Line Art Street

Installation#

CLI

npx shadcn@latest add https://hantui-theta.vercel.app/r/line-art-street.json

Manual

1. Install the dependencies

   npmpnpmbunyarn

   npm install clsx lucide-react tailwind-merge

2. Add the shared helpers

   Components use cn() from lib/utils.ts and the motion tokens below. See Installation if you have not set them up yet.

   lib/line-art/daynight.ts

   /**
    * Day and night for line art. `tau` runs 0 to 1 over a day: 0 is midnight, 0.5 is noon.
    * By day the drawing is dark ink on warm paper; at night it inverts to pale ink on indigo paper.
    */
   
   type Rgb = readonly [number, number, number];
   
   const hex = (value: string): Rgb => {
     const v = value.replace("#", "");
     return [parseInt(v.slice(0, 2), 16), parseInt(v.slice(2, 4), 16), parseInt(v.slice(4, 6), 16)];
   };
   const mix = (a: Rgb, b: Rgb, t: number) => `rgb(${a.map((value, i) => Math.round(value + (b[i] - value) * t)).join(" ")})`;
   const smooth = (edge0: number, edge1: number, x: number) => {
     const t = Math.min(1, Math.max(0, (x - edge0) / (edge1 - edge0)));
     return t * t * (3 - 2 * t);
   };
   
   const DAY = { paper: hex("#fdfcf8"), ink: hex("#1c1c1c"), skyTop: hex("#cfe4f2"), skyLow: hex("#fdf6e6") };
   const DUSK = { skyTop: hex("#f0a878"), skyLow: hex("#fbe3c2") };
   const NIGHT = { paper: hex("#1d2140"), ink: hex("#e9e6f2"), skyTop: hex("#10132c"), skyLow: hex("#2a2f5c") };
   
   export interface DayPalette {
     paper: string;
     ink: string;
     /** Sky gradient stops, top then horizon. */
     sky: [string, string];
     /** 0 by day, 1 in full night. Use it for window glow, stars and lamps. */
     night: number;
     /** Height of the sun or moon above the horizon, 0 to 1. */
     height: number;
     /** True while the body in the sky is the moon. */
     moon: boolean;
   }
   
   /** How dark it is at `tau`: 0 from mid-morning to late afternoon, 1 deep at night. */
   export function nightness(tau: number) {
     const t = ((tau % 1) + 1) % 1;
     return 1 - smooth(0.2, 0.3, t) * (1 - smooth(0.72, 0.82, t));
   }
   
   export function palette(tau: number): DayPalette {
     const t = ((tau % 1) + 1) % 1;
     const night = nightness(t);
     // Warm light around sunrise and sunset.
     const dusk = Math.max(0, 1 - Math.abs(night - 0.5) * 2) * 0.85;
     const top = mix(hex(mixHex(DAY.skyTop, DUSK.skyTop, dusk)), NIGHT.skyTop, night);
     const low = mix(hex(mixHex(DAY.skyLow, DUSK.skyLow, dusk)), NIGHT.skyLow, night);
     // Paper darkens gradually; ink flips quickly in the middle, so the two never meet in gray.
     const ink = mix(DAY.ink, NIGHT.ink, smooth(0.42, 0.58, night));
     const moon = t < 0.25 || t > 0.77;
     const arc = moon ? (t > 0.5 ? (t - 0.77) / 0.48 : (t + 0.23) / 0.48) : (t - 0.25) / 0.52;
     return { paper: mix(DAY.paper, NIGHT.paper, night), ink, sky: [top, low], night, height: Math.sin(Math.PI * Math.min(1, Math.max(0, arc))), moon };
   }
   
   function mixHex(a: Rgb, b: Rgb, t: number) {
     return `#${a.map((value, i) => Math.round(value + (b[i] - value) * t).toString(16).padStart(2, "0")).join("")}`;
   }
   
   /** Pushes a flat color toward the night palette: darker and bluer as night falls. */
   export function nightTint(color: string, tau: number) {
     return mix(hex(color), [58, 62, 110], nightness(tau) * 0.62);
   }

   Show all 62 lines

   lib/line-art/figures.ts

   import { gait, joint, standing, GROUND, type GaitPose } from "@/lib/line-art/gait";
   import { DETAIL_PEN, PEN, el, limb, line, paint, poly, shape, type Point } from "@/lib/line-art/ink";
   import { pendulum, type Pendulum } from "@/lib/line-art/physics";
   
   /**
    * Faceless, open-stroke figures in figure space (about 95 units tall, feet on y = 120, facing
    * +x). Each is one <g>: place it with a single transform. Poses come from the gait solver; hanging
    * things are pendulums; reactions are short keyed arm moves.
    */
   
   export type FigureKind = "commuter" | "courier" | "jogger" | "cyclist";
   
   export interface Figure {
     group: SVGGElement;
     /** Advances the figure by `dt` seconds at `factor` times its usual pace, with `wind` on its loose ends. Returns how far it travelled, in figure units, so feet and wheels never slip. */
     step(dt: number, factor: number, wind: number): number;
     /** Starts the figure's reaction: a tipped hat, a wave, a look at a watch or a rung bell. */
     react(): void;
     /** Draws a still pose. `reacting` holds the reaction at its peak. */
     still(reacting?: boolean): void;
     /** True while a reaction is playing. */
     busy(): boolean;
     /** What the reaction is, for labels: "tips a hat". */
     reaction: string;
     /** Rough half-width of the figure, for hit areas. */
     reach: number;
   }
   
   export interface FigureOptions {
     /** Flat accent for one small area: the scarf, the cap, the vest or the frame. */
     accent?: string;
     /** Leave out what the figure carries (the parcel, the briefcase and scarf), for a plain passer-by. */
     bare?: boolean;
   }
   
   const UPPER = 16;
   const FORE = 15;
   const circle = (cx: number, cy: number, r: number) => `M${(cx - r).toFixed(2)} ${cy.toFixed(2)}a${r} ${r} 0 1 0 ${r * 2} 0a${r} ${r} 0 1 0 ${-r * 2} 0`;
   const ease = (t: number) => t * t * (3 - 2 * t);
   /** 0 → 1 → 0 over a reaction: quick in, hold, quick out. */
   const envelope = (t: number, length: number) => ease(Math.min(1, Math.max(0, t / 0.3))) * ease(Math.min(1, Math.max(0, (length - t) / 0.35)));
   
   const REACTIONS = {
     commuter: { label: "tips a hat", length: 1.5 },
     courier: { label: "waves", length: 1.7 },
     jogger: { label: "checks a watch", length: 1.7 },
     cyclist: { label: "rings the bell", length: 1.1 },
   } as const;
   
   function walker(parent: Element, kind: Exclude<FigureKind, "cyclist">, accent: string, bare: boolean): Figure {
     const group = el("g", {}, parent);
     const running = kind === "jogger";
     const options = running ? { stride: 40, duty: 0.36, lift: 7 } : { stride: 26, duty: 0.62 };
     const cadence = running ? 1.3 : 0.95;
     const lean = running ? 6 : 1.6;
     const torsoLength = 30;
   
     // Far side first, so the near side draws over it.
     const farArm = limb(group, 4.2);
     const farLeg = limb(group, 5.4);
     const farFoot = line(group);
     const bag = kind === "commuter" && !bare ? shape(group) : null;
     const bagHandle = bag ? line(group, "", DETAIL_PEN) : null;
     const parcel = kind === "courier" && !bare ? shape(group) : null;
     const parcelTape = parcel ? line(group, "", DETAIL_PEN) : null;
     const torso = kind === "jogger" ? paint(group, accent) : shape(group);
     const nearLeg = limb(group, 5.4);
     const nearFoot = line(group);
     const scarf = kind === "commuter" && !bare ? limb(group, 3.4, accent) : null;
     const head = shape(group);
     const hat = kind === "commuter" ? shape(group) : kind === "courier" ? paint(group, accent) : line(group);
     const nearArm = limb(group, 4.2);
     const watch = kind === "jogger" ? line(group, "", PEN * 1.6) : null;
   
     let phase = 0.1;
     let reactionAt = -1;
     const scarfSwing: Pendulum = { angle: -0.4, velocity: 0 };
     const bagSwing: Pendulum = { angle: 0, velocity: 0 };
     const reaction = REACTIONS[kind];
   
     function draw(pose: GaitPose, moving: number, wind: number, dt: number) {
       const hip = pose.hip;
       const shoulder: Point = [hip[0] + lean, hip[1] - torsoLength];
       const headAt: Point = [shoulder[0] + 1.6, shoulder[1] - 9.5];
       const w = reactionAt >= 0 ? envelope(reactionAt, reaction.length) : 0;
   
       // Legs and feet.
       for (const [leg, legLimb, footLine] of [[pose.far, farLeg, farFoot], [pose.near, nearLeg, nearFoot]] as const) {
         legLimb.set([leg.hip, leg.knee, leg.ankle]);
         footLine.setAttribute("d", poly([[leg.ankle[0] - 1.5, leg.ankle[1] + 2.4], leg.toe]));
       }
   
