A line chart shows average engagement over time, with yearly mean values computed from a CSV dataset using d3.rollup and d3.mean. The SVG rendering uses d3.axisBottom and d3.axisLeft for axes, with a d3.line generator applying curveMonotoneX for smoothing. Data points appear as circles, and the y-axis measures average engagement while the x-axis displays years. The chart is built with D3 v7, drawn in an SVG container, and styled with a blue stroke and filled dots.