# Lodestone
> A field of hairlines that lines up like iron filings around your call to action. The button is a bar magnet, the pointer a second pole that bends the field toward it, the headline a stone the field flows around, and a success state swings every line to north in one wave.
An animated React component from KeyframeUI, installed as source with the shadcn CLI. Built with React, Tailwind CSS and Motion.
- Docs and live preview: https://keyframeui.com/components/lodestone
- Tags: Background, Interaction, Canvas
- npm dependencies: motion, clsx, tailwind-merge
## Installation
Register the @keyframeui registry in `components.json` once per project:
```json
{
"registries": {
"@keyframeui": "https://keyframeui.com/r/{name}.json"
}
}
```
Then add the component. It lands in `components/ui/lodestone.tsx`, and the CLI also adds `lib/utils.ts` (the `cn` helper) and installs the npm dependencies:
```bash
npx shadcn@latest add @keyframeui/lodestone
```
Or install by URL, without registering the namespace:
```bash
npx shadcn@latest add https://keyframeui.com/r/lodestone.json
```
## Usage
The main demo shows typical usage.
### Waitlist Hero
An AI startup's waitlist hero. The whole email pill is the magnet: the field loops out from it, parts around the headline, and bends toward the pointer. Join, and every hairline swings to north with `aligned`; Undo lets the field take them back.
Install this demo, with the component included:
```bash
npx shadcn@latest add @keyframeui/lodestone-demo
```
```tsx title="components/lodestone-demo.tsx"
"use client";
import * as React from "react";
import { Lodestone, LodestoneQuiet, LodestoneTarget } from "@/components/ui/lodestone";
export function LodestoneDemo() {
const [joined, setJoined] = React.useState(false);
const [email, setEmail] = React.useState("");
return (
Private beta · 2,480 teams waiting
Agents that pull in one direction
Meridian lines up every agent in your stack behind one goal, one plan and one log you
can read.
{joined ? (
You're in. Number 2,481.
) : (
)}
);
}
```
## Examples
Finished sections built with Lodestone. Each one installs whole, with the component included.
### Studio CTA
A studio's closing card in stone and orange. The button is a single pole (`poles="center"`), so the field fans into it from across the card, and the serif headline and the small print are both quiet zones.
Install this demo, with the component included:
```bash
npx shadcn@latest add @keyframeui/lodestone-studio-demo
```
```tsx title="components/lodestone-studio-demo.tsx"
import { Lodestone, LodestoneQuiet, LodestoneTarget } from "@/components/ui/lodestone";
export function LodestoneStudioDemo() {
return (
Booking Q1 · 2 slots left
Have something you want people to feel?
Brand, product and motion for teams
shipping their first big thing.
Book an intro call
);
}
```
### Two Paths
A hero with a primary and a secondary call to action. The field rests on the primary; lean toward the other and its `strength` takes over, so the field swings across in a wave from that button.
Install this demo, with the component included:
```bash
npx shadcn@latest add @keyframeui/lodestone-paths-demo
```
```tsx title="components/lodestone-paths-demo.tsx"
"use client";
import * as React from "react";
import { Lodestone, LodestoneQuiet, LodestoneTarget } from "@/components/ui/lodestone";
type Path = "build" | "sales";
export function LodestonePathsDemo() {
// The field rests on the primary path and follows whichever one the visitor leans toward.
const [leaning, setLeaning] = React.useState(null);
const active = leaning ?? "build";
const lean = (path: Path) => ({
strength: active === path ? 1 : 0.12,
onPointerEnter: () => setLeaning(path),
onPointerLeave: () => setLeaning(null),
onFocus: () => setLeaning(path),
onBlur: () => setLeaning(null),
});
return (
Your first agent ships this afternoon
Start from a template on your own, or walk through your stack with an engineer.
