08Loader an Arc-sweep Angle Value Sweeps Satellites Around

<main class="stage">
<div class="ld" id="ld">
  <p class="ld__hint">
    <svg class="ld__ico" viewBox="0 0 256 256" aria-hidden="true"><g fill="currentColor"><path d="M232 56v56a8 8 0 0 1-16 0V91.3l-25.6 25.7A80 80 0 1 1 174 60a8 8 0 1 1-9 13.2A64 64 0 1 0 179.7 128H216a8 8 0 0 1 0 16h-56a8 8 0 0 1-8-8V80a8 8 0 0 1 16 0v20.7L192.7 76A80.1 80.1 0 0 0 64 128a8 8 0 0 1-16 0a96 96 0 0 1 163.6-68.3L224 71.3V56a8 8 0 0 1 8 8" opacity=".2"/><path d="M224 48a8 8 0 0 0-8 8v15.3l-11.7-11.6a96 96 0 1 0 27.6 51.6a8 8 0 0 0-15.8 2.5a80 80 0 1 1-23-43l-25.7 25.7A8 8 0 0 0 173 112h56a8 8 0 0 0 8-8V56a8 8 0 0 0-13-8"/></g></svg>
    <span>Click or press the space bar to pause or restart</span>
  </p>
  <div class="ld__field" id="field" role="application" aria-label="Satellite orbit angle-sweep test panel" tabindex="0">
    <canvas class="ld__cv" id="cv"></canvas>
    <b class="ld__badge" aria-hidden="true"><span class="ld__badgeNum" id="pct">0%</span><span class="ld__badgeUnit">Orbit</span></b>
  </div>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;

// 위성 궤도 로더 — 각도 값이 0~360°를 쓸어가고, 궤도 3개의 위성이 반지름에 반비례하는 배속으로 꼬리를 남긴다.
// 움직임은 전부 캔버스 rAF 루프 안에 있다. CSS 는 무대·판·배지만 맡는다(@keyframes 0개 — 077 선례와 같은 이유).

$duration: $dur-loop;
$easing: $ease-pop;
$color: $subject-blue-deep;

@include stage($stage-paper);

.ld {
  --paper: #{$subject-cream};
  --orbit: #{rgba($subject-ink, .14)};
  --s1: #{$subject-blue};
  --s2: #{$subject-mint};
  --s3: #{$subject-pink};
  --core: #{$subject-ink};

  display: flex; flex-direction: column; gap: $sp-2;
  width: 100%; max-width: 424px;
}

.ld__hint {
  display: flex; align-items: center; gap: $sp-1; margin: 0;
  font-weight: 700; font-size: clamp(10px, 2.8vw, 12px); line-height: 1.35;
  color: $subject-ink;
}
.ld__ico { width: 16px; height: 16px; flex: 0 0 auto; color: $subject-blue-deep; }

.ld__field {
  position: relative; height: 208px;
  border-radius: $r-card; overflow: hidden;
  background: $subject-cream;
  box-shadow: inset 0 0 0 1px rgba($subject-ink, .16);
  cursor: pointer;
}
.ld__field:focus-visible { outline: 2px solid $subject-blue-deep; outline-offset: 2px; }

.ld__cv { display: block; width: 100%; height: 100%; }

.ld__badge {
  position: absolute; right: $sp-2; top: $sp-2;
  display: flex; align-items: baseline; gap: $sp-1;
  padding: $sp-1 $sp-2; border-radius: $r-pill;
  background: rgba($subject-ink, .78);
  color: $subject-cream; font-weight: 700; font-size: 11px;
}
.ld__badgeNum { font-size: 13px; color: $subject-blue-light; }
.ld__badgeUnit { font-weight: 700; }

@media (max-width: 340px) {
  .ld { gap: $sp-1; }
  .ld__field { height: 124px; }
  .ld__badge { font-size: 10px; padding: 0 $sp-1; }
  .ld__badgeNum { font-size: 11px; }
}

