01Loader a Progress Value Fills Like Rising Liquid

<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="Liquid wave progress 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">Progress</span></b>
  </div>
</div>
</main>

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

// 액체 파동 로더 — 진행률 0→1 을 캔버스 수면 높이로 매핑하고 사인파 두 개를 더해 표면을 흔든다.
// 움직임은 전부 캔버스 rAF 루프 안에 있다. CSS 는 무대·판·배지만 맡는다(@keyframes 0개 — 077 선례와 같은 이유).
// fluid-wave-frequency 상수(FREQ, JS)가 파동의 공간·시간 진동수를 함께 정한다 — 변형 01 의 조정 대상.

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

@include stage($stage-ink);

.ld {
  --paper: #{$subject-cream};
  --ink: #{$subject-ink};
  --liquid: #{$subject-blue};
  --liquid-deep: #{$subject-blue-deep};
  --glow: #{rgba($stage-paper, .82)};

  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-cream;
}
.ld__ico { width: 16px; height: 16px; flex: 0 0 auto; color: $subject-blue-light; }

.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-light; 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: $stage-yellow; }
.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: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.ld {
  --paper: #fff7e6;
  --ink: #17141a;
  --liquid: #2f6df6;
  --liquid-deep: #0a4fe8;
  --glow: rgba(255, 255, 255, 0.82);
  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: #fff7e6;
}

.ld__ico {
  width: 16px;
  height: 16px;
  flex: 0 0 auto;
  color: #5b8cf8;
}

.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 #5b8cf8;
  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: #ffd23f;
}

.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;
  }
}

// 액체 Ripple 로더 — 진행률(0~1)을 캔버스 수면 높이로 매핑하고 사인파 두 개를 겹쳐 표면을 흔든다.
// 움직임은 전부 캔버스 rAF 루프 안에 있다. CSS 는 무대·판·배지만 맡는다 — @keyframes 0개라야
// 렌더러가 시계를 고정하지 않고 실시간으로 24장을 찍어 파동이 실제로 도는 모습이 담긴다(077 선례).
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 LIQUID = css.getPropertyValue('--liquid').trim();
var LIQUID_DEEP = css.getPropertyValue('--liquid-deep').trim();
var GLOW = css.getPropertyValue('--glow').trim();

var LOOP = 1.6;               // 로더 한 바퀴(초) — 채웠다가 다시 빈다(반복 루프)
var FREQ = 0.045;             // Ripple 진동수(px 당 라디안) — fluid-wave-frequency, 공간·시간 흔들림을 함께 정한다
var AMP1 = 7, AMP2 = 3.6;
var SPEED1 = 2.1, SPEED2 = -3.0;

var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
var W = 0, H = 0, dpr = 1;
var paused = false;
var t0 = 0;
var raf = 0;

// 고DPI 대응 — 배킹 스토어는 devicePixelRatio 배, 그리기 좌표계는 CSS 픽셀 그대로.
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);
}

function level(p) { return H * (1 - p); }

function draw(sec) {
  ctx.clearRect(0, 0, W, H);
  ctx.fillStyle = PAPER;
  ctx.fillRect(0, 0, W, H);

  var t = sec % LOOP;
  var p = t / LOOP;                  // 0→1 진행률 — 사면톱니(로더는 반복 루프라 프레임이 계속 차야 정상)
  var y0 = level(p);

  function waveY(x) {
    return y0
      + AMP1 * Math.sin(x * FREQ + sec * SPEED1)
      + AMP2 * Math.sin(x * FREQ * 1.8 + sec * SPEED2);
  }

  ctx.beginPath();
  ctx.moveTo(0, H);
  ctx.lineTo(0, waveY(0));
  var step = 4;
  for (var x = 0; x <= W; x += step) ctx.lineTo(x, waveY(x));
  ctx.lineTo(W, H);
  ctx.closePath();
  var grad = ctx.createLinearGradient(0, y0 - 24, 0, H);
  grad.addColorStop(0, LIQUID);
  grad.addColorStop(1, LIQUID_DEEP);
  ctx.fillStyle = grad;
  ctx.fill();

  ctx.beginPath();
  for (var x2 = 0; x2 <= W; x2 += step) {
    var y2 = waveY(x2);
    if (x2 === 0) ctx.moveTo(x2, y2); else ctx.lineTo(x2, y2);
  }
  ctx.strokeStyle = GLOW;
  ctx.lineWidth = 2;
  ctx.stroke();

