# Magnetic connections

> Drag a cable towards a compatible port: it pulls in, crackles with electricity and snaps into place.

Prompt, noise and sampler nodes feed a processing node on a dotted canvas. A cable follows your pointer, its matching port pulls it in as it approaches, and an unsuccessful drop springs back. Move the nodes and the cables follow; connect all three inputs to complete the flow.

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

Category: Inputs.

## Anatomy

1. **Canvas**: A dotted board on one 720 by 480 coordinate model (360 by 720 when narrow), scaled to its width; nodes, sockets and cables are placed in it.
2. **Node**: A card with its own control: the prompt’s text, the noise seed, the sampler’s steps. Each feeds one channel.
3. **Drag handle**: The node’s title bar: drag it, or focus it and use the arrow keys (8 units a press), and its cables follow.
4. **Output socket**: Where a cable starts. Drag from it, or click or press Enter to pick it, then pick the matching input.
5. **Cable**: A cubic Bézier in the channel’s colour, 3.5 px with a soft glow, from the output to the pointer or its input.
6. **Electric arc**: Inside the snap radius (48 units) the cable is pulled in and four jagged contours flicker over its last stretch. Hidden under reduced motion.
7. **Input socket**: Takes only its own channel. Near it grows into a warm ring; connected, it takes the cable’s colour.
8. **Status**: Says Awaiting inputs until all three are connected, then All inputs ready in green.

## When to use

- A node editor or pipeline builder where people wire outputs to inputs by hand: prompts, filters, audio patches.
- Each output has one right input, so the editor can pull the cable towards it and refuse the rest.
- A handful of nodes on one canvas, where seeing every cable at once explains the flow.
- Onboarding or a demo that teaches a connection model: the autoplay draws each cable once, then hands over.

## When not to use

- Choosing one input from a list. Use a select or a combobox: no dragging, and it reads well to screen readers.
- Graphs of dozens of nodes, with zoom, pan and many-to-many links. Use a full graph editor.
- An order of steps with no real branching. Use a sortable list or a stepper.
- Where precise pointer work is hard, as on small touch screens, as the only way in: offer a menu of connections beside it.

## Installation

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

```sh
npx shadcn@latest add https://brunodelorence.com/r/magnetic-connections.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
import { MagneticConnections } from './magnetic-connections';

export function Flow() {
  return (
    <MagneticConnections
      autoplay={false}
      onConnectionsChange={(channels) => console.log(channels)}
    />
  );
}
```

## States

- **Waiting**: No cable yet: grey sockets, and the processing node awaits its inputs.
- **Output picked**: A click or Enter on an output picks it; its socket grows until the matching input is chosen. Escape lets go.
- **Cable in flight**: The cable follows the pointer. Dropped away from its input, it springs back with a decaying wobble.
- **Within snap radius**: Pulled towards its socket, with the electric arc. The arc’s flicker is CSS and keeps playing here.
- **Partly connected**: Each connected socket takes its cable’s colour; the status still waits for the third.
- **All inputs ready**: Three cables in: the status turns green.
- **Narrow container**: Under 440 px the nodes stack into a tall composition with larger sockets (44 px).

## How it works

- The nodes and sockets share one coordinate model. SVG cubic Bézier paths join the output positions to their connected inputs, so moving a node moves every attached cable.
- Pointer capture keeps a cable under control outside its small socket. Browser coordinates are converted into the canvas viewBox before measuring distances.
- Inside the snap radius, a non-linear attraction draws the cable towards its matching input. The socket expands into a warm ring and the cable takes its channel colour on connection.
- Near the matching socket, four jagged contours alternate over the cable’s last segment to form an electric arc: a sharp core inside a coloured halo, and a charging ring. A short discharge completes the connection. The effect uses SVG and CSS, runs only during attraction or the brief connection burst, and is hidden under reduced motion.
- An incompatible or distant drop springs the cable back using a decaying oscillation. A connected input can be pulled off; Escape cancels an unfinished connection.
- The flow is a local interactive demonstration. The prompt, seed and sampler controls are editable; it does not call an AI service. The optional callback receives the channels connected by the reader.
- Below a narrow container the nodes move into a taller composition, preserving readable controls and large touch targets. The demonstration pauses while hidden and stops when someone takes over.
- Every colour, each channel’s included, is a light-dark() token on the root, so the editor follows the page’s color-scheme, or the colorScheme prop. On light the cables are a shade deeper and their glow a soft tint, and the arc’s core turns from near-white to a deep tone of the cable’s colour.

## API reference

- **snapRadius** (`number`, default `48`): Magnetic attraction and release radius in canvas coordinates.
- **defaultState** (`MagneticConnectionsState`): Opens in a state, with the demo off: the channels already connected, an output picked (armed), and a cable held mid-drag (dragging, near its socket or not).
- **onConnectionsChange** (`(channels: string[]) => void`): Called after a reader connects, disconnects or resets the channels.
- **autoplay** (`boolean`, default `true`): Demonstrate the three connections while visible and untouched.
- **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`): An additional class for the node editor shell.

## Accessibility

- Every socket is a labelled button. Keyboard users select an output and then activate its matching input; Escape cancels selection. Connections are announced through a polite status region.
- The prompt, seed and sampler fields have labels. The source node handles support arrow-key movement, and Reset restores the nodes and clears their connections.
- Cable paths and the demonstration cursor are decorative. Reduced motion stops the demonstration and removes the unsuccessful-drop spring.