);
}
```
## Props
| Prop | Type | Default | Description |
| --- | --- | --- | --- |
| `children` (required) | `React.ReactNode` | | The section. Wrap the call to action in `LodestoneTarget` and the headline in `LodestoneQuiet`. |
| `aligned` | `boolean` | `false` | Swings every hairline to north in one wave from the strongest target, with a ring. Use it for a success state: a waitlist joined, a form sent. |
| `cursor` | `number` | `0.8` | Strength of the pointer's own pole, relative to a target. It fades out while a target is hovered. `0` turns it off. |
| `reach` | `number` | `1.3` | How far the targets' fields carry across the backdrop. |
| `spacing` | `number` | `24` | Distance between hairlines, in px. |
| `length` | `number` | `0.6` | Length of a hairline in a strong field, as a share of `spacing`. In a weak field they shrink toward a quarter of that. |
| `thickness` | `number` | `1` | Line width, in px. |
| `intro` | `boolean` | `true` | Scatter the hairlines and let them snap into line, in a ring from the target, the first time the field scrolls into view. |
| `marks` | `boolean` | `true` | Draw a faint static + every six cells, like engineering paper. |
| `fade` | `boolean` | `true` | Fade the field out toward the edges. |
| `fieldClassName` | `string` | `"text-zinc-900 dark:text-zinc-100"` | A `text-*` color for the hairlines. The canvas reads it, so `dark:` variants work; opacity comes from the field's strength. |
| `accentClassName` | `string` | `"text-indigo-500 dark:text-indigo-400"` | A `text-*` color that gathers around a hovered target and rides the shockwave. |
| `canvasClassName` | `string` | | Classes for the canvas, e.g. `opacity-60` to quiet the whole field. |
| `className` | `string` | | Classes for the section. Give it a background: the field draws behind the content, on top of it. |
| `target.strength` | `number` | `1` | `LodestoneTarget`: how strongly this target pulls. Change it and the field hands over in a wave that starts at this target. |
| `target.poles` | `"ends" \| "center"` | `"ends"` | `LodestoneTarget`: `ends` makes it a bar magnet whose field arcs from one end to the other; `center` is a single pole the field points into. |
| `target.className` | `string` | | `LodestoneTarget`: classes for the wrapper, an `inline-flex` div. Hovering or keyboard-focusing it charges the target up; pressing it sends a shockwave. |
| `quiet.className` | `string` | | `LodestoneQuiet`: classes for the wrapper. The field parts around it on a rounded outline and draws nothing under it, so text stays readable. |
## Source
```tsx title="components/ui/lodestone.tsx"
"use client";
import * as React from "react";
import { useReducedMotion } from "motion/react";
import { cn } from "@/lib/utils";
/* ─────────────────────────────────────────────────────────
* LODESTONE STORYBOARD
*
* intro the first time the field scrolls into view, the
* hairlines lie scattered like loose filings, then
* snap into line in a ring that spreads out from the
* call to action
* rest every `LodestoneTarget` is a bar magnet: its field
* arcs from one end of the button to the other and
* loops out across the backdrop, so the whole surface
* quietly leads back to it. Strong field: long, dark
* hairlines that swing fast. Weak field: short, faint
* ones that barely agree on a direction
* cursor the pointer is a second, weaker pole. Its field
* bends the loops toward it and, near the button,
* bridges into the far end like iron filings between
* two magnets
* hover pointer or focus on a target: the cursor's pull lets
* go and the target charges up. Its field takes over
* in a wave that starts at the button, and the accent
* color gathers around it
* press a shockwave rolls out from the target; each hairline
* twitches as it passes and springs back
* aligned `aligned` (a waitlist joined, a form sent) swings
* every hairline to north in one wave, with a ring
* quiet `LodestoneQuiet` (a headline, a paragraph) is a
* stone in the stream: the field parts and flows
* along its edges, and nothing draws under the text
* reduced the same field, drawn still: no intro, no cursor,
* states change in one frame
* ───────────────────────────────────────────────────────── */
const FIELD = {
falloff: 1.5, // field of one pole ~ 1/r^falloff; a real magnet is 2, this reaches further
soften: 14, // px, keeps the field finite right on a pole
waveSpeed: 1150, // px/s, how fast a change spreads out from where it started
