This example shows a monthly sales area chart with hover tooltips. It displays sales values over time, where moving the mouse over the transparent overlay rectangles reveals a tooltip showing the month and its exact sales figure. The visualization is built with D3 v7, using `d3.csv` to load the data from a Gist-hosted CSV file and `d3.area` to generate the filled path. The chart renders as an SVG, with axis labels for "Month" and "Sales," and the hover interaction is implemented via D3’s selection and event handling.