06蛍光ペンが引かれる強調

<main class="stage">
  <div class="mk">
    <div class="mk__scroll">
      <div class="mk__spacer"></div>
      <h2 class="mk__title">今シーズン <span class="mk__hl is-demo">たった一つのセール</span></h2>
      <p class="mk__sub">蛍光ペンを引くように強調が満ちます</p>
      <div class="mk__spacer"></div>
    </div>
  </div>
</main>

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

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

@include stage($stage-yellow);

.mk { width: min(400px, 88vw); }

.mk__scroll {
  height: clamp(150px, 62vh, 216px);
  overflow-y: auto;
  scrollbar-width: none;
  &::-webkit-scrollbar { display: none; }
}

.mk__spacer { height: 30%; }

.mk__title {
  margin: 0;
  padding: 0 $sp-4;
  text-align: center;
  color: $subject-ink;
  font: 800 clamp(22px, 5.5vw, 30px)/1.5 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  letter-spacing: -.01em;
}

.mk__sub {
  margin: $sp-3 0 0;
  text-align: center;
  color: rgba(23, 20, 26, .72);
  font: 600 13px/1.5 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

// ── 실제 동작: 형광펜 = 배경 그라디언트의 폭. 글자는 그대로 두고 배경만 자란다 ──
@supports (animation-timeline: view()) {
  .mk__hl:not(.is-demo) {
    animation: mk-sw linear both;
    animation-timeline: view();
    animation-range: entry 30% cover 60%;
  }
}
@supports not (animation-timeline: view()) {
  // 미지원 브라우저(Firefox·Safari): 강조가 처음부터 끝까지 그어져 있다
  .mk__hl:not(.is-demo) { background-size: 100% 58%; }
}
.mk__hl {
  background: linear-gradient($color, $color) no-repeat 0 62%;
  background-size: 0% 58%;
  border-radius: $r-xs;
  padding: 0 $sp-1;
}
@keyframes mk-sw {
  from { background-size: 0% 58%; }
  to   { background-size: 100% 58%; }
}

// 데모 루프: 실제 스크롤 대신 형광펜이 좌에서 우로 그어지는 걸 흉내(캡처용)
.mk__hl.is-demo { animation: mk-loop $duration $easing infinite; }
@keyframes mk-loop {
  0%, 10%  { background-size: 0% 58%; }
  55%, 88% { background-size: 100% 58%; }
  100%     { background-size: 0% 58%; }
}

@media (prefers-reduced-motion: reduce) {
  .mk__hl.is-demo { animation: none !important; background-size: 100% 58% !important; }
  .mk__scroll { scroll-behavior: auto; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.mk {
  width: min(400px, 88vw);
}

.mk__scroll {
  height: clamp(150px, 62vh, 216px);
  overflow-y: auto;
  scrollbar-width: none;
}
.mk__scroll::-webkit-scrollbar {
  display: none;
}

.mk__spacer {
  height: 30%;
}

.mk__title {
  margin: 0;
  padding: 0 16px;
  text-align: center;
  color: #17141a;
  font: 800 clamp(22px, 5.5vw, 30px)/1.5 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  letter-spacing: -0.01em;
}

.mk__sub {
  margin: 12px 0 0;
  text-align: center;
  color: rgba(23, 20, 26, 0.72);
  font: 600 13px/1.5 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

@supports (animation-timeline: view()) {
  .mk__hl:not(.is-demo) {
    animation: mk-sw linear both;
    animation-timeline: view();
    animation-range: entry 30% cover 60%;
  }
}
@supports not (animation-timeline: view()) {
  .mk__hl:not(.is-demo) {
    background-size: 100% 58%;
  }
}
.mk__hl {
  background: linear-gradient(#2f6df6, #2f6df6) no-repeat 0 62%;
  background-size: 0% 58%;
  border-radius: 4px;
  padding: 0 4px;
}

@keyframes mk-sw {
  from {
    background-size: 0% 58%;
  }
  to {
    background-size: 100% 58%;
  }
}
.mk__hl.is-demo {
  animation: mk-loop 2s ease-out infinite;
}

@keyframes mk-loop {
  0%, 10% {
    background-size: 0% 58%;
  }
  55%, 88% {
    background-size: 100% 58%;
  }
  100% {
    background-size: 0% 58%;
  }
}
@media (prefers-reduced-motion: reduce) {
  .mk__hl.is-demo {
    animation: none !important;
    background-size: 100% 58% !important;
  }
  .mk__scroll {
    scroll-behavior: auto;
  }
}

// 실제 동작: view() 타임라인이 background-size 를 0% → 100% 로 늘린다(0줄).
// is-demo 클래스는 캡처용 미리보기 루프일 뿐 — 실제 스크롤 반응은 그대로 살아있다.

import type { CSSProperties } from "react";
import styles from "./HighlighterSweep.module.scss";

export type HighlighterSweepProps = {
  duration?: number;
  easing?: string;
  color?: string;
  before?: string;
  highlight?: string;
  after?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };

export default function HighlighterSweep({
  duration = 300,
  easing = "linear",
  color = "#2f6df6",
  before = "이번 시즌",
  highlight = "단 하나의 세일",
  after,
}: HighlighterSweepProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  return (
    <div className={styles.mk} style={vars}>
      {/* 형광펜 = 배경 그라디언트의 폭(view() 타임라인). 글자는 그대로 두고 배경만 자란다 */}
      <div className={styles.scroll}>
        <div className={styles.spacer} />
        <h2 className={styles.title}>
          {before} <span className={styles.hl}>{highlight}</span> {after}
        </h2>
        <div className={styles.spacer} />
      </div>
    </div>
  );
}