# Glow icon

> A living app icon: a little ghost glowing in a glassy frame watches your pointer, blinks and jumps when you press it, shown on purple, on a phone and on light.

An app icon with a ghost living in it: it floats in its own light, blinks now and then and follows your pointer with its eyes while the glass tilts towards it. Press it and the icon squishes and the ghost, startled, jumps. A switch shows it on a purple backdrop, on the home screen of a phone held at an angle, where it flies into its slot among plain icons, and on light.

A React component by Bruno Delorence: https://brunodelorence.com/components/glow-icon. MIT License, Copyright (c) 2026 Bruno Delorence.

Category: Motion.

## Anatomy

1. **Backdrop**: The setting the icon is shown in, 16:10 (square on a phone). Its three colours are registered custom properties, so a change of setting cross-fades it in 500 ms.
2. **Aura**: The icon’s light on the backdrop: a radial gradient 1.7 times its size, behind it rather than in it, so the icon’s layer keeps its size as it tilts.
3. **Icon**: A rounded square (corners 22.5% of its size), 55% of the backdrop high: a violet rim, a lavender face and glass on top. It tilts up to 12° towards the pointer and squishes on a spring when pressed.
4. **Ghost**: Milky and translucent, glowing from its heart. It floats while on screen, leans with the tilt and jumps when the icon is let go.
5. **Eyes**: Look from the icon’s centre towards the pointer by up to 2.2 units, worked out in CSS. They blink every few seconds and go wide while the icon is held.
6. **Pool of light**: The glow on the floor under the ghost, breathing as it floats.
7. **Switch**: A `radiogroup` of the three settings; the arrow keys move along it, and its thumb slides on the same spring as the icon’s trip.
8. **Option**: One setting. The chosen one is in full ink, the others muted.

## When to use

- Presenting an app icon on a landing page or a launch post, where the icon is the hero and deserves to feel alive.
- Showing one icon in context: on brand colour, on a phone’s home screen and on light, with one switch between them.
- A mascot that reacts to the visitor: it follows the pointer with its eyes and jumps when pressed.
- A single, large instance with room around it: the scene is 16:10 on a wide page and square on a phone.

## When not to use

- As an actual app icon or favicon: those are flat images. Export the artwork as a PNG or SVG instead.
- In lists, grids or toolbars with many icons: one living icon draws the eye, a dozen compete. Use static images.
- As a button that does something important: pressing it only plays a jump. Use a real button with a label.
- Next to content that needs reading: the float, the blinks and the demo pull attention away from it.

## Installation

Install it with the shadcn CLI, into components/glow-icon of any React project:

```sh
npx shadcn@latest add https://brunodelorence.com/r/glow-icon.json
```

Or copy all the source files below into one folder of your project. Either way it needs React 19 and a bundler with CSS Modules (Next.js, Vite).

It has a dark colour scheme. Its colours are CSS light-dark() pairs, kept inside @supports so that builds which rewrite light-dark() for older browsers leave them alone: it follows your page’s color-scheme (light unless the page sets one) or its colorScheme prop, with nothing to configure. Browsers without light-dark() show it light.

## Usage

```tsx
'use client';

import { useState } from 'react';
import { GlowIcon } from './glow-icon';

export default function AppIconHero() {
  const [presses, setPresses] = useState(0);
  return (
    <>
      <GlowIcon defaultSetting="phone" onPress={() => setPresses((n) => n + 1)} autoplay={false} />
      <p>Pressed {presses} times</p>
    </>
  );
}
```

## States

- **On purple**: The default: the icon in the middle of a vivid purple backdrop, with a soft shadow under it.
- **On a phone**: The icon flies to the first slot of a phone’s home screen held at 24°, shrinks to its icons’ size and turns with it.
- **On light**: A pale lavender backdrop; the icon shrinks a little and its aura shows more.
- **Looking**: With `gaze` held up and to the right, the eyes look there and the icon tilts towards it. The float and the blinks keep playing in every state: they have no prop to stop them.
- **Held down**: `defaultMood="startled"`: the icon squished, the eyes wide. Letting go would make the ghost jump.
- **Dark stage**: With `colorScheme="dark"` (or on a dark page) the stage and the switch go dark; the scene keeps its colours.

## How it works

- The icon is SVG and CSS with no blur filters: a deep violet rim around a lavender face, and a ghost whose body is one radial gradient, violet light at its heart fading to milky white at the edge. A rim of light runs down its lit side, with a halo around it and a pool of light below.
- One pointer listener writes the pointer’s place for the eyes, as registered properties read with atan2() and hypot(), and the icon’s tilt, from -1 to 1 on each axis. The 3D turn, the sliding specular spot and the ghost’s lean are CSS transitions the compositor plays.
- The icon is 3D, with will-change, only while the pointer or the demo is on the stage. Its glow on the backdrop sits beside it rather than inside it, so the tilted layer stays the icon’s size.
- Pressing squishes the icon with the Web Animations API and springs it back on a linear() spring from wherever it had got to. The ghost’s eyes go wide while it is held, and it jumps when it is let go.
- A setting is three registered backdrop colours, so switching cross-fades the backdrop. On the phone, the icon flies into its slot with a translate, a scale and a rotate worked out from the phone drawing’s numbers, so its layer keeps its size.
- Only the frame around the picture, the stage and the switch, takes light-dark() tokens and follows the page’s color-scheme, or the colorScheme prop; the scene itself, icon, glow and backdrops, stays as it is.

## API reference

- **defaultSetting** (`'purple' | 'phone' | 'light'`, default `'purple'`): The setting at first: on a purple backdrop, on the home screen of a phone, or on light.
- **defaultMood** (`'calm' | 'startled'`): The ghost’s mood at first: 'startled' draws the icon held down, squished and wide-eyed, until the reader’s first press. Setting it turns the demo off.
- **gaze** (`{ x: number; y: number }`): Holds the eyes and the tilt on a point of the stage, in shares of its width and height (0 to 1); the reader’s pointer still takes over while on it. Setting it turns the demo off.
- **onPress** (`() => void`): Called when the reader presses the icon.
- **onSettingChange** (`(setting: 'purple' | 'phone' | 'light') => void`): Called when the reader picks a setting on the switch.
- **autoplay** (`boolean`, default `true`): While on screen and untouched, an invisible point wanders (the eyes follow it and the icon tilts towards it), presses the icon once, and changes the setting.
- **colorScheme** (`'light' | 'dark' | 'system'`): Its colours: light, dark, or the reader’s system setting. Without it the component follows the page’s color-scheme, which is light unless the page sets one.
- **className** (`string`): Extra class for the root, a stage of its own.

## Accessibility

- The icon is an image whose name follows the setting (“App icon: a little ghost glowing in a violet frame, on a purple backdrop”); the phone and its placeholder icons are hidden from screen readers.
- Pressing is a real button, “Press the icon”: hold Space or Enter for the squish and let go for the jump, and “Pressed. The ghost jumps.” is announced.
- The setting switch is a radiogroup labelled “Setting”: the arrow keys move the choice, and each change is announced (“On the home screen of a phone.”).
- Under reduced motion the ghost does not float or blink, the icon does not tilt, the eyes keep still, settings change at once, and the demo does not run.

