L'altezza della barra era dedotta dai padding delle voci e poi ricopiata a
occhio altrove: `pb-24` nel contenitore delle pagine, `pb-28` nella
celebrazione badge. Su iPhone i conti tornavano per 2 px — barra ~60 px più
34 px di safe area contro 96 px riservati — quindi bastava un inset diverso
(orizzontale, o un modello con home indicator più alta) perché l'ultimo
elemento della pagina finisse sotto la barra. Solo su iOS: su Android
avanzavano 36 px.
Ora la geometria sta in due token, `--altezza-nav` e `--pad-sicura-fondo`, e
le utility `spazio-nav` e `pad-sicura-fondo` la leggono da lì. La striscia
toccabile ha altezza fissa, così misura uguale sui due sistemi e sotto varia
solo l'inset: `max(env(safe-area-inset-bottom), 0.5rem)` dà ad Android un
respiro minimo dove iOS mette la home indicator. Identiche al pixel non
possono essere — quell'inset esiste per un motivo fisico che Android non ha —
ma la differenza è ora un margine in più, non un allineamento diverso.
`100vh` diventa `100dvh` ovunque: su iOS Safari `vh` misura il viewport con la
toolbar collassata, cioè più alto di quello visibile, e le schermate a tutta
altezza risultavano più lunghe dello schermo. `dvh` segue la toolbar.
Aggiunto il ripiego per Chrome su Android, che disattiva `backdrop-filter`
senza accelerazione hardware: senza, su quei device la barra restava
semitrasparente e il contenuto si leggeva attraverso.
Resta fuori portata una differenza sola: in Safari non installata la toolbar
di sistema sta in basso e collassa allo scroll, quindi la barra si muove con
essa. Su Chrome la toolbar è in alto. Si risolve installando la PWA.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
@@ -5,7 +5,7 @@ description: Apple's approach to interface design and fluid, physical motion, tr
# Apple Design
How Apple builds interfaces that stop feeling like a computer and start feeling like an extension of you. This knowledge comes from Apple's WWDC design talks — chiefly *Designing Fluid Interfaces* (WWDC 2018) — distilled and translated into the web platform (CSS, Pointer Events, `requestAnimationFrame`, spring libraries like Motion/Framer Motion).
How Apple builds interfaces that stop feeling like a computer and start feeling like an extension of you. This knowledge comes from Apple's WWDC design talks — chiefly _Designing Fluid Interfaces_ (WWDC 2018) — distilled and translated into the web platform (CSS, Pointer Events, `requestAnimationFrame`, spring libraries like Motion/Framer Motion).
The through-line: **an interface feels alive when motion starts from the current on-screen value, inherits the user's velocity, projects momentum forward, and can be grabbed and reversed at any instant.** Springs are the tool that makes all of this natural, because they are inherently interruptible and velocity-aware.
@@ -23,7 +23,7 @@ The moment lag appears, the feeling of directness "falls off a cliff." Response
- **Respond on pointer-down, not on release.** Highlight a button the instant it's pressed. Waiting for `click`/touch-up to show feedback feels dead.
- **Be vigilant about every latency.** Audit debounces, artificial timers, transition waits, and the ~300ms tap delay. Anything on the input path that isn't essential is a regression.
- **Feedback must be continuous *during* the interaction, not just at the end.** For a drag, slider, or drawer, update the UI 1:1 with the pointer the whole way through — never animate only when the gesture completes.
- **Feedback must be continuous _during_ the interaction, not just at the end.** For a drag, slider, or drawer, update the UI 1:1 with the pointer the whole way through — never animate only when the gesture completes.
```css
/* Feedback lives on the press, and it's instant */
@@ -37,13 +37,13 @@ The moment lag appears, the feeling of directness "falls off a cliff." Response
> "Touch and content should move together."
When the user drags something, it must stay glued to the finger — and respect the offset from *where they grabbed it*. Snapping to the element's center on grab breaks the illusion immediately.
When the user drags something, it must stay glued to the finger — and respect the offset from _where they grabbed it_. Snapping to the element's center on grab breaks the illusion immediately.
- Use Pointer Events with `setPointerCapture` so tracking continues even when the pointer leaves the element's bounds.
- Track a short **velocity/position history** (last few `pointermove` events), not just the current point — you'll need velocity at release.
```js
el.addEventListener('pointerdown',(e)=>{
el.addEventListener("pointerdown",(e)=>{
el.setPointerCapture(e.pointerId);
constgrabOffset=e.clientY-el.getBoundingClientRect().top;// respect where they grabbed
// ...track position + timestamp history for velocity
Every animation must be interruptible and redirectable at any moment. A user must be able to grab a moving element mid-flight and reverse it without waiting for the animation to finish. A closing modal the user grabs again should follow the finger — not finish closing first, then reopen.