tween: 0.55, // s, a target's charge or hover changing at one spot
alignTween: 0.75, // s, swinging to north at one spot
intro: 0.9, // s, a filing finding its line at one spot
hoverBoost: 1.5, // a hovered target's charge, on top of 1
cursorFollow: 0.18, // s, time constant of the cursor's pole fading in and out
stiffness: [55, 320], // spring stiffness from the weakest to the strongest field
damping: 0.5, // damping ratio, a little under 1 so each hairline settles with a small overshoot
jitter: 0.55, // rad, how much hairlines in a weak field disagree
minLength: 0.22, // a hairline in no field is this share of `length`
alpha: [0.06, 0.6], // opacity from the weakest to the strongest field
accentReach: 1.2, // how far the accent gathers around a target, relative to its field
ring: { speed: 820, width: 46, decay: 0.85, kick: 34 }, // shockwave: px/s, px, s, rad/s²
marks: 6, // a static + every this many cells
markAlpha: 0.2,
fadeCells: 3, // edge fade, in cells
levels: 14, // opacity steps hairlines are batched into
accents: 4, // accent mix steps
maxDpr: 2,
} as const;
type Tween = { from: number; to: number; t0: number; dur: number; ox: number; oy: number };
type Poles = "ends" | "center";
type Target = {
el: HTMLElement;
poles: Poles;
strength: Tween;
hover: Tween;
hovered: boolean;
// per frame, relative to the root
x0: number;
y0: number;
x1: number;
y1: number;
};
type Options = {
spacing: number;
length: number;
thickness: number;
reach: number;
cursor: number;
intro: boolean;
marks: boolean;
fade: boolean;
reduced: boolean;
};
const clamp01 = (t: number) => Math.min(1, Math.max(0, t));
const smoothstep = (a: number, b: number, x: number) => {
const t = clamp01((x - a) / (b - a));
return t * t * (3 - 2 * t);
};
const easeInOut = (t: number) => (t < 0.5 ? 4 * t * t * t : 1 - Math.pow(-2 * t + 2, 3) / 2);
/** A hairline has no head, so angles that differ by π are the same: wraps to (-π/2, π/2]. */
const wrapAxial = (a: number) => a - Math.PI * Math.round(a / Math.PI);
const NORTH = Math.PI / 2;
function still(value: number): Tween {
return { from: value, to: value, t0: 0, dur: 0, ox: 0, oy: 0 };
}
/** The tween's value at a point `d` px from where it started: the change reaches it `d / waveSpeed` s late. */
function tweenAt(tw: Tween, t: number, d: number) {
if (tw.from === tw.to) return tw.to;
const p = (t - tw.t0 - d / FIELD.waveSpeed) / tw.dur;
if (p <= 0) return tw.from;
if (p >= 1) return tw.to;
return tw.from + (tw.to - tw.from) * easeInOut(p);
}
function tweenDone(tw: Tween, t: number, maxDistance: number) {
return tw.from === tw.to || t > tw.t0 + tw.dur + maxDistance / FIELD.waveSpeed;
}
/** Signed distance from a point to a rounded box, and the outward normal there. */
function boxDistance(
px: number,
py: number,
x0: number,
y0: number,
x1: number,
y1: number,
radius: number,
out: { d: number; nx: number; ny: number },
) {
const cx = (x0 + x1) / 2;
const cy = (y0 + y1) / 2;
const sx = px < cx ? -1 : 1;
const sy = py < cy ? -1 : 1;
const qx = Math.abs(px - cx) - ((x1 - x0) / 2 - radius);
const qy = Math.abs(py - cy) - ((y1 - y0) / 2 - radius);
if (qx > 0 && qy > 0) {
const len = Math.hypot(qx, qy);
out.d = len - radius;
out.nx = (sx * qx) / len;
out.ny = (sy * qy) / len;
} else if (qx > qy) {
out.d = qx - radius;
out.nx = sx;
out.ny = 0;
} else {
out.d = qy - radius;
out.nx = 0;
out.ny = sy;
}
return out;
}
function createField() {
let root: HTMLElement | null = null;
let canvas: HTMLCanvasElement | null = null;
let ctx: CanvasRenderingContext2D | null = null;
let probes: { ink: HTMLElement; accent: HTMLElement } | null = null;
let colors: string[] = [];
let options: Options = {
spacing: 22,
length: 0.6,
thickness: 1,
reach: 1,
cursor: 0.8,
intro: true,
marks: true,
fade: true,
reduced: false,
};
const targets = new Map();
const quiet = new Map();
// Hairlines, rebuilt when the root changes size.
let count = 0;
let px = new Float32Array(0);
let py = new Float32Array(0);
let theta = new Float32Array(0);
let omega = new Float32Array(0);
let scatter = new Float32Array(0); // a filing's angle before the intro
let jitter = new Float32Array(0); // -1…1, how this filing disagrees in a weak field
let marks: number[] = [];
let width = 0;
let height = 0;
let dpr = 1;
let settled = false; // hairlines have been placed on their field once
// Draw batches: one Float32Array of segments per opacity level × accent step.