## Source

### glow-icon/glow-icon.tsx

```tsx
// Copyright (c) 2026 Bruno Delorence. MIT License.

'use client';

import {
  useEffect,
  useLayoutEffect,
  useRef,
  useState,
  type CSSProperties,
  type KeyboardEvent,
  type PointerEvent,
} from 'react';
import { IconArt, type Mood } from './icon-art';
import { Phone } from './phone';
import { SETTINGS, type SettingId } from './settings';
import { easingOf, spring } from './spring';
import { runTimeline } from './timeline';
import { useAutoplay } from './use-autoplay';
import styles from './glow-icon.module.css';

/*
 * Glow icon: a living app icon. A little ghost floats in a glassy rounded square, glowing from
 * within; it looks at the pointer, blinks now and then, and jumps when the icon is pressed. A
 * switch shows the icon in three settings: on purple, on the home screen of a phone held at an
 * angle, and on light.
 *
 * - One pointer listener does everything as the pointer moves, without a render: it writes the
 *   pointer's place in the stage's px to registered custom properties (--gi-px, --gi-py), from
 *   which the eyes work out their direction in CSS; and it writes the icon's tilt, -1 to 1 on
 *   each axis (--tx, --ty), which turns the icon in 3D, slides the glass's specular spot and
 *   leans the ghost, all through CSS transitions the compositor plays.
 * - The icon is 3D, and has will-change, only while the pointer (or the demo) is on the stage.
 * - Pressing squishes the icon on a spring (the Web Animations API); the ghost is startled, its
 *   eyes wide, and jumps when the icon is let go.
 * - A change of setting cross-fades the backdrop (its colours are registered custom properties)
 *   and moves the icon: to the middle, or to its slot on the phone's screen, as a translate, a
 *   scale and a turn, so its layer keeps its size.
 * - While on screen and untouched, the demo plays: an invisible point wanders (the eyes follow and
 *   the icon tilts towards it), presses the icon once, and changes the setting.
 * - Light or dark: the stage and the switch are light-dark() tokens in the CSS, so they follow the
 *   page's color-scheme, or the one the colorScheme prop sets. The scene is the picture, the same
 *   in both: the icon, its glow, the phone and the three backdrops.
 */

/** The squish's way back: a spring with a good bounce. */
const BACK = spring(0.5, 520);
/** The springy moves: the switch's thumb, and the icon's trip from one setting to the next. */
const POP = spring(0.22, 520);

/** The demo's invisible point: where it goes (shares of the stage) and how long it takes. */
const WANDER = [
  { x: 0.14, y: 0.18, ms: 1100 },
  { x: 0.88, y: 0.28, ms: 1300 },
  { x: 0.68, y: 0.86, ms: 1100 },
  { x: 0.08, y: 0.74, ms: 1200 },
  { x: 0.46, y: 0.06, ms: 1000 },
];

const reducedMotion = () => window.matchMedia('(prefers-reduced-motion: reduce)').matches;

const clamp = (value: number) => Math.min(1, Math.max(-1, value));

/** Closes and opens the eyes; one time in four, twice. */
function blink(eyes: Element) {
  const twice = Math.random() < 0.25;
  eyes.animate(
    twice
      ? [
          { scale: '1 1' },
          { scale: '1 0.08', offset: 0.2 },
          { scale: '1 1', offset: 0.42 },
          { scale: '1 0.08', offset: 0.62 },
          { scale: '1 1' },
        ]
      : [{ scale: '1 1' }, { scale: '1 0.08', offset: 0.45 }, { scale: '1 1' }],
    { duration: twice ? 440 : 200, easing: 'ease-in-out' },
  );
}

export function GlowIcon({
  defaultSetting = 'purple',
  defaultMood,
  gaze,
  onPress,
  onSettingChange,
  autoplay = true,
  colorScheme,
  className = '',
}: {
  /** The setting at first: on purple, on a phone's home screen, or on light. */
  defaultSetting?: SettingId;
  /**
   * Opens with the ghost in this mood: 'startled' draws the icon held down (squished, eyes wide)
   * until the reader's first press. Setting it turns the demo off.
   */
  defaultMood?: Mood;
  /**
   * Holds the gaze on a point of the stage, in shares of its width and height (0 to 1): the eyes
   * look at it and the icon tilts towards it; the reader's pointer still takes over while on it.
   * Setting it turns the demo off.
   */
  gaze?: { x: number; y: number };
  /** Called when the reader presses the icon. */
  onPress?: () => void;
  /** Called when the reader picks a setting on the switch. */
  onSettingChange?: (setting: SettingId) => void;
  /** While on screen and untouched, an invisible point plays with the icon on its own. */
  autoplay?: boolean;
  /** Light or dark colours, or 'system' for the reader's; without it, the page's color-scheme. */
  colorScheme?: 'light' | 'dark' | 'system';
  className?: string;
}) {
  const { ref: root, playing, take } = useAutoplay<HTMLDivElement>(6000);
  const [settingId, setSettingId] = useState<SettingId>(defaultSetting);
  const [mood, setMood] = useState<Mood>(defaultMood ?? 'calm');
  /** Drawn held down by defaultMood, until the reader's first press. */
  const [held, setHeld] = useState(defaultMood === 'startled');
  /** The reader is on the keyboard in here: the demo waits until they leave. */
  const [keyboard, setKeyboard] = useState(false);
  const [message, setMessage] = useState('');

  const hero = useRef<HTMLDivElement>(null);
  const squish = useRef<HTMLDivElement>(null);
  const ghost = useRef<HTMLDivElement>(null);
  const eyes = useRef<SVGGElement>(null);
  const options = useRef<(HTMLButtonElement | null)[]>([]);
  /** The squish in progress. */
  const squishing = useRef<Animation | null>(null);
  const moodTimer = useRef(0);
  const measureTimer = useRef(0);
  /** A press that pointer or keys began, so the click that follows is not a second one. */
  const pressing = useRef(false);
  const skipClick = useRef(false);
  /** The icon's centre is measured and current: its eyes look, and it tilts, from there. */
  const measured = useRef(false);
  const centre = useRef({ x: 0, y: 0 });
  const stopDemo = useRef<(() => void) | null>(null);

  const setting = SETTINGS.find((s) => s.id === settingId) ?? SETTINGS[0];
  const settingIndex = SETTINGS.indexOf(setting);

  /** Repeats are made to differ, so screen readers announce them again. */
  const announce = (text: string) => setMessage((now) => (now === text ? `${text}\u00a0` : text));

  /**
   * The icon's centre, in the stage's px, as --cx and --cy: its eyes look from there. Read from
   * the screen, so that it is where its last trip took it (on the phone, its slot).
   */
  const measure = () => {
    const stage = root.current;
    const art = hero.current?.querySelector<HTMLElement>('[data-looker]');
    if (!stage || !art || measured.current) return;
    measured.current = true;
    const frame = stage.getBoundingClientRect();
    const scale = frame.width / stage.offsetWidth || 1;
    const box = art.getBoundingClientRect();
    centre.current = {
      x: (box.left + box.width / 2 - frame.left) / scale,
      y: (box.top + box.height / 2 - frame.top) / scale,
    };
    art.style.setProperty('--cx', `${centre.current.x}px`);
    art.style.setProperty('--cy', `${centre.current.y}px`);
  };

  /**
   * Looks at a point of the stage (in its px): the eyes turn to it, and the icon tilts towards
   * it, more the farther it is. `ms` is how long the tilt takes to get there.
   */
  const aim = (x: number, y: number, ms: number) => {
    const stage = root.current;
    const icon = hero.current;
    if (!stage || !icon) return;
    measure();
    const reach = Math.max(200, stage.offsetWidth * 0.36);
    icon.dataset.active = '';
    icon.style.setProperty('--tilt-ms', `${ms}ms`);
    icon.style.setProperty('--tx', clamp((x - centre.current.x) / reach).toFixed(3));
    icon.style.setProperty('--ty', clamp((y - centre.current.y) / reach).toFixed(3));
    stage.style.setProperty('--gi-px', `${x}px`);
    stage.style.setProperty('--gi-py', `${y}px`);
    stage.style.setProperty('--gi-look', '1');
  };

  /** Back to rest: the eyes to the middle, the icon flat and back in its own plane. */
  const relax = () => {
    const icon = hero.current;
    root.current?.style.setProperty('--gi-look', '0');
    if (!icon) return;
    icon.style.setProperty('--tilt-ms', '700ms');
    icon.style.setProperty('--tx', '0');
    icon.style.setProperty('--ty', '0');
    delete icon.dataset.active;
  };

  /** Held down: the icon squishes, the ghost is startled. */
  const pressDown = () => {
    window.clearTimeout(moodTimer.current);
    setMood('startled');
    setHeld(false);
    const element = squish.current;
    if (!element || reducedMotion()) return;
    squishing.current?.cancel();
    squishing.current = element.animate([{ scale: '1 1' }, { scale: '1.07 0.88' }], {
      duration: 170,
      easing: 'cubic-bezier(0.3, 0, 0.3, 1)',
      fill: 'forwards',
    });
  };

  /** Let go: the icon springs back, and the ghost jumps before it calms down. */
  const pressUp = (byReader: boolean) => {
    window.clearTimeout(moodTimer.current);
    moodTimer.current = window.setTimeout(() => setMood('calm'), 650);
    if (byReader) {
      onPress?.();
      announce('Pressed. The ghost jumps.');
    }
    const element = squish.current;
    if (!element || reducedMotion()) return;
    // From wherever the squish had got to.
    const from = getComputedStyle(element).scale;
    squishing.current?.cancel();
    squishing.current = element.animate(
      [{ scale: from === 'none' ? '1 1' : from }, { scale: '1 1' }],
      { duration: BACK.duration, easing: easingOf(BACK) },
    );
    ghost.current?.animate(
      [
        { transform: 'none' },
        { transform: 'translateY(-9%) rotate(-4deg)', offset: 0.3 },
        { transform: 'translateY(-4%) rotate(3deg)', offset: 0.55 },
        { transform: 'translateY(1%) rotate(-1deg)', offset: 0.8 },
        { transform: 'none' },
      ],
      { duration: 620, easing: 'ease-out' },
    );
  };

  const changeSetting = (id: SettingId, byReader: boolean) => {
    if (id === settingId) return;
    setSettingId(id);
    // The icon moves: its centre is measured again once it has got there.
