01Scroll hint that bounces only on the first screen

<main class="stage">
  <section class="sh is-demo" id="sh" aria-label="First-screen scroll hint">
    <header class="sh__head">
      <p class="sh__kicker">Spring newsletter</p>
      <p class="sh__state"><span class="sh__s sh__s--top" id="sh-state">At the top · hint showing</span><span class="sh__s sh__s--gone" aria-hidden="true">Reading · hint stepped back</span></p>
    </header>
    <div class="sh__view" id="sh-view" tabindex="0" role="region" aria-label="Newsletter body">
      <div class="sh__pad">
        <p class="sh__lede">The screen looks full, but there is more below.</p>
        <p class="sh__line"></p>
        <p class="sh__line"></p>
        <p class="sh__line"></p>
        <p class="sh__line"></p>
        <p class="sh__line"></p>
        <p class="sh__tail">Scroll all the way down and this is the last line.</p>
      </div>
    </div>
    <div class="sh__hint" id="sh-hint" aria-hidden="true">
      <span class="sh__pill"><svg viewBox="0 0 256 256" width="14" height="14" aria-hidden="true"><path d="M200,144l-72,72L56,144Z" opacity="0.2"/><path d="M207.39,140.94A8,8,0,0,0,200,136H136V40a8,8,0,0,0-16,0v96H56a8,8,0,0,0-5.66,13.66l72,72a8,8,0,0,0,11.32,0l72-72A8,8,0,0,0,207.39,140.94ZM128,204.69,75.31,152H180.69Z"/></svg></span>
      <span class="sh__bob"><svg viewBox="0 0 256 256" width="1em" height="1em" fill="currentColor" aria-hidden="true"><path d="M200,144l-72,72L56,144Z" opacity="0.2"/><path d="M207.39,140.94A8,8,0,0,0,200,136H136V40a8,8,0,0,0-16,0v96H56a8,8,0,0,0-5.66,13.66l72,72a8,8,0,0,0,11.32,0l72-72A8,8,0,0,0,207.39,140.94ZM128,204.69,75.31,152H180.69Z"/></svg></span>
      <span class="sh__note">Scroll down</span>
    </div>
  </section>
</main>

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

// 첫 화면에서만 흔들리는 아래로 힌트 — 스크롤이 8px 만 움직여도 힌트는 물러난다
$duration: $dur-loop;
$easing: $ease-spring;
$color: $subject-cream;

@include stage($stage-ink);

.sh {
  position: relative;
  box-sizing: border-box;
  width: min(300px, 92vw);
  border-radius: $r-card;
  background: $subject-cream;
  color: $subject-ink;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  overflow: hidden;
}

.sh__head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: $sp-2;
  padding: $sp-2 $sp-3 0;
}
.sh__kicker {
  margin: 0;
  font-size: 12px;
  font-weight: 700;
  line-height: 1.3;
}
.sh__state {
  position: relative;
  margin: 0;
  font-size: 10px;
  line-height: 1.3;
  color: rgba($stage-ink, .72);
  white-space: nowrap;
}
// 미리보기 루프에서만 쓰는 두 번째 문구 — 정적 경로에서는 JS 가 첫 칸의 글자를 갈아 쓴다
.sh__s--gone { display: none; }

.sh__view {
  box-sizing: border-box;
  height: 148px;
  margin: $sp-2;
  padding-right: $sp-2;
  overflow-y: auto;
  scrollbar-width: none;
  &::-webkit-scrollbar { display: none; }
  &:focus-visible { outline: 2px solid $color; outline-offset: 2px; }
}

.sh__pad {
  display: grid;
  gap: $sp-2;
  padding: $sp-1 $sp-1 96px;
}
.sh__lede {
  margin: 0;
  font-size: 11px;
  font-weight: 700;
  line-height: 1.5;
}
.sh__line {
  height: 8px;
  margin: 0;
  border-radius: $r-pill;
  background: rgba(23, 20, 26, .12);
}
.sh__line:nth-child(3) { width: 92%; }
.sh__line:nth-child(4) { width: 78%; }
.sh__line:nth-child(5) { width: 88%; }
.sh__line:nth-child(6) { width: 64%; }
.sh__tail {
  margin: 0;
  font-size: 10px;
  line-height: 1.5;
  color: rgba($stage-ink, .72);
}

