This example shows an adjacency matrix visualization of a directed weighted graph, with nodes listed along the top and left axes and cells representing edge weights. The code loads two CSV files (`nodelist.csv` and `edgelist.csv`) using `d3.csv` and a custom Promise wrapper to build the matrix. It renders SVG `<rect>` elements for each grid cell, with fill opacity proportional to weight, and adds `<text>` labels for node names. Hovering over a cell highlights all cells in the same row and column by adjusting `stroke-width` via `d3.selectAll`. The visualization uses `d3-selection-multi` for attribute styling, though the primary logic relies on standard D3 v4 selections.