    measured.current = false;
    window.clearTimeout(measureTimer.current);
    measureTimer.current = window.setTimeout(() => {
      measured.current = false;
    }, POP.duration);
    if (byReader) {
      announce(`On ${SETTINGS.find((s) => s.id === id)?.place ?? id}.`);
      onSettingChange?.(id);
    }
  };

  // The centre moves when the stage changes size.
  useEffect(() => {
    const stage = root.current;
    if (!stage) return;
    const observer = new ResizeObserver(() => {
      measured.current = false;
    });
    observer.observe(stage);
    return () => observer.disconnect();
  }, [root]);

  // Awake while on screen in a visible tab: the ghost floats (CSS, on data-awake) and blinks
  // every few seconds, sometimes twice.
  useEffect(() => {
    const stage = root.current;
    if (!stage) return;
    const motion = window.matchMedia('(prefers-reduced-motion: reduce)');
    let onScreen = false;
    let timer = 0;
    const update = () => {
      const awake = onScreen && !document.hidden;
      stage.toggleAttribute('data-awake', awake);
      window.clearTimeout(timer);
      if (awake && !motion.matches) timer = window.setTimeout(tick, 1800 + Math.random() * 2600);
    };
    const tick = () => {
      // Not while startled: its eyes are wide open.
      if (eyes.current && !eyes.current.closest('[data-mood="startled"]')) blink(eyes.current);
      update();
    };
    const observer = new IntersectionObserver(([entry]) => {
      onScreen = entry.isIntersecting;
      update();
    });
    observer.observe(stage);
    document.addEventListener('visibilitychange', update);
    motion.addEventListener('change', update);
    return () => {
      observer.disconnect();
      document.removeEventListener('visibilitychange', update);
      motion.removeEventListener('change', update);
      window.clearTimeout(timer);
    };
  }, [root]);

  useEffect(
    () => () => {
      window.clearTimeout(moodTimer.current);
      window.clearTimeout(measureTimer.current);
      squishing.current?.cancel();
    },
    [],
  );

  // The demo calls the handlers of the latest render.
  const actions = useRef({ aim, relax, pressDown, pressUp, changeSetting, settingIndex });
  useLayoutEffect(() => {
    actions.current = { aim, relax, pressDown, pressUp, changeSetting, settingIndex };
  });

  // The demo: the invisible point wanders, presses the icon, and the setting changes; again while
  // on screen and untouched.
  const demo = autoplay && !gaze && !defaultMood && playing && !keyboard;

  // A held gaze: aimed once laid out, and again once a change of setting has moved the icon.
  const gazeX = gaze?.x;
  const gazeY = gaze?.y;
  useEffect(() => {
    const stage = root.current;
    if (gazeX === undefined || gazeY === undefined || !stage) return;
    const look = () => {
      measured.current = false;
      actions.current.aim(gazeX * stage.offsetWidth, gazeY * stage.offsetHeight, 500);
    };
    const frame = requestAnimationFrame(look);
    const timer = window.setTimeout(look, POP.duration + 50);
    return () => {
      cancelAnimationFrame(frame);
      window.clearTimeout(timer);
    };
  }, [gazeX, gazeY, settingId, root]);
  useEffect(() => {
    const stage = root.current;
    if (!demo || !stage) return;
    const act = () => actions.current;
    stage.dataset.demo = '';
    const stop = runTimeline(async (wait) => {
      await wait(600);
      for (let round = 0; ; round += 1) {
        // Three stops of the wander, a different three each round.
        for (let i = 0; i < 3; i += 1) {
          const point = WANDER[(round * 3 + i) % WANDER.length];
          stage.style.setProperty('--move', `${point.ms}ms`);
          act().aim(point.x * stage.offsetWidth, point.y * stage.offsetHeight, point.ms);
          await wait(point.ms + 250);
        }
        // Onto the icon, and a press.
        const { x, y } = centre.current;
        stage.style.setProperty('--move', '700ms');
        act().aim(x + 6, y + 10, 700);
        await wait(800);
        act().pressDown();
        await wait(240);
        act().pressUp(false);
        await wait(1500);
        act().changeSetting(SETTINGS[(act().settingIndex + 1) % SETTINGS.length].id, false);
        await wait(1500);
      }
    });
    stopDemo.current = () => {
      stop();
      delete stage.dataset.demo;
      actions.current.relax();
    };
    return () => {
      stopDemo.current?.();
      stopDemo.current = null;
    };
  }, [demo, root]);

  /** The reader takes over: the demo stops at once, and waits until they leave it alone. */
  const readerActs = () => {
    stopDemo.current?.();
    stopDemo.current = null;
    take();
  };

  const onPointerMove = (event: PointerEvent<HTMLDivElement>) => {
    if (event.pointerType !== 'touch') readerActs();
    const stage = event.currentTarget;
    const frame = stage.getBoundingClientRect();
    // Screen pixels to the stage's own, should the stage sit in a scaled container.
    const scale = frame.width / stage.offsetWidth || 1;
    aim((event.clientX - frame.left) / scale, (event.clientY - frame.top) / scale, 500);
  };

  const onSwitchKeyDown = (event: KeyboardEvent<HTMLDivElement>) => {
    const step = { ArrowRight: 1, ArrowDown: 1, ArrowLeft: -1, ArrowUp: -1 }[event.key];
    if (!step) return;
    event.preventDefault();
    const next = (settingIndex + step + SETTINGS.length) % SETTINGS.length;
    changeSetting(SETTINGS[next].id, true);
    options.current[next]?.focus();
  };

  const isPressKey = (event: KeyboardEvent) => event.key === ' ' || event.key === 'Enter';

  return (
    <div
      ref={root}
      className={`${styles.root} ${className}`}
      data-color-scheme={colorScheme}
      style={
        {
          '--gi-top': setting.top,
          '--gi-middle': setting.middle,
          '--gi-bottom': setting.bottom,
          '--pop': POP.easing,
          '--pop-ms': `${POP.duration}ms`,
        } as CSSProperties
      }
      onPointerDownCapture={readerActs}
      onKeyDownCapture={readerActs}
      onPointerMove={onPointerMove}
      onPointerLeave={() => {
        const stage = root.current;
        if (gazeX === undefined || gazeY === undefined || !stage) relax();
        else aim(gazeX * stage.offsetWidth, gazeY * stage.offsetHeight, 700);
      }}
      onFocus={(event) => {
        if ((event.target as Element).matches(':focus-visible')) setKeyboard(true);
      }}
      onBlur={(event) => {
        if (!event.currentTarget.contains(event.relatedTarget)) setKeyboard(false);
      }}
    >
      <div className={styles.frame}>
        <div className={styles.scene} data-setting={setting.id} data-part="scene">
          <Phone />
          {/* Its light on the backdrop: beside the icon, not in it, so the icon's layer stays
              the icon's size as it tilts. */}
          <span className={styles.aura} data-part="aura" />
          <div ref={hero} className={styles.hero}>
            <div
              ref={squish}
              className={styles.squish}
              style={held ? { scale: '1.07 0.88' } : undefined}
            >
              <IconArt
                mood={mood}
                eyes={eyes}
                ghost={ghost}
                label={`App icon: a little ghost glowing in a violet frame, on ${setting.place}`}
              />
            </div>
            <button
              type="button"
              className={styles.press}
              data-part="press"
              aria-label="Press the icon"
              onPointerDown={(event) => {
                if (event.button !== 0) return;
                event.currentTarget.setPointerCapture(event.pointerId);
                pressing.current = true;
                pressDown();
              }}
              onPointerUp={() => {
                if (!pressing.current) return;
                pressing.current = false;
                skipClick.current = true;
                pressUp(true);
              }}
              onPointerCancel={() => {
                if (!pressing.current) return;
                pressing.current = false;
                pressUp(false);
              }}
              onKeyDown={(event) => {
                if (!isPressKey(event)) return;
                event.preventDefault();
                if (event.repeat || pressing.current) return;
                pressing.current = true;
                pressDown();
              }}
              onKeyUp={(event) => {
                if (!isPressKey(event) || !pressing.current) return;
                pressing.current = false;
                skipClick.current = true;
                pressUp(true);
              }}
              onClick={() => {
                // A click with no pointer or key before it (a screen reader's): a whole press.
                if (skipClick.current) {
                  skipClick.current = false;
                  return;
                }
                pressDown();
                window.setTimeout(() => pressUp(true), 160);
              }}
            />
          </div>
        </div>

        <div
          role="radiogroup"
          aria-label="Setting"
          className={styles.switch}
          data-part="switch"
          style={{ '--i': settingIndex } as CSSProperties}
          onKeyDown={onSwitchKeyDown}
        >
          <span className={styles.thumb} aria-hidden="true" data-part="thumb" />
          {SETTINGS.map((option, i) => (
            <button
              key={option.id}
              ref={(element) => {
                options.current[i] = element;
              }}
              type="button"
              role="radio"
              aria-checked={option.id === setting.id}
              tabIndex={option.id === setting.id ? 0 : -1}
              className={styles.option}
              data-part="option"
              onClick={() => changeSetting(option.id, true)}
            >
              {option.label}
            </button>
          ))}
        </div>
      </div>
      <p className={styles.hidden} role="status">
        {message}
      </p>
    </div>
  );
}
```