## Source

### magnetic-connections/magnetic-connections.tsx

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

'use client';

import {
  useEffect,
  useLayoutEffect,
  useRef,
  useState,
  type CSSProperties,
  type PointerEvent,
} from 'react';
import { Icon } from './icons';
import { useDemo } from './use-demo';
import { cableTail, ElectricArc } from './electric-arc';
import styles from './magnetic-connections.module.css';

type Point = { x: number; y: number };
type Drag = { index: number; point: Point; near: boolean; demo?: boolean };
/**
 * The channels. Their colours are tokens of the stylesheet, light-dark() pairs, so they follow the
 * page's color-scheme, or the one the colorScheme prop sets: the cable's colour, and the core of
 * its electric arc (near white at night, a deep tone of the cable's colour on light).
 */
const CHANNELS = [
  {
    name: 'conditioning',
    colour: 'var(--wire-conditioning)',
    core: 'var(--wire-conditioning-core)',
    node: 'Prompt',
    icon: 'prompt',
  },
  {
    name: 'noise',
    colour: 'var(--wire-noise)',
    core: 'var(--wire-noise-core)',
    node: 'Random noise',
    icon: 'grid',
  },
  {
    name: 'sampler',
    colour: 'var(--wire-sampler)',
    core: 'var(--wire-sampler-core)',
    node: 'Sampler',
    icon: 'list',
  },
];
const EMPTY = [false, false, false];
/** A channel's name: its output, its cable and its input. */
export type Channel = 'conditioning' | 'noise' | 'sampler';
/**
 * A state to open in, for documentation and tests: the channels already connected, an output
 * picked (as a click or Enter picks it), and a cable held in mid-drag, far from its socket or
 * within the snap radius, where it crackles. Setting it turns the demo off.
 */
export type MagneticConnectionsState = {
  connected?: Channel[];
  armed?: Channel;
  dragging?: { channel: Channel; near?: boolean };
};
const channelIndex = (name: Channel) => CHANNELS.findIndex((c) => c.name === name);
function curve(from: Point, to: Point) {
  const bend = Math.max(52, Math.abs(to.x - from.x) * 0.48);
  return `M${from.x} ${from.y}C${from.x + bend} ${from.y},${to.x - bend} ${to.y},${to.x} ${to.y}`;
}

