This animation visualizes the mergesort algorithm on 64 shuffled values, displaying every pass through the sort as a separate row of rectangles so the progressive reordering remains visible. Each rectangle’s fill opacity encodes its value, and the sort steps animate via chained d3 transitions. The code uses d3.v3 with ordinal scales for positioning, d3.shuffle to generate the initial array, and SVG rect elements with custom transition timing to copy items between rows, ultimately returning all sorted values to a single row.