### glow-icon/glow-icon.module.css

```css
/* Glow icon (glow-icon.tsx): a light stage with the scene, the setting the icon is shown in, and
   the switch under it; at night the stage and the switch go dark, and the scene (the icon, its
   glow, the phone and the three backdrops) keeps its colours. The backdrop's colours are
   registered custom properties, so a change of setting cross-fades it; the pointer's place
   (--gi-px, --gi-py) and --gi-look are registered so that the demo can glide them and the eyes
   ease back. Prefixed, as @property names are global. */

@property --gi-top {
  syntax: '<color>';
  inherits: true;
  initial-value: #7d43f0;
}
@property --gi-middle {
  syntax: '<color>';
  inherits: true;
  initial-value: #6a2fdc;
}
@property --gi-bottom {
  syntax: '<color>';
  inherits: true;
  initial-value: #5b24c8;
}
@property --gi-px {
  syntax: '<length>';
  inherits: true;
  initial-value: 0px;
}
@property --gi-py {
  syntax: '<length>';
  inherits: true;
  initial-value: 0px;
}
@property --gi-look {
  syntax: '<number>';
  inherits: true;
  initial-value: 0;
}

.root {
  /* Its colours, light and dark: each light-dark() pair resolves by the color-scheme the root
     inherits from the page, or the one the colorScheme prop sets (below). */
  /* The stage, then the switch's thumb a step up, on its track. */
  --surface: #e8e8eb;
  --surface-2: #fff;
  --track: #dcdce3;
  /* The chosen setting's name, then the others'. */
  --ink: #1d1d1f;
  --ink-muted: #6e6e73;
  /* The stage's edge and dots, the scene's edge, the thumb's edge. */
  --line: rgb(0 0 0 / 0.06);
  --dots: rgb(0 0 0 / 0.05);
  --scene-line: rgb(0 0 0 / 0.06);
  --thumb-line: rgb(0 0 0 / 0.05);
  /* The focus ring, and what would sit on it. */
  --accent: #0a84ff;
  --accent-ink: #fff;
  /* The thumb's shade right under it and its soft drop. */
  --shadow-near: rgb(0 0 0 / 0.08);
  --shadow: rgb(0 0 0 / 0.14);
  --tilt-ease: cubic-bezier(0.2, 0.8, 0.3, 1);
  --move: 0ms;
  position: relative;
  container-type: inline-size;
  overflow: hidden;
  overflow: clip;
  border-radius: 18px;
  background:
    radial-gradient(var(--dots) 1px, transparent 1px) 0 0 / 14px 14px,
    var(--surface);
  box-shadow: inset 0 0 0 1px var(--line);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, 'SF Pro Text', Inter, 'Segoe UI', sans-serif;
  -webkit-font-smoothing: antialiased;
  -webkit-tap-highlight-color: transparent;
  -webkit-user-select: none;
  user-select: none;
  transition:
    --gi-top 0.5s ease,
    --gi-middle 0.5s ease,
    --gi-bottom 0.5s ease,
    --gi-look 0.4s ease;
}
@supports (color: light-dark(#fff, #000)) {
  .root {
    --surface: light-dark(#e8e8eb, #111113);
    --surface-2: light-dark(#fff, #48484c);
    --track: light-dark(#dcdce3, #2a2a2e);
    --ink: light-dark(#1d1d1f, #f5f5f7);
    --ink-muted: light-dark(#6e6e73, #a1a1a6);
    --line: light-dark(rgb(0 0 0 / 0.06), rgb(255 255 255 / 0.07));
    --dots: light-dark(rgb(0 0 0 / 0.05), rgb(255 255 255 / 0.05));
    --scene-line: light-dark(rgb(0 0 0 / 0.06), rgb(255 255 255 / 0.08));
    --thumb-line: light-dark(rgb(0 0 0 / 0.05), rgb(255 255 255 / 0.06));
    --accent: light-dark(#0a84ff, #3594ff);
    --shadow-near: light-dark(rgb(0 0 0 / 0.08), rgb(0 0 0 / 0.3));
    --shadow: light-dark(rgb(0 0 0 / 0.14), rgb(0 0 0 / 0.45));
  }
}
/* The demo's invisible point glides. */
.root[data-demo] {
  transition:
    --gi-top 0.5s ease,
    --gi-middle 0.5s ease,
    --gi-bottom 0.5s ease,
    --gi-look 0.4s ease,
    --gi-px var(--move) cubic-bezier(0.45, 0, 0.3, 1),
    --gi-py var(--move) cubic-bezier(0.35, 0.1, 0.3, 1);
}
:where(.root) button {
  margin: 0;
  font: inherit;
  color: inherit;
}

/* The colorScheme prop. Without it the root sets nothing and inherits the page's color-scheme. */
.root[data-color-scheme='light'] {
  color-scheme: light;
}
.root[data-color-scheme='dark'] {
  color-scheme: dark;
}
.root[data-color-scheme='system'] {
  color-scheme: light dark;
}

.frame {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
  padding: 22px 24px 20px;
}

/* The scene: 16:10, a square on a phone, measured in its own height (cqh) so that the icon and
   the phone scale with it. The icon is 55% of it high. */
.scene {
  --hero: 55cqh;
  position: relative;
  container-type: size;
  width: 100%;
  aspect-ratio: 16 / 10;
  overflow: hidden;
  overflow: clip;
  border-radius: 22px;
  background: linear-gradient(180deg, var(--gi-top), var(--gi-middle) 55%, var(--gi-bottom));
  box-shadow: inset 0 0 0 1px var(--scene-line);
}
.scene[data-setting='purple'] {
  --aura: 0.42;
  --icon-shadow: 0 2.6cqh 7cqh -2cqh rgb(36 4 104 / 0.6);
}
.scene[data-setting='phone'] {
  --aura: 0.85;
  --icon-shadow: none;
}
.scene[data-setting='light'] {
  --aura: 0.75;
  --icon-shadow: 0 2.6cqh 7cqh -2.4cqh rgb(84 44 196 / 0.36);
}

/* The phone (phone.tsx), in phone units of 0.15cqh. Its body's top left corner, 30 units in from
   the drawing's left edge, sits 41.3cqh left of the middle and 23cqh down, and the phone turns
   24° about it. That brings the centre of the first icon slot (192, 246 units in) to 5cqh above
   the middle of the scene: where the icon goes. */
.phone {
  position: absolute;
  top: 23cqh;
  left: calc(50cqw - 45.8cqh);
  width: 154.5cqh;
  height: 300cqh;
  transform-origin: 4.5cqh 0;
  rotate: -24deg;
  visibility: hidden;
}
.scene[data-setting='phone'] .phone {
  visibility: visible;
}

/* The icon, and its light behind it. Both sit in the middle; on light they shrink a little, and
   on the phone they go to the icon's slot, shrink to the screen's icon size (172 units, 25.8cqh)
   and turn with the phone. A translate, a scale and a rotate: their layers keep their size. */
.hero,
.aura {
  position: absolute;
  top: 50%;
  left: 50%;
  width: var(--hero);
  height: var(--hero);
  margin: calc(var(--hero) / -2);
  transition:
    translate var(--pop-ms) var(--pop),
    scale var(--pop-ms) var(--pop),
    rotate var(--pop-ms) var(--pop),
    opacity 0.5s ease;
}
.scene[data-setting='light'] :is(.hero, .aura) {
  scale: 0.84;
}