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

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);
}

// FluidWave — vanilla 판(run/395/demo/01-canvas-loader-fluid-wave-fill-level/index.html) 의 React 포트.
// 진행률(0~1)을 캔버스 수면 높이로 매핑하고 사인파 두 개를 겹쳐 표면을 흔든다.
// 움직임은 캔버스 rAF 루프가 전부 그리므로 @keyframes 가 없다 — props 는 CSS 변수로 내려간다.
import { useEffect, useRef } from "react";
import type { CSSProperties } from "react";
import styles from "./FluidWave.module.scss";

export type FluidWaveProps = {
  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 };

const LOOP = 1.6;              // 로더 한 바퀴(초)
const FREQ = 0.045;            // 파동 진동수(px 당 라디안) — fluid-wave-frequency
const AMP1 = 7, AMP2 = 3.6;
const SPEED1 = 2.1, SPEED2 = -3.0;
const FIELD_LABEL = "액체 파동 진행 실험판";

export default function FluidWave({
  duration = "1.6s",                          // vanilla LOOP
  easing = "cubic-bezier(.2, .8, .2, 1)",     // vanilla $easing: $ease-spring
  color = "#2f6df6",                          // vanilla $color: $subject-blue
}: FluidWaveProps) {
  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 }) as Box<{ w: number; h: number; dpr: 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;
    if (!field || !cv) return;
    const r = field.getBoundingClientRect();
    const dpr = window.devicePixelRatio || 1;
    sizeRef.current.w = r.width;
    sizeRef.current.h = r.height;
    sizeRef.current.dpr = dpr;
    cv.width = Math.round(r.width * dpr);
    cv.height = Math.round(r.height * dpr);
    const ctx = ctxRef.current;
    if (ctx) ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
  }

  function level(p: number): number {
    return sizeRef.current.h * (1 - p);
  }

  function draw(sec: number): void {
    const ctx = ctxRef.current;
    const root = rootRef.current;
    if (!ctx || !root) return;
    const W = sizeRef.current.w, H = sizeRef.current.h;
    const cssv = (n: string) => getComputedStyle(root).getPropertyValue(n).trim();
    const PAPER = cssv("--paper"), LIQUID = cssv("--liquid"), LIQUID_DEEP = cssv("--liquid-deep"), GLOW = cssv("--glow");

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

    const t = sec % LOOP;
    const p = t / LOOP;
    const y0 = level(p);
    const waveY = (x: number) => y0
      + AMP1 * Math.sin(x * FREQ + sec * SPEED1)
      + AMP2 * Math.sin(x * FREQ * 1.8 + sec * SPEED2);

    ctx.beginPath();
    ctx.moveTo(0, H);
    ctx.lineTo(0, waveY(0));
    const step = 4;
    for (let x = 0; x <= W; x += step) ctx.lineTo(x, waveY(x));
    ctx.lineTo(W, H);
    ctx.closePath();
    const grad = ctx.createLinearGradient(0, y0 - 24, 0, H);
    grad.addColorStop(0, LIQUID);
    grad.addColorStop(1, LIQUID_DEEP);
    ctx.fillStyle = grad;
    ctx.fill();

    ctx.beginPath();
    for (let x2 = 0; x2 <= W; x2 += step) {
      const y2 = waveY(x2);
      if (x2 === 0) ctx.moveTo(x2, y2); else ctx.lineTo(x2, y2);
    }
    ctx.strokeStyle = GLOW;
    ctx.lineWidth = 2;
    ctx.stroke();

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

  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}>진행</span></b>
        </div>
      </div>
    </main>
  );
}