// reduce — 루프를 시작하지 않고 진행률 62% 언저리에서 멈춘 한 장만 그린다.
@media (prefers-reduced-motion: reduce) {
  .ld.is-still .ld__field { cursor: default !important; }
  .ld.is-still .ld__badge { opacity: .92 !important; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffffff;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.ld {
  --paper: #fff7e6;
  --orbit: rgba(23, 20, 26, 0.14);
  --s1: #2f6df6;
  --s2: #4cd4a6;
  --s3: #ff9ebb;
  --core: #17141a;
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 100%;
  max-width: 424px;
}

.ld__hint {
  display: flex;
  align-items: center;
  gap: 4px;
  margin: 0;
  font-weight: 700;
  font-size: clamp(10px, 2.8vw, 12px);
  line-height: 1.35;
  color: #17141a;
}

.ld__ico {
  width: 16px;
  height: 16px;
  flex: 0 0 auto;
  color: #0a4fe8;
}

.ld__field {
  position: relative;
  height: 208px;
  border-radius: 16px;
  overflow: hidden;
  background: #fff7e6;
  box-shadow: inset 0 0 0 1px rgba(23, 20, 26, 0.16);
  cursor: pointer;
}

.ld__field:focus-visible {
  outline: 2px solid #0a4fe8;
  outline-offset: 2px;
}

.ld__cv {
  display: block;
  width: 100%;
  height: 100%;
}

.ld__badge {
  position: absolute;
  right: 8px;
  top: 8px;
  display: flex;
  align-items: baseline;
  gap: 4px;
  padding: 4px 8px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.78);
  color: #fff7e6;
  font-weight: 700;
  font-size: 11px;
}

.ld__badgeNum {
  font-size: 13px;
  color: #5b8cf8;
}

.ld__badgeUnit {
  font-weight: 700;
}

@media (max-width: 340px) {
  .ld {
    gap: 4px;
  }
  .ld__field {
    height: 124px;
  }
  .ld__badge {
    font-size: 10px;
    padding: 0 4px;
  }
  .ld__badgeNum {
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .ld.is-still .ld__field {
    cursor: default !important;
  }
  .ld.is-still .ld__badge {
    opacity: 0.92 !important;
  }
}

// 위성 Orbit 로더 — 각도 값 하나가 0~360°를 쓸어가고, Orbit 3개의 위성이 반지름에 반비례하는
// 배속(가까운 궤도일수록 빠름 — 단순화한 케플러 감각)으로 그 각도를 따라가며 꼬리를 남긴다.
var root = document.getElementById('ld');
var field = document.getElementById('field');
var cv = document.getElementById('cv');
var ctx = cv.getContext('2d');
var pctEl = document.getElementById('pct');

var css = getComputedStyle(root);
var PAPER = css.getPropertyValue('--paper').trim();
var ORBIT = css.getPropertyValue('--orbit').trim();
var S1 = css.getPropertyValue('--s1').trim();
var S2 = css.getPropertyValue('--s2').trim();
var S3 = css.getPropertyValue('--s3').trim();
var CORE = css.getPropertyValue('--core').trim();

var RINGS = [
  { rf: 0.30, speed: 1.0,  color: S1 },
  { rf: 0.58, speed: 0.62, color: S2 },
  { rf: 0.86, speed: 0.38, color: S3 }
];
var LOOP = 3.0;
var TRAIL_SEG = 26;
var TRAIL_SPAN = 1.1;                // 꼬리가 덮는 라디안 폭

var W = 0, H = 0, dpr = 1, cxp = 0, cyp = 0, baseR = 0;

function fit() {
  var r = field.getBoundingClientRect();
  dpr = window.devicePixelRatio || 1;
  W = r.width; H = r.height;
  cv.width = Math.round(W * dpr); cv.height = Math.round(H * dpr);
  ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
  cxp = W * 0.5; cyp = H * 0.5;
  baseR = Math.min(W, H) * 0.46;
}

function draw(sec) {
  var t = sec % LOOP;
  var p = t / LOOP;
  var sweep = p * Math.PI * 2;         // 0→2π — 전역 스윕 각도

  ctx.fillStyle = PAPER;
  ctx.fillRect(0, 0, W, H);

