This line chart tracks cumulative song popularity for the top four singers over time, revealing how each artist’s total popularity grows across released years. The code filters a CSV dataset using `d3.rollups` and `d3.groups`, then sorts by singer and computes running sums of popularity. It renders with D3 v7’s `d3.line`, `d3.scaleLinear`, and `d3.axisBottom`/`axisLeft`, applying `curveMonotoneX` for smooth paths and a color legend via `d3.scaleOrdinal`. The SVG is drawn inside a fixed 800×500 canvas.