02Mũi tên nảy lên

<main class="stage">
  <button type="button" class="totop" aria-label="Lên đầu trang">
    <svg class="totop__arrow is-demo" viewBox="0 0 24 24" aria-hidden="true"><polyline points="5,14 12,7 19,14"/><polyline points="5,19 12,12 19,19"/></svg>
  </button>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: 1.4s;
$easing: $ease-out;
$color: $stage-yellow;     // 화살표 색

@include stage($stage-yellow);

.totop {
  position: relative;
  width: 52px; height: 52px;
  border: 0;
  border-radius: $r-pill;
  background: $subject-ink;
  display: grid;
  place-items: center;
  overflow: hidden;
  box-shadow: $shadow-raised;
  cursor: pointer;
}

.totop__arrow {
  width: 24px; height: 24px;
  fill: none;
  stroke: $color;
  stroke-width: 2.2;
  stroke-linecap: round;
  stroke-linejoin: round;
}
// 상시 반복 — 실제 사용도 버튼이 화면에 있는 동안 계속 튄다
.totop__arrow.is-demo { animation: arrow-bounce $duration $easing infinite; }
@keyframes arrow-bounce {
  0%, 100% { transform: translateY(0); }
  50%      { transform: translateY(-5px); }
}

@media (prefers-reduced-motion: reduce) {
  .totop__arrow.is-demo { animation: none; }
}

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);
}

.totop {
  position: relative;
  width: 52px;
  height: 52px;
  border: 0;
  border-radius: 999px;
  background: #17141a;
  display: grid;
  place-items: center;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  cursor: pointer;
}

.totop__arrow {
  width: 24px;
  height: 24px;
  fill: none;
  stroke: #ffd23f;
  stroke-width: 2.2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.totop__arrow.is-demo {
  animation: arrow-bounce 1.4s ease-out infinite;
}

@keyframes arrow-bounce {
  0%, 100% {
    transform: translateY(0);
  }
  50% {
    transform: translateY(-5px);
  }
}
@media (prefers-reduced-motion: reduce) {
  .totop__arrow.is-demo {
    animation: none;
  }
}

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

export type ArrowBounceButtonProps = {
  /** 한 번 튕기는 데 걸리는 시간 (기본 1.4s) */
  duration?: number;
  easing?: string;
  color?: string;
};

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

export default function ArrowBounceButton({
  duration = 1400,
  easing = "ease-out",
  color = "#ffd23f",
}: ArrowBounceButtonProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  return (
    <button
      type="button"
      className={styles.totop}
      style={vars}
      aria-label="맨 위로"
      onClick={() => window.scrollTo({ top: 0, behavior: "smooth" })}
    >
      <svg className={styles.arrow} viewBox="0 0 24 24" aria-hidden="true">
        <polyline points="5,14 12,7 19,14" />
        <polyline points="5,19 12,12 19,19" />
      </svg>
    </button>
  );
}