let batches: Float32Array[] = [];
let batchCounts: Int32Array = new Int32Array(0);
let aligned = still(0);
let intro = still(1);
let introStarted = false;
const rings: { t0: number; x: number; y: number; amp: number }[] = [];
const cursor = { x: 0, y: 0, inside: false, charge: 0 };
let raf = 0;
let last = 0;
let visible = false;
const cleanups: (() => void)[] = [];
const now = () => performance.now() / 1000;
function readColors() {
if (!probes) return;
const ink = getComputedStyle(probes.ink).color;
const accent = getComputedStyle(probes.accent).color;
colors = [];
for (let i = 0; i < FIELD.accents; i++) {
const share = Math.round((i / (FIELD.accents - 1)) * 100);
probes.ink.style.color = `color-mix(in oklab, ${ink}, ${accent} ${share}%)`;
colors.push(getComputedStyle(probes.ink).color);
}
probes.ink.style.color = "";
}
function layout() {
if (!root || !canvas) return;
const w = root.clientWidth;
const h = root.clientHeight;
dpr = Math.min(window.devicePixelRatio || 1, FIELD.maxDpr);
if (w === width && h === height && canvas.width === Math.round(w * dpr)) return;
width = w;
height = h;
canvas.width = Math.round(w * dpr);
canvas.height = Math.round(h * dpr);
const s = options.spacing;
const cols = Math.max(1, Math.floor(w / s));
const rows = Math.max(1, Math.floor(h / s));
const ox = (w - (cols - 1) * s) / 2;
const oy = (h - (rows - 1) * s) / 2;
count = cols * rows;
px = new Float32Array(count);
py = new Float32Array(count);
const oldTheta = theta;
theta = new Float32Array(count);
omega = new Float32Array(count);
scatter = new Float32Array(count);
jitter = new Float32Array(count);
// Seeded, so the filings scatter the same way on every render.
let seed = 1234567;
const random = () => ((seed = (seed * 16807) % 2147483647) / 2147483647);
for (let r = 0, i = 0; r < rows; r++) {
for (let c = 0; c < cols; c++, i++) {
px[i] = ox + c * s;
py[i] = oy + r * s;
scatter[i] = (random() - 0.5) * Math.PI;
jitter[i] = random() * 2 - 1;
theta[i] = oldTheta.length === count ? oldTheta[i] : scatter[i];
}
}
marks = [];
for (let r = 0; r < rows - 1; r++) {
for (let c = 0; c < cols - 1; c++) {
if ((r + 3) % FIELD.marks === 0 && (c + 3) % FIELD.marks === 0) {
marks.push(ox + (c + 0.5) * s, oy + (r + 0.5) * s);
}
}
}
batches = Array.from({ length: FIELD.levels * FIELD.accents }, () => new Float32Array(count * 4));
batchCounts = new Int32Array(FIELD.levels * FIELD.accents);
if (oldTheta.length !== count) settled = false;
wake();
}
function readRects() {
if (!root) return { quietRects: [] as number[][] };
const base = root.getBoundingClientRect();
for (const target of targets.values()) {
const r = target.el.getBoundingClientRect();
target.x0 = r.left - base.left;
target.y0 = r.top - base.top;
target.x1 = r.right - base.left;
target.y1 = r.bottom - base.top;
}
const quietRects: number[][] = [];
for (const el of quiet.values()) {
const r = el.getBoundingClientRect();
if (r.width === 0 && r.height === 0) continue;
quietRects.push([r.left - base.left, r.top - base.top, r.right - base.left, r.bottom - base.top]);
}
return { quietRects };
}
/** Where waves start: the strongest target, else the middle. */
function origin(): [number, number] {
let best: Target | null = null;
for (const target of targets.values()) {
if (!best || target.strength.to > best.strength.to) best = target;
}
if (!best) return [width / 2, height / 2];
return [(best.x0 + best.x1) / 2, (best.y0 + best.y1) / 2];
}
function retarget(tw: Tween, to: number, dur: number, ox: number, oy: number): Tween {
if (tw.to === to) return tw;
const t = now();
if (options.reduced) return still(to);
// Restart from wherever the source spot is right now.
return { from: tweenAt(tw, t, Math.hypot(ox - tw.ox, oy - tw.oy)), to, t0: t, dur, ox, oy };
}
const box = { d: 0, nx: 0, ny: 0 };
function frame() {
raf = 0;
if (!ctx || !canvas || !root) return;
const t = now();
const dt = Math.min(last ? t - last : 1 / 60, 1 / 20);
last = t;
const { quietRects } = readRects();
const { spacing, length, thickness, reach, reduced } = options;
const maxDistance = Math.hypot(width, height);
// The cursor's pole: fades in while the pointer is over the field and no target is hovered.
let anyHover = false;
for (const target of targets.values()) anyHover ||= target.hovered;
const cursorGoal = cursor.inside && !anyHover && !reduced ? options.cursor : 0;
cursor.charge = reduced
? cursorGoal
: cursor.charge + (cursorGoal - cursor.charge) * (1 - Math.exp(-dt / FIELD.cursorFollow));
if (Math.abs(cursor.charge - cursorGoal) < 0.002) cursor.charge = cursorGoal;
// Poles for this frame. Each target's charge is read per hairline, since changes travel as a wave.