       // Torso: a coat with a hem, or a short running top.
       const hem = running ? 1 : 6;
       const [sx, sy] = shoulder;
       const [hx, hy] = hip;
       torso.setAttribute(
         "d",
         `M${sx - 6.5} ${sy + 1.5}Q${sx} ${sy - 3.5} ${sx + 6.5} ${sy + 1.5}L${hx + 8} ${hy + hem}Q${hx} ${hy + hem + 2} ${hx - 8} ${hy + hem}Z`,
       );
   
       // Arms swing against the legs. A reaction takes the near arm to a target with IK.
       const arm = (angle: number, bend: number): [Point, Point] => {
         const elbow: Point = [sx + Math.sin(angle) * UPPER, sy + 2 + Math.cos(angle) * UPPER];
         return [elbow, [elbow[0] + Math.sin(angle + bend) * FORE, elbow[1] + Math.cos(angle + bend) * FORE]];
       };
       const amplitude = (running ? 0.75 : 0.42) * moving;
       const bend = running ? 1.35 : 0.22;
       const [farElbow, farHand] = arm(amplitude * pose.swing, bend + Math.max(0, pose.swing) * 0.3 * moving);
       farArm.set([[sx, sy + 2], farElbow, farHand]);
       // The courier's near arm holds the parcel instead of swinging.
       let [nearElbow, nearHand] = parcel ? arm(0.25, 1.25) : arm(-amplitude * pose.swing, bend + Math.max(0, -pose.swing) * 0.3 * moving);
       if (w > 0) {
         const t = reactionAt;
         const target: Point =
           kind === "commuter"
             ? [headAt[0] + 9, headAt[1] - 5]
             : kind === "courier"
               ? [sx + 15 + Math.sin(t * 11) * 4, sy - 15]
               : [sx + 10, sy + 9];
         nearHand = [nearHand[0] + (target[0] - nearHand[0]) * w, nearHand[1] + (target[1] - nearHand[1]) * w];
         nearElbow = joint([sx, sy + 2], nearHand, UPPER, FORE, 1);
       }
       nearArm.set([[sx, sy + 2], nearElbow, nearHand]);
   
       // Head, looking down a little while checking a watch.
       const nod = kind === "jogger" ? w * 1.6 : 0;
       const hxp = headAt[0] + nod;
       const hyp = headAt[1] + nod;
       head.setAttribute("d", circle(hxp, hyp, 7));
       if (kind === "commuter") {
         // A brimmed hat that lifts off the head when tipped.
         const up = w * 4.5;
         hat.setAttribute("d", `M${hxp - 9.5} ${hyp - 4 - up}L${hxp + 10} ${hyp - 5 - up}M${hxp - 6} ${hyp - 4.3 - up}Q${hxp} ${hyp - 14 - up} ${hxp + 6.5} ${hyp - 4.8 - up}Z`);
       } else if (kind === "courier") {
         hat.setAttribute("d", `M${hxp - 6.6} ${hyp - 2.5}Q${hxp} ${hyp - 12} ${hxp + 6.8} ${hyp - 3}L${hxp + 12.5} ${hyp - 2}L${hxp + 6.8} ${hyp - 1.2}Z`);
       } else {
         hat.setAttribute("d", `M${hxp - 6.8} ${hyp - 2}L${hxp + 6.8} ${hyp - 3.2}`);
       }
   
       // Loose ends: the scarf trails behind and the briefcase swings from the far hand.
       if (scarf) {
         const a = pendulum(scarfSwing, -(0.5 + moving * 2.4) + wind * 9, dt, 9, 3);
         const root: Point = [sx - 3.5, sy + 1.5];
         const mid: Point = [root[0] + Math.sin(a) * 8, root[1] + Math.cos(a) * 8];
         scarf.set([root, mid, [mid[0] + Math.sin(a * 1.45) * 8, mid[1] + Math.cos(a * 1.45) * 8]]);
       }
       if (bag && bagHandle) {
         const a = pendulum(bagSwing, -pose.swing * 2.4 * moving + wind * 6, dt, 10, 2.6);
         const cos = Math.cos(a);
         const sin = Math.sin(a);
         const at = (x: number, y: number): Point => [farHand[0] + x * cos - y * sin, farHand[1] + x * sin + y * cos];
         bag.setAttribute("d", poly([at(-7, 3), at(7, 3), at(7, 13), at(-7, 13)], true));
         bagHandle.setAttribute("d", poly([at(-3, 3), at(-3, 0.5), at(3, 0.5), at(3, 3)]));
       }
       if (parcel && parcelTape) {
         const px = sx + 2;
         const py = sy + 12;
         parcel.setAttribute("d", poly([[px, py], [px + 13, py - 1], [px + 13.5, py + 9], [px + 0.5, py + 10]], true));
         parcelTape.setAttribute("d", poly([[px + 6.5, py - 0.5], [px + 7, py + 9.5]]));
       }
       if (watch) watch.setAttribute("d", poly([[nearHand[0] - 2.2, nearHand[1] - 3], [nearHand[0] + 1.2, nearHand[1] - 4.4]]));
     }
   
     return {
       group,
       reaction: reaction.label,
       reach: 16,
       step(dt, factor, wind) {
         const before = phase;
         phase += cadence * factor * dt;
         if (reactionAt >= 0) {
           reactionAt += dt;
           if (reactionAt > reaction.length) reactionAt = -1;
         }
         draw(gait(phase, options), Math.min(1, factor), wind, dt);
         return ((phase - before) * options.stride) / options.duty;
       },
       react() {
         reactionAt = 0;
       },
       still(reacting = false) {
         reactionAt = reacting ? reaction.length / 2 : -1;
         scarfSwing.angle = -0.25;
         scarfSwing.velocity = 0;
         bagSwing.angle = 0;
         bagSwing.velocity = 0;
         draw(standing(), 0, 0, 0);
         reactionAt = -1;
       },
       busy: () => reactionAt >= 0,
     };
   }
   
   function cyclist(parent: Element, accent: string): Figure {
     const group = el("g", {}, parent);
     const R = 13;
     const rear: Point = [-18, GROUND - R];
     const front: Point = [20, GROUND - R];
     const bracket: Point = [-1, GROUND - R + 1.5];
     const saddle: Point = [-8, 80];
     const bars: Point = [14, 79];
     const headTube: Point = [13, 86];
     const hip: Point = [-7, 77.5];
     const shoulder: Point = [6.5, 55];
     const headAt: Point = [11, 46.5];
     const CRANK = 6.5;
   
     const farArm = limb(group, 4);
     const farLeg = limb(group, 5.2);
     const farPedal = line(group);
     // Wheels turn as groups, spokes and all.
     const wheels = [rear, front].map((hub) => {
       const wheel = el("g", {}, group);
       shape(wheel, circle(hub[0], hub[1], R));
       for (let i = 0; i < 3; i++) {
         const a = (i * Math.PI) / 3;
         line(wheel, poly([[hub[0] - Math.cos(a) * (R - 1), hub[1] - Math.sin(a) * (R - 1)], [hub[0] + Math.cos(a) * (R - 1), hub[1] + Math.sin(a) * (R - 1)]]), DETAIL_PEN);
       }
       return { wheel, hub };
     });
     // Frame: one flat accent, the rest ink.
     paint(group, accent, poly([bracket, [saddle[0] + 1, saddle[1] + 3], headTube], true), PEN);
     line(group, poly([rear, bracket]) + poly([rear, [saddle[0] + 1, saddle[1] + 3]]) + poly([headTube, front]) + poly([headTube, bars]) + poly([[bars[0] - 2, bars[1] - 1], [bars[0] + 3, bars[1] + 1.5]]));
     line(group, poly([[saddle[0] - 4, saddle[1]], [saddle[0] + 4, saddle[1] - 0.6]]), PEN * 1.5);
     const cranks = line(group);
     const lamp = paint(group, "var(--la-glow, #f6c453)", circle(headTube[0] + 3.5, headTube[1] - 2, 1.8), DETAIL_PEN);
     lamp.setAttribute("data-lamp", "");
     const torso = shape(group);
     const nearLeg = limb(group, 5.2);
     const nearPedal = line(group);
     const head = shape(group);
     const helmet = paint(group, accent);
     const nearArm = limb(group, 4);
     const bell = line(group, "", DETAIL_PEN);
   
     let distance = 0;
     let reactionAt = -1;
     const reaction = REACTIONS.cyclist;
   
