01Word-by-word fade-up

<main class="stage">
  <p class="ws-line is-demo">
    <span class="ws-word">Ship</span>
    <span class="ws-word">It</span>
    <span class="ws-word">Beautifully</span>
  </p>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: $dur-loop;
$easing: $ease-out;
$color: $subject-cream;

@include stage($stage-ink);

.ws-line {
  margin: 0;
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: $sp-2;
  font: 700 clamp(22px, 6vw, 34px)/1.2 -apple-system, "Segoe UI", sans-serif;
  color: $color;
}

.ws-word {
  display: inline-block;
  opacity: 0;
  transform: translateY($sp-4);
  filter: blur(var(--blur, 6px));
}

// 데모 루프: 단어가 하나씩 지연을 두고 떠올랐다가 다시 가라앉아 반복 재생된다 (캡처용)
// 한 겹: 단어별 관성 lerp + blur→focus — 등장 구간(0→20%)을 $ease-lerp-settle 로 목표를 살짝 지나쳤다
// 되돌아오게 하고, 단어마다 --blur 깊이(6→9→12px)를 달리해 무거운 단어일수록 늦게 초점이 맞는다.
@keyframes ws-rise {
  0% { opacity: 0; transform: translateY($sp-4); filter: blur(var(--blur, 6px)); animation-timing-function: $ease-lerp-settle; }
  20%, 80% { opacity: 1; transform: none; filter: blur(0); }
  100% { opacity: 0; transform: translateY($sp-4); filter: blur(var(--blur, 6px)); }
}

.ws-line.is-demo .ws-word { animation: ws-rise $duration $easing infinite; }
.ws-line.is-demo .ws-word:nth-child(2) { animation-delay: 160ms; --blur: 9px; }
.ws-line.is-demo .ws-word:nth-child(3) { animation-delay: 320ms; --blur: 12px; }

@media (prefers-reduced-motion: reduce) {
  .ws-word,
  .ws-line.is-demo .ws-word {
    animation: none !important;
    opacity: 1 !important;
    transform: none !important;
    filter: none !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);
}

.ws-line {
  margin: 0;
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 8px;
  font: 700 clamp(22px, 6vw, 34px)/1.2 -apple-system, "Segoe UI", sans-serif;
  color: #fff7e6;
}

.ws-word {
  display: inline-block;
  opacity: 0;
  transform: translateY(16px);
  filter: blur(var(--blur, 6px));
}

@keyframes ws-rise {
  0% {
    opacity: 0;
    transform: translateY(16px);
    filter: blur(var(--blur, 6px));
    animation-timing-function: linear(0, 0.051, 0.176, 0.341, 0.518, 0.685, 0.831, 0.947, 1.032, 1.087, 1.117, 1.126, 1.121, 1.105, 1.085, 1.062, 1.041, 1.022, 1.008, 0.997, 1);
  }
  20%, 80% {
    opacity: 1;
    transform: none;
    filter: blur(0);
  }
  100% {
    opacity: 0;
    transform: translateY(16px);
    filter: blur(var(--blur, 6px));
  }
}
.ws-line.is-demo .ws-word {
  animation: ws-rise 2s ease-out infinite;
}

.ws-line.is-demo .ws-word:nth-child(2) {
  animation-delay: 160ms;
  --blur: 9px;
}

.ws-line.is-demo .ws-word:nth-child(3) {
  animation-delay: 320ms;
  --blur: 12px;
}

@media (prefers-reduced-motion: reduce) {
  .ws-word,
  .ws-line.is-demo .ws-word {
    animation: none !important;
    opacity: 1 !important;
    transform: none !important;
    filter: none !important;
  }
}

import { CSSProperties, useEffect, useRef, useState } from "react";
import styles from "./WordStaggerFade.module.scss";

export interface WordStaggerFadeProps {
  words?: string[];
  duration?: string;
  easing?: string;
  stagger?: string;
}

// 실사용: IntersectionObserver 가 문장이 뷰포트에 들어올 때 한 번 in 을 켠다. 단어마다 transition-delay 만 다르다.
export default function WordStaggerFade({
  words = ["Ship", "It", "Beautifully"],
  duration = "500ms",
  easing = "ease-out",
  stagger = "140ms",
}: WordStaggerFadeProps) {
  const ref = useRef<HTMLParagraphElement>(null);
  const [inView, setInView] = useState(false);

  useEffect(() => {
    const el = ref.current;
    if (!el) return;
    const io = new IntersectionObserver((entries) => {
      entries.forEach((e) => { if (e.isIntersecting) { setInView(true); io.unobserve(e.target); } });
    }, { threshold: 0.3 });
    io.observe(el);
    return () => io.disconnect();
  }, []);

  const style = { "--duration": duration, "--easing": easing } as CSSProperties;

  return (
    <p className={styles.line} style={style} ref={ref}>
      {words.map((w, i) => (
        <span
          key={w + i}
          className={`${styles.word} ${inView ? styles.in : ""}`}
          style={{ transitionDelay: inView ? `calc(${stagger} * ${i})` : undefined }}
        >
          {w}
        </span>
      ))}
    </p>
  );
}