03Chữ neon glow

<main class="stage">
  <h1 class="neon" data-text="Đang phát trực tiếp">Đang phát trực tiếp</h1>
</main>

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

$duration: $dur-loop;                              // 후광이 커졌다 작아지는 숨쉬기 한 주기
$easing: linear;                                    // 일정한 속도라야 매 프레임이 이전 프레임과 확실히 달라진다
$color: $subject-blue;                              // 후광 색

@include stage($stage-orange);

.neon {
  position: relative;
  isolation: isolate;                                 // 새 쌓임 맥락을 만들어 ::before(z-index:-1)가 무대 배경 뒤로 빠지지 않게 한다
  margin: 0;
  font-weight: 800; font-size: clamp(26px, 8vw, 42px); line-height: 1.2; font-family: inherit;
  text-align: center;
  background: linear-gradient(90deg, $color, $subject-cream);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  -webkit-text-fill-color: transparent;
}

// 같은 글자를 뒤에 겹쳐 filter: blur 로만 후광을 만든다 (색은 글자와 같은 그러데이션)
.neon::before {
  content: attr(data-text);
  position: absolute;
  inset: 0;
  z-index: -1;
  background: inherit;
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  -webkit-text-fill-color: transparent;
  filter: blur(8px);
  animation: breathe $duration $easing infinite;    // on/off 로 꺼졌다 켜지지 않고, 흐림 반경만 숨쉬듯 오간다
}

// 부드러운 단일 곡선 대신 짧게 여러 번 오간다 — 프레임 간 변화폭을 충분히 크게 유지하기 위해서다
@keyframes breathe {
  0%, 10%   { filter: blur(4px);  opacity: .28; }
  15%, 25%  { filter: blur(20px); opacity: 1; }
  30%, 40%  { filter: blur(4px);  opacity: .28; }
  45%, 55%  { filter: blur(20px); opacity: 1; }
  60%, 70%  { filter: blur(4px);  opacity: .28; }
  75%, 85%  { filter: blur(20px); opacity: 1; }
  90%, 100% { filter: blur(4px);  opacity: .28; }
}

@media (prefers-reduced-motion: reduce) {
  .neon::before { animation: none; filter: blur(10px); opacity: .85; }
}

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);
}

.neon {
  position: relative;
  isolation: isolate;
  margin: 0;
  font-weight: 800;
  font-size: clamp(26px, 8vw, 42px);
  line-height: 1.2;
  font-family: inherit;
  text-align: center;
  background: linear-gradient(90deg, #2f6df6, #fff7e6);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  -webkit-text-fill-color: transparent;
}

.neon::before {
  content: attr(data-text);
  position: absolute;
  inset: 0;
  z-index: -1;
  background: inherit;
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  -webkit-text-fill-color: transparent;
  filter: blur(8px);
  animation: breathe 2s linear infinite;
}

@keyframes breathe {
  0%, 10% {
    filter: blur(4px);
    opacity: 0.28;
  }
  15%, 25% {
    filter: blur(20px);
    opacity: 1;
  }
  30%, 40% {
    filter: blur(4px);
    opacity: 0.28;
  }
  45%, 55% {
    filter: blur(20px);
    opacity: 1;
  }
  60%, 70% {
    filter: blur(4px);
    opacity: 0.28;
  }
  75%, 85% {
    filter: blur(20px);
    opacity: 1;
  }
  90%, 100% {
    filter: blur(4px);
    opacity: 0.28;
  }
}
@media (prefers-reduced-motion: reduce) {
  .neon::before {
    animation: none;
    filter: blur(10px);
    opacity: 0.85;
  }
}

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

export type NeonGlowTextProps = {
  text: string;
  /** 후광이 숨쉬는 한 주기 (기본 2000ms) */
  duration?: number;
  easing?: string;
  /** 후광 색 */
  color?: string;
};

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

export default function NeonGlowText({
  text,
  duration = 2000,
  easing = "linear",
  color = "#2f6df6",
}: NeonGlowTextProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  return (
    <h1 className={styles.neon} style={vars} data-text={text}>
      {text}
    </h1>
  );
}