     function draw() {
       // Rolling without slipping: the wheel's angle is the distance travelled over its radius.
       const wheelAngle = (distance / R) * (180 / Math.PI);
       for (const { wheel, hub } of wheels) wheel.setAttribute("transform", `rotate(${wheelAngle.toFixed(2)} ${hub[0]} ${hub[1]})`);
       const crankAngle = (distance / R) * 0.42;
       const pedal = (offset: number): Point => [bracket[0] + Math.cos(crankAngle + offset) * CRANK, bracket[1] + Math.sin(crankAngle + offset) * CRANK];
       const near = pedal(0);
       const far = pedal(Math.PI);
       cranks.setAttribute("d", poly([far, near]));
       for (const [foot, legLimb, pedalLine] of [[far, farLeg, farPedal], [near, nearLeg, nearPedal]] as const) {
         const ankle: Point = [foot[0] - 1.5, foot[1] - 3];
         legLimb.set([hip, joint(hip, ankle, 21, 21, -1), ankle]);
         pedalLine.setAttribute("d", poly([[foot[0] - 3.5, foot[1]], [foot[0] + 4, foot[1] - 0.6]]));
       }
       torso.setAttribute("d", `M${hip[0] - 5.5} ${hip[1] + 2}Q${hip[0] - 5} ${shoulder[1] + 4} ${shoulder[0] - 3} ${shoulder[1] - 2}Q${shoulder[0] + 3} ${shoulder[1] - 3} ${shoulder[0] + 5} ${shoulder[1] + 3}L${hip[0] + 6} ${hip[1] + 3}Z`);
       head.setAttribute("d", circle(headAt[0], headAt[1], 6.8));
       helmet.setAttribute("d", `M${headAt[0] - 7} ${headAt[1] - 1.5}Q${headAt[0]} ${headAt[1] - 12} ${headAt[0] + 7.4} ${headAt[1] - 1}Z`);
       const grip: Point = [bars[0] + 0.5, bars[1]];
       const start: Point = [shoulder[0] + 1, shoulder[1] + 2];
       farArm.set([start, joint(start, grip, 15, 14, -1), grip]);
       // Ringing the bell: the thumb works and three short marks flash by the bars.
       const w = reactionAt >= 0 ? envelope(reactionAt, reaction.length) : 0;
       const press: Point = [grip[0] - 1.5 + Math.sin(reactionAt * 24) * 0.8 * w, grip[1] - 1.5 * w];
       nearArm.set([start, joint(start, press, 15, 14, -1), press]);
       const flash = w > 0 && Math.floor(reactionAt * 9) % 2 === 0;
       bell.setAttribute("d", flash ? `M${bars[0] + 5} ${bars[1] - 5}l3 -3M${bars[0] + 6.5} ${bars[1] - 1.5}l4 -0.6M${bars[0] + 2.5} ${bars[1] - 7}l1 -4` : "");
     }
   
     return {
       group,
       reaction: reaction.label,
       reach: 34,
       step(dt, factor) {
         const moved = 118 * factor * dt;
         distance += moved;
         if (reactionAt >= 0) {
           reactionAt += dt;
           if (reactionAt > reaction.length) reactionAt = -1;
         }
         draw();
         return moved;
       },
       react() {
         reactionAt = 0;
       },
       still(reacting = false) {
         reactionAt = reacting ? 0.34 : -1;
         draw();
         reactionAt = -1;
       },
       busy: () => reactionAt >= 0,
     };
   }
   
   /** Builds a figure inside `parent`. It draws nothing until its first `step` or `still`. */
   export function createFigure(parent: Element, kind: FigureKind, options: FigureOptions = {}): Figure {
     const accent = options.accent ?? "#c8553d";
     return kind === "cyclist" ? cyclist(parent, accent) : walker(parent, kind, accent, options.bare ?? false);
   }

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   lib/line-art/gait.ts

   import type { Point } from "@/lib/line-art/ink";
   
   /**
    * A walk and run solver in figure space: about 95 units tall, feet on y = 120, facing +x.
    * Feet are placed first and everything else follows from them: a planted toe never slides, the
    * hip's height comes from the planted leg, and knees are solved with two-bone IK.
    */
   
   export const GROUND = 120;
   export const THIGH = 22;
   export const SHIN = 22;
   /** How high the ankle sits above the sole, and how far behind the toe. */
   const ANKLE_UP = 3.2;
   const FOOT = 6.5;
   
   /**
    * Two-bone IK: the middle joint between `a` and `b` for bones of length `l1` and `l2`.
    * `bend` picks the side the joint folds to (1 or -1). Out of reach, the chain straightens.
    */
   export function joint(a: Point, b: Point, l1: number, l2: number, bend = 1): Point {
     const dx = b[0] - a[0];
     const dy = b[1] - a[1];
     const distance = Math.min(Math.hypot(dx, dy), l1 + l2 - 0.001) || 0.001;
     const along = (l1 * l1 - l2 * l2 + distance * distance) / (2 * distance);
     const off = Math.sqrt(Math.max(0, l1 * l1 - along * along)) * bend;
     const length = Math.hypot(dx, dy) || 0.001;
     const nx = dx / length;
     const ny = dy / length;
     return [a[0] + nx * along - ny * off, a[1] + ny * along + nx * off];
   }
   
   /** Minimum-jerk easing: starts and ends with zero velocity and acceleration. */
   const minJerk = (u: number) => u * u * u * (10 - 15 * u + 6 * u * u);
   
   export interface GaitOptions {
     /** Distance a foot travels per step, in figure units. @default 26 */
     stride?: number;
     /** Share of the cycle each foot spends on the ground: about 0.62 walking, 0.36 running. @default 0.62 */
     duty?: number;
     /** How high a swinging foot lifts. Kept low. @default 3.2 */
     lift?: number;
   }
   
   export interface Leg {
     hip: Point;
     knee: Point;
     ankle: Point;
     toe: Point;
     /** True while the toe is on the ground. */
     planted: boolean;
   }
   
   export interface GaitPose {
     /** Hip joint, x relative to the figure's origin. */
     hip: Point;
     near: Leg;
     far: Leg;
     /** -1 to 1, in step with the near leg: drive the arms against it. */
     swing: number;
   }
   
   function foot(phase: number, stride: number, duty: number, lift: number) {
     const p = ((phase % 1) + 1) % 1;
     if (p < duty) {
       // Stance: the toe is fixed on the ground, so relative to the hip it slides straight back.
       const u = p / duty;
       const toeX = stride / 2 - stride * u + FOOT * 0.5;
       // Heel-off: over the last 14% of stance the foot pivots on the toe and the heel rises.
       const heel = Math.max(0, (u - 0.86) / 0.14);
       const angle = heel * heel * 0.7;
       return { toe: [toeX, GROUND] as Point, ankle: [toeX - FOOT * Math.cos(angle) + ANKLE_UP * Math.sin(angle) * 0.4, GROUND - ANKLE_UP - FOOT * Math.sin(angle)] as Point, planted: true };
     }
     // Swing: a minimum-jerk reach from behind to in front, with a low lift.
     const u = (p - duty) / (1 - duty);
     const reach = minJerk(u);
     const toeX = -stride / 2 + stride * reach + FOOT * 0.5;
     const raise = Math.sin(Math.PI * u) * lift;
     const angle = 0.7 * (1 - u) * (1 - u) - 0.18 * Math.sin(Math.PI * u) * u;
     return { toe: [toeX, GROUND - raise] as Point, ankle: [toeX - FOOT * Math.cos(angle), GROUND - raise - ANKLE_UP - FOOT * Math.sin(angle)] as Point, planted: false };
   }
   
   /** Solves one instant of the cycle. `phase` runs 0 to 1 per two steps. */
   export function gait(phase: number, options: GaitOptions = {}): GaitPose {
     const stride = options.stride ?? 26;
     const duty = options.duty ?? 0.62;
     const lift = options.lift ?? 3.2;
     const near = foot(phase, stride, duty, lift);
     const far = foot(phase + 0.5, stride, duty, lift);
     // The hip is as high as the planted leg allows when almost straight, and never higher.
     const reach = (THIGH + SHIN) * 0.985;
     const hipOver = (ankle: Point) => ankle[1] - Math.sqrt(Math.max(reach * reach - ankle[0] * ankle[0], 1));
     let hipY = -Infinity;
     for (const leg of [near, far]) if (leg.planted) hipY = Math.max(hipY, hipOver(leg.ankle));
     if (hipY === -Infinity) {
       // Flight (running): both feet are off the ground. The hip rides a shallow arc from where the
       // pushing leg left it to where the landing leg will take it.
       const p = ((phase % 0.5) + 0.5) % 0.5;
       const u = Math.min(1, Math.max(0, (p - duty) / (0.5 - duty)));
       const takeoff = hipOver(foot(duty - 1e-6, stride, duty, lift).ankle);
       const landing = hipOver(foot(0, stride, duty, lift).ankle);
       hipY = takeoff + (landing - takeoff) * u - Math.sin(Math.PI * u) * 2.2;
     }
     const hip: Point = [0, hipY];
     const leg = (f: typeof near): Leg => {
       // A swinging foot that reaches past the leg's length is pulled back in, so bones never stretch.
       const dx = f.ankle[0] - hip[0];
       const dy = f.ankle[1] - hip[1];
       const over = Math.hypot(dx, dy) / (THIGH + SHIN - 0.05);
       if (f.planted || over <= 1) return { hip, knee: joint(hip, f.ankle, THIGH, SHIN, -1), ankle: f.ankle, toe: f.toe, planted: f.planted };
       const ankle: Point = [hip[0] + dx / over, hip[1] + dy / over];
       const toe: Point = [f.toe[0] + ankle[0] - f.ankle[0], f.toe[1] + ankle[1] - f.ankle[1]];
       return { hip, knee: joint(hip, ankle, THIGH, SHIN, -1), ankle, toe, planted: false };
     };
     return { hip, near: leg(near), far: leg(far), swing: Math.sin(phase * Math.PI * 2 + Math.PI * duty) };
   }
   