export function MagneticConnections({
  snapRadius = 48,
  autoplay = true,
  onConnectionsChange,
  colorScheme,
  defaultState,
  className = '',
}: {
  snapRadius?: number;
  autoplay?: boolean;
  /** Opens in this state (connections, a picked output, a held cable), with the demo off. */
  defaultState?: MagneticConnectionsState;
  onConnectionsChange?: (channels: string[]) => void;
  /** Light or dark colours, or 'system' for the reader's; without it, the page's color-scheme. */
  colorScheme?: 'light' | 'dark' | 'system';
  className?: string;
}) {
  const { root, playing, reduced, take } = useDemo<HTMLDivElement>();
  const board = useRef<HTMLDivElement>(null);
  const [compact, setCompact] = useState(false);
  const [connected, setConnected] = useState<boolean[]>(() =>
    defaultState?.connected
      ? CHANNELS.map((c) => defaultState.connected!.includes(c.name as Channel))
      : EMPTY,
  );
  const [drag, setDrag] = useState<Drag | null>(null);
  const [armed, setArmed] = useState<number | null>(() =>
    defaultState?.armed ? channelIndex(defaultState.armed) : null,
  );
  const held = useRef(defaultState?.dragging);
  const demo = autoplay && !defaultState;
  const [pulse, setPulse] = useState<{ index: number; key: number } | null>(null);
  const pulseKey = useRef(0);
  const [offsets, setOffsets] = useState<Point[]>([
    { x: 0, y: 0 },
    { x: 0, y: 0 },
    { x: 0, y: 0 },
    { x: 0, y: 0 },
  ]);
  const [prompt, setPrompt] = useState(
    'A quiet world,\nin vivid color. Soft light, subtle\ntextures, a little unexpected magic.',
  );
  const [seed, setSeed] = useState('432512');
  const [steps, setSteps] = useState('24');
  const [announcement, setAnnouncement] = useState('');
  const returnFlight = useRef(0),
    liveConnections = useRef(connected);
  liveConnections.current = connected;
  const gesture = useRef<{
    kind: 'cable' | 'node';
    index: number;
    id: number;
    from: Point;
    offset?: Point;
    fromTarget?: boolean;
    moved: boolean;
  } | null>(null);
  const W = compact ? 360 : 720,
    H = compact ? 720 : 480;
  const boxes = compact
    ? [
        { x: 22, y: 34, w: 226, h: 132 },
        { x: 22, y: 204, w: 178, h: 92 },
        { x: 22, y: 334, w: 226, h: 94 },
        { x: 26, y: 506, w: 310, h: 184 },
      ]
    : [
        { x: 66, y: 55, w: 235, h: 164 },
        { x: 28, y: 249, w: 186, h: 99 },
        { x: 114, y: 359, w: 234, h: 91 },
        { x: 483, y: 72, w: 195, h: 269 },
      ];
  const positioned = boxes.map((b, i) => ({ ...b, x: b.x + offsets[i].x, y: b.y + offsets[i].y }));
  const outputs = positioned
    .slice(0, 3)
    .map((b, i) => ({ x: b.x + b.w, y: b.y + b.h - (i === 0 ? 25 : 23) }));
  const inputs = CHANNELS.map((_, i) => ({
    x: positioned[3].x,
    y: positioned[3].y + (compact ? 62 : 77) + i * (compact ? 35 : 60),
  }));
  const points = useRef({ outputs, inputs });
  points.current = { outputs, inputs };
  const dimensions = useRef({ W, H });
  dimensions.current = { W, H };
  // The held cable of defaultState, placed again when the layout changes until someone takes over.
  useLayoutEffect(() => {
    const hold = held.current;
    if (!hold) return;
    const index = channelIndex(hold.channel),
      from = points.current.outputs[index],
      to = points.current.inputs[index];
    const point = hold.near
      ? { x: to.x - 24, y: to.y + 16 }
      : { x: from.x + (to.x - from.x) * 0.55, y: (from.y + to.y) / 2 + 44 };
    setDrag({ index, ...magnet(index, point) });
  }, [compact]);
  useEffect(() => {
    const el = root.current;
    if (!el) return;
    const resize = new ResizeObserver(() => setCompact(el.clientWidth < 440));
    resize.observe(el);
    return () => resize.disconnect();
  }, [root]);
  useEffect(() => () => cancelAnimationFrame(returnFlight.current), []);
  useEffect(() => {
    if (!pulse) return;
    const timer = window.setTimeout(
      () => setPulse((now) => (now?.key === pulse.key ? null : now)),
      450,
    );
    return () => window.clearTimeout(timer);
  }, [pulse]);
  const pointOf = (x: number, y: number) => {
    const b = board.current!.getBoundingClientRect();
    return { x: ((x - b.x) * W) / b.width, y: ((y - b.y) * H) / b.height };
  };
  const magnet = (index: number, p: Point) => {
    const end = points.current.inputs[index],
      d = Math.hypot(p.x - end.x, p.y - end.y),
      near = d < snapRadius,
      pull = near ? Math.pow(1 - d / snapRadius, 1.5) * 0.94 : 0;
    return { point: { x: p.x + (end.x - p.x) * pull, y: p.y + (end.y - p.y) * pull }, near };
  };
  const change = (index: number, value: boolean) => {
    const next = [...liveConnections.current];
    next[index] = value;
    liveConnections.current = next;
    setConnected(next);
    setPulse(value ? { index, key: ++pulseKey.current } : null);
    onConnectionsChange?.(CHANNELS.filter((_, i) => next[i]).map((c) => c.name));
  };
  const beginCable = (e: PointerEvent<HTMLButtonElement>, index: number, fromTarget = false) => {
    if (e.button !== 0) return;
    e.preventDefault();
    e.currentTarget.focus();
    cancelAnimationFrame(returnFlight.current);
    e.currentTarget.setPointerCapture(e.pointerId);
    const point = fromTarget ? points.current.inputs[index] : points.current.outputs[index];
    gesture.current = {
      kind: 'cable',
      index,
      id: e.pointerId,
      from: point,
      fromTarget,
      moved: false,
    };
    setArmed(null);
    change(index, false);
    setDrag({ index, point, near: false });
  };
  const beginNode = (e: PointerEvent<HTMLButtonElement>, index: number) => {
    if (e.button !== 0) return;
    e.currentTarget.setPointerCapture(e.pointerId);
    gesture.current = {
      kind: 'node',
      index,
      id: e.pointerId,
      from: pointOf(e.clientX, e.clientY),
      offset: offsets[index],
      moved: false,
    };
  };
  const move = (e: PointerEvent<HTMLDivElement>) => {
    const g = gesture.current;
    if (!g || g.id !== e.pointerId) return;
    const p = pointOf(e.clientX, e.clientY);
    if (Math.hypot(p.x - g.from.x, p.y - g.from.y) > 4) g.moved = true;
    if (g.kind === 'cable') setDrag({ index: g.index, ...magnet(g.index, p) });
    else {
      const b = boxes[g.index];
      setOffsets((before) =>
        before.map((o, i) =>
          i === g.index
            ? {
                x: Math.max(5 - b.x, Math.min(W - b.w - 5 - b.x, g.offset!.x + p.x - g.from.x)),
                y: Math.max(5 - b.y, Math.min(H - b.h - 5 - b.y, g.offset!.y + p.y - g.from.y)),
              }
            : o,
        ),
      );
    }
  };
  const release = (e: PointerEvent<HTMLDivElement>, cancel = false) => {
    const g = gesture.current;
    if (!g || g.id !== e.pointerId) return;
    gesture.current = null;
    if (g.kind === 'node') return;
    const p = pointOf(e.clientX, e.clientY),
      end = points.current.inputs[g.index],
      matches = Math.hypot(p.x - end.x, p.y - end.y) < snapRadius;
