This vizhub fork displays a grouped bar chart of student grades (A, B, C, D) across different sleep pattern categories. The chart shows the number of students in each grade category for each sleep pattern, with color-encoded bars for each grade level. Built with D3 v7, the code uses `d3.csv` to load a Gist-hosted dataset, `d3.rollups` for aggregation, `d3.scaleBand` and `d3.scaleLinear` for axes, and `d3.schemeSet2` for color encoding. The visualization includes axis labels, a title, and a tooltip on mouseover.