   /** Standing still, feet a little apart. */
   export function standing(): GaitPose {
     const reach = (THIGH + SHIN) * 0.992;
     const hip: Point = [0, GROUND - ANKLE_UP - reach];
     const leg = (toeX: number): Leg => {
       const ankle: Point = [toeX - FOOT, GROUND - ANKLE_UP];
       return { hip, knee: joint(hip, ankle, THIGH, SHIN, -1), ankle, toe: [toeX, GROUND], planted: true };
     };
     return { hip, near: leg(6), far: leg(3), swing: 0 };
   }

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   lib/line-art/ink.ts

   /**
    * Ink: a tiny, dependency-free SVG drawing kit for line art. Thin, slightly wobbly strokes in
    * `currentColor` over paper-colored fills, so a scene inverts cleanly at night by changing two
    * CSS colors. Browser only: call these from effects.
    */
   
   export type Point = readonly [x: number, y: number];
   
   /** Pen width in figure units (a figure is about 95 units tall). */
   export const PEN = 1.35;
   /** Width of the detail pen, for mullions, brick courses and other fine marks. */
   export const DETAIL_PEN = PEN * 0.5;
   /** Day colors. Night swaps them through CSS variables. */
   export const INK = "#1c1c1c";
   export const PAPER = "#fdfcf8";
   
   const SVG_NS = "http://www.w3.org/2000/svg";
   
   /** Creates an SVG element, sets its attributes and appends it to `parent` when given. */
   export function el<K extends keyof SVGElementTagNameMap>(name: K, attributes: Record<string, string | number> = {}, parent?: Element): SVGElementTagNameMap[K] {
     const node = document.createElementNS(SVG_NS, name);
     for (const key in attributes) node.setAttribute(key, String(attributes[key]));
     parent?.appendChild(node);
     return node;
   }
   
   /**
    * Adds the one wobble filter a drawing needs and returns its `url(#…)` reference: light
    * turbulence displaces the strokes by under half a unit and a hair of blur softens them, so
    * lines read as ink on paper, not as vectors. Keep it on the drawing group only.
    */
   export function inkDefs(svg: SVGSVGElement, id: string, seed = 3) {
     const defs = el("defs", {}, svg);
     const filter = el("filter", { id, x: "-5%", y: "-5%", width: "110%", height: "110%" }, defs);
     el("feTurbulence", { type: "fractalNoise", baseFrequency: 0.6, numOctaves: 1, seed, result: "noise" }, filter);
     el("feDisplacementMap", { in: "SourceGraphic", in2: "noise", scale: 0.45, xChannelSelector: "R", yChannelSelector: "G", result: "moved" }, filter);
     el("feGaussianBlur", { in: "moved", stdDeviation: 0.12 }, filter);
     return `url(#${id})`;
   }
   
   const STROKE = { fill: "none", stroke: "currentColor", "stroke-linecap": "round", "stroke-linejoin": "round" } as const;
   
   /** An open ink line. */
   export function line(parent: Element, d = "", width = PEN) {
     return el("path", { d, ...STROKE, "stroke-width": width }, parent);
   }
   
   /** A closed outline filled with paper, so it hides what is behind it. */
   export function shape(parent: Element, d = "", width = PEN) {
     return el("path", { d, ...STROKE, fill: "var(--la-paper)", "stroke-width": width }, parent);
   }
   
   /** A solid ink fill. */
   export function blot(parent: Element, d = "") {
     return el("path", { d, fill: "currentColor", stroke: "currentColor", "stroke-width": PEN * 0.5, "stroke-linejoin": "round" }, parent);
   }
   
   /** A flat color fill with an ink outline. One or two of these per scene, in small areas. */
   export function paint(parent: Element, color: string, d = "", width = PEN) {
     return el("path", { d, ...STROKE, fill: color, "stroke-width": width }, parent);
   }
   
   const n = (value: number) => value.toFixed(2);
   
   /** A smooth open path through points (quadratic segments through the midpoints). */
   export function through(points: readonly Point[]) {
     if (points.length < 2) return "";
     let d = `M${n(points[0][0])} ${n(points[0][1])}`;
     for (let i = 1; i < points.length - 1; i++) {
       const mx = (points[i][0] + points[i + 1][0]) / 2;
       const my = (points[i][1] + points[i + 1][1]) / 2;
       d += `Q${n(points[i][0])} ${n(points[i][1])} ${n(mx)} ${n(my)}`;
     }
     const last = points[points.length - 1];
     return `${d}L${n(last[0])} ${n(last[1])}`;
   }
   
   /** A straight polyline. */
   export function poly(points: readonly Point[], close = false) {
     return points.map(([x, y], i) => `${i ? "L" : "M"}${n(x)} ${n(y)}`).join("") + (close ? "Z" : "");
   }
   
   /** The points of a curve pushed sideways by `offset` (positive is to the left of travel). */
   function offsetPoints(points: readonly Point[], offset: number): Point[] {
     return points.map((point, i) => {
       const before = points[Math.max(0, i - 1)];
       const after = points[Math.min(points.length - 1, i + 1)];
       const dx = after[0] - before[0];
       const dy = after[1] - before[1];
       const length = Math.hypot(dx, dy) || 1;
       return [point[0] + (dy / length) * offset, point[1] - (dx / length) * offset] as const;
     });
   }
   
   export interface Limb {
     /** Redraws the limb through its joints, root first. */
     set(joints: readonly Point[]): void;
     group: SVGGElement;
   }
   
   /**
    * A limb drawn the way a pen would: two open strokes, one down each side of a curve through the
    * joints, with round caps and a paper fill between them. `fill` paints the inside a flat color.
    */
   export function limb(parent: Element, width: number, fill = "var(--la-paper)"): Limb {
     const group = el("g", {}, parent);
     const inside = el("path", { fill, stroke: "none" }, group);
     const left = line(group);
     const right = line(group);
     return {
       group,
       set(joints) {
         const a = offsetPoints(joints, width / 2);
         const b = offsetPoints(joints, -width / 2);
         const da = through(a);
         const db = through(b);
         left.setAttribute("d", da);
         right.setAttribute("d", db);
         inside.setAttribute("d", `${da}${through([...b].reverse()).replace("M", "L")}Z`);
       },
     };
   }

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   lib/line-art/loop.ts

   /**
    * The one animation loop a line-art scene runs: it ticks only while the host is on screen, the
    * tab is visible, nothing has paused it and the user has not asked for reduced motion. Under
    * reduced motion it calls `still` once instead, and again whenever asked to redraw. Browser only.
    */
   export interface SceneLoopOptions {
     /** Element watched for visibility. */
     host: Element;
     /** Advance by `dt` seconds (capped at 0.05) and draw. */
     tick: (dt: number, time: number) => void;
     /** Draw a still picture. Called under reduced motion. */
     still: () => void;
     /** Read before every frame; while true the loop rests. */
     isPaused?: () => boolean;
   }
   
   export interface SceneLoop {
     /** Re-checks everything and starts, stops or redraws. Call it when props change. */
     wake(): void;
     /** True when the user prefers reduced motion. */
     reduced(): boolean;
     dispose(): void;
   }
   
   export function runSceneLoop({ host, tick, still, isPaused }: SceneLoopOptions): SceneLoop {
     const reducedMotion = window.matchMedia("(prefers-reduced-motion: reduce)");
     let frame = 0;
     let last = 0;
     let time = 0;
     let inView = false;
     let disposed = false;
   
     const shouldRun = () => !disposed && inView && !document.hidden && !reducedMotion.matches && !isPaused?.();
     const step = (now: number) => {
       frame = 0;
       if (!shouldRun()) return;
       const dt = last ? Math.min(0.05, (now - last) / 1000) : 0;
       last = now;
       time += dt;
       tick(dt, time);
       frame = requestAnimationFrame(step);
     };
     const wake = () => {
       if (disposed) return;
       if (shouldRun()) {
         if (!frame) {
           last = 0;
           frame = requestAnimationFrame(step);
         }
         return;
       }
       if (frame) cancelAnimationFrame(frame);
       frame = 0;
       if (reducedMotion.matches) still();
     };
   
     const observer = new IntersectionObserver(
       ([entry]) => {
         inView = entry?.isIntersecting ?? true;
         wake();
       },
       { rootMargin: "80px" },
     );
     observer.observe(host);
     document.addEventListener("visibilitychange", wake);
     reducedMotion.addEventListener("change", wake);
     if (reducedMotion.matches) still();
   
     return {
       wake,
       reduced: () => reducedMotion.matches,
       dispose() {
         disposed = true;
         if (frame) cancelAnimationFrame(frame);
         observer.disconnect();
         document.removeEventListener("visibilitychange", wake);
         reducedMotion.removeEventListener("change", wake);
       },
     };
   }

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   lib/line-art/physics.ts

   /**
    * Small physics for line art: a seeded generator, a spring, a pendulum for things that hang,
    * pointer speed as wind, and keyed pose timelines for reactions. Framework-free.
    */
   
