This example demonstrates a single red rectangle that smoothly transitions to green and dramatically thickens its stroke when hovered, using CSS transitions on SVG `rect` elements. The code relies on plain HTML, CSS, and JavaScript, with no external libraries or data sources. It sets initial styles for the rectangle and defines a hover state, allowing the browser to interpolate the fill color and stroke width over three seconds. The empty script tag suggests the visualization is static, with all interaction handled purely through CSS.