fork of exercise 1: SVG Fundamental
This example demonstrates a simple animated landscape composed of SVG shapes, including a gradient-filled sky, a moving circle representing the sun or moon, and two layered landmasses. The scene uses SVG `<rect>`, `<circle>`, and `<path>` elements alongside `<radialGradient>` and `<linearGradient>` definitions. Animation is driven by SVG's native `<animate>` elements, which cycle color changes for the sky gradient and vertical movement for the circle. The code relies solely on standard SVG and HTML APIs, with no external JavaScript libraries.