   /** A seeded generator (mulberry32): the same seed always gives the same scene. */
   export function rng(seed: number) {
     let a = seed >>> 0;
     return () => {
       a = (a + 0x6d2b79f5) >>> 0;
       let t = a;
       t = Math.imul(t ^ (t >>> 15), t | 1);
       t ^= t + Math.imul(t ^ (t >>> 7), t | 61);
       return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
     };
   }
   
   export interface Spring {
     value: number;
     velocity: number;
   }
   
   /** Steps a damped spring toward `target`. Stable for the frame times a canvas loop produces. */
   export function spring(state: Spring, target: number, stiffness: number, damping: number, dt: number) {
     const step = Math.min(dt, 1 / 30);
     state.velocity += ((target - state.value) * stiffness - state.velocity * damping) * step;
     state.value += state.velocity * step;
     return state.value;
   }
   
   export interface Pendulum {
     /** Angle from hanging straight down, in radians. */
     angle: number;
     velocity: number;
   }
   
   /**
    * Steps something that hangs: scarves, bags, signs, lanterns. `push` is a sideways acceleration
    * (wind, or the carrier speeding up), `length` sets how slowly it swings.
    */
   export function pendulum(state: Pendulum, push: number, dt: number, length = 12, damping = 2.2) {
     const step = Math.min(dt, 1 / 30);
     state.velocity += (-(60 / length) * Math.sin(state.angle) + push * Math.cos(state.angle) - state.velocity * damping) * step;
     state.angle += state.velocity * step;
     return state.angle;
   }
   
   export interface PointerWind {
     /** Signed wind right now: positive blows toward +x. Decays to 0 when the pointer rests. */
     read(dt: number): number;
     dispose(): void;
   }
   
   /** Turns pointer speed over `target` into wind. */
   export function pointerWind(target: HTMLElement | SVGElement, strength = 0.02): PointerWind {
     let lastX = 0;
     let lastTime = 0;
     let gust = 0;
     const onMove = (event: Event) => {
       const pointer = event as PointerEvent;
       const now = performance.now();
       if (lastTime && now - lastTime < 120) {
         const speed = (pointer.clientX - lastX) / Math.max(1, now - lastTime);
         gust += Math.max(-1, Math.min(1, speed * strength * 16)) * 0.35;
         gust = Math.max(-1.5, Math.min(1.5, gust));
       }
       lastX = pointer.clientX;
       lastTime = now;
     };
     target.addEventListener("pointermove", onMove, { passive: true });
     return {
       read(dt) {
         gust *= Math.pow(0.08, dt);
         return gust;
       },
       dispose() {
         target.removeEventListener("pointermove", onMove);
       },
     };
   }
   
   export type Key<T extends readonly number[]> = readonly [time: number, value: T];
   
   /**
    * A keyed timeline of poses: `sample(t)` eases between the keys on either side of `t`.
    * Times are in seconds; before the first key and after the last, the nearest key holds.
    */
   export function sequence<T extends readonly number[]>(keys: readonly Key<T>[]) {
     const end = keys[keys.length - 1][0];
     return {
       duration: end,
       sample(t: number): number[] {
         if (t <= keys[0][0]) return [...keys[0][1]];
         if (t >= end) return [...keys[keys.length - 1][1]];
         let i = 1;
         while (keys[i][0] < t) i++;
         const [t0, a] = keys[i - 1];
         const [t1, b] = keys[i];
         const u = (t - t0) / (t1 - t0);
         const eased = u * u * (3 - 2 * u);
         return a.map((value, index) => value + (b[index] - value) * eased);
       },
     };
   }

   Show all 104 lines

3. Copy the source

   components/ui/line-art-street/line-art-street.tsx

   "use client";
   
   import { useEffect, useId, useRef, useState, type ComponentProps, type CSSProperties, type ReactNode } from "react";
   import { Pause, Play } from "lucide-react";
   import { cn } from "@/lib/utils";
   import { nightTint, palette } from "@/lib/line-art/daynight";
   import { createFigure, type Figure } from "@/lib/line-art/figures";
   import { GROUND } from "@/lib/line-art/gait";
   import { PEN, el, inkDefs, type Point } from "@/lib/line-art/ink";
   import { runSceneLoop } from "@/lib/line-art/loop";
   import { pendulum, pointerWind, rng, type Pendulum } from "@/lib/line-art/physics";
   
   export type StreetFigure = "commuter" | "cyclist" | "child" | "shopkeeper";
   
   export interface LineArtStreetProps extends Omit<ComponentProps<"div">, "children"> {
     /** Pins the time of day: 0 is midnight, 0.5 is noon. Leave it out to let the day run. */
     tau?: number;
     /** Seconds from dawn to nightfall while the day runs. @default 60 */
     dayLength?: number;
     /** Time of day the scene opens on. @default 0.34 */
     startTau?: number;
     /** The flat accent for awnings, flowers and the bicycle frame. @default "#c8553d" */
     accent?: string;
     /** Who is on the street: a list of figures, or how many to take from the default order. @default all four */
     figures?: StreetFigure[] | number;
     /** Let people, windows, birds and the sun react to the pointer. @default true */
     interactive?: boolean;
     /** Start paused. The Pause button toggles it from there. @default false */
     paused?: boolean;
     /** Content laid over the paper, such as a headline. */
     children?: ReactNode;
   }
   
   /** The street is drawn in these units. Figures are scaled down into it. */
   const W = 520;
   const TOP = -52;
   const BOTTOM = 136;
   const S = 0.55;
   /** Pen widths in street units, matched to the figures' scaled strokes. */
   const P = PEN * S;
   const D = P * 0.5;
   const ALL: StreetFigure[] = ["commuter", "cyclist", "child", "shopkeeper"];
   const SECOND_ACCENT = "#3d4a8f";
   const SECOND_ACCENT_VAR = "var(--la-accent-2)";
   
   const TIME_NAMES = ["Midnight", "Night", "Dawn", "Morning", "Noon", "Afternoon", "Dusk", "Night", "Midnight"];
   const timeName = (tau: number) => TIME_NAMES[Math.round((((tau % 1) + 1) % 1) * 8)];
   
   export function LineArtStreet({
     tau,
     dayLength = 60,
     startTau = 0.34,
     accent = "#c8553d",
     figures,
     interactive = true,
     paused = false,
     children,
     className,
     style,
     ...props
   }: LineArtStreetProps) {
     const id = useId().replace(/[^a-zA-Z0-9]/g, "");
     const rootRef = useRef<HTMLDivElement>(null);
     const svgRef = useRef<SVGSVGElement>(null);
     const sliderRef = useRef<HTMLInputElement>(null);
     const [isPaused, setIsPaused] = useState(paused);
     const control = useRef<{ paused: boolean; setTau: (value: number) => void; wake: () => void }>({ paused, setTau: () => {}, wake: () => {} });
     const latest = useRef({ tau, dayLength, interactive });
     useEffect(() => {
       latest.current = { tau, dayLength, interactive };
       control.current.paused = isPaused;
       control.current.wake();
     });
     const cast = (typeof figures === "number" ? ALL.slice(0, Math.max(0, figures)) : (figures ?? ALL)).join(",");
   
     useEffect(() => {
       const root = rootRef.current;
       const svg = svgRef.current;
       if (!root || !svg) return;
       svg.replaceChildren();
       const controls = control.current;
       const random = rng(235);
       const who = cast ? (cast.split(",") as StreetFigure[]) : [];
   
       // ---- Layers, back to front.
       const defs = el("defs", {}, svg);
       const skyGradient = el("linearGradient", { id: `${id}-sky`, x1: 0, y1: 0, x2: 0, y2: 1 }, defs);
       const skyTop = el("stop", { offset: 0 }, skyGradient);
       const skyLow = el("stop", { offset: 1 }, skyGradient);
       const halo = el("radialGradient", { id: `${id}-halo` }, defs);
       el("stop", { offset: 0, "stop-color": "#ffd98a", "stop-opacity": 0.95 }, halo);
       el("stop", { offset: 1, "stop-color": "#ffd98a", "stop-opacity": 0 }, halo);
       el("rect", { x: 0, y: TOP, width: W, height: GROUND - TOP, fill: `url(#${id}-sky)` }, svg);
       const stars = el("g", { fill: "#f4f1ff" }, svg);
       const starDots = Array.from({ length: 26 }, () => {
         const star = el("circle", { cx: random() * W, cy: TOP + 4 + random() * 46, r: 0.5 + random() * 0.5 }, stars);
         return { star, phase: random() * 6.28, rate: 1 + random() * 2 };
       });
       const sky = el("g", {}, svg);
       const sun = el("circle", { r: 9, fill: "#ffd77a", stroke: "currentColor", "stroke-width": P }, sky);
       const moon = el("path", { d: "M0 -8a8 8 0 1 0 6.9 12 6.4 6.4 0 1 1 -6.9 -12z", fill: "#f1eedc", stroke: "currentColor", "stroke-width": P }, sky);
       const grab = el("circle", { r: 16, fill: "transparent", style: "cursor:grab;touch-action:none" }, sky);
       const filter = inkDefs(svg, `${id}-ink`, 5);
       svg.querySelector(`#${id}-ink feDisplacementMap`)?.setAttribute("scale", String(0.45 * S + 0.1));
       const drawing = el("g", { filter }, svg);
       const scenery = el("g", {}, drawing);
       const moving = el("g", {}, drawing);
       const glow = el("g", { style: "mix-blend-mode:screen" }, svg);
       const hits = el("g", { fill: "transparent" }, svg);
   