const list = [...targets.values()];
const L = Math.min(Math.max(0.32 * Math.min(width, height), 110), 280) * reach;
const scale = Math.pow(L, FIELD.falloff);
const power = (FIELD.falloff + 1) / 2;
const soft2 = FIELD.soften * FIELD.soften;
for (let i = rings.length - 1; i >= 0; i--) {
if (t - rings[i].t0 > FIELD.ring.decay * 4) rings.splice(i, 1);
}
batchCounts.fill(0);
let moving = false;
const fadePx = spacing * FIELD.fadeCells;
const [stiffMin, stiffMax] = FIELD.stiffness;
const [alphaMin, alphaMax] = FIELD.alpha;
for (let i = 0; i < count; i++) {
const x = px[i];
const y = py[i];
// Edge fade and quiet zones (headlines, and the targets themselves) decide visibility.
let visibility = options.fade
? smoothstep(0, fadePx, Math.min(x, y, width - x, height - y) + spacing * 0.5)
: 1;
let bx = 0;
let by = 0;
let tx = 0;
let ty = 0;
let hoverMax = 0;
for (const target of list) {
const cx = (target.x0 + target.x1) / 2;
const cy = (target.y0 + target.y1) / 2;
const strength = tweenAt(target.strength, t, Math.hypot(x - target.strength.ox, y - target.strength.oy));
const hover = tweenAt(target.hover, t, Math.hypot(x - target.hover.ox, y - target.hover.oy));
hoverMax = Math.max(hoverMax, hover);
const q = strength * (1 + FIELD.hoverBoost * hover);
if (q === 0) continue;
if (target.poles === "ends") {
const h = target.y1 - target.y0;
const inset = Math.min(h / 2, (target.x1 - target.x0) / 4);
// North pole on the left end, south on the right: the field runs from one to the other.
for (const [ax, sign] of [
[target.x0 + inset, 1],
[target.x1 - inset, -1],
] as const) {
const dx = x - ax;
const dy = y - cy;
const f = (sign * q * scale) / Math.pow(dx * dx + dy * dy + soft2, power);
tx += dx * f;
ty += dy * f;
}
} else {
const dx = x - cx;
const dy = y - cy;
const f = (-q * scale) / Math.pow(dx * dx + dy * dy + soft2, power);
tx += dx * f;
ty += dy * f;
}
boxDistance(x, y, target.x0, target.y0, target.x1, target.y1, Math.min(8, (target.y1 - target.y0) / 2), box);
visibility *= smoothstep(spacing * 0.15, spacing * 0.75, box.d);
}
bx = tx;
by = ty;
if (cursor.charge > 0) {
const dx = x - cursor.x;
const dy = y - cursor.y;
const f = (cursor.charge * scale) / Math.pow(dx * dx + dy * dy + soft2, power);
bx += dx * f;
by += dy * f;
}
for (const r of quietRects) {
// A rounded, pebble-like outline, so the clearing never reads as a box.
const pad = spacing * 0.5;
const round = Math.min(r[2] - r[0], r[3] - r[1]) * 0.42 + pad;
boxDistance(x, y, r[0] - pad, r[1] - pad, r[2] + pad, r[3] + pad, round, box);
if (box.d < spacing * 3) {
// Part around the stone: take away the part of the field that runs into it.
const along = bx * box.nx + by * box.ny;
const bend = 1 - smoothstep(0, spacing * 3, box.d);
bx -= box.nx * along * bend;
by -= box.ny * along * bend;
}
visibility *= smoothstep(0, spacing * 1.6, box.d);
}
const magnitude = Math.hypot(bx, by);
const strengthHere = clamp01((Math.log2(magnitude + 1e-6) + 3.5) / 5);
const targetHere = clamp01((Math.log2(Math.hypot(tx, ty) + 1e-6) + FIELD.accentReach) / 3.2);
const a = tweenAt(aligned, t, Math.hypot(x - aligned.ox, y - aligned.oy));
const introAt = tweenAt(intro, t, Math.hypot(x - intro.ox, y - intro.oy));
let goal = magnitude > 1e-6 ? Math.atan2(by, bx) : theta[i];
goal += jitter[i] * FIELD.jitter * (1 - strengthHere) * (1 - strengthHere) * (1 - a);
if (introAt < 1) goal = scatter[i] + wrapAxial(goal - scatter[i]) * introAt;
if (a > 0) goal += wrapAxial(NORTH - goal) * a;
const s = strengthHere + (0.72 - strengthHere) * a;
// The shockwave: a ring that passes once, twitching hairlines as it goes.
