07Dotted line growing

<main class="stage">
  <p class="line">See the <span class="hl">help docs<span class="hl__dots" aria-hidden="true"></span></span>for details.</p>
</main>

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

// ── 변수 3개 ─────────────────────────────
$duration: 700ms;
$easing: $ease-out;
$color: $stage-ink;            // 점선 색

// ── 데모 무대 ───────────────────────────────
@include stage($stage-yellow);

.line {
  max-width: 92%;
  margin: 0;
  color: $stage-ink;
  font-weight: 600;
  font-size: clamp(16px, 4.6vw, 22px);
  line-height: 1.6;
  font-family: inherit;
  text-align: center;
}

.hl {
  position: relative;
  font-weight: 700;
}

// 일정 간격의 점을 그린 얇은 막대를 글자 아래 두고 왼쪽부터 늘린다
.hl__dots {
  position: absolute;
  left: 0;
  right: 0;
  bottom: -4px;
  height: 3px;
  background-image: repeating-linear-gradient(90deg, $color 0 3px, transparent 3px 8px);
  transform: scaleX(0);
  transform-origin: left center; // 규칙8: 점선 왼쪽에서 늘어남
  animation: grow $duration $easing infinite, grow-thick $duration $easing infinite;
}

@keyframes grow {
  0%   { transform: scaleX(0); }
  40%  { transform: scaleX(1); }
  80%  { transform: scaleX(1); }
  100% { transform: scaleX(0); }
}

// 페인트 물성: 점선 두께(펜 압력)가 늘어나는 주기와 같은 리듬으로 불규칙 진동 — height 는 transform 아님
@keyframes grow-thick {
  0%   { height: 3px; }
  15%  { height: 4px; }
  30%  { height: 2.5px; }
  45%  { height: 3.5px; }
  60%  { height: 2.5px; }
  75%  { height: 4px; }
  90%  { height: 3px; }
  100% { height: 3px; }
}

@media (prefers-reduced-motion: reduce) {
  .hl__dots { animation: none; transform: scaleX(1); }
}

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);
}

.line {
  max-width: 92%;
  margin: 0;
  color: #17141a;
  font-weight: 600;
  font-size: clamp(16px, 4.6vw, 22px);
  line-height: 1.6;
  font-family: inherit;
  text-align: center;
}

.hl {
  position: relative;
  font-weight: 700;
}

.hl__dots {
  position: absolute;
  left: 0;
  right: 0;
  bottom: -4px;
  height: 3px;
  background-image: repeating-linear-gradient(90deg, #17141a 0 3px, transparent 3px 8px);
  transform: scaleX(0);
  transform-origin: left center;
  animation: grow 700ms ease-out infinite, grow-thick 700ms ease-out infinite;
}

@keyframes grow {
  0% {
    transform: scaleX(0);
  }
  40% {
    transform: scaleX(1);
  }
  80% {
    transform: scaleX(1);
  }
  100% {
    transform: scaleX(0);
  }
}
@keyframes grow-thick {
  0% {
    height: 3px;
  }
  15% {
    height: 4px;
  }
  30% {
    height: 2.5px;
  }
  45% {
    height: 3.5px;
  }
  60% {
    height: 2.5px;
  }
  75% {
    height: 4px;
  }
  90% {
    height: 3px;
  }
  100% {
    height: 3px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .hl__dots {
    animation: none;
    transform: scaleX(1);
  }
}

import type { CSSProperties, ReactNode } from "react";
import styles from "./DottedGrow.module.scss";

export type DottedGrowProps = {
  before: ReactNode;
  keyword: ReactNode;
  after?: ReactNode;
  /** 점선이 다 자라는 시간 (기본 700ms) */
  duration?: number;
  easing?: string;
  /** 점선 색 */
  color?: string;
};

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

export default function DottedGrow({
  before,
  keyword,
  after,
  duration = 700,
  easing = "ease-out",
  color = "#17141a",
}: DottedGrowProps) {
  const vars: Vars = {
    "--duration": `${duration}ms`,
    "--easing": easing,
    "--color": color,
  };
  return (
    <p className={styles.line} style={vars}>
      {before} <span className={styles.hl}>{keyword}<span className={styles.dots} aria-hidden="true" /></span>{after}
    </p>
  );
}