The chart fills the entire browser viewport using CSS positioning, and an SVG drawing updates its dimensions to match the container’s computed width and height. The visualization draws a large green X spanning the full diagonal of the canvas, with its stroke width and opacity fixed. The code uses `d3.select` and `d3.append` from D3 v5 to create the SVG, and it redraws the X by reading `clientWidth` and `clientHeight` and re-appending line elements whenever the window resizes via the `resize` event listener.