This example demonstrates core SVG fundamentals using four primitive shapes: a circle with a red-to-blue radial gradient, a larger circle with a centered radial gradient, a blue-outlined rectangle, and a red line. The SVG markup defines two radialGradient elements within a defs block, using stop tags to specify color transitions. A linearGradient is also declared but not referenced by any shape. The 800x400 canvas is rendered directly in HTML, with gradients using the url(#id) reference syntax.