let pulse = 0;
for (const ring of rings) {
const age = t - ring.t0;
const d = Math.hypot(x - ring.x, y - ring.y) - age * FIELD.ring.speed;
pulse += ring.amp * Math.exp(-(d * d) / (FIELD.ring.width * FIELD.ring.width)) * Math.exp(-age / FIELD.ring.decay);
}
if (reduced || (!settled && !options.intro)) {
theta[i] = goal;
omega[i] = 0;
} else {
const k = stiffMin + (stiffMax - stiffMin) * s;
const c = 2 * Math.sqrt(k) * FIELD.damping;
const delta = wrapAxial(goal - theta[i]);
omega[i] += (k * delta - c * omega[i] + pulse * FIELD.ring.kick) * dt;
theta[i] = wrapAxial(theta[i] + omega[i] * dt);
if (Math.abs(omega[i]) > 0.004 || Math.abs(delta) > 0.004) moving = true;
}
if (visibility <= 0.01) continue;
const alpha = clamp01((alphaMin + (alphaMax - alphaMin) * s + 0.35 * pulse) * visibility);
const level = Math.round(alpha * (FIELD.levels - 1));
if (level === 0) continue;
const accent = clamp01(Math.max(targetHere * (0.3 + 0.7 * hoverMax) * (1 - a * 0.5), pulse * 0.8));
const shade = Math.round(accent * (FIELD.accents - 1));
const half = ((length * spacing) / 2) * (FIELD.minLength + (1 - FIELD.minLength) * s) * (1 + 0.5 * pulse);
const dx = Math.cos(theta[i]) * half;
const dy = Math.sin(theta[i]) * half;
const b = level * FIELD.accents + shade;
const n = batchCounts[b]++ * 4;
const seg = batches[b];
seg[n] = x - dx;
seg[n + 1] = y - dy;
seg[n + 2] = x + dx;
seg[n + 3] = y + dy;
}
settled = true;
ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
ctx.clearRect(0, 0, width, height);
ctx.lineCap = "round";
ctx.lineWidth = thickness;
for (let level = 1; level < FIELD.levels; level++) {
for (let shade = 0; shade < FIELD.accents; shade++) {
const b = level * FIELD.accents + shade;
const n = batchCounts[b];
if (!n) continue;
const seg = batches[b];
ctx.globalAlpha = level / (FIELD.levels - 1);
ctx.strokeStyle = colors[shade] ?? colors[0] ?? "currentColor";
ctx.beginPath();
for (let j = 0; j < n * 4; j += 4) {
ctx.moveTo(seg[j], seg[j + 1]);
ctx.lineTo(seg[j + 2], seg[j + 3]);
}
ctx.stroke();
}
}
if (options.marks && marks.length) {
ctx.strokeStyle = colors[0] ?? "currentColor";
ctx.lineWidth = thickness * 0.75;
const arm = 2.5;
ctx.beginPath();
let drawn = false;
for (let j = 0; j < marks.length; j += 2) {
const x = marks[j];
const y = marks[j + 1];
let visibility = options.fade ? smoothstep(0, fadePx, Math.min(x, y, width - x, height - y)) : 1;
for (const r of quietRects) {
boxDistance(x, y, r[0], r[1], r[2], r[3], 0, box);
visibility *= smoothstep(0, spacing, box.d);
}
for (const target of list) {
boxDistance(x, y, target.x0, target.y0, target.x1, target.y1, 0, box);
visibility *= smoothstep(0, spacing, box.d);
}
if (visibility < 0.5) continue;
ctx.moveTo(x - arm, y);
ctx.lineTo(x + arm, y);
ctx.moveTo(x, y - arm);
ctx.lineTo(x, y + arm);
drawn = true;
}
if (drawn) {
ctx.globalAlpha = FIELD.markAlpha;
ctx.stroke();
}
}
ctx.globalAlpha = 1;
let busy = moving || rings.length > 0 || cursor.charge !== cursorGoal;
busy ||= !tweenDone(aligned, t, maxDistance) || !tweenDone(intro, t, maxDistance);
for (const target of list) {
busy ||= !tweenDone(target.strength, t, maxDistance) || !tweenDone(target.hover, t, maxDistance);
}
if (busy && visible) raf = requestAnimationFrame(frame);
else last = 0;
}
function wake() {
if (raf || !visible || !ctx) return;
raf = requestAnimationFrame(frame);
}
function startIntro() {
if (introStarted) return;
introStarted = true;
if (!options.intro || options.reduced) {
intro = still(1);
return;
}
readRects();
const [ox, oy] = origin();
intro = { from: 0, to: 1, t0: now() + 0.15, dur: FIELD.intro, ox, oy };
}
return {
connect(el: { root: HTMLElement; canvas: HTMLCanvasElement; ink: HTMLElement; accent: HTMLElement }) {
root = el.root;
canvas = el.canvas;
ctx = canvas.getContext("2d");
probes = { ink: el.ink, accent: el.accent };
readColors();
width = 0;
layout();
const resize = new ResizeObserver(() => {
layout();
wake();
