This example displays monthly sales data as a light-blue area chart with an overlaid blue line. It uses D3 v7 to construct a point scale for the months and a linear scale for sales values, then applies the `d3.area` and `d3.line` generators to create the paths. The React starter HTML page renders the visualization as SVG, with axes added via `d3.axisBottom` and `d3.axisLeft`, and text labels for both dimensions. The hardcoded dataset spans January through August with sales increasing from 200 to 750.