A single red rectangle with a thick yellow border occupies the center of an SVG canvas. When hovered over, the rectangle smoothly transitions its fill color to green and expands its border width to 100 pixels. The animation is implemented using pure CSS transitions applied to the SVG `<rect>` element, with a 3000-millisecond duration for all property changes. The example demonstrates how CSS properties like `fill` and `stroke-width` can animate SVG shapes without JavaScript.