Svelte Guideline: Animation — Use GSAP for scroll-driven and staggered. Description: GSAP ScrollTrigger for complex sequences and scroll-based choreography. Do: gsap.from('.card', { y: 60, opacity: 0, stagger: 0.1, scrollTrigger }). Don't: CSS IntersectionObserver with manual animation logic. Good Example: gsap.from(cards, { stagger: 0.1, scrollTrigger: { trigger } }). Bad Example: observer.observe(el); el.classList.add('visible'). Severity: Medium. Docs: https://gsap.com/docs/v3/Plugins/ScrollTrigger.