If you're building meditation apps, healthcare interfaces, or anything that needs to feel gentle and undemanding, this gives you the timing and easing curves to pull it off. Think 4-6 second breathing cycles, minimal squash and stretch (2-5%), and long settling times that make elements drift to rest like leaves on water. The CSS easing functions and duration tables are immediately useful, and the principle-by-principle breakdown keeps you from accidentally introducing tension through quick movements or aggressive staging. It's opinionated about what calm actually means in motion: slow, predictable, organic, with heavy easing on both ends.
npx skills add https://github.com/dylantarre/animation-principles --skill calm-relaxation