    if (!cancel && g.moved && matches) {
      change(g.index, true);
      setDrag(null);
      setAnnouncement(`${CHANNELS[g.index].name} connected.`);
      return;
    }
    if (!cancel && !g.moved && !g.fromTarget) {
      setArmed(g.index);
      setDrag(null);
      setAnnouncement(`Select the ${CHANNELS[g.index].name} input to connect.`);
      return;
    }
    setArmed(null);
    if (reduced) {
      setDrag(null);
      return;
    }
    const from = drag?.point ?? p,
      to = points.current.outputs[g.index],
      start = performance.now();
    const tick = (now: number) => {
      const t = (now - start) / 1000;
      if (t > 0.55) {
        setDrag(null);
        return;
      }
      const k = Math.exp(-10 * t) * Math.cos(13 * t);
      setDrag({
        index: g.index,
        point: { x: to.x + (from.x - to.x) * k, y: to.y + (from.y - to.y) * k },
        near: false,
      });
      returnFlight.current = requestAnimationFrame(tick);
    };
    returnFlight.current = requestAnimationFrame(tick);
  };
  useEffect(() => {
    if (!demo || !playing) return;
    let alive = true,
      frame = 0,
      timer = 0,
      step = 0;
    const next = () => {
      if (!alive) return;
      const index = step++ % 3,
        from = points.current.outputs[index],
        to = points.current.inputs[index],
        start = performance.now();
      if (step % 4 === 0) {
        setConnected(EMPTY);
        liveConnections.current = EMPTY;
      }
      const tick = (now: number) => {
        if (!alive) return;
        const p = Math.min(1, (now - start) / 1250),
          t = p * p * (3 - 2 * p),
          point = {
            x: from.x + (to.x - from.x) * t,
            y: from.y + (to.y - from.y) * t + Math.sin(p * Math.PI) * 36,
          };
        setDrag({ index, ...magnet(index, point), demo: true });
        if (p < 1) frame = requestAnimationFrame(tick);
        else {
          setDrag(null);
          const c = [...liveConnections.current];
          c[index] = true;
          liveConnections.current = c;
          setConnected(c);
          setPulse({ index, key: ++pulseKey.current });
          timer = window.setTimeout(next, 1800);
        }
      };
      frame = requestAnimationFrame(tick);
    };
    timer = window.setTimeout(next, 850);
    return () => {
      alive = false;
      clearTimeout(timer);
      cancelAnimationFrame(frame);
      setDrag((before) => (before?.demo ? null : before));
    };
  }, [demo, playing, compact, snapRadius]);
  const position = (b: { x: number; y: number; w: number; h: number }) => ({
    left: `${(b.x / W) * 100}%`,
    top: `${(b.y / H) * 100}%`,
    width: `${(b.w / W) * 100}%`,
    height: `${(b.h / H) * 100}%`,
  });
  const socket = (p: Point) => ({ left: `${(p.x / W) * 100}%`, top: `${(p.y / H) * 100}%` });
  /** Someone takes over: the demo stops, and a cable held by defaultState is let go. */
  const letGo = () => {
    if (held.current) {
      held.current = undefined;
      setDrag(null);
    }
    take();
  };
  const reset = () => {
    cancelAnimationFrame(returnFlight.current);
    gesture.current = null;
    setDrag(null);
    setArmed(null);
    setPulse(null);
    liveConnections.current = EMPTY;
    setConnected(EMPTY);
    setOffsets([
      { x: 0, y: 0 },
      { x: 0, y: 0 },
      { x: 0, y: 0 },
      { x: 0, y: 0 },
    ]);
    onConnectionsChange?.([]);
    setAnnouncement('Connections reset.');
  };
  return (
    <div
      ref={root}
      className={`${styles.root} ${className}`}
      data-color-scheme={colorScheme}
      data-magnetic-connections
      onPointerDownCapture={letGo}
      onKeyDownCapture={letGo}
      onKeyDown={(e) => {
        if (e.key === 'Escape') {
          cancelAnimationFrame(returnFlight.current);
          gesture.current = null;
          setArmed(null);
          setDrag(null);
          setAnnouncement('Connection cancelled.');
        }
      }}
    >
      <div
        ref={board}
        className={styles.board}
        data-part="canvas"
        style={{ aspectRatio: `${W}/${H}` }}
        onPointerMove={move}
        onPointerUp={(e) => release(e)}
        onPointerCancel={(e) => release(e, true)}
      >
        <svg className={styles.wires} viewBox={`0 0 ${W} ${H}`} aria-hidden="true">
          {CHANNELS.map((c, i) => {
            const endpoint = drag?.index === i ? drag.point : connected[i] ? inputs[i] : null;
            if (!endpoint) return null;
            return (
              <g
                key={c.name}
                style={{ color: c.colour, '--arc-core': c.core } as CSSProperties}
                data-charged={(drag?.index === i && drag.near) || undefined}
              >
                <path className={styles.glow} d={curve(outputs[i], endpoint)} />
                <path className={styles.wire} data-part="cable" d={curve(outputs[i], endpoint)} />
                {!reduced && drag?.index === i && drag.near && (
                  <ElectricArc from={cableTail(outputs[i], endpoint)} to={inputs[i]} />
                )}
                {!reduced && connected[i] && pulse?.index === i && (
                  <g
                    key={pulse.key}
                    onAnimationEnd={(event) => {
                      if (event.target !== event.currentTarget.firstElementChild) return;
                      setPulse((now) => (now?.key === pulse.key ? null : now));
                    }}
                  >
                    <ElectricArc from={cableTail(outputs[i], endpoint)} to={inputs[i]} burst />
                  </g>
                )}
                {drag?.index === i && (
                  <circle cx={endpoint.x} cy={endpoint.y} r="5" fill="currentColor" />
                )}
              </g>
            );
          })}
          {drag?.demo && (
            <path
              d="M0 0v17l4-4 4 7 3-2-4-6h6Z"
              transform={`translate(${drag.point.x - 2} ${drag.point.y - 1})`}
              className={styles.pointer}
              strokeWidth="1"
            />
          )}
        </svg>
        {CHANNELS.map((c, i) => (
          <section
            key={c.node}
            className={styles.node}
            data-part="node"
            style={position(positioned[i])}
          >
            <button
              type="button"
              className={styles.nodeHeader}
              data-part="handle"
              aria-label={`Move ${c.node} node`}
              onPointerDown={(e) => beginNode(e, i)}
              onKeyDown={(e) => {
                if (['ArrowLeft', 'ArrowRight', 'ArrowUp', 'ArrowDown'].includes(e.key)) {
                  e.preventDefault();
                  setOffsets((before) =>
                    before.map((o, j) =>
                      j === i
                        ? {
                            x: Math.max(
                              5 - boxes[i].x,
                              Math.min(