- **Never lock out input during a transition.**
- **Always animate from the *presentation* (current) value, never the target value.** On interrupt, read the element's live on-screen transform and start the new animation from there. Starting from the logical/target value causes a visible jump.
- **Always animate from the _presentation_ (current) value, never the target value.** On interrupt, read the element's live on-screen transform and start the new animation from there. Starting from the logical/target value causes a visible jump.
- **Avoid CSS transitions and `@keyframes` for anything gesture-driven** — they can't be smoothly grabbed and reversed mid-flight. Springs animate from the current value by default, which is exactly what interruption needs.
- **When a gesture reverses, blend velocity — don't hard-cut it.** Replacing one animation with another at a reversal creates a velocity discontinuity, a "brick wall." Spring libraries that carry velocity through a re-target avoid it. (This is what iOS's *additive animations* do natively; on the web, choose a spring library that re-targets from the current velocity.)
- **When a gesture reverses, blend velocity — don't hard-cut it.** Replacing one animation with another at a reversal creates a velocity discontinuity, a "brick wall." Spring libraries that carry velocity through a re-target avoid it. (This is what iOS's _additive animations_ do natively; on the web, choose a spring library that re-targets from the current velocity.)
- **Decompose 2D motion into independent X and Y springs.** A single spring on a 2D distance desyncs when X and Y have different velocities.
## 4. Behavior over animation — use springs
@@ -74,27 +74,28 @@ Apple deliberately replaced the physics triplet (mass/stiffness/damping) with tw
- **Response** — how quickly the value reaches the target, in seconds. Lower = snappier. **This is not "duration"** — a spring has no fixed duration; its settle time emerges from the parameters.
**Defaults:**
- Start most UI at **damping `1.0`** (critically damped) — graceful and non-distracting.
- Add bounce (**damping ~`0.8`**) **only when the gesture itself carried momentum** (a flick, a throw, a drag release). Overshoot on a menu that just faded in feels wrong; overshoot on a card you flicked feels right.
**Web mapping (Motion / Framer Motion):** the `bounce` + `duration` spring API maps closely to Apple's damping + response. A safe house style is `damping: 1.0` springs everywhere by default; reserve bounce for momentum-driven, physical interactions.
Example: element at `y=50`, target `y=150` (100px to go), finger moving 50px/s → initial spring velocity = `50 / 100 = 0.5`. Framer Motion / Motion take absolute px/s velocity directly (`velocity` option), so you usually hand it the raw value.
## 6. Momentum projection — animate to where the gesture is *going*
## 6. Momentum projection — animate to where the gesture is _going_
> "Take a small input and make a big output."
Don't snap to the nearest boundary from the *release point*. Use velocity to **project the resting position** — exactly like scroll deceleration — then snap to the target nearest that projected point. This is what makes a flick feel like it throws the element.
Don't snap to the nearest boundary from the _release point_. Use velocity to **project the resting position** — exactly like scroll deceleration — then snap to the target nearest that projected point. This is what makes a flick feel like it throws the element.
Apple's exact projection function (from the *Designing Fluid Interfaces* sample code):
Apple's exact projection function (from the _Designing Fluid Interfaces_ sample code):
```js
// decelerationRate ≈ 0.998 for normal scroll feel; 0.99 for snappier
consttarget=nearestSnapPoint(projectedEndpoint);// choose target from the projection
consttarget=nearestSnapPoint(projectedEndpoint);// choose target from the projection
animateSpringTo(target,{velocity:releaseVelocity});// then hand off velocity (§5)
```
Note: the physics-textbook `v²/(2·decel)` is *not* what Apple ships — use the exponential-decay form above. This is the standard behavior in good bottom-sheets and carousels (Vaul, Embla).
Note: the physics-textbook `v²/(2·decel)` is _not_ what Apple ships — use the exponential-decay form above. This is the standard behavior in good bottom-sheets and carousels (Vaul, Embla).
## 10. Gesture design details (the "feel" checklist)
- **Tap:** highlight on touch-*down* (instant), commit on touch-*up*. Add ~10px of hysteresis/hit padding around the target, and allow cancel-by-dragging-away and back.
- **Tap:** highlight on touch-_down_ (instant), commit on touch-_up_. Add ~10px of hysteresis/hit padding around the target, and allow cancel-by-dragging-away and back.
- **Drag/swipe:** require a small movement threshold (hysteresis, ~10px) before committing to a direction, then track 1:1.
- **Detect all plausible gestures in parallel from the first move**, then confidently cancel the losers once intent is clear. Avoid recognizers that only report a *final* state (`swipeleft`-type events) — they throw away the continuous tracking you need for feedback.
