Two pie charts compare the distribution of student grades from the previous term versus the current term. Each donut chart segment is colored by the dominant stress level (high, medium, low), with the percentage label displayed on each slice. Clicking a segment reveals a tooltip with the student count, average study hours, and stress level. The visualization uses D3 v7's `d3.pie`, `d3.arc`, and `.join()` methods on SVG paths, with data loaded from a CSV file and a custom opacity-transition tooltip.