This interactive area chart visualizes monthly sales data for a product category, with a gradient-filled area beneath a smoothed line and circular markers for each data point. Hovering over a point reveals a tooltip displaying the month and sales value. Built with D3.js v7, it uses `d3.area` and `d3.line` generators with `d3.scaleBand` and `d3.scaleLinear` for axes, rendered as SVG. The code defines a linear gradient via `linearGradient` and attaches mouseover/mouseout handlers for interactivity.