color encoding from `d3.schemeTableau10`. Interactive tooltips appear on hover over data points, showing sport name, year, and average revenue. A legend identifies each sport, rendered within the 800x500 SVG canvas.