This visualization shows an adjacency matrix of the top 200 nodes from a Bitcoin transaction network, with blue cells indicating directed edges between source and target nodes. The matrix is rendered as an SVG grid using D3 v7, where each row and column represents a node, allowing users to identify connection patterns and hubs. Hovering over any cell highlights the corresponding row and column labels and displays a tooltip with the source and target IDs. The code uses `d3.csv` to load the node and edge data, then constructs and displays the matrix with `d3.select` and SVG `<rect>` elements.