This line chart visualizes solar radiation levels across the eight planets, ordered from Mercury to Neptune. The graph shows a steep decline in radiation from the inner to the outer planets. Using D3 v7, the code loads CSV data, applies a monotone curve to create a smooth line, and renders interactive dots with tooltips. The chart uses `d3.scalePoint` for the x-axis, `d3.scaleLinear` for the y-axis, and `d3.axisBottom`/`d3.axisLeft` for ticks, with SVG output.