02Nút phát sáng khi hover

<main class="stage is-demo">
  <button class="btn" type="button" aria-label="Tiếp theo">
    <svg viewBox="0 0 24 24" width="22" height="22" fill="none" aria-hidden="true">
      <path d="M5 12h13M13 6l6 6-6 6" stroke="currentColor" stroke-width="2.4" stroke-linecap="round" stroke-linejoin="round"/>
    </svg>
  </button>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: $dur-loop;    // 2s — 호버 루프 한 주기
$easing: $ease-out;
$color: #00e5ff;         // 네온 시안

@include stage($stage-ink);

.btn {
  display: grid; place-items: center;
  width: $sp-12; height: $sp-12;
  border: 0; border-radius: 50%;
  background: rgba($stage-paper, .06);
  color: $color;
  cursor: pointer; -webkit-tap-highlight-color: transparent;
  box-shadow: 0 0 $sp-2 rgba($color, .3), 0 0 $sp-4 rgba($color, .12);
  transition: box-shadow $dur-base $easing, transform $dur-base $easing, background $dur-base $easing;
}

.btn:hover,
.btn:focus-visible {
  background: rgba($stage-paper, .1);
  box-shadow: 0 0 $sp-3 $color, 0 0 $sp-8 rgba($color, .65), 0 0 $sp-12 rgba($color, .3);
  transform: scale(1.06);
  outline: none;
}

// box-shadow·transform 만 바뀐다 — 레이아웃은 그대로
.stage.is-demo .btn {
  animation: hover-loop $duration $easing infinite;
}

@keyframes hover-loop {
  0%, 12%, 100% {
    box-shadow: 0 0 $sp-2 rgba($color, .3), 0 0 $sp-4 rgba($color, .12);
    transform: scale(1);
  }
  35%, 75% {
    box-shadow: 0 0 $sp-3 $color, 0 0 $sp-8 rgba($color, .65), 0 0 $sp-12 rgba($color, .3);
    transform: scale(1.06);
  }
  92% {
    box-shadow: 0 0 $sp-2 rgba($color, .3), 0 0 $sp-4 rgba($color, .12);
    transform: scale(1);
  }
}

@media (prefers-reduced-motion: reduce) {
  .stage.is-demo .btn { animation: none; }
  .btn { transition-duration: 1ms; }
}

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);
}

.btn {
  display: grid;
  place-items: center;
  width: 48px;
  height: 48px;
  border: 0;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.06);
  color: #00e5ff;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
  box-shadow: 0 0 8px rgba(0, 229, 255, 0.3), 0 0 16px rgba(0, 229, 255, 0.12);
  transition: box-shadow 300ms ease-out, transform 300ms ease-out, background 300ms ease-out;
}

.btn:hover,
.btn:focus-visible {
  background: rgba(255, 255, 255, 0.1);
  box-shadow: 0 0 12px #00e5ff, 0 0 32px rgba(0, 229, 255, 0.65), 0 0 48px rgba(0, 229, 255, 0.3);
  transform: scale(1.06);
  outline: none;
}

.stage.is-demo .btn {
  animation: hover-loop 2s ease-out infinite;
}

@keyframes hover-loop {
  0%, 12%, 100% {
    box-shadow: 0 0 8px rgba(0, 229, 255, 0.3), 0 0 16px rgba(0, 229, 255, 0.12);
    transform: scale(1);
  }
  35%, 75% {
    box-shadow: 0 0 12px #00e5ff, 0 0 32px rgba(0, 229, 255, 0.65), 0 0 48px rgba(0, 229, 255, 0.3);
    transform: scale(1.06);
  }
  92% {
    box-shadow: 0 0 8px rgba(0, 229, 255, 0.3), 0 0 16px rgba(0, 229, 255, 0.12);
    transform: scale(1);
  }
}
@media (prefers-reduced-motion: reduce) {
  .stage.is-demo .btn {
    animation: none;
  }
  .btn {
    transition-duration: 1ms;
  }
}

// 실제 사람이 누르면 강제 루프를 떼고 :hover · :focus-visible 에 맡긴다.
document.querySelector('.btn').addEventListener('pointerdown', function () {
  document.querySelector('.stage').classList.remove('is-demo');
});

import type { CSSProperties, MouseEvent } from "react";
import styles from "./ButtonGlowHover.module.scss";

export type ButtonGlowHoverProps = {
  duration?: number;
  easing?: string;
  color?: string;
  label?: string;
  onClick?: (e: MouseEvent<HTMLButtonElement>) => void;
};

export default function ButtonGlowHover({
  duration = 300,
  easing = "ease-out",
  color = "#00e5ff",
  label = "다음",
  onClick,
}: ButtonGlowHoverProps) {
  const vars: CSSProperties = { "--duration": `${duration}ms`, "--easing": easing, "--color": color } as CSSProperties;
  return (
    <button className={styles.btn} type="button" style={vars} aria-label={label} onClick={onClick}>
      <svg viewBox="0 0 24 24" width={22} height={22} fill="none" aria-hidden="true">
        <path d="M5 12h13M13 6l6 6-6 6" stroke="currentColor" strokeWidth={2.4} strokeLinecap="round" strokeLinejoin="round" />
      </svg>
    </button>
  );
}