This grouped bar chart visualizes how students' grades (A, B, C, D, E) correlate with their self-reported sleep patterns (e.g., Good, Fair, Poor). The chart uses a D3.js v7 SVG renderer with `d3.scaleBand` for the categorical axes and `d3.scaleOrdinal` with `d3.schemeSet2` for color. It reads a CSV from a Gist, aggregates counts with `d3.rollups`, and displays a tooltip on hover.