});
resize.observe(root);
const io = new IntersectionObserver(([entry]) => {
visible = entry.isIntersecting;
if (visible) {
startIntro();
wake();
}
});
io.observe(root);
const scheme = window.matchMedia("(prefers-color-scheme: dark)");
const recolor = () => {
readColors();
wake();
};
scheme.addEventListener("change", recolor);
const themeAttrs = new MutationObserver(recolor);
themeAttrs.observe(document.documentElement, { attributes: true, attributeFilter: ["class", "data-theme", "style"] });
const move = (e: PointerEvent) => {
if (!root) return;
if (e.pointerType === "touch" && e.type === "pointermove" && !cursor.inside) return;
const r = root.getBoundingClientRect();
cursor.x = e.clientX - r.left;
cursor.y = e.clientY - r.top;
cursor.inside = true;
wake();
};
const leave = () => {
cursor.inside = false;
wake();
};
root.addEventListener("pointermove", move);
root.addEventListener("pointerdown", move);
root.addEventListener("pointerleave", leave);
root.addEventListener("pointercancel", leave);
const touchUp = (e: PointerEvent) => {
if (e.pointerType === "touch") leave();
};
root.addEventListener("pointerup", touchUp);
cleanups.push(
() => resize.disconnect(),
() => io.disconnect(),
() => scheme.removeEventListener("change", recolor),
() => themeAttrs.disconnect(),
() => {
root?.removeEventListener("pointermove", move);
root?.removeEventListener("pointerdown", move);
root?.removeEventListener("pointerleave", leave);
root?.removeEventListener("pointercancel", leave);
root?.removeEventListener("pointerup", touchUp);
},
);
return () => {
cancelAnimationFrame(raf);
raf = 0;
cleanups.splice(0).forEach((fn) => fn());
root = canvas = null;
ctx = null;
probes = null;
};
},
setOptions(next: Options) {
const relayout = next.spacing !== options.spacing;
options = next;
if (next.reduced) {
intro = still(1);
rings.length = 0;
}
if (relayout) width = 0;
layout();
wake();
},
setAligned(value: boolean) {
readRects();
const [ox, oy] = origin();
const goal = value ? 1 : 0;
if (aligned.to === goal) return;
aligned = retarget(aligned, goal, FIELD.alignTween, ox, oy);
if (value && !options.reduced && introStarted) rings.push({ t0: now(), x: ox, y: oy, amp: 1 });
wake();
},
addTarget(id: string, el: HTMLElement, poles: Poles, strength: number) {
const existing = targets.get(id);
if (existing) existing.el = el;
else {
targets.set(id, {
el,
poles,
strength: still(strength),
hover: still(0),
hovered: false,
x0: 0,
y0: 0,
x1: 0,
y1: 0,
});
}
wake();
return () => {
targets.delete(id);
wake();
};
},
updateTarget(id: string, poles: Poles, strength: number) {
const target = targets.get(id);
if (!target) return;
target.poles = poles;
if (target.strength.to !== strength) {
readRects();
const ox = (target.x0 + target.x1) / 2;
const oy = (target.y0 + target.y1) / 2;
target.strength = retarget(target.strength, strength, FIELD.tween, ox, oy);
}
wake();
},
hoverTarget(id: string, hovered: boolean) {
const target = targets.get(id);
if (!target || target.hovered === hovered) return;
target.hovered = hovered;
readRects();
const ox = (target.x0 + target.x1) / 2;
const oy = (target.y0 + target.y1) / 2;
target.hover = retarget(target.hover, hovered ? 1 : 0, FIELD.tween, ox, oy);
wake();
},
pulse(id: string) {
const target = targets.get(id);
if (!target || options.reduced) return;
readRects();
rings.push({ t0: now(), x: (target.x0 + target.x1) / 2, y: (target.y0 + target.y1) / 2, amp: 0.7 });
wake();
},
addQuiet(id: string, el: HTMLElement) {
quiet.set(id, el);
wake();
return () => {
quiet.delete(id);
wake();
};
},
};
}
type Field = ReturnType;
const LodestoneContext = React.createContext(null);
export interface LodestoneProps extends React.HTMLAttributes {
/** Distance between hairlines, in px. */
spacing?: number;
/** Length of a hairline in a strong field, as a share of `spacing`. */
length?: number;
/** Line width, in px. */
thickness?: number;
