This visualization shows the average fitness levels of males and females across six age groups ranging from 18 to 50 years old. The code imports and averages data from the `@ayush-shinde/cardio_data` package, aggregating individual fitness scores by gender within each age range. Using `d3.scaleBand`, `d3.scaleLinear`, and `d3.stack`, it renders grouped bar charts with steelblue bars for males and salmon for females. Interactive tooltips appear on mouseover, and a legend identifies the gender categories. The animation rendering reveals the comparative fitness trends between genders as age progresses.