  var WIDE_SEG = 30, WIDE_SPAN = 1.7;
  for (var w = WIDE_SEG; w >= 0; w--) {
    var wa0 = sweep - WIDE_SPAN * (w / WIDE_SEG);
    var wa1 = sweep - WIDE_SPAN * ((w - 1) / WIDE_SEG);
    var walpha = (1 - w / WIDE_SEG);
    ctx.fillStyle = S1;
    ctx.globalAlpha = walpha * walpha * 0.14;
    ctx.beginPath();
    ctx.moveTo(cxp, cyp);
    ctx.arc(cxp, cyp, baseR, wa0, wa1);
    ctx.closePath();
    ctx.fill();
  }
  ctx.globalAlpha = 1;

  for (var i = 0; i < RINGS.length; i++) {
    var ring = RINGS[i];
    var rad = baseR * ring.rf;
    ctx.strokeStyle = ORBIT;
    ctx.lineWidth = 1;
    ctx.beginPath();
    ctx.arc(cxp, cyp, rad, 0, Math.PI * 2);
    ctx.stroke();

    var ang = sweep * ring.speed;
    for (var s = TRAIL_SEG; s >= 0; s--) {
      var a0 = ang - TRAIL_SPAN * (s / TRAIL_SEG);
      var a1 = ang - TRAIL_SPAN * ((s - 1) / TRAIL_SEG);
      var alpha = 1 - s / TRAIL_SEG;
      ctx.strokeStyle = ring.color;
      ctx.globalAlpha = alpha * alpha * 0.85;
      ctx.lineWidth = 2.6;
      ctx.beginPath();
      ctx.arc(cxp, cyp, rad, a0, a1);
      ctx.stroke();
    }
    ctx.globalAlpha = 1;

    var sx = cxp + Math.cos(ang) * rad;
    var sy = cyp + Math.sin(ang) * rad;
    ctx.fillStyle = ring.color;
    ctx.beginPath();
    ctx.arc(sx, sy, 4.6, 0, Math.PI * 2);
    ctx.fill();
  }

  ctx.fillStyle = CORE;
  ctx.beginPath();
  ctx.arc(cxp, cyp, 7, 0, Math.PI * 2);
  ctx.fill();

  pctEl.textContent = Math.round(p * 100) + '%';
}

var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
var paused = false;
var t0 = 0;
var raf = 0;

function togglePause() {
  paused = !paused;
  root.classList.toggle('is-paused', paused);
}
function restart() {
  t0 = performance.now();
  draw(0);
}

field.addEventListener('click', function () { togglePause(); });
field.addEventListener('keydown', function (e) {
  if (e.key === ' ' || e.key === 'Enter') { e.preventDefault(); togglePause(); }
  else if (e.key === 'r' || e.key === 'R') { e.preventDefault(); restart(); }
});
window.addEventListener('resize', function () {
  fit();
  if (paused || reduce) draw(((performance.now() - t0) / 1000));
});

function frame(now) {
  if (!paused) draw((now - t0) / 1000);
  raf = requestAnimationFrame(frame);
}

t0 = performance.now();
fit();
if (reduce) {
  root.classList.add('is-still');
  draw(LOOP * 0.62);
} else {
  raf = requestAnimationFrame(frame);
}

// OrbitSweep — vanilla 판(run/395/demo/08-canvas-loader-orbit-satellite-arc-sweep/index.html) 의 React 포트.
// 각도 값 하나가 0~360°를 쓸어가고, 궤도 3개의 위성이 반지름에 반비례하는 배속으로 꼬리를 남긴다.
import { useEffect, useRef } from "react";
import type { CSSProperties } from "react";
import styles from "./OrbitSweep.module.scss";

export type OrbitSweepProps = {
  duration?: string;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type Box<T> = { current: T };
type KeyEvt = { key: string; preventDefault(): void };
type Ring = { rf: number; speed: number };

const RINGS: Ring[] = [
  { rf: 0.30, speed: 1.0 },
  { rf: 0.58, speed: 0.62 },
  { rf: 0.86, speed: 0.38 },
];
const LOOP = 3.0;
const TRAIL_SEG = 26;
const TRAIL_SPAN = 1.1;
const FIELD_LABEL = "위성 궤도 각도 스윕 실험판";

