Svelte Guideline: Animation — Use tiered animation approach. Description: CSS transitions < tw-animate-css < GSAP < Lottie based on complexity. Do: Simple hover = Tailwind; entry/exit = tw-animate-css; scroll = GSAP; illustrative = Lottie. Don't: GSAP for simple hover states; CSS for complex timelines. Good Example: class='transition-colors hover:bg-primary/90'. Bad Example: gsap.to(btn, { backgroundColor: 'red' }) for hover. Severity: High. Docs: .