                                W - boxes[i].w - 5 - boxes[i].x,
                                o.x + (e.key === 'ArrowRight' ? 8 : e.key === 'ArrowLeft' ? -8 : 0),
                              ),
                            ),
                            y: Math.max(
                              5 - boxes[i].y,
                              Math.min(
                                H - boxes[i].h - 5 - boxes[i].y,
                                o.y + (e.key === 'ArrowDown' ? 8 : e.key === 'ArrowUp' ? -8 : 0),
                              ),
                            ),
                          }
                        : o,
                    ),
                  );
                }
              }}
            >
              <Icon name={c.icon} size={13} />
              <span>{c.node}</span>
              <b aria-hidden="true">⠿</b>
            </button>
            {i === 0 ? (
              <textarea
                aria-label="Prompt text"
                value={prompt}
                onChange={(e) => setPrompt(e.target.value)}
              />
            ) : i === 1 ? (
              <input
                className={styles.seed}
                type="text"
                inputMode="numeric"
                aria-label="Noise seed"
                value={seed}
                onChange={(e) => setSeed(e.target.value.replace(/\D/g, ''))}
              />
            ) : (
              <label className={styles.sampler}>
                euler ·{' '}
                <select
                  aria-label="Sampler steps"
                  value={steps}
                  onChange={(e) => setSteps(e.target.value)}
                >
                  {['16', '24', '32', '48'].map((n) => (
                    <option key={n}>{n}</option>
                  ))}
                </select>{' '}
                steps
              </label>
            )}
          </section>
        ))}
        <section
          className={`${styles.node} ${styles.processing}`}
          data-part="processing"
          style={position(positioned[3])}
        >
          <button
            type="button"
            className={styles.nodeHeader}
            data-part="handle"
            aria-label="Move Processing node"
            onPointerDown={(e) => beginNode(e, 3)}
            onKeyDown={(e) => {
              if (!['ArrowLeft', 'ArrowRight', 'ArrowUp', 'ArrowDown'].includes(e.key)) return;
              e.preventDefault();
              setOffsets((before) =>
                before.map((o, i) =>
                  i !== 3
                    ? o
                    : {
                        x: Math.max(
                          5 - boxes[3].x,
                          Math.min(
                            W - boxes[3].w - 5 - boxes[3].x,
                            o.x + (e.key === 'ArrowRight' ? 8 : e.key === 'ArrowLeft' ? -8 : 0),
                          ),
                        ),
                        y: Math.max(
                          5 - boxes[3].y,
                          Math.min(
                            H - boxes[3].h - 5 - boxes[3].y,
                            o.y + (e.key === 'ArrowDown' ? 8 : e.key === 'ArrowUp' ? -8 : 0),
                          ),
                        ),
                      },
                ),
              );
            }}
          >
            <Icon name="cpu" size={14} />
            <span>Processing</span>
            <b aria-hidden="true">⠿</b>
          </button>
          <p
            className={styles.processStatus}
            data-part="status"
            data-ready={connected.every(Boolean) || undefined}
          >
            <i />
            {connected.every(Boolean) ? 'All inputs ready' : 'Awaiting inputs'}
          </p>
        </section>
        {CHANNELS.map((c, i) => (
          <div key={c.name} style={{ '--wire-colour': c.colour } as CSSProperties}>
            <span
              className={styles.outputLabel}
              data-part="label"
              style={{
                left: `${((outputs[i].x - 20) / W) * 100}%`,
                top: `${(outputs[i].y / H) * 100}%`,
              }}
            >
              {c.name}
            </span>
            <button
              type="button"
              className={styles.port}
              data-part="output"
              style={socket(outputs[i])}
              data-output
              data-connected={connected[i] || undefined}
              data-armed={armed === i || undefined}
              aria-label={`${connected[i] ? 'Disconnect' : 'Connect'} ${c.name} output`}
              aria-pressed={armed === i}
              onPointerDown={(e) => beginCable(e, i)}
              onClick={(e) => {
                if (e.detail === 0) {
                  if (connected[i]) change(i, false);
                  else {
                    setArmed(i);
                    setAnnouncement(`Select the ${c.name} input to connect.`);
                  }
                }
              }}
            >
              <i />
            </button>
            <button
              type="button"
              className={styles.port}
              data-part="input"
              style={socket(inputs[i])}
              data-input
              data-connected={connected[i] || undefined}
              data-near={(drag?.index === i && drag.near) || undefined}
              aria-label={`${connected[i] ? 'Disconnect' : 'Connect'} ${c.name} input`}
              onPointerDown={(e) => {
                if (connected[i]) beginCable(e, i, true);
              }}
              onClick={(e) => {
                if (e.detail !== 0 && connected[i]) return;
                if (armed === i) {
                  change(i, true);
                  setArmed(null);
                  setAnnouncement(`${c.name} connected.`);
                } else if (e.detail === 0 && connected[i]) {
                  change(i, false);
                  setAnnouncement(`${c.name} disconnected.`);
                } else if (armed !== null) {
                  setAnnouncement(`Choose the ${CHANNELS[armed].name} input for this cable.`);
                }
              }}
            >
              <i />
            </button>
            <span
              className={styles.inputLabel}
              style={{
                left: `${((inputs[i].x + 28) / W) * 100}%`,
                top: `${(inputs[i].y / H) * 100}%`,
              }}
            >
              {c.name}
            </span>
          </div>
        ))}
      </div>
      <footer className={styles.footer} data-part="footer">
        <span>Drag an output to its matching input.</span>
        <button type="button" onClick={reset} aria-label="Reset connections">
          <Icon name="replay" size={13} />
          Reset
        </button>
      </footer>
      <span className={styles.sr} role="status">
        {announcement}
      </span>
    </div>
  );
}
```

### magnetic-connections/electric-arc.tsx