export default function OrbitSweep({
  duration = "3s",
  easing = "cubic-bezier(.2, 1.4, .4, 1)",   // vanilla $easing: $ease-pop
  color = "#0a4fe8",                          // vanilla $color: $subject-blue-deep
}: OrbitSweepProps) {
  const rootRef = useRef<HTMLDivElement | null>(null);
  const fieldRef = useRef<HTMLDivElement | null>(null);
  const cvRef = useRef<HTMLCanvasElement | null>(null);
  const ctxRef = useRef<CanvasRenderingContext2D | null>(null);
  const pctRef = useRef<HTMLSpanElement | null>(null);
  const sizeRef = useRef({ w: 0, h: 0, dpr: 1, cx: 0, cy: 0, baseR: 0 }) as Box<{ w: number; h: number; dpr: number; cx: number; cy: number; baseR: number }>;
  const pausedRef = useRef(false) as Box<boolean>;
  const t0Ref = useRef(0) as Box<number>;
  const rafRef = useRef(0) as Box<number>;
  const vars: Vars = { "--duration": duration, "--easing": easing, "--color": color };

  function reduced(): boolean {
    return window.matchMedia("(prefers-reduced-motion: reduce)").matches;
  }

  function fit(): void {
    const field = fieldRef.current;
    const cv = cvRef.current;
    const ctx = ctxRef.current;
    if (!field || !cv || !ctx) return;
    const r = field.getBoundingClientRect();
    const dpr = window.devicePixelRatio || 1;
    const size = sizeRef.current;
    size.w = r.width; size.h = r.height; size.dpr = dpr;
    cv.width = Math.round(r.width * dpr);
    cv.height = Math.round(r.height * dpr);
    ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
    size.cx = r.width * 0.5; size.cy = r.height * 0.5;
    size.baseR = Math.min(r.width, r.height) * 0.46;
  }

  function draw(sec: number): void {
    const ctx = ctxRef.current;
    const root = rootRef.current;
    if (!ctx || !root) return;
    const size = sizeRef.current;
    const W = size.w, H = size.h;
    const t = sec % LOOP;
    const p = t / LOOP;
    const sweep = p * Math.PI * 2;

    const cssv = (n: string) => getComputedStyle(root).getPropertyValue(n).trim();
    const PAPER = cssv("--paper"), ORBIT = cssv("--orbit"), CORE = cssv("--core");
    const COLORS = [cssv("--s1"), cssv("--s2"), cssv("--s3")];

    ctx.fillStyle = PAPER;
    ctx.fillRect(0, 0, W, H);

    const WIDE_SEG = 30, WIDE_SPAN = 1.7;
    for (let w = WIDE_SEG; w >= 0; w--) {
      const wa0 = sweep - WIDE_SPAN * (w / WIDE_SEG);
      const wa1 = sweep - WIDE_SPAN * ((w - 1) / WIDE_SEG);
      const walpha = 1 - w / WIDE_SEG;
      ctx.fillStyle = COLORS[0];
      ctx.globalAlpha = walpha * walpha * 0.14;
      ctx.beginPath();
      ctx.moveTo(size.cx, size.cy);
      ctx.arc(size.cx, size.cy, size.baseR, wa0, wa1);
      ctx.closePath();
      ctx.fill();
    }
    ctx.globalAlpha = 1;

    for (let i = 0; i < RINGS.length; i++) {
      const ring = RINGS[i];
      const rad = size.baseR * ring.rf;
      ctx.strokeStyle = ORBIT;
      ctx.lineWidth = 1;
      ctx.beginPath();
      ctx.arc(size.cx, size.cy, rad, 0, Math.PI * 2);
      ctx.stroke();

      const ang = sweep * ring.speed;
      for (let s = TRAIL_SEG; s >= 0; s--) {
        const a0 = ang - TRAIL_SPAN * (s / TRAIL_SEG);
        const a1 = ang - TRAIL_SPAN * ((s - 1) / TRAIL_SEG);
        const alpha = 1 - s / TRAIL_SEG;
        ctx.strokeStyle = COLORS[i];
        ctx.globalAlpha = alpha * alpha * 0.85;
        ctx.lineWidth = 2.6;
        ctx.beginPath();
        ctx.arc(size.cx, size.cy, rad, a0, a1);
        ctx.stroke();
      }
      ctx.globalAlpha = 1;

