Animations (React Native / Expo)

Produces or reviews React Native animations that hold 60/120 fps by running motion on the UI thread via Reanimated worklets, respect the OS Reduce Motion setting, and use the cheapest tool for the job — the Reanimated CSS API first, the worklet/hooks API for interactive motion, gesture-handler for touch, and asset runtimes (Lottie / Rive) only for designer-authored art.

This SKILL.md is a thin index. Detailed rules live in rules/*.md and load on demand. This is the native sibling of the animations skill — that one owns web (CSS, Motion, View Transitions); this one owns React Native / Expo.

Core Bet

Animate transform and opacity, and drive the value from the UI thread. Those are the properties the New Architecture applies to a mounted view without a Yoga layout recalculation — the RN analog of the web "composite-only" rule. Layout props (width, height, top, left, flex, margin) recompute layout every frame and jank. Driving the value from the UI thread (a Reanimated shared value, not React useState) keeps motion smooth even when the JS thread is busy. Full property table and the threading model in rules/reanimated-core.md.