```tsx
import type { CSSProperties } from 'react';
import styles from './magnetic-connections.module.css';

type Point = { x: number; y: number };

/** The last section of the cable: the discharge follows its actual approach to the socket. */
export function cableTail(from: Point, to: Point): Point {
  const bend = Math.max(52, Math.abs(to.x - from.x) * 0.48);
  const t = 0.8;
  const u = 1 - t;
  return {
    x:
      u ** 3 * from.x +
      3 * u ** 2 * t * (from.x + bend) +
      3 * u * t ** 2 * (to.x - bend) +
      t ** 3 * to.x,
    y: (u ** 3 + 3 * u ** 2 * t) * from.y + (3 * u * t ** 2 + t ** 3) * to.y,
  };
}

/** Four distinct jagged contours alternate in CSS; no JavaScript animation loop is needed. */
function discharge(from: Point, to: Point, frame: number) {
  const dx = to.x - from.x;
  const dy = to.y - from.y;
  const distance = Math.hypot(dx, dy) || 1;
  const strength = Math.min(5.5, Math.max(2.4, distance * 0.13));
  return Array.from({ length: 13 }, (_, i) => {
    const t = i / 12;
    const noise = Math.sin(i * 7.31 + frame * 2.43) * Math.cos(i * 1.77 + frame);
    const jitter = noise * strength * Math.sin(Math.PI * t);
    return `${i ? 'L' : 'M'}${(from.x + dx * t - (dy / distance) * jitter).toFixed(2)} ${(from.y + dy * t + (dx / distance) * jitter).toFixed(2)}`;
  }).join('');
}

export function ElectricArc({
  from,
  to,
  burst = false,
}: {
  from: Point;
  to: Point;
  burst?: boolean;
}) {
  return (
    <g className={`${styles.electric} ${burst ? styles.burst : ''}`} data-electric-arc="">
      {[0, 1, 2, 3].map((frame) => {
        const path = discharge(from, to, frame);
        return (
          <g
            key={frame}
            className={styles.arcFrame}
            style={{ '--arc-delay': `${-frame * 60}ms` } as CSSProperties}
          >
            <path className={styles.arcGlow} d={path} />
            <path className={styles.arcColour} d={path} />
            <path className={styles.arcCore} d={path} />
          </g>
        );
      })}
      <circle className={styles.arcRing} cx={to.x} cy={to.y} r="10.5" />
    </g>
  );
}
```

### magnetic-connections/magnetic-connections.module.css

```css
/* Magnetic connections (magnetic-connections.tsx): a node editor on a light canvas, or at night a
   dark one. The cables are SVG paths in their channel's colour; near its socket a cable crackles
   with an electric arc (electric-arc.tsx).

   Colours are the tokens below, light-dark(light, dark): the component takes the color-scheme it
   inherits from the page (light unless the page says otherwise), or the one its colorScheme prop
   sets (data-color-scheme). The channels' colours are tokens too, which the component's CHANNELS
   name as var(--wire-…). */