/** How far the targets' fields carry. `2` reaches about twice as far. */
reach?: number;
/** Strength of the pointer's own pole, relative to a target. `0` turns it off. */
cursor?: number;
/** Swing every hairline to north in one wave from the target, for a success state. */
aligned?: boolean;
/** Scatter the hairlines and let them snap into line the first time the field scrolls into view. */
intro?: boolean;
/** Draw a faint static + every few cells, like engineering paper. */
marks?: boolean;
/** Fade the field out toward the edges. */
fade?: boolean;
/** Classes that set the hairlines' color (a `text-*` color). */
fieldClassName?: string;
/** Classes that set the accent near a hovered target (a `text-*` color). */
accentClassName?: string;
/** Classes for the canvas, e.g. an opacity. */
canvasClassName?: string;
}
export function Lodestone({
spacing = 24,
length = 0.6,
thickness = 1,
reach = 1.3,
cursor = 0.8,
aligned = false,
intro = true,
marks = true,
fade = true,
fieldClassName,
accentClassName,
canvasClassName,
className,
children,
...props
}: LodestoneProps) {
const rootRef = React.useRef(null);
const canvasRef = React.useRef(null);
const inkRef = React.useRef(null);
const accentRef = React.useRef(null);
const [field] = React.useState(createField);
const reduced = useReducedMotion() ?? false;
React.useLayoutEffect(() => {
const root = rootRef.current;
const canvas = canvasRef.current;
const ink = inkRef.current;
const accent = accentRef.current;
if (!root || !canvas || !ink || !accent) return;
return field.connect({ root, canvas, ink, accent });
}, [field]);
React.useEffect(() => {
field.setOptions({ spacing, length, thickness, reach, cursor, intro, marks, fade, reduced });
}, [field, spacing, length, thickness, reach, cursor, intro, marks, fade, reduced]);
React.useEffect(() => {
field.setAligned(aligned);
}, [field, aligned]);
return (
{/* Probes the canvas reads its colors from. Defaults apply only when no class is given, so a `dark:` default can't win over yours. */}
{children}
);
}
export interface LodestoneTargetProps extends React.HTMLAttributes {
/** How strongly this target pulls the field. Change it to hand the field from one target to another. */
strength?: number;
/** `ends`: a bar magnet whose field arcs from one end to the other. `center`: one pole the field points into. */
poles?: Poles;
}
export function LodestoneTarget({
strength = 1,
poles = "ends",
className,
onPointerEnter,
onPointerLeave,
onPointerDown,
onFocus,
onBlur,
...props
}: LodestoneTargetProps) {
const field = React.useContext(LodestoneContext);
const ref = React.useRef(null);
const id = React.useId();
const initial = React.useRef({ poles, strength });
React.useLayoutEffect(() => {
const el = ref.current;
if (!field || !el) return;
return field.addTarget(id, el, initial.current.poles, initial.current.strength);
}, [field, id]);
React.useEffect(() => {
field?.updateTarget(id, poles, strength);
}, [field, id, poles, strength]);
return (
{
if (e.pointerType !== "touch") field?.hoverTarget(id, true);
onPointerEnter?.(e);
}}
onPointerLeave={(e) => {
field?.hoverTarget(id, false);
onPointerLeave?.(e);
}}
onPointerDown={(e) => {
field?.pulse(id);
onPointerDown?.(e);
}}
onFocus={(e) => {
if (e.target.matches(":focus-visible")) field?.hoverTarget(id, true);
onFocus?.(e);
}}
onBlur={(e) => {
if (!e.currentTarget.contains(e.relatedTarget as Node | null)) field?.hoverTarget(id, false);
onBlur?.(e);
}}
{...props}
/>
);
}
export type LodestoneQuietProps = React.HTMLAttributes;
/** Content the field flows around, like water around a stone. Nothing draws under it. */
export function LodestoneQuiet({ className, ...props }: LodestoneQuietProps) {
const field = React.useContext(LodestoneContext);
const ref = React.useRef(null);
const id = React.useId();
React.useLayoutEffect(() => {
const el = ref.current;
if (!field || !el) return;
return field.addQuiet(id, el);
}, [field, id]);
return ;
}
```