02Shine sweep button

<main class="stage is-demo">
  <button class="btn" type="button"><span class="btn__label">Buy now</span></button>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: $dur-loop;      // 2s — 스윕 한 주기
$easing: $ease-out;
$color: $subject-ink;      // 버튼 바탕

@include stage($stage-yellow);

.btn {
  box-sizing: border-box;
  position: relative;
  width: 240px;
  height: 64px;
  border: none;
  border-radius: $r-control;
  background: $color;
  color: $subject-cream;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 700;
  font-size: 17px;
  cursor: pointer;
  overflow: hidden;        // 빛 띠가 밖으로 새지 않게
  box-shadow: $shadow-raised;
}

.btn__label { position: relative; z-index: 1; }

// 기울어진 흰 빛 띠 — transform 만으로 통과시킨다
.btn::after {
  content: "";
  position: absolute;
  top: 0; bottom: 0;
  left: -60%;
  width: 60%;
  background: linear-gradient(115deg,
    transparent 0%, rgba(255, 255, 255, .85) 50%, transparent 100%);
  transform: skewX(-20deg) translateX(-10%);
}

// 실사용: 올릴 때마다 한 번 쓸고 지나감
.btn:hover::after { animation: sweep $dur-enter $easing 1; }

.btn:focus-visible { outline: 3px solid $subject-ink; outline-offset: 4px; }

// 격자 미리보기: 2초 루프로 강제 발동
.stage.is-demo .btn::after { animation: sweep $duration $easing infinite; }

@keyframes sweep {
  0%, 10%  { transform: skewX(-20deg) translateX(-10%); }
  55%      { transform: skewX(-20deg) translateX(310%); }
  100%     { transform: skewX(-20deg) translateX(310%); }
}

@media (prefers-reduced-motion: reduce) {
  .btn:hover::after, .stage.is-demo .btn::after { animation: none; transform: skewX(-20deg) translateX(-10%); }
}

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);
}

.btn {
  box-sizing: border-box;
  position: relative;
  width: 240px;
  height: 64px;
  border: none;
  border-radius: 12px;
  background: #17141a;
  color: #fff7e6;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 700;
  font-size: 17px;
  cursor: pointer;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
}

.btn__label {
  position: relative;
  z-index: 1;
}

.btn::after {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  left: -60%;
  width: 60%;
  background: linear-gradient(115deg, transparent 0%, rgba(255, 255, 255, 0.85) 50%, transparent 100%);
  transform: skewX(-20deg) translateX(-10%);
}

.btn:hover::after {
  animation: sweep 600ms ease-out 1;
}

.btn:focus-visible {
  outline: 3px solid #17141a;
  outline-offset: 4px;
}

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

@keyframes sweep {
  0%, 10% {
    transform: skewX(-20deg) translateX(-10%);
  }
  55% {
    transform: skewX(-20deg) translateX(310%);
  }
  100% {
    transform: skewX(-20deg) translateX(310%);
  }
}
@media (prefers-reduced-motion: reduce) {
  .btn:hover::after, .stage.is-demo .btn::after {
    animation: none;
    transform: skewX(-20deg) translateX(-10%);
  }
}

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

export type ShineSweepButtonProps = {
  duration?: number;
  easing?: string;
  color?: string;
  children?: ReactNode;
};

export default function ShineSweepButton({
  duration = 600,
  easing = "ease-out",
  color = "#17141a",
  children = "지금 구매하기",
}: ShineSweepButtonProps) {
  const vars: CSSProperties = { "--duration": `${duration}ms`, "--easing": easing, "--color": color } as CSSProperties;
  return (
    <button className={styles.btn} style={vars} type="button">
      <span className={styles.label}>{children}</span>
    </button>
  );
}