This scatter plot displays insurance charges against patient age, with points colored by a user-selected attribute such as smoker status, sex, region, BMI category, or number of children. A legend updates dynamically, and linear regression lines are calculated for each color group to reveal trends. Built with React and D3.js (d3.v7), the visualization uses `d3.csv`, `d3.scaleLinear`, `d3.scaleOrdinal`, and `d3.axisBottom`/`d3.axisLeft` to render the chart from the `data.csv` file.