07Chữ nhấp nháy

<main class="stage">
  <h1 class="marquee">
    <span style="--i:0">Li</span><span style="--i:1">v</span><span style="--i:2">e</span><span class="marquee__gap" aria-hidden="true"></span><span style="--i:3">Sta</span><span style="--i:4">rt</span>
  </h1>
</main>

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

$duration: $dur-loop;                              // 전구 하나가 어두워졌다 돌아오는 한 주기
$easing: linear;
$color: $subject-cream;                             // 전구 색

@include stage($stage-orange);

.marquee {
  margin: 0;
  font-weight: 800; font-size: clamp(28px, 9vw, 46px); line-height: 1.2; font-family: inherit;
  text-align: center;
}
.marquee span {
  display: inline-block;
  color: $color;
  animation: bulb $duration $easing infinite;
  animation-delay: calc(var(--i, 0) * 120ms);       // 글자마다 지연이 달라 하나씩 따로 깜빡인다
}
.marquee__gap { width: .3em; }

@keyframes bulb {
  0%, 40%, 100% { opacity: 1; }
  47%           { opacity: .22; }                    // 통째로 꺼지는 네온과 달리 글자 하나만 잠깐 어두워진다
  54%           { opacity: 1; }
}

@media (prefers-reduced-motion: reduce) {
  .marquee span { animation: none; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ff4d1f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.marquee {
  margin: 0;
  font-weight: 800;
  font-size: clamp(28px, 9vw, 46px);
  line-height: 1.2;
  font-family: inherit;
  text-align: center;
}

.marquee span {
  display: inline-block;
  color: #fff7e6;
  animation: bulb 2s linear infinite;
  animation-delay: calc(var(--i, 0) * 120ms);
}

.marquee__gap {
  width: 0.3em;
}

@keyframes bulb {
  0%, 40%, 100% {
    opacity: 1;
  }
  47% {
    opacity: 0.22;
  }
  54% {
    opacity: 1;
  }
}
@media (prefers-reduced-motion: reduce) {
  .marquee span {
    animation: none;
  }
}

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

export type FlickerTextProps = {
  /** 글자를 하나씩 나눠 넣는다 (공백은 별도 span 으로) */
  letters: string[];
  /** 전구 하나가 어두워졌다 돌아오는 한 주기 (기본 2000ms) */
  duration?: number;
  easing?: string;
  /** 전구 색 */
  color?: string;
};

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

export default function FlickerText({
  letters,
  duration = 2000,
  easing = "linear",
  color = "#fff7e6",
}: FlickerTextProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  return (
    <h1 className={styles.marquee} style={vars}>
      {letters.map((ch, i) =>
        ch === " " ? (
          <span key={i} className={styles.gap} aria-hidden="true" />
        ) : (
          <span key={i} style={{ "--i": i } as LetterVars}>{ch}</span>
        )
      )}
    </h1>
  );
}