A scatter plot visualizes sepal length versus sepal width from Fisher's Iris dataset, with points colored by species and a hoverable legend that fades non-matching points. Built with D3.js v7, the code uses `d3.csv` for data loading, `scaleLinear`, `scaleOrdinal`, `axisBottom`, and `axisLeft` for scales and axes, and a `ResizeObserver` to make the SVG responsive. A BBC-inspired color theme distinguishes the three species.