This example shows a simple line chart of monthly sales data, with each data point marked by a circle. The chart uses D3.js v7 to render an SVG, with a steelblue line and white-bordered circles. Hovering over a circle reveals a tooltip displaying the month and sales value. The code sets up band and linear scales for the x and y axes, uses the `d3.line` generator to draw the path, and labels both axes for clarity.