This area chart visualizes long-term sales performance across four regions (North, South, East, West), using a stacked layout to show the total sales composition by year. Built with D3 v7, it reads CSV data, parses years, and applies `d3.stack()` with `d3.stackOffsetNone` to create the layered areas, colored via `d3.schemeCategory10`. The chart includes axes, labels, and a legend, with interactive tooltips that display region-specific sales values on mouseover using the `pointer-events` attribute and custom HTML tooltip styling.