- **Detect all plausible gestures in parallel from the first move**, then confidently cancel the losers once intent is clear. Avoid recognizers that only report a _final_ state (`swipeleft`-type events) — they throw away the continuous tracking you need for feedback.
- **Minimize disambiguation delays.** Double-tap detection unavoidably delays single taps; only pay that cost where double-tap truly exists.
## 11. Frame-level smoothness
Smoothness is about *what's in the frames*, not just the frame rate.
Smoothness is about _what's in the frames_, not just the frame rate.
- Keep the per-frame positional change below the perception threshold to avoid strobing.
- For very fast motion, a subtle **motion blur / stretch** encodes speed and reads better than a hard sharp streak.
@@ -175,7 +176,7 @@ Apple uses translucent materials as a floating functional layer that brings stru
- **Build nav/toolbars/sheets as translucent layers** (`backdrop-filter: blur()` + a semi-transparent background) with content scrolling underneath — not opaque bars that consume a fixed strip.
- **Material weight encodes hierarchy:** darker/heavier materials separate structural regions (sidebars); lighter materials draw attention to interactive elements (buttons). **Never stack a light translucent surface on another** — legibility collapses.
- **Bigger surfaces should read as thicker:** stronger blur + a deeper shadow than small chips. Consider context-aware shadow — heavier over busy/text content for separation, lighter over plain backgrounds.
- **Dim to focus, separate to keep flow.** A modal task pairs the surface with a dimming scrim and pushes the background back/down. A parallel, non-blocking panel uses translucency and offset *without* a scrim so the flow isn't broken. For stacked sheets, progressively dim and push back each parent layer.
- **Dim to focus, separate to keep flow.** A modal task pairs the surface with a dimming scrim and pushes the background back/down. A parallel, non-blocking panel uses translucency and offset _without_ a scrim so the flow isn't broken. For stacked sheets, progressively dim and push back each parent layer.
- **Vibrancy keeps text legible over changing backgrounds.** Over blurred/translucent surfaces, don't use flat gray text — use higher-contrast, slightly heavier weight, and a small letter-spacing bump. Put color on a solid layer, not the translucent foreground.
- **Scroll edge effects, not hard dividers.** Instead of a 1px border under a sticky header, fade a small blur/gradient mask where content meets floating chrome — only where floating UI actually overlaps content.
- **Materialize, don't just fade.** For glass/blur surfaces, animate blur radius and scale together on enter/exit, so the surface reads as a real material arriving rather than a plain opacity fade.
@@ -190,7 +191,7 @@ Apple uses translucent materials as a floating functional layer that brings stru
Three rules for combining senses (from *Designing Audio-Haptic Experiences*):
Three rules for combining senses (from _Designing Audio-Haptic Experiences_):
1.**Causality** — it must be obvious what caused the feedback. Trigger it on the actual causal event (the toggle flipping, the item snapping home), and match its character to the action's physicality.
2.**Harmony** — the visual, the sound, and the haptic must fire on the **same frame**. Latency between them destroys the illusion. Don't let a CSS transition lag the audio/haptic (Vibration API).
@@ -198,7 +199,7 @@ Three rules for combining senses (from *Designing Audio-Haptic Experiences*):
## 14. Reduced motion & accessibility
Reduced motion doesn't mean *no* feedback — it means a gentler, non-vestibular equivalent. Respond to three independent signals and bake them into your components:
Reduced motion doesn't mean _no_ feedback — it means a gentler, non-vestibular equivalent. Respond to three independent signals and bake them into your components:
- **`prefers-reduced-motion: reduce`** — replace slides/springs/parallax with short opacity **cross-fades or static transitions**. Drop elastic/overshoot. Keep opacity/color changes that aid comprehension.
- **`prefers-reduced-transparency: reduce`** — make translucent surfaces frostier/solid: raise background opacity, drop the blur.
## 15. Typography — optical sizing, tracking, leading
Apple designs type to change shape with size; the same discipline applies on the web. (From *The Details of UI Typography*, WWDC 2020.)
Apple designs type to change shape with size; the same discipline applies on the web. (From _The Details of UI Typography_, WWDC 2020.)
- **Tracking (letter-spacing) is size-specific — never one value for all sizes.** Large display text wants *negative* tracking (letters read too far apart as they grow); small text wants slightly *positive* tracking for legibility. A fixed `letter-spacing` is wrong somewhere. Tighten headings, leave body near `0`.
- **Tracking (letter-spacing) is size-specific — never one value for all sizes.** Large display text wants _negative_ tracking (letters read too far apart as they grow); small text wants slightly _positive_ tracking for legibility. A fixed `letter-spacing` is wrong somewhere. Tighten headings, leave body near `0`.
