03Bounce downward

<main class="stage">
  <span class="bd-wrap" aria-hidden="true">
    <span class="bd-chevron"></span>
    <span class="bd-trail"></span>
  </span>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: 1.4s;
$easing: $ease-pop;
$color: $subject-cream;

@include stage($stage-orange);

.bd-wrap {
  position: relative;
  display: inline-block;
  width: 28px;
  height: 40px;
}

.bd-chevron {
  position: absolute;
  top: 8px;
  left: 0;
  display: block;
  width: 28px;
  height: 28px;
  border-bottom: 4px solid $color;
  border-right: 4px solid $color;
  transform: rotate(45deg) translateY(0);
}

// 자동 재생: 아래를 가리키는 화살표가 42%에서 오버슛했다 50%에서 정착하며 튄다(고무줄 신장). translateY 만 움직인다
@keyframes bd-bounce {
  0%, 100% { transform: rotate(45deg) translateY(0); }
  42%      { transform: rotate(45deg) translateY(15px); }
  50%      { transform: rotate(45deg) translateY(12px); }
}
.bd-chevron { animation: bd-bounce $duration $easing infinite; }

// 트레일 파티클 — 화살표 위로 작은 잔상이 살짝 늦게 따라 내려온다
.bd-trail {
  position: absolute;
  top: 4px;
  left: 7px;
  display: block;
  width: 14px;
  height: 14px;
  border-bottom: 3px solid $color;
  border-right: 3px solid $color;
  opacity: 0;
}
@keyframes bd-trail {
  0%, 100% { opacity: 0; transform: rotate(45deg) translateY(-4px) scale(.6); }
  50%      { opacity: .3; transform: rotate(45deg) translateY(6px) scale(.8); }
}
.bd-trail { animation: bd-trail $duration $easing 90ms infinite; }

@media (prefers-reduced-motion: reduce) {
  .bd-chevron { animation: none !important; transform: rotate(45deg) translateY(0) !important; }
  .bd-trail { animation: none !important; opacity: 0 !important; }
}

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);
}

.bd-wrap {
  position: relative;
  display: inline-block;
  width: 28px;
  height: 40px;
}

.bd-chevron {
  position: absolute;
  top: 8px;
  left: 0;
  display: block;
  width: 28px;
  height: 28px;
  border-bottom: 4px solid #fff7e6;
  border-right: 4px solid #fff7e6;
  transform: rotate(45deg) translateY(0);
}

@keyframes bd-bounce {
  0%, 100% {
    transform: rotate(45deg) translateY(0);
  }
  42% {
    transform: rotate(45deg) translateY(15px);
  }
  50% {
    transform: rotate(45deg) translateY(12px);
  }
}
.bd-chevron {
  animation: bd-bounce 1.4s cubic-bezier(0.2, 1.4, 0.4, 1) infinite;
}

.bd-trail {
  position: absolute;
  top: 4px;
  left: 7px;
  display: block;
  width: 14px;
  height: 14px;
  border-bottom: 3px solid #fff7e6;
  border-right: 3px solid #fff7e6;
  opacity: 0;
}

@keyframes bd-trail {
  0%, 100% {
    opacity: 0;
    transform: rotate(45deg) translateY(-4px) scale(0.6);
  }
  50% {
    opacity: 0.3;
    transform: rotate(45deg) translateY(6px) scale(0.8);
  }
}
.bd-trail {
  animation: bd-trail 1.4s cubic-bezier(0.2, 1.4, 0.4, 1) 90ms infinite;
}

@media (prefers-reduced-motion: reduce) {
  .bd-chevron {
    animation: none !important;
    transform: rotate(45deg) translateY(0) !important;
  }
  .bd-trail {
    animation: none !important;
    opacity: 0 !important;
  }
}

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

export interface BounceDownwardProps {
  duration?: string;
  easing?: string;
  color?: string;
}

export default function BounceDownward({
  duration = "1.4s",
  easing = "cubic-bezier(.2, 1.4, .4, 1)",
  color = "#fff7e6",
}: BounceDownwardProps) {
  const style = { "--duration": duration, "--easing": easing, "--color": color } as CSSProperties;
  return (
    <span className={styles.wrap} style={style} aria-hidden="true">
      <span className={styles.chevron} />
      <span className={styles.trail} />
    </span>
  );
}