// ── 힌트 묶음: 본문 아래 가운데에 붙는다 ──
.sh__hint {
  position: absolute;
  left: 0;
  right: 0;
  bottom: $sp-1;
  display: grid;
  justify-items: center;
  gap: $sp-1;
  color: $subject-ink;
  // 힌트가 본문 글자 위에 그냥 얹히면 글자가 원 뒤로 비쳐 지저분하다 — 제 자리만큼 바탕을 덮는다
  isolation: isolate;
  &::before {
    content: "";
    position: absolute;
    inset: -$sp-5 0 -$sp-1;
    background: linear-gradient(to bottom, transparent, $subject-cream 58%);
    z-index: -1;
  }
  // 정적(실제 사용) 경로 — 스크롤되면 .is-gone 로 물러난다
  transition: transform $dur-quick $easing, opacity $dur-instant linear;
}
.sh.is-gone .sh__hint {
  transform: translateY(120%);
  opacity: 0;
}
.sh__pill {
  display: inline-grid;
  place-items: center;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: $subject-ink;
  color: $stage-yellow;
}
.sh__pill svg { width: 14px; height: 14px; }
.sh__bob {
  display: inline-grid;
  place-items: center;
  font-size: 18px;
  line-height: 1;
}
.sh__note {
  padding: $sp-1 $sp-2;
  border-radius: $r-pill;
  background: rgba(23, 20, 26, .08);
  font-size: 10px;
  font-weight: 700;
  line-height: 1.4;
}

// ── 격자 미리보기 루프: 화살표는 계속 점프하고, 중간에 본문이 흐르면 힌트가 물러난다 ──
@keyframes sh-bob {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(5px); }
}
// 물러남은 네 프레임에 나눠 흐리게, 돌아옴은 한 프레임 컷 — 그래야 대표 이미지가
// 「힌트가 사라진 빈 화면」 이 아니라 힌트가 서 있는 장이 된다 (퇴장이 등장을 이기는 함정)
@keyframes sh-fade {
  0%, 37% { opacity: 1; }
  54%, 79% { opacity: 0; }
  80%, 100% { opacity: 1; }
}
@keyframes sh-drop {
  0%, 37% { transform: translateY(0); }
  54%, 79% { transform: translateY(120%); }
  80%, 100% { transform: translateY(0); }
}
@keyframes sh-flow {
  0%, 38% { transform: translateY(0); }
  78% { transform: translateY(-20%); }
  82%, 100% { transform: translateY(0); }
}
// 머리말도 두 문구를 겹쳐 두고 컷으로 갈아 낀다 — 힌트가 물러났는데 「보이는 중」 이라고
// 적힌 장이 대표 이미지로 나가면 글과 그림이 서로 다른 말을 한다
@keyframes sh-state-0 { 0%, 37% { opacity: 1; } 38%, 79% { opacity: 0; } 80%, 100% { opacity: 1; } }
@keyframes sh-state-1 { 0%, 37% { opacity: 0; } 38%, 79% { opacity: 1; } 80%, 100% { opacity: 0; } }
.sh.is-demo {
  .sh__bob {
    animation-name: sh-bob;
    animation-duration: 1s;
    animation-timing-function: $easing;
    animation-iteration-count: infinite;
  }
  .sh__hint {
    animation-name: sh-fade, sh-drop;
    animation-duration: $duration, $duration;
    animation-timing-function: $ease-out, $easing;
    animation-iteration-count: infinite, infinite;
    animation-fill-mode: backwards, backwards;
  }
  .sh__pad {
    animation-name: sh-flow;
    animation-duration: $duration;
    animation-timing-function: $ease-out;
    animation-iteration-count: infinite;
  }
  .sh__s--gone { display: block; position: absolute; right: 0; top: 0; }
  .sh__s {
    animation-duration: $duration;
    animation-timing-function: steps(1, end);
    animation-iteration-count: infinite;
  }
  .sh__s--top { animation-name: sh-state-0; }
  .sh__s--gone { animation-name: sh-state-1; }
}

@media (max-width: 340px) {
  .sh__view { height: 124px; }
  .sh__lede { font-size: 10px; }
  .sh__line { height: 6px; }
}

@media (prefers-reduced-motion: reduce) {
  .sh.is-demo .sh__bob,
  .sh.is-demo .sh__pad,
  .sh.is-demo .sh__s { animation: none !important; transform: none !important; }
  .sh.is-demo .sh__hint { animation: none !important; transform: none !important; opacity: 1 !important; }
  // 정지 상태에서도 힌트가 무엇인지는 보인다 — 움직임만 뺀다. 머리말은 맨 위 문구 하나만
  .sh.is-demo .sh__s--top { opacity: 1 !important; }
  .sh.is-demo .sh__s--gone { opacity: 0 !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);
}

.sh {
  position: relative;
  box-sizing: border-box;
  width: min(300px, 92vw);
  border-radius: 16px;
  background: #fff7e6;
  color: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  overflow: hidden;
}