.root {
  /* The canvas and its dots; the shell's edge. */
  --surface: #f4f4f5;
  --dots: rgb(0 0 0 / 0.16);
  --edge: #e4e4e7;
  /* The nodes: their face, edge and shadow; their text; the drag handles. */
  --surface-2: #fff;
  --line: #e4e4e7;
  --shadow: rgb(0 0 0 / 0.06);
  --ink: #27272a;
  --handle: #8e8e96;
  /* The prompt's field: its face, text and edge; the seed; the sampler's line and its select. */
  --field: #f7f7f8;
  --field-ink: #3f3f46;
  --field-line: #e4e4e7;
  --seed-ink: #52525b;
  --sampler-ink: #63636b;
  --select-ink: #3f3f46;
  /* The processing node's status, waiting; then ready: its text, its dot and the dot's glow. */
  --ink-muted: #6b6b73;
  --status-dot: #8e8e96;
  --ready: #2b8452;
  --ready-dot: #2f9e62;
  --ready-glow: rgb(47 158 98 / 0.35);
  /* A socket's dot at rest and the ring round it; near, its wider ring, the warm edge and the
     glow round that. */
  --socket: #82828a;
  --socket-ring: #ececef;
  --socket-ring-near: #fff;
  --near-edge: rgb(196 108 48 / 0.6);
  --near-glow: rgb(214 122 52 / 0.3);
  /* The sockets' labels; the footer, and its button; the focus ring. */
  --label-ink: #6b6b73;
  --footer-ink: #6b6b73;
  --footer-button: #52525b;
  --focus: #7c4dde;
  /* The channels' cables, a shade deeper on light; and the electric arc's core: near white at
     night, on light a deep tone of the cable's own colour. */
  --wire-conditioning: #cc6528;
  --wire-noise: #a87e00;
  --wire-sampler: #8455e0;
  --wire-conditioning-core: #93370c;
  --wire-noise-core: #7a5200;
  --wire-sampler-core: #4f22b3;
  /* The demo's pointer. */
  --pointer: #1c1c1e;
  --pointer-edge: #fff;
  width: 100%;
  min-width: 0;
  position: relative;
  background: var(--surface);
  color: var(--ink);
  padding: 12px;
  border: 1px solid var(--edge);
  border-radius: 20px;
  font:
    12px/1.5 'Library Inter',
    Arial,
    sans-serif;
  box-sizing: border-box;
  container-type: inline-size;
}
@supports (color: light-dark(#fff, #000)) {
  .root {
    --surface: light-dark(#f4f4f5, #111);
    --dots: light-dark(rgb(0 0 0 / 0.16), #29292980);
    --edge: light-dark(#e4e4e7, #262626);
    --surface-2: light-dark(#fff, #1c1c1c);
    --line: light-dark(#e4e4e7, #303030);
    --shadow: light-dark(rgb(0 0 0 / 0.06), #00000020);
    --ink: light-dark(#27272a, #ddd);
    --handle: light-dark(#8e8e96, #505050);
    --field: light-dark(#f7f7f8, #171717);
    --field-ink: light-dark(#3f3f46, #b4b4b4);
    --field-line: light-dark(#e4e4e7, #353535);
    --seed-ink: light-dark(#52525b, #a6a6a6);
    --sampler-ink: light-dark(#63636b, #909090);
    --select-ink: light-dark(#3f3f46, #aaa);
    --ink-muted: light-dark(#6b6b73, #7f7f7f);
    --status-dot: light-dark(#8e8e96, #5e5e5e);
    --ready: light-dark(#2b8452, #78c298);
    --ready-dot: light-dark(#2f9e62, #6cbb88);
    --ready-glow: light-dark(rgb(47 158 98 / 0.35), #50b58180);
    --socket: light-dark(#82828a, #ccc);
    --socket-ring: light-dark(#ececef, #242424);
    --socket-ring-near: light-dark(#fff, #1d1d1d);
    --near-edge: light-dark(rgb(196 108 48 / 0.6), #ca94658f);
    --near-glow: light-dark(rgb(214 122 52 / 0.3), #cf8e434a);
    --label-ink: light-dark(#6b6b73, #969696);
    --footer-ink: light-dark(#6b6b73, #717171);
    --footer-button: light-dark(#52525b, #999);
    --focus: light-dark(#7c4dde, #b48ef1);
    --wire-conditioning: light-dark(#cc6528, #f4a06a);
    --wire-noise: light-dark(#a87e00, #edd65a);
    --wire-sampler: light-dark(#8455e0, #b38af1);
    --wire-conditioning-core: light-dark(#93370c, #fff5ff);
    --wire-noise-core: light-dark(#7a5200, #fff5ff);
    --wire-sampler-core: light-dark(#4f22b3, #fff5ff);
    --pointer: light-dark(#1c1c1e, #eee);
    --pointer-edge: light-dark(#fff, #111);
  }
}
/* The colorScheme prop. Without it, nothing is set: color-scheme is inherited from the page. */
.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;
}
.root * {
  box-sizing: border-box;
}
.root button {
  color: inherit;
  font: inherit;
  cursor: pointer;
}
.board {
  position: relative;
  width: 100%;
  background-color: var(--surface);
  background-image: radial-gradient(var(--dots) 0.7px, transparent 0.7px);
  background-size: 20px 20px;
  overflow: hidden;
  border-radius: 12px;
  min-height: 300px;
}
.root .wires {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  overflow: visible;
  pointer-events: none;
}
.wire {
  fill: none;
  stroke: currentColor;
  stroke-width: 3.5;
  stroke-linecap: round;
  stroke-linejoin: round;
}
/* The cable's glow: its colour at night; on light, about half as strong, a soft tint. */
.glow {
  fill: none;
  stroke: color-mix(in srgb, currentColor 55%, transparent);
  stroke-width: 9;
  opacity: 0.2;
  filter: blur(3px);
}
@supports (color: light-dark(#fff, #000)) {
  /* The cable's glow: its colour at night; on light, about half as strong, a soft tint. */
  .glow {
    stroke: light-dark(color-mix(in srgb, currentColor 55%, transparent), currentColor);
  }
}
.wires [data-charged] .glow {
  opacity: 0.46;
}
.electric {
  pointer-events: none;
}
.arcFrame {
  opacity: 0;
  animation: electricFlicker 240ms steps(1, end) var(--arc-delay) infinite;
}
.arcGlow,
.arcColour,
.arcCore,
.arcRing {
  fill: none;
  stroke-linecap: round;
  stroke-linejoin: round;
}
/* The arc's halo: the cable's colour glowing at night; on light, half as strong, a soft tinted
   light round the deep core rather than neon. */
.arcGlow {
  stroke: color-mix(in srgb, currentColor 50%, transparent);
  stroke-width: 7;
  opacity: 0.85;
  filter: blur(2.5px);
}
@supports (color: light-dark(#fff, #000)) {
  /* The arc's halo: the cable's colour glowing at night; on light, half as strong, a soft tinted
   light round the deep core rather than neon. */
  .arcGlow {
    stroke: light-dark(color-mix(in srgb, currentColor 50%, transparent), currentColor);
  }
}
.arcColour {
  stroke: currentColor;
  stroke-width: 2.8;
}
/* The core: --arc-core, the channel's, set by the component on each cable. */
.arcCore {
  stroke: var(--arc-core);
  stroke-width: 1.4;
}
.arcRing {
  stroke: currentColor;
  stroke-width: 1.5;
  opacity: 0.7;
  transform-box: fill-box;
  transform-origin: center;
  animation: socketCharge 380ms ease-in-out infinite alternate;
}
.burst {
  animation: dischargeFade 420ms ease-out forwards;
}
@keyframes electricFlicker {
  0%,
  24.99% {
    opacity: 1;
  }
  25%,
  100% {
    opacity: 0;
  }
}
@keyframes socketCharge {
  from {
    scale: 0.82;
    opacity: 0.4;
  }
  to {
    scale: 1.14;
    opacity: 0.9;
  }
}
@keyframes dischargeFade {
  0%,
  25% {
    opacity: 1;
  }
  100% {
    opacity: 0;
  }
}
.node {
  position: absolute;
  padding: 15px 14px;
  background: var(--surface-2);
  border: 1px solid var(--line);
  border-radius: 16px;
  box-shadow: 0 4px 15px var(--shadow);
  color: var(--ink);
  user-select: none;
}
.nodeHeader {
  width: 100%;
  padding: 0;
  margin: 0;
  display: flex;
  align-items: center;
  gap: 7px;
  background: transparent;
  border: 0;
  text-align: left;
  font-size: 11px !important;
  cursor: grab !important;
  touch-action: none;
}
.nodeHeader svg {
  opacity: 0.55;
}
.nodeHeader span {
  font-weight: 600;
}
.nodeHeader b {
  margin-left: auto;
  color: var(--handle);
  font-size: 17px;
  line-height: 1;
}
.nodeHeader:active {
  cursor: grabbing !important;
}
.node textarea {
  width: 100%;
  height: calc(100% - 42px);
  min-height: 38px;
  resize: none;
  margin-top: 12px;
  font:
    10px/1.5 'Library Inter',
    Arial,
    sans-serif;
  background: var(--field);
  color: var(--field-ink);
  padding: 10px;
  border: 1px solid var(--field-line);
  border-radius: 9px;
  scrollbar-width: thin;
  user-select: text;
}
.seed {
  margin-top: 11px;
  width: 100%;
  background: transparent;
  color: var(--seed-ink);
  font:
    11px 'Library Mono',
    monospace;
  border: 0;
}
.sampler {
  display: flex;
  align-items: center;
  gap: 4px;
  color: var(--sampler-ink);
  font-size: 11px;
  margin-top: 14px;
}
.sampler select {
  background: transparent;
  border: 0;
  appearance: none;
  color: var(--select-ink);
  font: inherit;
  cursor: pointer;
}
.processing .nodeHeader {
  font-size: 12px !important;
}
.processStatus {
  position: absolute;
  bottom: 19px;
  left: 20px;
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--ink-muted);
  font-size: 11px;
  margin: 0;
}
.processStatus i {
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: var(--status-dot);
}
.processStatus[data-ready] {
  color: var(--ready);
}
.processStatus[data-ready] i {
  background: var(--ready-dot);
  box-shadow: 0 0 12px var(--ready-glow);
}
.port {
  position: absolute;
  z-index: 5;
  width: 36px;
  height: 36px;
  transform: translate(-50%, -50%);
  border: 0;
  background: transparent;
  border-radius: 50%;
  display: grid;
  place-items: center;
  touch-action: none;
  cursor: crosshair !important;
}
.port i {
  display: block;
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: var(--socket);
  box-shadow: 0 0 0 4px var(--socket-ring);
  transition:
    transform 0.2s,
    box-shadow 0.2s,
    background 0.2s;
}
.port[data-connected] i {
  background: var(--wire-colour);
  box-shadow:
    0 0 0 4px var(--socket-ring),
    0 0 10px color-mix(in srgb, var(--wire-colour) 25%, transparent);
}
.port:hover i,
.port[data-armed] i {
  transform: scale(1.35);
  background: var(--wire-colour);
}
.port[data-near] i {
  background: var(--wire-colour);
  box-shadow:
    0 0 0 5px var(--socket-ring-near),
    0 0 0 6px var(--near-edge),
    0 0 23px var(--near-glow);
  transform: scale(1.6);
}
.port:focus-visible {
  outline: 1px solid var(--wire-colour);
  outline-offset: 0;
}
.outputLabel,
.inputLabel {
  position: absolute;
  z-index: 4;
  font-size: 10px;
  color: var(--label-ink);
  pointer-events: none;
}
.outputLabel {
  transform: translate(-100%, -50%);
}
.inputLabel {
  transform: translateY(-50%);
  font-size: 11px;
}
.footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 7px 10px 0;
  color: var(--footer-ink);
  font-size: 10px;
}
.footer button {
  display: flex;
  align-items: center;
  gap: 5px;
  border: 0;
  background: transparent;
  padding: 6px 0;
  color: var(--footer-button);
  font-size: 10px;
}
.root input:focus-visible,
.root textarea:focus-visible,
.root select:focus-visible,
.root button:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 3px;
}
/* The demo's pointer. */
.pointer {
  fill: var(--pointer);
  stroke: var(--pointer-edge);
}
.sr {
  position: absolute;
  width: 1px;
  height: 1px;
  clip-path: inset(50%);
  overflow: hidden;
}
@container (max-width:440px) {
  .node {
    padding: 14px 12px;
    border-radius: 14px;
  }
  .nodeHeader {
    font-size: 11px !important;
  }
  .node textarea {
    font-size: 11px;
    padding: 8px;
    line-height: 1.4;
  }
  .board {
    background-size: 16px 16px;
  }
  .port {
    width: 44px;
    height: 44px;
  }
  .port i {
    width: 10px;
    height: 10px;
  }
  .inputLabel {
    font-size: 12px;
  }
  .outputLabel {
    font-size: 10px;
  }
  .footer {
    font-size: 9px;
    padding-inline: 4px;
  }
  .processStatus {
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .electric {
    display: none;
  }
  .root * {
    transition: none !important;
    animation: none !important;
  }
}
```

### magnetic-connections/use-demo.ts

