This scatter plot visualizes heart health data from a CSV source, plotting BMI against age categories with circles colored by sex. Built using D3.js, the visualization fetches data via d3-fetch's `csv` function and renders responsive axes with the `@curran/responsive-axes` library. Each circle includes a tooltip via `append('title')` that displays BMI and age values on hover, while mouseover transitions enlarge the circle radius using `select(this).transition().attr('r')`. The plot uses a linear scale for both axes and a gray background rectangle to highlight the data area.