       // ---- Drawing helpers, in street units.
       const stroke = { fill: "none", stroke: "currentColor", "stroke-linecap": "round", "stroke-linejoin": "round" } as const;
       const ink = (d: string, width = P, parent: Element = scenery) => el("path", { d, ...stroke, "stroke-width": width }, parent);
       const paper = (d: string, parent: Element = scenery) => el("path", { d, ...stroke, fill: "var(--la-paper)", "stroke-width": P }, parent);
       const flat = (d: string, color = "var(--la-accent)", parent: Element = scenery) => el("path", { d, ...stroke, fill: color, "stroke-width": P }, parent);
       const box = (x: number, y: number, w: number, h: number) => `M${x} ${y}h${w}v${h}h${-w}z`;
       const sign = (text: string, x: number, y: number, size = 5.4) => {
         const node = el("text", { x, y, "font-size": size, "text-anchor": "middle", fill: "currentColor", "letter-spacing": 0.9, "font-weight": 600 }, scenery);
         node.textContent = text.toUpperCase();
       };
       /** Short dashes in rows: brick courses, drawn with the detail pen and left mostly as paper. */
       const courses = (x: number, y: number, w: number, h: number) => {
         let d = "";
         for (let row = y + 3; row < y + h - 1; row += 5) for (let n = 0; n < w / 22; n++) d += `M${(x + 3 + random() * (w - 12)).toFixed(1)} ${row}h${(3 + random() * 5).toFixed(1)}`;
         ink(d, D);
       };
       const windows: { lit: boolean; pane: SVGElement }[] = [];
       /** A window: frame, mullions, a warm pane on the glow layer and a click target that toggles its light. */
       const windowAt = (x: number, y: number, w: number, h: number, columns: number, rows: number, startsLit: boolean) => {
         paper(box(x, y, w, h));
         let d = "";
         for (let c = 1; c < columns; c++) d += `M${x + (w / columns) * c} ${y}v${h}`;
         for (let r = 1; r < rows; r++) d += `M${x} ${y + (h / rows) * r}h${w}`;
         ink(d, D);
         ink(`M${x - 1.5} ${y + h + 1}h${w + 3}`);
         const pane = el("rect", { x: x - 2, y: y - 2, width: w + 4, height: h + 4, rx: 2, fill: "#ffd98a", opacity: 0 }, glow);
         const entry = { lit: startsLit, pane };
         windows.push(entry);
         const target = el("rect", { x, y, width: w, height: h, style: "cursor:pointer" }, hits);
         target.addEventListener("click", () => {
           if (!latest.current.interactive) return;
           entry.lit = !entry.lit;
           paint();
         });
       };
       const door = (x: number, w: number) => {
         paper(box(x, GROUND - 58, w, 58));
         ink(`M${x + 3} ${GROUND - 54}h${w - 6}v22h${-(w - 6)}zM${x + w - 4.5} ${GROUND - 26}v3`, D);
       };
       /** A striped awning from y to y + drop. */
       const awning = (x: number, y: number, w: number, drop: number, stripes: number) => {
         paper(`M${x} ${y}h${w}l4 ${drop}h${-(w + 8)}z`);
         for (let i = 0; i < stripes; i += 2) {
           const a = x + (w / stripes) * i;
           const b = x + (w / stripes) * (i + 1);
           const spread = (v: number) => x - 4 + ((v - x) / w) * (w + 8);
           flat(`M${a} ${y}H${b}L${spread(b)} ${y + drop}H${spread(a)}z`);
         }
       };
   
       // ---- Things that hang, and sway with the wind.
       const hanging: { state: Pendulum; length: number; draw: (angle: number) => void }[] = [];
       const hang = (x: number, y: number, length: number, make: (group: SVGGElement) => void) => {
         const group = el("g", {}, scenery);
         make(group);
         hanging.push({ state: { angle: 0, velocity: 0 }, length, draw: (angle) => group.setAttribute("transform", `rotate(${((angle * 180) / Math.PI).toFixed(2)} ${x} ${y})`) });
       };
   
       const R = -12;
       const F = 48;
       // Tram rails along the whole street.
       ink(`M0 ${GROUND + 7}H${W}M0 ${GROUND + 10}H${W}`, D);
   
       // A. The bakery.
       paper(box(8, R, 104, GROUND - R));
       ink(`M8 ${R + 5}h104M8 ${F}h104`);
       courses(10, R + 6, 100, F - R - 8);
       windowAt(22, 2, 28, 34, 2, 2, true);
       windowAt(70, 2, 28, 34, 2, 2, false);
       paper(box(20, F + 1.5, 80, 9));
       sign("Fernwick", 60, F + 8.2);
       awning(12, F + 13, 96, 9, 12);
       windowAt(16, F + 26, 54, 36, 1, 1, false);
       // Bread in the window: loaves, a baguette and a round.
       ink(`M22 ${GROUND - 14}q5 -8 10 0zM36 ${GROUND - 14}q6 -9 12 0zM52 ${GROUND - 14}q5 -7 10 0zM24 ${GROUND - 26}l16 -3M46 ${GROUND - 27}a4 4 0 1 0 8 0a4 4 0 1 0 -8 0M20 ${GROUND - 14}h46M20 ${GROUND - 24}h46`, D);
       door(78, 24);
   
       // B. The bookshop, a little taller, with a cat in the middle window.
       paper(box(116, R - 8, 90, GROUND - R + 8));
       ink(`M116 ${R - 3}h90M116 ${F}h90`);
       courses(118, R - 2, 86, F - R);
       windowAt(124, -6, 18, 38, 1, 2, false);
       windowAt(152, -6, 18, 38, 1, 2, true);
       windowAt(180, -6, 18, 38, 1, 2, false);
       paper(`M156 32q0 -9 3 -10l1 -3l1.6 3h2l1.6 -3l1 3q3 3 2.4 10z`);
       ink(`M166.6 32q4 -1 3 -6`, D);
       paper(box(126, F + 1.5, 70, 9));
       sign("Brightloom Books", 161, F + 8.2, 4.8);
       windowAt(122, F + 16, 50, 46, 3, 2, false);
       let books = "";
       for (let shelf = 0; shelf < 2; shelf++) for (let b = 0; b < 15; b++) books += `M${124.5 + b * 3.1} ${F + 36 + shelf * 23}v${-(5 + random() * 6).toFixed(1)}`;
       ink(books, D);
       door(178, 22);
   
       // C. The flower stall, in front of a low garden wall.
       paper(box(210, 30, 56, GROUND - 30));
       courses(212, 32, 52, 22);
       ink(`M210 30h56`);
       paper(`M212 56h52v7q-4.3 5 -8.6 0q-4.3 5 -8.7 0q-4.3 5 -8.7 0q-4.3 5 -8.6 0q-4.3 5 -8.7 0q-4.3 5 -8.7 0z`);
       ink(`M216 63V${GROUND}M260 63V${GROUND}`);
       for (const [bx, n] of [[222, 4], [238, 5], [252, 4]] as const) {
         paper(`M${bx - 6} ${GROUND - 20}h12l-2 20h-8z`);
         let stems = "";
         for (let i = 0; i < n; i++) {
           const fx = bx - 5 + (10 / (n - 1)) * i;
           const fy = GROUND - 28 - random() * 8;
           stems += `M${bx - 3 + i * 1.5} ${GROUND - 20}L${fx.toFixed(1)} ${fy.toFixed(1)}`;
           flat(`M${(fx - 2.4).toFixed(1)} ${fy.toFixed(1)}a2.4 2.4 0 1 0 4.8 0a2.4 2.4 0 1 0 -4.8 0`, i % 2 ? "var(--la-accent)" : "var(--la-paper)");
         }
         ink(stems, D);
       }
       for (const rx of [226, 239, 251]) hang(rx, 63, 9, (group) => flat(`M${rx - 1.2} 63v11l1.2 -2l1.2 2v-11z`, "var(--la-accent)", group));
   
       // The street lamp.
       ink(`M272 ${GROUND}V40q0 -8 8 -8M269 ${GROUND}h6`);
       paper(`M276 32h9l-1.6 8h-5.8z`);
       const lampGlow = el("circle", { cx: 280.5, cy: 38, r: 34, fill: `url(#${id}-halo)`, opacity: 0 }, glow);
   
       // D. The tram stop.
       ink(`M286 ${GROUND}V56M348 ${GROUND}V56`);
       paper(`M280 56q37 -9 74 0v4h-74z`);
       ink(`M290 64v40h54v-40M308 64v40M326 64v40`, D);
       paper(box(294, GROUND - 16, 46, 3.5));
       ink(`M298 ${GROUND - 12}v12M336 ${GROUND - 12}v12M358 ${GROUND}V38`);
       paper(`M352 32a6 6 0 1 0 12 0a6 6 0 1 0 -12 0`);
       sign("T", 358, 34.2, 6.5);
   