.scene[data-setting='phone'] :is(.hero, .aura) {
  translate: 0 -5cqh;
  scale: 0.469;
  rotate: -24deg;
}
/* While the pointer (or the demo) is on the stage, the icon turns in 3D to face it (--tx, --ty
   from -1 to 1), and only then has will-change. */
.hero {
  --tx: 0;
  --ty: 0;
  --tilt-ms: 500ms;
  --hero-scale: 1;
  transition:
    translate var(--pop-ms) var(--pop),
    scale var(--pop-ms) var(--pop),
    rotate var(--pop-ms) var(--pop),
    transform var(--tilt-ms) var(--tilt-ease);
}
.scene[data-setting='light'] .hero {
  --hero-scale: 0.84;
}
.scene[data-setting='phone'] .hero {
  --hero-scale: 0.469;
}
.hero[data-active] {
  transform: perspective(calc(var(--hero) * 3.6)) rotateX(calc(var(--ty) * -12deg))
    rotateY(calc(var(--tx) * 12deg));
  will-change: transform;
}
/* Its glow on the backdrop, drawn bigger than the icon from the same box. */
.aura {
  border-radius: 50%;
  background: radial-gradient(
    closest-side,
    rgb(226 212 255 / 0.62),
    rgb(186 154 255 / 0.2) 55%,
    transparent
  );
  opacity: var(--aura);
  pointer-events: none;
  transform: scale(1.7);
}
.squish {
  position: absolute;
  inset: 0;
  border-radius: 22.5%;
  box-shadow: var(--icon-shadow);
  transform-origin: 50% 75%;
}
.press {
  position: absolute;
  inset: 0;
  padding: 0;
  border: 0;
  border-radius: 22.5%;
  background: none;
  cursor: pointer;
  touch-action: manipulation;
}
.press:focus-visible {
  outline: calc(2px / var(--hero-scale)) solid var(--accent);
  outline-offset: calc(5px / var(--hero-scale));
}

/* The icon (icon-art.tsx): its layers measured in its own size. */
.icon {
  position: relative;
  container-type: size;
  overflow: hidden;
  width: 100%;
  height: 100%;
  border-radius: 22.5%;
  background: #4a1ea9;
}
.layer {
  position: absolute;
  inset: 0;
  display: block;
  width: 100%;
  height: 100%;
}
/* The pool of light under the ghost. */
.pool {
  position: absolute;
  top: 78.5%;
  left: 23%;
  width: 54%;
  height: 10%;
  border-radius: 50%;
  background: radial-gradient(
    closest-side,
    rgb(255 255 255 / 0.78),
    rgb(238 230 255 / 0.28) 55%,
    transparent
  );
}
.ghost,
.bob {
  position: absolute;
  inset: 0;
}
.arm {
  fill: #ece4ff;
  opacity: 0.94;
}
.rim,
.backlight {
  fill: none;
  stroke-width: 1.3;
  stroke-linecap: round;
}
.backlight {
  stroke: #fff;
  stroke-opacity: 0.35;
  stroke-width: 1;
}
.blush {
  fill: #ff8ccc;
  opacity: 0.32;
}
/* The glass: a sheen from the top, a rim of light, and a specular spot. */
.sheen {
  position: absolute;
  inset: 0;
  border-radius: inherit;
  background: linear-gradient(160deg, rgb(255 255 255 / 0.16), rgb(255 255 255 / 0) 42%);
  box-shadow:
    inset 0 0.7cqw 0 -0.2cqw rgb(255 255 255 / 0.3),
    inset 0 0 0 0.5cqw rgb(255 255 255 / 0.06);
}
.spot {
  position: absolute;
  top: -25%;
  left: -25%;
  width: 150%;
  height: 150%;
  background: radial-gradient(
    closest-side,
    rgb(255 255 255 / 0.3),
    rgb(255 255 255 / 0.08) 42%,
    transparent 70%
  );
  translate: calc(-15% + var(--tx, 0) * 22%) calc(-19% + var(--ty, 0) * 22%);
  transition: translate var(--tilt-ms, 0.5s) var(--tilt-ease);
}
/* The ghost leans towards the pointer as the icon tilts, floats while awake, and its pool of
   light breathes with it. */
.ghost {
  translate: calc(var(--tx, 0) * 2.4%) calc(var(--ty, 0) * 2.4%);
  transition: translate var(--tilt-ms, 0.5s) var(--tilt-ease);
}
.bob {
  animation: float 3.4s ease-in-out infinite alternate paused;
}
.pool {
  animation: breathe 3.4s ease-in-out infinite alternate paused;
}
.root[data-awake] .bob,
.root[data-awake] .pool {
  animation-play-state: running;
}

/* The eyes look from the icon's centre (--cx, --cy) towards the pointer: in its direction
   (atan2), by up to 2.2 units, less when the pointer is close (hypot). --gi-look eases them in
   and back. Blinks squash them with `scale`; a fright widens them. */
.eyes {
  --dx: calc(var(--gi-px) - var(--cx));
  --dy: calc(var(--gi-py) - var(--cy));
  --reach: calc(min(2.2px, hypot(var(--dx), var(--dy)) * 0.03) * var(--gi-look));
  transform-box: fill-box;
  transform-origin: center;
  translate: calc(cos(atan2(var(--dy), var(--dx))) * var(--reach))
    calc(sin(atan2(var(--dy), var(--dx))) * var(--reach));
  transition: scale 0.15s ease;
}
.icon[data-mood='startled'] .eyes {
  scale: 1.24;
}

/* The switch. */
.switch {
  position: relative;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  width: min(100%, 300px);
  padding: 3px;
  border-radius: 999px;
  background: var(--track);
}
.thumb {
  position: absolute;
  top: 3px;
  bottom: 3px;
  left: 3px;
  width: calc((100% - 6px) / 3);
  border-radius: 999px;
  background: var(--surface-2);
  box-shadow:
    0 0 0 0.5px var(--thumb-line),
    0 1px 2px var(--shadow-near),
    0 3px 8px -3px var(--shadow);
  translate: calc(var(--i) * 100%) 0;
  transition: translate var(--pop-ms) var(--pop);
}
.option {
  position: relative;
  height: 34px;
  padding: 0 8px;
  border: 0;
  border-radius: 999px;
  background: none;
  font-size: 13.5px;
  font-weight: 600;
  color: var(--ink-muted);
  cursor: pointer;
  transition: color 0.2s ease;
}
.option[aria-checked='true'] {
  color: var(--ink);
}
.option:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
}

/* For screen readers only: the announcements. */
.hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
}

@keyframes float {
  from {
    transform: translateY(1.5%);
  }
  to {
    transform: translateY(-2.5%);
  }
}
@keyframes breathe {
  from {
    opacity: 1;
    transform: scale(1);
  }
  to {
    opacity: 0.7;
    transform: scale(0.86);
  }
}

/* A phone: a square scene. */
@container (max-width: 479px) {
  .frame {
    padding: 14px 14px 16px;
  }
  .scene {
    aspect-ratio: 1;
    border-radius: 18px;
  }
}

/* Final states at once: no float, no tilt, no blink. */
@media (prefers-reduced-motion: reduce) {
  .root *,
  .root *::before,
  .root *::after {
    animation: none !important;
    transition: none !important;
  }
  .hero[data-active] {
    transform: none;
  }
  .eyes {
    translate: none;
  }
}
```

