- Parse @keyframes rules with from/to keywords, percentage stops, and multiple selectors per block (including -webkit-/-moz- prefixes) - Parse animation shorthand and all 8 longhand properties: animation-name, animation-duration, animation-timing-function, animation-delay, animation-iteration-count, animation-direction, animation-fill-mode, animation-play-state - Animation engine reuses transition timing functions and interpolation: cubic-bezier, steps, linear, and all ease-* variants - Multi-keyframe interpolation across arbitrary percentage stops - Direction support: normal, reverse, alternate, alternate-reverse - Fill modes: none, forwards, backwards, both - Iteration count: finite numbers and infinite - Pause/resume support with elapsed time tracking - Animation events: animationstart, animationiteration, animationend - AnimationMap for per-element animation state management - Keyframe property resolution with value resolver callback - Style system integration: AnimationSpec in ComputedStyle, cascade handling for animation properties at all priority levels - 40+ new tests covering parsing, keyframe interpolation, timing, direction, fill modes, pause/resume, events, and animation map Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>