      const sx = size.cx + Math.cos(ang) * rad;
      const sy = size.cy + Math.sin(ang) * rad;
      ctx.fillStyle = COLORS[i];
      ctx.beginPath();
      ctx.arc(sx, sy, 4.6, 0, Math.PI * 2);
      ctx.fill();
    }

    ctx.fillStyle = CORE;
    ctx.beginPath();
    ctx.arc(size.cx, size.cy, 7, 0, Math.PI * 2);
    ctx.fill();

    if (pctRef.current) pctRef.current.textContent = Math.round(p * 100) + "%";
  }

  function togglePause(): void {
    pausedRef.current = !pausedRef.current;
    const root = rootRef.current;
    if (root) root.classList.toggle("is-paused", pausedRef.current);
  }

  function restart(): void {
    t0Ref.current = performance.now();
    draw(0);
  }

  function onKey(e: KeyEvt): void {
    if (e.key === " " || e.key === "Enter") { e.preventDefault(); togglePause(); }
    else if (e.key === "r" || e.key === "R") { e.preventDefault(); restart(); }
  }

  function onClick(): void {
    togglePause();
  }

  function onResize(): void {
    fit();
    if (pausedRef.current || reduced()) draw((performance.now() - t0Ref.current) / 1000);
  }

  function frame(now: number): void {
    if (!pausedRef.current) draw((now - t0Ref.current) / 1000);
    rafRef.current = requestAnimationFrame(frame);
  }

  useEffect(() => {
    const cv = cvRef.current;
    if (!cv) return;
    ctxRef.current = cv.getContext("2d");
    if (!ctxRef.current) return;
    t0Ref.current = performance.now();
    fit();
    window.addEventListener("resize", onResize);
    if (reduced()) {
      const root = rootRef.current;
      if (root) root.classList.add("is-still");
      draw(LOOP * 0.62);
    } else {
      rafRef.current = requestAnimationFrame(frame);
    }
    return () => {
      window.removeEventListener("resize", onResize);
      cancelAnimationFrame(rafRef.current);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.root} ref={rootRef} style={vars}>
        <p className={styles.hint}>
          <svg className={styles.ico} viewBox="0 0 256 256" aria-hidden="true"><g fill="currentColor"><path d="M232 56v56a8 8 0 0 1-16 0V91.3l-25.6 25.7A80 80 0 1 1 174 60a8 8 0 1 1-9 13.2A64 64 0 1 0 179.7 128H216a8 8 0 0 1 0 16h-56a8 8 0 0 1-8-8V80a8 8 0 0 1 16 0v20.7L192.7 76A80.1 80.1 0 0 0 64 128a8 8 0 0 1-16 0a96 96 0 0 1 163.6-68.3L224 71.3V56a8 8 0 0 1 8 8" opacity=".2"/><path d="M224 48a8 8 0 0 0-8 8v15.3l-11.7-11.6a96 96 0 1 0 27.6 51.6a8 8 0 0 0-15.8 2.5a80 80 0 1 1-23-43l-25.7 25.7A8 8 0 0 0 173 112h56a8 8 0 0 0 8-8V56a8 8 0 0 0-13-8"/></g></svg>
          <span>클릭하거나 스페이스바를 누르면 멈추거나 다시 갑니다</span>
        </p>
        <div
          className={styles.field}
          ref={fieldRef}
          role="application"
          aria-label={FIELD_LABEL}
          tabIndex={0}
          onClick={onClick}
          onKeyDown={onKey}
        >
          <canvas className={styles.cv} ref={cvRef}></canvas>
          <b className={styles.badge} aria-hidden="true"><span className={styles.badgeNum} ref={pctRef}>0%</span><span className={styles.badgeUnit}>궤도</span></b>
        </div>
      </div>
    </main>
  );
}