### glow-icon/icon-art.tsx

```tsx
'use client';

import { useId, type Ref } from 'react';
import styles from './glow-icon.module.css';

/*
 * The app icon: a rounded square with a deep violet rim around a lavender face, and a little ghost
 * floating in it, glowing from within. All of it is SVG and CSS, and every glow is a radial
 * gradient: no blur filters.
 *
 * - The ghost is milky and translucent: its body is one radial gradient, violet light at its
 *   heart fading to white at the edge, with a rim of light on the side the light comes from and a
 *   glint on its head. Its two glassy eyes are a gradient of dark violet with two glints.
 * - Around it, a soft halo on the face and a pool of light on the floor, which breathes as it
 *   floats.
 * - The icon is built as a few layers: the face, the ghost (which floats, and leans and looks),
 *   and the glass on top: a fixed sheen, and a specular spot that slides as the icon tilts.
 */

/** How the ghost feels: calm, or startled while the icon is held down. */
export type Mood = 'calm' | 'startled';

export function IconArt({
  label,
  mood = 'calm',
  eyes,
  ghost,
  className = '',
}: {
  /** What the icon shows, for screen readers. */
  label: string;
  /** Startled, its eyes go wide. */
  mood?: Mood;
  /** The eyes, to make them blink. */
  eyes?: Ref<SVGGElement>;
  /** The ghost, to make it jump. */
  ghost?: Ref<HTMLDivElement>;
  className?: string;
}) {
  // The gradients' ids: unique to each icon, and safe inside url(#…).
  const id = `gi${useId().replace(/[^\w-]/g, '')}`;
  return (
    <div
      role="img"
      aria-label={label}
      className={`${styles.icon} ${className}`}
      data-mood={mood}
      data-looker=""
      data-part="icon"
    >
      <svg className={styles.layer} viewBox="0 0 100 100" aria-hidden="true" focusable="false">
        <defs>
          <linearGradient id={`${id}-rim`} x1="0" y1="0" x2="0.3" y2="1">
            <stop offset="0" stopColor="#6c3de2" />
            <stop offset="1" stopColor="#4a1ea9" />
          </linearGradient>
          <linearGradient id={`${id}-bevel`} x1="0" y1="0" x2="0" y2="1">
            <stop offset="0" stopColor="#fff" stopOpacity="0.5" />
            <stop offset="0.3" stopColor="#fff" stopOpacity="0" />
            <stop offset="0.75" stopColor="#1a0548" stopOpacity="0" />
            <stop offset="1" stopColor="#1a0548" stopOpacity="0.4" />
          </linearGradient>
          <radialGradient id={`${id}-face`} cx="0.5" cy="0.64" r="0.78">
            <stop offset="0" stopColor="#f0eaff" />
            <stop offset="0.45" stopColor="#b6aaff" />
            <stop offset="1" stopColor="#7d6af0" />
          </radialGradient>
          <linearGradient id={`${id}-sky`} x1="0" y1="0" x2="1" y2="1">
            <stop offset="0" stopColor="#a3b6ff" stopOpacity="0.8" />
            <stop offset="0.5" stopColor="#a3b6ff" stopOpacity="0" />
          </linearGradient>
          <linearGradient id={`${id}-depth`} x1="0" y1="0" x2="0" y2="1">
            <stop offset="0" stopColor="#24086a" stopOpacity="0.4" />
            <stop offset="0.12" stopColor="#24086a" stopOpacity="0" />
            <stop offset="0.9" stopColor="#24086a" stopOpacity="0" />
            <stop offset="1" stopColor="#24086a" stopOpacity="0.18" />
          </linearGradient>
          <radialGradient id={`${id}-halo`}>
            <stop offset="0" stopColor="#fff" stopOpacity="0.6" />
            <stop offset="0.55" stopColor="#f3edff" stopOpacity="0.22" />
            <stop offset="1" stopColor="#f3edff" stopOpacity="0" />
          </radialGradient>
        </defs>
        {/* The rim, with a bevel catching the light at the top, then the face, sunk in it. */}
        <rect width="100" height="100" rx="22.5" fill={`url(#${id}-rim)`} />
        <rect
          x="0.7"
          y="0.7"
          width="98.6"
          height="98.6"
          rx="21.9"
          fill="none"
          stroke={`url(#${id}-bevel)`}
          strokeWidth="1.4"
        />
        <rect x="5.6" y="5.6" width="88.8" height="88.8" rx="17.6" fill={`url(#${id}-face)`} />
        <rect x="5.6" y="5.6" width="88.8" height="88.8" rx="17.6" fill={`url(#${id}-sky)`} />
        <rect x="5.6" y="5.6" width="88.8" height="88.8" rx="17.6" fill={`url(#${id}-depth)`} />
        <ellipse cx="50" cy="55" rx="41" ry="39" fill={`url(#${id}-halo)`} />
      </svg>
      <span className={styles.pool} data-part="pool" />
      <div ref={ghost} className={styles.ghost}>
        <div className={styles.bob}>
          <Ghost id={id} eyes={eyes} />
        </div>
      </div>
      <span className={styles.sheen} data-part="glass" />
      <span className={styles.spot} data-part="spot" />
    </div>
  );
}

/** The ghost's body: a dome, straight sides, and a hem of four soft scallops. */
const BODY =
  'M25 74C25 66 25 56 25 47C25 32 36 22 50 22C64 22 75 32 75 47C75 56 75 66 75 74C73.5 82.5 64 83 62.5 76.5C61 83 51.5 83 50 76.5C48.5 83 39 83 37.5 76.5C36 83 26.5 82.5 25 74Z';

/** The ghost, drawn back to front in the icon's 100-unit box. */
function Ghost({ id, eyes }: { id: string; eyes?: Ref<SVGGElement> }) {
  return (
    <svg className={styles.layer} viewBox="0 0 100 100" aria-hidden="true" focusable="false">
      <defs>
        <radialGradient id={`${id}-body`} cx="0.5" cy="0.6" r="0.68">
          <stop offset="0" stopColor="#ae7bff" />
          <stop offset="0.3" stopColor="#d3bdff" stopOpacity="0.97" />
          <stop offset="0.62" stopColor="#f2ecff" stopOpacity="0.95" />
          <stop offset="0.85" stopColor="#fbf9ff" stopOpacity="0.9" />
          <stop offset="1" stopColor="#e6d8ff" stopOpacity="0.72" />
        </radialGradient>
        <linearGradient id={`${id}-shade`} x1="0" y1="0" x2="1" y2="0.3">
          <stop offset="0.55" stopColor="#9b7bff" stopOpacity="0" />
          <stop offset="1" stopColor="#9b7bff" stopOpacity="0.3" />
        </linearGradient>
        <radialGradient id={`${id}-heart`}>
          <stop offset="0" stopColor="#c09bff" stopOpacity="0.85" />
          <stop offset="0.6" stopColor="#d4bcff" stopOpacity="0.3" />
          <stop offset="1" stopColor="#d4bcff" stopOpacity="0" />
        </radialGradient>
        <linearGradient id={`${id}-edge`} x1="0" y1="0" x2="0" y2="1">
          <stop offset="0" stopColor="#fff" stopOpacity="0.95" />
          <stop offset="1" stopColor="#fff" stopOpacity="0" />
        </linearGradient>
        <radialGradient id={`${id}-glint`}>
          <stop offset="0" stopColor="#fff" stopOpacity="0.95" />
          <stop offset="1" stopColor="#fff" stopOpacity="0" />
        </radialGradient>
        <linearGradient id={`${id}-eye`} x1="0" y1="0" x2="0" y2="1">
          <stop offset="0" stopColor="#2a0b60" />
          <stop offset="1" stopColor="#6430d6" />
        </linearGradient>
      </defs>
      {/* Two little arms, behind the body. */}
      <ellipse
        className={styles.arm}
        cx="25.4"
        cy="61"
        rx="3.4"
        ry="4.8"
        transform="rotate(24 25.4 61)"
      />
      <ellipse
        className={styles.arm}
        cx="74.6"
        cy="61"
        rx="3.4"
        ry="4.8"
        transform="rotate(-24 74.6 61)"
      />
      {/* The body, with a shade on its far side and a glow at its heart. */}
      <path d={BODY} fill={`url(#${id}-body)`} data-part="ghost" />
      <path d={BODY} fill={`url(#${id}-shade)`} />
      <ellipse cx="50" cy="60" rx="18" ry="16" fill={`url(#${id}-heart)`} />
      {/* Light along its edges: strong on the lit side, faint where the face lights it from
          behind. */}
      <path
        className={styles.rim}
        stroke={`url(#${id}-edge)`}
        d="M27.6 70C26.6 57 26.7 45 29.2 37C31.6 30.2 36 25.6 42 23.8"
      />
      <path className={styles.backlight} d="M72.5 69C73.4 58 73.3 47 71.3 39" />
      <ellipse
        cx="37.6"
        cy="31.4"
        rx="6.6"
        ry="3.4"
        transform="rotate(-38 37.6 31.4)"
        fill={`url(#${id}-glint)`}
      />
      <g className={styles.blush}>
        <ellipse cx="36.4" cy="57.4" rx="3.3" ry="1.7" />
        <ellipse cx="63.6" cy="57.4" rx="3.3" ry="1.7" />
      </g>
      <g ref={eyes} className={styles.eyes} data-eyes="" data-part="eyes">
        <ellipse cx="42.6" cy="49.6" rx="4.1" ry="5.4" fill={`url(#${id}-eye)`} />
        <ellipse cx="57.4" cy="49.6" rx="4.1" ry="5.4" fill={`url(#${id}-eye)`} />
        <circle cx="41.3" cy="47.3" r="1.5" fill="#fff" />
        <circle cx="56.1" cy="47.3" r="1.5" fill="#fff" />
        <circle cx="43.9" cy="52.1" r="0.65" fill="#fff" opacity="0.8" />
        <circle cx="58.7" cy="52.1" r="0.65" fill="#fff" opacity="0.8" />
      </g>
    </svg>
  );
}
```

