A circular sun rises and sets over layered mountain silhouettes in an endless 15-second loop, while the backdrop and landscape colors shift between aliceblue and indigo to simulate day and night. This SVG animation uses SMIL `<animate>` elements on radial and linear gradient stops and on the sun’s `cy` attribute, producing a continuous cycle without JavaScript. Two irregular polygon paths and a curved Bézier path compose the terrain, filled with animated gradients from the inline `<defs>` section.