Use this when you're building those big, theatrical animations that take 1.2 to 2 seconds, like app launch sequences or achievement celebrations. It's grounded in Disney's animation principles adapted for interfaces: anticipation curves of 300-400ms, 30-40% squash and stretch for personality, extended follow-through settling. The easing curves and keyframe examples are specific and tested. The critical bit is knowing these are brand moments, not standard UI. They require skip buttons, returning user detection, and motion sensitivity checks. If you're animating anything users will see more than once, you're probably in the wrong duration range.
npx skills add https://github.com/dylantarre/animation-principles --skill deliberate-1200-2000ms