### glow-icon/phone.tsx

```tsx
'use client';

import { useId } from 'react';
import styles from './glow-icon.module.css';

/*
 * The phone of the "Phone" setting: the top corner of a phone held at an angle, with a steel edge
 * and its side buttons, a dark screen, and a grid of plain, dimmed placeholder icons. The first
 * slot is left empty: the icon flies there. Drawn in phone units (1000 wide); the stylesheet
 * places and turns it, and the icon's slot is worked out from the same numbers.
 */

/** An icon's size on the screen, the step from one to the next, and the first one's corner. */
const ICON = 172;
const STEP = { x: 248, y: 268 };
const FIRST = { x: 106, y: 160 };

/** The placeholders around the icon's slot: column, row, and a dim tint. */
const APPS = [
  { column: 1, row: 0, tint: 'rgb(84 190 110 / 0.3)' },
  { column: 2, row: 0, tint: 'rgb(255 255 255 / 0.1)' },
  { column: 3, row: 0, tint: 'rgb(255 168 76 / 0.22)' },
  { column: 0, row: 1, tint: 'rgb(70 140 255 / 0.28)' },
  { column: 1, row: 1, tint: 'rgb(255 255 255 / 0.12)' },
  { column: 2, row: 1, tint: 'rgb(84 190 110 / 0.22)' },
  { column: 3, row: 1, tint: 'rgb(255 255 255 / 0.08)' },
  { column: 0, row: 2, tint: 'rgb(255 255 255 / 0.1)' },
  { column: 1, row: 2, tint: 'rgb(255 92 120 / 0.2)' },
  { column: 2, row: 2, tint: 'rgb(70 140 255 / 0.18)' },
];

export function Phone() {
  const id = `ph${useId().replace(/[^\w-]/g, '')}`;
  return (
    <svg
      className={styles.phone}
      data-part="phone"
      viewBox="-30 0 1030 2000"
      aria-hidden="true"
      focusable="false"
    >
      <defs>
        <linearGradient id={`${id}-steel`} x1="0" y1="0" x2="1" y2="0.55">
          <stop offset="0" stopColor="#f3f5f8" />
          <stop offset="0.06" stopColor="#9aa0a9" />
          <stop offset="0.14" stopColor="#e9ecf0" />
          <stop offset="0.3" stopColor="#5f646c" />
          <stop offset="0.6" stopColor="#c9cdd3" />
          <stop offset="1" stopColor="#3a3d43" />
        </linearGradient>
        <linearGradient id={`${id}-button`} x1="0" y1="0" x2="1" y2="0">
          <stop offset="0" stopColor="#5d626b" />
          <stop offset="0.45" stopColor="#f1f3f6" />
          <stop offset="1" stopColor="#8b9098" />
        </linearGradient>
        <radialGradient id={`${id}-screen`} cx="0.2" cy="0.05" r="0.9">
          <stop offset="0" stopColor="#17171c" />
          <stop offset="1" stopColor="#09090c" />
        </radialGradient>
      </defs>
      {/* The side buttons, then the body: a steel band, a black bezel, the screen. */}
      <rect x="-15" y="300" width="22" height="74" rx="9" fill={`url(#${id}-button)`} />
      <rect x="-17" y="440" width="24" height="150" rx="10" fill={`url(#${id}-button)`} />
      <rect x="-17" y="625" width="24" height="150" rx="10" fill={`url(#${id}-button)`} />
      <rect width="1000" height="2000" rx="172" fill={`url(#${id}-steel)`} />
      <rect
        x="5"
        y="5"
        width="990"
        height="1990"
        rx="167"
        fill="none"
        stroke="#fff"
        strokeOpacity="0.55"
        strokeWidth="2.5"
      />
      <rect x="17" y="17" width="966" height="1966" rx="156" fill="#040405" />
      <rect x="44" y="44" width="912" height="1912" rx="130" fill={`url(#${id}-screen)`} />
      {/* The earpiece, a camera, and the time as a short bar. */}
      <rect x="420" y="66" width="150" height="15" rx="7.5" fill="#1d1d22" />
      <circle cx="612" cy="74" r="9" fill="#15151a" />
      <rect x="118" y="92" width="74" height="22" rx="11" fill="#2b2b31" />
      <g>
        {APPS.map(({ column, row, tint }) => (
          <rect
            key={`${column}-${row}`}
            x={FIRST.x + column * STEP.x}
            y={FIRST.y + row * STEP.y}
            width={ICON}
            height={ICON}
            rx={ICON * 0.225}
            fill={tint}
          />
        ))}
      </g>
    </svg>
  );
}
```