       // E. The corner café.
       paper(box(366, R - 4, 146, GROUND - R + 4));
       ink(`M366 ${R + 1}h146M366 ${F}h146`);
       courses(368, R + 2, 142, F - R - 4);
       windowAt(380, 0, 26, 36, 2, 2, true);
       windowAt(426, 0, 26, 36, 2, 2, false);
       windowAt(472, 0, 26, 36, 2, 2, true);
       paper(box(398, F + 1.5, 82, 9));
       sign("Café Halvane", 439, F + 8.2);
       awning(372, F + 13, 134, 9, 16);
       // The awning's fringe: a row of short tabs that swing together.
       for (let i = 0; i < 12; i++) {
         const fx = 374 + i * 11.6;
         hang(fx, F + 22, 5, (group) => ink(`M${fx} ${F + 22}v3.4`, P, group));
       }
       windowAt(374, F + 26, 58, 36, 2, 1, false);
       door(440, 24);
       windowAt(472, F + 26, 34, 36, 1, 1, false);
       // A hanging sign on a bracket.
       ink(`M366 44h-13`);
       hang(357, 44, 12, (group) => {
         paper(`M350 47h14v10h-14z`, group);
         ink(`M353 44v3M361 44v3M354 52h6`, D, group);
       });
       // A bistro table and two chairs.
       ink(`M388 ${GROUND - 20}h18M397 ${GROUND - 20}V${GROUND}M393 ${GROUND}h8`);
       ink(`M378 ${GROUND - 30}v30M378 ${GROUND - 14}h9v14M378 ${GROUND - 30}q3 -3 6 0M416 ${GROUND - 30}v30M416 ${GROUND - 14}h-9v14M416 ${GROUND - 30}q-3 -3 -6 0`, D * 1.4);
   
       // The pavement line, drawn last so it sits over the walls' feet.
       ink(`M0 ${GROUND + 0.6}Q130 ${GROUND + 1.4} 260 ${GROUND + 0.4}T${W} ${GROUND + 0.8}`);
   
       // A wire between the roofs, and three birds on it.
       ink(`M112 ${R}Q240 ${R + 16} 366 ${R - 4}`, D);
       const wireY = (x: number) => {
         const t = (x - 112) / 254;
         return (1 - t) * (1 - t) * R + 2 * (1 - t) * t * (R + 16) + t * t * (R - 4);
       };
       const birds = [196, 214, 252].map((home, i) => {
         const group = el("g", {}, moving);
         el("path", { d: "M-3 0q0 -4.5 3 -4.5q2.6 0 3.2 2.4l2 0.6l-2 0.5q-0.6 3.6 -3.2 3.6q-3 0 -3 -2.6z", ...stroke, fill: "var(--la-paper)", "stroke-width": P }, group);
         el("path", { d: "M-2.6 0l-3 1.6", ...stroke, "stroke-width": D }, group);
         return { group, home, x: home, y: wireY(home), away: 0, hop: random() * 4, seed: i };
       });
       const birdTarget = el("rect", { x: 186, y: R - 6, width: 78, height: 22, style: "cursor:pointer" }, hits);
       const scatter = () => {
         if (!latest.current.interactive) return;
         for (const bird of birds) if (bird.away <= 0) bird.away = 0.001;
         loop.wake();
       };
       birdTarget.addEventListener("click", scatter);
       birdTarget.addEventListener("pointerenter", scatter);
   
       // ---- People.
       interface Walker {
         kind: StreetFigure;
         figure: Figure;
         x: number;
         direction: 1 | -1;
         scale: number;
         pace: number;
         wait: number;
       }
       const people: Walker[] = [];
       const accentVar = "var(--la-accent)";
       const add = (kind: StreetFigure, figure: Figure, x: number, direction: 1 | -1, scale: number, pace: number) => {
         const person = { kind, figure, x, direction, scale, pace, wait: 0 };
         people.push(person);
         // A generous, invisible area over the figure takes the click.
         const target = el("rect", { x: -figure.reach, y: 18, width: figure.reach * 2, height: 104, fill: "transparent", style: "cursor:pointer" }, figure.group);
         target.addEventListener("click", () => {
           if (!latest.current.interactive) return;
           if (loop.reduced()) {
             figure.still(true);
             window.setTimeout(() => !disposed && stillFrame(), 1200);
           } else figure.react();
         });
         return person;
       };
       let broom: SVGElement | null = null;
       let dog: SVGGElement | null = null;
       let dogLegs: SVGElement | null = null;
       let leash: SVGElement | null = null;
       let bikeGlow: SVGElement | null = null;
       if (who.includes("shopkeeper")) {
         add("shopkeeper", createFigure(moving, "courier", { accent: accentVar, bare: true }), 96, 1, S, 0);
         broom = el("path", { ...stroke, "stroke-width": P * 1.2 }, moving);
       }
       if (who.includes("child")) {
         const group = el("g", {}, moving);
         dog = el("g", {}, group);
         el("path", { d: "M-9 -9q0 -4 5 -4h9q4 0 5 -4l3 -1l1 -3l1.6 3l3.4 1.4l-1 2.6l-3 0.4q-1 6 -6 7.6h-13q-5 0 -5 -3z", ...stroke, fill: "var(--la-paper)", "stroke-width": P / 0.36 / 2.2 }, dog);
         dogLegs = el("path", { ...stroke, "stroke-width": P / 0.36 / 2.2 }, dog);
         leash = el("path", { ...stroke, "stroke-width": D }, moving);
         add("child", createFigure(moving, "courier", { accent: accentVar, bare: true }), 330, -1, S * 0.68, 0.82);
       }
       if (who.includes("commuter")) add("commuter", createFigure(moving, "commuter", { accent: SECOND_ACCENT_VAR }), 150, 1, S, 1);
       if (who.includes("cyclist")) {
         add("cyclist", createFigure(moving, "cyclist", { accent: accentVar }), 440, -1, S, 0.75);
         bikeGlow = el("circle", { r: 16, fill: `url(#${id}-halo)`, opacity: 0 }, glow);
       }
   
       // ---- Time of day.
       let now = latest.current.tau ?? startTau;
       let painted = -1;
       let time = 0;
       let disposed = false;
       let dragging = false;
       function paint() {
         const colors = palette(now);
         root!.style.setProperty("--la-paper", colors.paper);
         root!.style.setProperty("--la-ink", colors.ink);
         root!.style.setProperty("--la-accent", nightTint(accent, now));
         root!.style.setProperty("--la-accent-2", nightTint(SECOND_ACCENT, now));
         skyTop.setAttribute("stop-color", colors.sky[0]);
         skyLow.setAttribute("stop-color", colors.sky[1]);
         stars.setAttribute("opacity", colors.night.toFixed(3));
         // By day a lit window barely shows; at night it glows.
         for (const entry of windows) entry.pane.setAttribute("opacity", entry.lit ? (0.12 + colors.night * 0.78).toFixed(3) : "0");
         lampGlow.setAttribute("opacity", colors.night.toFixed(3));
         bikeGlow?.setAttribute("opacity", colors.night.toFixed(3));
         // The sun crosses by day and the moon by night, on the same arc.
         const t = ((now % 1) + 1) % 1;
         const along = colors.moon ? (t > 0.5 ? (t - 0.77) / 0.48 : (t + 0.23) / 0.48) : (t - 0.25) / 0.52;
         const bx = 36 + Math.min(1, Math.max(0, along)) * (W - 72);
         const by = 4 - colors.height * 40;
         sun.setAttribute("transform", `translate(${bx.toFixed(1)} ${by.toFixed(1)})`);
         moon.setAttribute("transform", `translate(${bx.toFixed(1)} ${by.toFixed(1)})`);
         grab.setAttribute("transform", `translate(${bx.toFixed(1)} ${by.toFixed(1)})`);
         sun.setAttribute("opacity", colors.moon ? "0" : "1");
         moon.setAttribute("opacity", colors.moon ? "1" : "0");
         painted = now;
         const slider = sliderRef.current;
         if (slider && !dragging && document.activeElement !== slider) slider.value = t.toFixed(3);
         slider?.setAttribute("aria-valuetext", timeName(t));
       }
       controls.setTau = (value) => {
         now = value;
         paint();
         if (loop.reduced()) stillFrame();
       };
   
