Everything runs off one Reanimated shared value. useAnimatedScrollHandler writes the ScrollView's contentOffset.y into scrollY on the UI thread, and a single useAnimatedStyle on the header reads it, so the motion never touches the JS thread. The trick is layering: the header sits behind an Animated.ScrollView whose content starts with a transparent spacer the height of the header (364.5pt), then the feed on an opaque black background, so the feed covers the header as you scroll. On overscroll the header translates by -scrollY and rides with the content, exposing a pull-down arrow above it. On scroll it stays pinned, scales linearly from 1 to 0.75 around transformOrigin top, and its opacity and upward drift follow interpolate tables sampled frame by frame from a recording of the X app. Because the header is behind the scroll view, the 1D / 1W / 1M / 1Y / ALL selector is tapped through invisible Pressables in the spacer; it moves the active pill but does not swap chart data. The chart is react-native-svg: a line path traced from the recording, a gradient fill and a dashed baseline. Text uses allowFontScaling={false} so sizes ignore Dynamic Type. Tested in a development build on the iOS simulator with Expo SDK 56, React Native 0.85 and Reanimated 4. Positions are fixed points measured on a 402pt-wide iPhone, so other widths need tuning, and Android has not been verified.
A collapsing scroll header with a price chart, matched to X's coin page: as the feed slides over it, the header shrinks from its top edge and fades. Pull down and it rides with the content to reveal an arrow, with opacity and drift curves sampled frame by frame from a screen recording. Drop it into a crypto, stock or token detail screen.
A React Native camera screen that opens out of the Dynamic Island, then prints each shot as an instant photo that develops on screen. Pull down and the island grows into a live VisionCamera lens; press the shutter and a Skia print feeds out of a slot and comes up over a minute, faster if you shake it. Drop it into a photo or journaling app as its capture screen.
A long-press share menu matched frame by frame to Telegram: hold the share button, slide across recent chats and let go to send. The chosen avatar arcs into a toast and turns into a checkmark, with an envelope-to-bookmark variant for Saved Messages. Drop it into a chat, feed or post list that needs one-gesture sharing.
A horizontal gallery whose slides are wrapped around the inside of a cylinder — works squeeze hard as they roll off toward the edges while growing slightly taller, the way the inside of a partly unrolled scroll does. Drag, fling, or tap a slide that has rolled off to bring it back. Each slide is a Skia triangle mesh re-projected on the UI thread. Dressed as a small gallery archive — putty wall, numbered labels, a live catalogue counter — and hung with seven public-domain paintings, but drop it in for an editorial carousel, a product shelf, or any list that deserves more than a flat swipe.