### glow-icon/settings.ts

```tsx
/*
 * The settings the icon is shown in: a vivid purple backdrop, the home screen of a phone held at
 * an angle, and a light backdrop. Each sets the backdrop's three colours, which the stylesheet
 * transitions as registered custom properties, so a change of setting cross-fades the backdrop.
 */

export type SettingId = 'purple' | 'phone' | 'light';

export type Setting = {
  id: SettingId;
  /** Its button's label. */
  label: string;
  /** Where it puts the icon, as read out: "On a purple backdrop." */
  place: string;
  /** The backdrop, from top to bottom. */
  top: string;
  middle: string;
  bottom: string;
};

export const SETTINGS: readonly Setting[] = [
  {
    id: 'purple',
    label: 'Purple',
    place: 'a purple backdrop',
    top: '#7d43f0',
    middle: '#6a2fdc',
    bottom: '#5b24c8',
  },
  {
    id: 'phone',
    label: 'Phone',
    place: 'the home screen of a phone',
    top: '#0a0a0d',
    middle: '#08080a',
    bottom: '#050507',
  },
  {
    id: 'light',
    label: 'Light',
    place: 'a light backdrop',
    top: '#ffffff',
    middle: '#f4effe',
    bottom: '#e9e0fd',
  },
];
```

### glow-icon/timeline.ts

```tsx
/*
 * The demo's timeline: a script of awaited waits. Stopping it (the reader takes over, or the icon
 * scrolls away) rejects the wait in progress, which ends the script right there; nothing of it
 * runs afterwards.
 */

/** What a stopped timeline's pending wait rejects with. */
class Stopped extends Error {}

/** Plays `script`; returns the function that stops it. */
export function runTimeline(script: (wait: (ms: number) => Promise<void>) => Promise<void>) {
  let alive = true;
  const timers = new Set<number>();
  const pending = new Set<() => void>();

  const wait = (ms: number) =>
    new Promise<void>((resolve, reject) => {
      if (!alive) return reject(new Stopped());
      const cancel = () => reject(new Stopped());
      const timer = window.setTimeout(() => {
        timers.delete(timer);
        pending.delete(cancel);
        resolve();
      }, ms);
      timers.add(timer);
      pending.add(cancel);
    });

  script(wait).catch((error: unknown) => {
    if (!(error instanceof Stopped)) throw error;
  });

  return () => {
    if (!alive) return;
    alive = false;
    timers.forEach((timer) => window.clearTimeout(timer));
    pending.forEach((cancel) => cancel());
  };
}
```

### glow-icon/spring.ts

```tsx
/*
 * Springs as CSS easings. A spring pulls a value to its target and lets it settle: fast at first,
 * then slowing down, overshooting a little and coming back if it is bouncy. CSS `linear()` draws
 * any curve through a list of points, so the spring's motion is sampled once, and the same curve
 * serves CSS transitions and the Web Animations API.
 */

export type Spring = {
  /** The curve, as a CSS `linear()` easing. */
  easing: string;
  /** How long it takes to settle, in ms: the duration to play the curve over. */
  duration: number;
};

/** Points sampled along the curve: plenty for a smooth motion. */
const SAMPLES = 40;

/**
 * A spring that covers most of the distance in about `response` ms. With a `bounce` of 0 it
 * settles without overshooting; at 0.3 it overshoots by about 5% and comes back.
 */
export function spring(bounce: number, response: number): Spring {
  // The damping ratio (1: no overshoot) and the natural frequency, in radians per second.
  const damping = 1 - bounce;
  const omega = (2 * Math.PI * 1000) / response;
  const position = (t: number) => {
    if (damping >= 1) return 1 - Math.exp(-omega * t) * (1 + omega * t);
    const wobble = omega * Math.sqrt(1 - damping * damping);
    const decay = Math.exp(-damping * omega * t);
    return 1 - decay * (Math.cos(wobble * t) + ((damping * omega) / wobble) * Math.sin(wobble * t));
  };
  // Settled: from then on, within 0.1% of the target.
  let settled = 0;
  for (let t = 0; t < 3; t += 0.002) if (Math.abs(1 - position(t)) > 0.001) settled = t;
  const points = Array.from({ length: SAMPLES + 1 }, (_, i) =>
    i === SAMPLES ? 1 : Math.round(position((i / SAMPLES) * settled) * 1e4) / 1e4,
  );
  return { easing: `linear(${points.join(', ')})`, duration: Math.round(settled * 1000) };
}

/** The spring's easing for `element.animate()`, or an ease-out where `linear()` is unknown. */
export function easingOf({ easing }: Spring) {
  return CSS.supports('transition-timing-function', easing)
    ? easing
    : 'cubic-bezier(0.2, 0.8, 0.2, 1)';
}
```

### glow-icon/use-autoplay.ts

```tsx
'use client';

import { useCallback, useEffect, useRef, useState } from 'react';

/*
 * When a demo may play on its own: while part of it is on screen and the tab is visible, never
 * under reduced motion, and not while the reader is using it. `take()` hands it to the reader; it
 * takes back over `idle` ms after their last input.
 */
export function useAutoplay<T extends HTMLElement>(idle = 6000) {
  const ref = useRef<T>(null);
  const [visible, setVisible] = useState(false);
  const [reduced, setReduced] = useState(true);
  const [taken, setTaken] = useState(false);
  const timer = useRef(0);

  useEffect(() => {
    const element = ref.current;
    if (!element) return;
    let onScreen = false;
    const update = () => setVisible(onScreen && !document.hidden);
    const observer = new IntersectionObserver(
      ([entry]) => {
        onScreen = entry.isIntersecting;
        update();
      },
      { threshold: 0.3 },
    );
    observer.observe(element);
    document.addEventListener('visibilitychange', update);
    const motion = window.matchMedia('(prefers-reduced-motion: reduce)');
    const readMotion = () => setReduced(motion.matches);
    readMotion();
    motion.addEventListener('change', readMotion);
    return () => {
      observer.disconnect();
      document.removeEventListener('visibilitychange', update);
      motion.removeEventListener('change', readMotion);
    };
  }, []);

  const take = useCallback(() => {
    setTaken(true);
    window.clearTimeout(timer.current);
    timer.current = window.setTimeout(() => setTaken(false), idle);
  }, [idle]);
  useEffect(() => () => window.clearTimeout(timer.current), []);

  return { ref, take, playing: visible && !reduced && !taken };
}
```