This example visualizes monthly sales trends from a CSV data source, comparing three product lines from 2019 to 2023. It shows a multi-series line chart with time-scale axes, using D3 v7 and SVG rendering. The code loads data with `d3.csv`, maps dates via `d3.timeParse`, and draws lines with `d3.line`, alongside a legend and axis labels. The second part combines a bar chart for total sales with an overlaid line for average price, using a dual y-axis scale.