Gesture-Driven UI

How to build gestures that feel physical. A gesture is direct manipulation: while the finger is down, the UI is the finger; the moment it lifts, physics takes over. Every rule below follows from that split.

First decision: build it, or use a solution that exists?

Doing a drawer gesture right means momentum-based dragging, overlay opacity matched to drag progress, velocity-aware dismissal, focus trapping, and Escape-to-close. That is weeks of edge cases, not an afternoon. For a bottom sheet / drawer, default to Vaul — it exists precisely because this is hard to hand-roll. Build the gesture yourself only when no library covers the interaction (custom swipe cards, bespoke drag interactions). Use the pick-ui-library skill when unsure.

The two phases of every gesture

Walk this split for any gesture you build. Mixing the phases up is the #1 cause of gestures that feel wrong.

Is the pointer currently down?
├── Yes → TRACK phase: position maps 1:1 to the pointer.
│         No easing. No duration. No spring. The element IS the finger.
└── No  → RELEASE phase: physics finishes the motion.
          A spring seeded with the release velocity. Never a keyframe.

Track phase rules

• 1:1 means 1:1. Drive position from a useMotionValue (or direct transform writes), never a spring or a transition — a spring during tracking makes the element trail the finger and feel disconnected, like dragging something through syrup.
• Write transform directly on the dragged element. Never update a CSS variable on a parent to move children: CSS variables are inheritable, so every change recalculates styles for all descendants. This exact bug made Vaul's drag laggy past ~20 list items; setting transform on the element fixed it.
• No React state per move event. A re-render every pointermove drops frames. Motion values and direct style writes bypass the render cycle.
• Rubber-band at the edges. Dragging past a boundary should move the element a fraction of the distance (Motion: dragElastic ≈ 0.2), not stop dead — hard stops feel like hitting a wall; resistance communicates "there's nothing further" physically.

Release phase rules

• Finish with a spring, seeded with the gesture's velocity. The element should leave the finger at the speed it was moving. A fixed-duration ease here makes every fling land identically, which reads as fake.
• Dismiss on distance OR velocity. Passing a distance threshold (~40–50% of travel) dismisses, but so does a fast flick over a short distance. In Motion, read both from onDragEnd's info.offset and info.velocity. Distance-only thresholds make flicks feel ignored.
• Bounce belongs only at the end of a drag. A drag applies force — like throwing a ball at a wall — so a slight bounce on release feels physical. The same element closed by a button press gets zero bounce: no force was applied. Keep the value small, and remember bounce scales inversely with element size (smaller elements need more bounce to read the same).
• Snap-back is fast. If the gesture doesn't pass the threshold, return quickly with the spring — a slow snap-back feels like the UI is disagreeing with the user in slow motion.

Interruptibility is non-negotiable

The user must be able to catch a sheet mid-close and drag it back. Springs allow this: when retargeted mid-flight they keep their current velocity, so the redirect is seamless. CSS @keyframes restart from zero and cannot be caught — this is why Sonner's early CSS enter animation made toasts jump when a second toast arrived. Never use a keyframe animation on anything a gesture can touch. CSS transitions and springs only.

Linked values

The dragged element is rarely alone — an overlay fades, the page behind scales. Derive these from drag progress, don't animate them separately:

const y = useMotionValue(0);
const overlayOpacity = useTransform(y, [0, drawerHeight], [1, 0]);

One source of truth means the overlay is always exactly as faded as the drawer is dismissed — including mid-gesture, including when the user reverses. Two separate animations drift apart the moment a gesture is interrupted.

Motion drag props

<motion.div
  drag="y"
  dragConstraints={{ top: 0 }}
  dragElastic={0.2}
  onDragEnd={(e, info) => {
    if (info.offset.y > threshold || info.velocity.y > 500) dismiss();
  }}
/>

dragMomentum is on by default — right for a flung card, wrong for a simple reposition; disable it when the element should stop where the finger stops. dragConstraints takes a ref or bounds object.

Sheets without springs: the Vaul curve

Vaul mimics the iOS sheet with pure CSS to stay small: cubic-bezier(0.32, 0.72, 0, 1) over 500ms. The curve is extremely steep at the start — that's what lets a 500ms duration still feel snappy while landing with a spring-like gentle settle. Two rules from it:

• A small floating drawer (not touching the screen edge) should override to ~200ms — the 500ms iOS timing only reads right on a full-width edge-attached sheet:

  [vaul-drawer]  { transition: transform 0.2s cubic-bezier(0.165, 0.84, 0.44, 1); }
  [vaul-overlay] { transition: opacity  0.2s cubic-bezier(0.165, 0.84, 0.44, 1); }

• The component must feel like a single entity. If the drawer opens in 200ms, its height changes and content crossfades must live in the same timing family — one slow sub-animation makes the whole thing feel broken.

Mark interactive children with data-vaul-no-drag so pressing a button inside the drawer doesn't start a drag.

Spatial consistency

An element dismisses in the direction it entered. Sonner's toast slides up from the bottom, so swipe-down dismisses it — enter and exit share one axis, which is what makes the gesture feel discoverable and intuitive without instruction. A gesture that dismisses along an axis the element never moved on has to be learned; one that reverses the entrance is felt.

Hold gestures are asymmetric

Hold-to-delete and similar press-and-hold interactions use linear during the hold — the animation visualizes time passing, and time passes linearly; any other curve lies about how long is left. On release before completion, snap back fast with ease-out. The deliberate phase is slow and honest; the cancel is instant. Symmetric timing here is a bug.

Touch checklist

Run through this for every gesture you ship:

• Test on a real phone — hit the dev server by local IP. Trackpad simulation lies about touch, and a 60Hz desktop monitor hides opacity-transition roughness that a 120Hz phone shows.
• Hit targets ≥ 44×44px. Enlarge small visual targets with an invisible ::before hitbox instead of growing the layout.
• touch-action on the drag axis (touch-action: pan-x for a vertical drag, etc.) so the browser doesn't fight the gesture with native scrolling.
• Gate hover effects behind @media (hover: hover) and (pointer: fine) — touch fires phantom hovers on tap.

Reduced motion

Tracking is direct manipulation — the user is producing the motion — so it stays. What reduces: momentum flings, bounce, and any decorative motion around the gesture. On release under prefers-reduced-motion, settle with a short opacity/position change instead of a bouncy spring. See the animation-accessibility skill for the full two-variant workflow.

When it still feels wrong

A "weird" spring is usually fixed by increasing damping. A gesture that stutters is a performance problem — check the track-phase rules above first, then use the animation-performance skill. To diagnose a feeling you can't name, use the debug-animation skill: record the gesture and scrub it frame by frame.