       // ---- Layout: the street crops to its center in narrow containers.
       let view = W;
       function layout() {
         const narrow = root!.clientWidth < 520;
         view = narrow ? 300 : W;
         const x = narrow ? 118 : 0;
         svg!.setAttribute("viewBox", `${x} ${TOP} ${view} ${BOTTOM - TOP}`);
         // Fewer figures when cropped: the cyclist and the child stay home.
         for (const person of people) person.figure.group.style.display = narrow && (person.kind === "cyclist" || person.kind === "child") ? "none" : "";
         if (dog) dog.style.display = narrow ? "none" : "";
         if (leash) leash.style.display = narrow ? "none" : "";
       }
   
       function place(person: Walker) {
         person.figure.group.setAttribute("transform", `translate(${person.x.toFixed(2)} ${(GROUND * (1 - person.scale)).toFixed(2)}) scale(${(person.direction * person.scale).toFixed(3)} ${person.scale})`);
       }
   
       function drawExtras(sweep: number) {
         const keeper = people.find((person) => person.kind === "shopkeeper");
         if (keeper && broom) {
           // The broom swings from the hands; its head brushes the pavement.
           const hand: Point = [keeper.x + 4, GROUND - 28];
           const head: Point = [keeper.x + 15 + Math.sin(sweep) * 7, GROUND - 0.5];
           broom.setAttribute("d", `M${hand[0]} ${hand[1]}L${head[0].toFixed(2)} ${head[1]}M${(head[0] - 3.5).toFixed(2)} ${head[1]}h7`);
         }
         const child = people.find((person) => person.kind === "child");
         if (child && dog && dogLegs && leash) {
           const dx = child.x + child.direction * 21;
           const trot = time * 9;
           dog.setAttribute("transform", `translate(${dx.toFixed(2)} ${GROUND}) scale(${(child.direction * 0.36).toFixed(3)} 0.36)`);
           const step = (phase: number) => (Math.sin(trot + phase) * 3.4).toFixed(2);
           dogLegs.setAttribute("d", `M-6 -8l${step(0)} 8M-2 -8l${step(3.14)} 8M8 -8l${step(3.14)} 8M12 -8l${step(0)} 8M-9 -11q-5 ${(-3 + Math.sin(trot * 1.6) * 2).toFixed(2)} -6 -8`);
           leash.setAttribute("d", `M${(child.x + child.direction * 5).toFixed(2)} ${GROUND - 21}Q${(child.x + child.direction * 13).toFixed(2)} ${GROUND - 9} ${(dx + child.direction * 3.6).toFixed(2)} ${GROUND - 6.4}`);
         }
         const rider = people.find((person) => person.kind === "cyclist");
         if (rider && bikeGlow) {
           bikeGlow.setAttribute("cx", (rider.x + rider.direction * 9).toFixed(1));
           bikeGlow.setAttribute("cy", String(GROUND - 19));
         }
       }
   
       function stillFrame() {
         // Reduced motion: one figure mid-stride, everyone else at rest, at whatever time is set.
         people.forEach((person, i) => {
           if (i === people.findIndex((p) => p.kind === "commuter")) person.figure.step(0, 1, 0);
           else person.figure.still();
           place(person);
         });
         for (const item of hanging) item.draw(0);
         for (const bird of birds) bird.group.setAttribute("transform", `translate(${bird.home} ${wireY(bird.home) - 3.4})`);
         drawExtras(0.6);
         paint();
       }
   
       const wind = pointerWind(root);
       const loop = runSceneLoop({
         host: root,
         isPaused: () => controls.paused,
         still: stillFrame,
         tick: (dt, clock) => {
           time = clock;
           const fixed = latest.current.tau;
           if (fixed !== undefined) now = fixed;
           // Dawn to nightfall is 0.6 of a day.
           else if (!dragging) now = (now + (0.6 / Math.max(1, latest.current.dayLength)) * dt) % 1;
           if (Math.abs(now - painted) > 0.0015) paint();
           const gust = latest.current.interactive ? wind.read(dt) : 0;
           const breeze = gust + Math.sin(clock * 0.7) * 0.05;
   
           for (const person of people) {
             if (person.kind === "shopkeeper") {
               person.figure.step(dt, 0, breeze);
               place(person);
               continue;
             }
             if (person.wait > 0) {
               person.wait -= dt;
               continue;
             }
             person.x += person.figure.step(dt, person.pace, breeze) * person.scale * person.direction;
             // Off one end, a short wait, then back in from the other.
             if (person.x > W + 40 || person.x < -40) {
               person.x = person.direction === 1 ? -40 : W + 40;
               person.wait = 1.5 + random() * 4;
             }
             place(person);
           }
           drawExtras(clock * 2.6);
           for (const item of hanging) item.draw(pendulum(item.state, breeze * 9, dt, item.length, 1.6));
   
           // Birds hop on the wire, take off when startled and come back after a while.
           for (const bird of birds) {
             if (bird.away > 0) {
               bird.away += dt;
               const out = Math.min(1, bird.away / 1.2);
               const back = Math.min(1, Math.max(0, (bird.away - 6) / 1.4));
               const lift = out * (1 - back);
               bird.x = bird.home + lift * (40 + bird.seed * 26) * (bird.seed % 2 ? 1 : -1);
               bird.y = wireY(bird.home) - 3.4 - lift * (34 + bird.seed * 7) - Math.sin(bird.away * 18) * 1.2 * (lift > 0.05 && lift < 0.98 ? 1 : 0);
               if (back >= 1) bird.away = 0;
             } else {
               bird.hop += dt;
               const hop = bird.hop % 4 < 0.25 ? Math.sin(((bird.hop % 4) / 0.25) * Math.PI) * 1.6 : 0;
               bird.x = bird.home;
               bird.y = wireY(bird.home) - 3.4 - hop;
             }
             bird.group.setAttribute("transform", `translate(${bird.x.toFixed(2)} ${bird.y.toFixed(2)})`);
           }
           const night = palette(now).night;
           if (night > 0.05) for (const dot of starDots) dot.star.setAttribute("opacity", (0.55 + Math.sin(clock * dot.rate + dot.phase) * 0.45).toFixed(2));
         },
       });
   
       // ---- Dragging the sun or moon scrubs the time.
       const onGrab = (event: PointerEvent) => {
         if (!latest.current.interactive || latest.current.tau !== undefined) return;
         dragging = true;
         grab.setPointerCapture(event.pointerId);
       };
       const onDrag = (event: PointerEvent) => {
         if (!dragging) return;
         const rect = svg.getBoundingClientRect();
         const viewX = Number(svg.getAttribute("viewBox")?.split(" ")[0] ?? 0);
         const x = viewX + ((event.clientX - rect.left) / rect.width) * view;
         const along = Math.min(0.995, Math.max(0.005, (x - 36) / (W - 72)));
         now = palette(now).moon ? (0.77 + along * 0.48) % 1 : 0.25 + along * 0.52;
         paint();
         if (loop.reduced()) stillFrame();
       };
       const onRelease = () => {
         dragging = false;
       };
       grab.addEventListener("pointerdown", onGrab);
       grab.addEventListener("pointermove", onDrag);
       grab.addEventListener("pointerup", onRelease);
       grab.addEventListener("pointercancel", onRelease);
   
       const observer = new ResizeObserver(layout);
       observer.observe(root);
       layout();
       stillFrame();
       controls.wake = loop.wake;
       loop.wake();
   
       return () => {
         disposed = true;
         controls.setTau = () => {};
         controls.wake = () => {};
         observer.disconnect();
         loop.dispose();
         wind.dispose();
         svg.replaceChildren();
       };
     }, [id, cast, accent, startTau]);
   
     // Pausing and a pinned time are read by the loop; nudge it when they change.
     useEffect(() => {
       if (tau !== undefined) control.current.setTau(tau);
     }, [tau]);
   
     const day = palette(tau ?? startTau);
     return (
       <div
         ref={rootRef}
         style={{ "--la-paper": day.paper, "--la-ink": day.ink, "--la-accent": accent, "--la-accent-2": SECOND_ACCENT, ...style } as CSSProperties}
         className={cn("@container relative w-full overflow-hidden rounded-2xl bg-(--la-paper) text-(--la-ink)", className)}
         {...props}
       >
         <svg
           ref={svgRef}
           role="img"
           aria-label="A line drawing of a street: a bakery, a bookshop, a flower stall, a tram stop and a corner café, with people passing by as the day turns to night"
           className="block aspect-[520/188] w-full font-sans text-(--la-ink) @max-[32.5rem]:aspect-[300/188]"
         />
         {children ? <div className="pointer-events-none absolute inset-x-0 top-0 p-5 *:pointer-events-auto">{children}</div> : null}
         <div className="flex items-center gap-3 px-3 pb-3">
           <button
             type="button"
             aria-label={isPaused ? "Play" : "Pause"}
             onClick={() => setIsPaused((value) => !value)}
             className="grid size-10 shrink-0 cursor-pointer place-items-center rounded-full border border-(--la-ink)/25 outline-none transition-colors hover:bg-(--la-ink)/10 focus-visible:ring-2 focus-visible:ring-(--la-ink) motion-reduce:hidden"
           >
             {isPaused ? <Play aria-hidden="true" className="size-4" fill="currentColor" strokeWidth={0} /> : <Pause aria-hidden="true" className="size-4" fill="currentColor" strokeWidth={0} />}
           </button>
           <label className="flex min-w-0 flex-1 items-center gap-3 text-xs font-medium">
             <span className="shrink-0">Time of day</span>
             <input
               ref={sliderRef}
               type="range"
               min={0}
               max={1}
               step={0.005}
               defaultValue={tau ?? startTau}
               disabled={tau !== undefined}
               aria-valuetext={timeName(tau ?? startTau)}
               onInput={(event) => control.current.setTau(Number(event.currentTarget.value))}
               className="h-10 min-w-0 flex-1 cursor-pointer accent-(--la-ink) disabled:cursor-default disabled:opacity-50"
             />
           </label>
         </div>
       </div>
     );
   }

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