- **Leading (line-height) tracks size inversely.** Tight on large headings, looser on body copy. Increase it for scripts with tall ascenders/descenders; tighten it for dense, information-heavy UI.
- **Build hierarchy from weight + size + leading as a set,** not size alone. Emphasize with weight — it adds presence without taking more space.
- **Respect the user's text-size setting** (Dynamic Type). Scale layout *with* the text — spacing in `rem`/`em`, not fixed px — so a larger font doesn't break the layout.
- **Respect the user's text-size setting** (Dynamic Type). Scale layout _with_ the text — spacing in `rem`/`em`, not fixed px — so a larger font doesn't break the layout.
- **Default to the platform's system font** before a custom face; it already ships optical sizing, tracking tables, and legibility tuning. Override only with a reason.
```css
:root{font:100%/1.5system-ui,sans-serif;}/* body: system font, comfortable leading */
:root{
font:
100%/1.5system-ui,
sans-serif;
}/* body: system font, comfortable leading */
.display{
font-size:clamp(2rem,5vw,4rem);
line-height:1.05;/* tight leading for large text */
letter-spacing:-0.02em;/* negative tracking as it grows */
line-height:1.05;/* tight leading for large text */
letter-spacing:-0.02em;/* negative tracking as it grows */
font-optical-sizing:auto;
}
```
## 16. Design foundations — the eight principles
The motion and craft above serve Apple's eight design principles (*Principles of Great Design*, WWDC 2026). Use these as the names you reason with:
The motion and craft above serve Apple's eight design principles (_Principles of Great Design_, WWDC 2026). Use these as the names you reason with:
1.**Purpose.** Make with intention; decide what *not* to build. Every feature asks for the user's time, attention, and trust — spend that budget only where it pays off.
1.**Purpose.** Make with intention; decide what _not_ to build. Every feature asks for the user's time, attention, and trust — spend that budget only where it pays off.
2.**Agency.** Keep people in control: offer choices, don't force a single path. Back it with forgiveness — easy undo for slips, a confirmation dialog only for genuinely destructive, irreversible actions (use sparingly; overusing it trains people to click through).
3.**Responsibility.** Act in the user's interest. Privacy: ask at the right moment, only for what's needed, transparently. Safety: anticipate misuse and harm — especially with AI (an allergy-aware recipe app must not suggest a harmful ingredient). Add previews, confirmations, disclaimers; cut a feature whose risk outweighs its value.
4.**Familiarity.** Build on what people already know. Use metaphors that are neither too literal nor too abstract (a trash can means delete), and honor their physics. Be consistent: things that look the same must behave the same and live in the same place (close is always top-left on macOS) so people can predict what happens next. Only break a familiar pattern if you can prove it's better — then test it, don't assume.
5.**Flexibility.** Design for different contexts, devices, and the full range of abilities. Adapt to the platform (iPhone = quick touch; desktop = deep workflows with precise pointer control) and to the situation. Design inclusively (age, language, expertise, accessibility). When no single layout fits everyone, let people personalize — rearrange controls, hide what they don't use.
6.**Simplicity — not minimalism.** Strip the unnecessary so the core purpose shines; burying everything in one place looks minimal but isn't simple. Be concise (plain language, no jargon, fewer steps) and clear (use hierarchy — order, spacing, contrast — so the most important thing is the most obvious). Every element earns its place; sometimes *adding* context simplifies (a video scrubber that shows time remaining). Show the common path first, advanced options one level deeper.
6.**Simplicity — not minimalism.** Strip the unnecessary so the core purpose shines; burying everything in one place looks minimal but isn't simple. Be concise (plain language, no jargon, fewer steps) and clear (use hierarchy — order, spacing, contrast — so the most important thing is the most obvious). Every element earns its place; sometimes _adding_ context simplifies (a video scrubber that shows time remaining). Show the common path first, advanced options one level deeper.
7.**Craft.** Uncompromising attention to detail builds trust. Beautiful typography, colors that adapt to light/dark, clear iconography, and responsive animations that give immediate, natural feedback. Nothing is random — every spacing, timing, and alignment value is a deliberate choice you can defend. Jittery scroll, misaligned icons, and layouts that break on rotation read as carelessness. Craft needs iteration and longevity — keep evolving the design as features and hardware change.
8.**Delight.** The result of getting the other seven right, not confetti tacked on top. Decide the emotion you want people to feel (calm, confident, excited) and reinforce it in every decision.
@@ -264,19 +275,19 @@ Tactical rules that serve these:
## Quick Reference
| Need | Technique | Concrete value |
| --- | --- | --- |
| Default UI spring | Critically damped, no overshoot | `damping 1.0`, `response 0.3–0.4` |
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Claude Opus 5