This example shows how a hovering cursor over an area chart reveals the underlying data point for that year. The chart visualizes the relationship between age and monthly income using a smooth, semi-transparent blue area. Built with D3.js v7, it renders to an SVG canvas, with the area's path created via `d3.area` and its curve smoothed using `d3.curveMonotoneX`. Interactive tooltips appear on mouseover, displaying the exact year and sales values, with the code also incorporating standard D3 axes and scales for plotting.