.sh__head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 8px;
  padding: 8px 12px 0;
}

.sh__kicker {
  margin: 0;
  font-size: 12px;
  font-weight: 700;
  line-height: 1.3;
}

.sh__state {
  position: relative;
  margin: 0;
  font-size: 10px;
  line-height: 1.3;
  color: rgba(23, 20, 26, 0.72);
  white-space: nowrap;
}

.sh__s--gone {
  display: none;
}

.sh__view {
  box-sizing: border-box;
  height: 148px;
  margin: 8px;
  padding-right: 8px;
  overflow-y: auto;
  scrollbar-width: none;
}
.sh__view::-webkit-scrollbar {
  display: none;
}
.sh__view:focus-visible {
  outline: 2px solid #fff7e6;
  outline-offset: 2px;
}

.sh__pad {
  display: grid;
  gap: 8px;
  padding: 4px 4px 96px;
}

.sh__lede {
  margin: 0;
  font-size: 11px;
  font-weight: 700;
  line-height: 1.5;
}

.sh__line {
  height: 8px;
  margin: 0;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.12);
}

.sh__line:nth-child(3) {
  width: 92%;
}

.sh__line:nth-child(4) {
  width: 78%;
}

.sh__line:nth-child(5) {
  width: 88%;
}

.sh__line:nth-child(6) {
  width: 64%;
}

.sh__tail {
  margin: 0;
  font-size: 10px;
  line-height: 1.5;
  color: rgba(23, 20, 26, 0.72);
}

.sh__hint {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 4px;
  display: grid;
  justify-items: center;
  gap: 4px;
  color: #17141a;
  isolation: isolate;
}
.sh__hint::before {
  content: "";
  position: absolute;
  inset: -20px -4px;
  background: linear-gradient(to bottom, transparent, #fff7e6 58%);
  z-index: -1;
}
.sh__hint {
  transition: transform 220ms cubic-bezier(0.2, 0.8, 0.2, 1), opacity 140ms linear;
}

.sh.is-gone .sh__hint {
  transform: translateY(120%);
  opacity: 0;
}

.sh__pill {
  display: inline-grid;
  place-items: center;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: #17141a;
  color: #ffd23f;
}

.sh__pill svg {
  width: 14px;
  height: 14px;
}

.sh__bob {
  display: inline-grid;
  place-items: center;
  font-size: 18px;
  line-height: 1;
}

.sh__note {
  padding: 4px 8px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.08);
  font-size: 10px;
  font-weight: 700;
  line-height: 1.4;
}

@keyframes sh-bob {
  0%, 100% {
    transform: translateY(0);
  }
  50% {
    transform: translateY(5px);
  }
}
@keyframes sh-fade {
  0%, 37% {
    opacity: 1;
  }
  54%, 79% {
    opacity: 0;
  }
  80%, 100% {
    opacity: 1;
  }
}
@keyframes sh-drop {
  0%, 37% {
    transform: translateY(0);
  }
  54%, 79% {
    transform: translateY(120%);
  }
  80%, 100% {
    transform: translateY(0);
  }
}
@keyframes sh-flow {
  0%, 38% {
    transform: translateY(0);
  }
  78% {
    transform: translateY(-20%);
  }
  82%, 100% {
    transform: translateY(0);
  }
}
@keyframes sh-state-0 {
  0%, 37% {
    opacity: 1;
  }
  38%, 79% {
    opacity: 0;
  }
  80%, 100% {
    opacity: 1;
  }
}
@keyframes sh-state-1 {
  0%, 37% {
    opacity: 0;
  }
  38%, 79% {
    opacity: 1;
  }
  80%, 100% {
    opacity: 0;
  }
}
.sh.is-demo .sh__bob {
  animation-name: sh-bob;
  animation-duration: 1s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}
.sh.is-demo .sh__hint {
  animation-name: sh-fade, sh-drop;
  animation-duration: 2s, 2s;
  animation-timing-function: ease-out, cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite, infinite;
  animation-fill-mode: backwards, backwards;
}
.sh.is-demo .sh__pad {
  animation-name: sh-flow;
  animation-duration: 2s;
  animation-timing-function: ease-out;
  animation-iteration-count: infinite;
}
.sh.is-demo .sh__s--gone {
  display: block;
  position: absolute;
  right: 0;
  top: 0;
}
.sh.is-demo .sh__s {
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}
.sh.is-demo .sh__s--top {
  animation-name: sh-state-0;
}
.sh.is-demo .sh__s--gone {
  animation-name: sh-state-1;
}