```tsx
'use client';

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

/** A visible demo may play until someone takes over. Restarting the preview resets it. */
export function useDemo<T extends HTMLElement>() {
  const root = useRef<T>(null);
  const [visible, setVisible] = useState(false);
  const [reduced, setReduced] = useState(true);
  const [manual, setManual] = useState(false);
  useEffect(() => {
    const element = root.current;
    if (!element) return;
    let intersecting = false;
    const update = () => setVisible(intersecting && !document.hidden);
    const observer = new IntersectionObserver(
      ([entry]) => {
        intersecting = entry.isIntersecting;
        update();
      },
      { threshold: 0.15 },
    );
    observer.observe(element);
    document.addEventListener('visibilitychange', update);
    const media = window.matchMedia('(prefers-reduced-motion: reduce)');
    const motion = () => setReduced(media.matches);
    motion();
    media.addEventListener('change', motion);
    return () => {
      observer.disconnect();
      document.removeEventListener('visibilitychange', update);
      media.removeEventListener('change', motion);
    };
  }, []);
  const take = useCallback(() => setManual(true), []);
  return { root, visible, reduced, take, playing: visible && !reduced && !manual };
}
```

### magnetic-connections/icons.tsx

```tsx
/** The small line icons this component draws, on a 24-unit grid in the current colour. */
export function Icon({ name, size = 16 }: { name: string; size?: number }) {
  const paths: Record<string, React.ReactNode> = {
    grid: (
      <>
        <rect x="3" y="3" width="6" height="6" rx="1" />
        <rect x="13" y="3" width="6" height="6" rx="1" />
        <rect x="3" y="13" width="6" height="6" rx="1" />
        <rect x="13" y="13" width="6" height="6" rx="1" />
      </>
    ),
    list: (
      <>
        <path d="M9 5h12M9 12h12M9 19h12" />
        <path d="M3 5h1M3 12h1M3 19h1" />
      </>
    ),
    replay: (
      <>
        <path d="M4 10a8 8 0 1 1 1 7M4 4v6h6" />
      </>
    ),
    cpu: (
      <>
        <rect x="6" y="6" width="12" height="12" rx="2" />
        <rect x="9" y="9" width="6" height="6" />
        <path d="M9 2v4M15 2v4M9 18v4M15 18v4M2 9h4M2 15h4M18 9h4M18 15h4" />
      </>
    ),
    prompt: (
      <>
        <path d="m3 6 6 6-6 6M11 3v18M15 8h6M15 12h6M15 16h4" />
      </>
    ),
  };
  return (
    <svg
      aria-hidden="true"
      viewBox="0 0 24 24"
      style={{ width: size, height: size, flexShrink: 0 }}
      fill="none"
      stroke="currentColor"
      strokeWidth="1.5"
      strokeLinecap="round"
      strokeLinejoin="round"
    >
      {paths[name]}
    </svg>
  );
}
```