@media (max-width: 340px) {
  .sh__view {
    height: 124px;
  }
  .sh__lede {
    font-size: 10px;
  }
  .sh__line {
    height: 6px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .sh.is-demo .sh__bob,
  .sh.is-demo .sh__pad,
  .sh.is-demo .sh__s {
    animation: none !important;
    transform: none !important;
  }
  .sh.is-demo .sh__hint {
    animation: none !important;
    transform: none !important;
    opacity: 1 !important;
  }
  .sh.is-demo .sh__s--top {
    opacity: 1 !important;
  }
  .sh.is-demo .sh__s--gone {
    opacity: 0 !important;
  }
}

// 첫 화면에서만 흔들리는 아래로 힌트 — scrollTop 8px 기준으로 보였다 물러난다
var sh = document.getElementById('sh');
var view = document.getElementById('sh-view');
var state = document.getElementById('sh-state');
view.addEventListener('scroll', function () {
  sh.classList.remove('is-demo');
  var gone = view.scrollTop > 8;
  sh.classList.toggle('is-gone', gone);
  state.textContent = gone ? 'Reading · hint stepped back' : 'At the top · hint showing';
});

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

export type ScrollHintFirstviewProps = {
  kicker?: string;
  stateVisible?: string;
  stateHidden?: string;
  lede?: string;
  tail?: string;
  note?: string;
  groupLabel?: string;
  bodyLabel?: string;
  /** 격자 미리보기용 2초 자동 루프. 사람이 손대면 꺼진다 */
  demo?: boolean;
  duration?: number;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
// ambient 가 얇아 DOM 요소 타입을 못 쓴다 — 필요한 꼴만 로컬 타입으로 선언
type ScrollBox = { scrollTop: number };

function ArrowDownIcon() {
  return (
    <svg viewBox="0 0 256 256" width="1em" height="1em" fill="currentColor" aria-hidden="true"><path d="M200,144l-72,72L56,144Z" opacity="0.2"/><path d="M207.39,140.94A8,8,0,0,0,200,136H136V40a8,8,0,0,0-16,0v96H56a8,8,0,0,0-5.66,13.66l72,72a8,8,0,0,0,11.32,0l72-72A8,8,0,0,0,207.39,140.94ZM128,204.69,75.31,152H180.69Z"/></svg>
  );
}

export default function ScrollHintFirstview({
  kicker = "봄 소식지",
  stateVisible = "맨 위 · 힌트 보이는 중",
  stateHidden = "읽는 중 · 힌트 물러남",
  lede = "화면이 꽉 차 보이지만 아래가 더 길어요.",
  tail = "끝까지 내려오면 여기가 마지막 줄이에요.",
  note = "아래로 내려 보세요",
  groupLabel = "첫 화면 스크롤 힌트",
  bodyLabel = "소식지 본문",
  demo = true,
  duration = 2000,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#fff7e6",
}: ScrollHintFirstviewProps) {
  const [hidden, setHidden] = useState(false);
  const [live, setLive] = useState(demo);
  const viewRef = useRef<ScrollBox>(null);

  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  // scrollTop 8px 기준 — 처음 화면에서만 힌트가 살아 있다
  function onScroll() {
    const el = viewRef.current;
    if (!el) return;
    setLive(false);
    setHidden(el.scrollTop > 8);
  }

  const cls = [styles.sh, live ? styles.isDemo : "", hidden ? styles.isGone : ""].filter(Boolean).join(" ");

  return (
    <section className={cls} style={vars} aria-label={groupLabel}>
      <header className={styles.head}>
        <p className={styles.kicker}>{kicker}</p>
        <p className={styles.state}>
          {live ? (
            // 미리보기 루프 — 두 문구를 겹쳐 두고 힌트가 물러나는 순간에 맞춰 컷으로 갈아 낀다
            <>
              <span className={`${styles.s} ${styles.sTop}`}>{stateVisible}</span>
              <span className={`${styles.s} ${styles.sGone}`} aria-hidden="true">{stateHidden}</span>
            </>
          ) : (
            hidden ? stateHidden : stateVisible
          )}
        </p>
      </header>
      <div className={styles.view} ref={viewRef} onScroll={onScroll} tabIndex={0} role="region" aria-label={bodyLabel}>
        <div className={styles.pad}>
          <p className={styles.lede}>{lede}</p>
          <p className={styles.line}></p>
          <p className={styles.line}></p>
          <p className={styles.line}></p>
          <p className={styles.line}></p>
          <p className={styles.tail}>{tail}</p>
        </div>
      </div>
      <div className={styles.hint} aria-hidden="true">
        <span className={styles.pill}><ArrowDownIcon /></span>
        <span className={styles.bob}><ArrowDownIcon /></span>
        <span className={styles.shnote}>{note}</span>
      </div>
    </section>
  );
}