02Confetti rain

<main class="stage">
  <div class="cr-wrap is-demo">
    <span class="cr-banner">Congrats on your prize</span>
    <span class="cr-piece"></span><span class="cr-piece"></span><span class="cr-piece"></span>
    <span class="cr-piece"></span><span class="cr-piece"></span><span class="cr-piece"></span>
    <span class="cr-piece"></span><span class="cr-piece"></span><span class="cr-piece"></span>
    <span class="cr-piece"></span><span class="cr-piece"></span><span class="cr-piece"></span>
    <span class="cr-piece"></span><span class="cr-piece"></span><span class="cr-piece"></span>
    <span class="cr-piece"></span><span class="cr-piece"></span><span class="cr-piece"></span>
  </div>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: 2s;
$easing: linear;
$color: $subject-blue;

@include stage($stage-yellow);

$piece-colors: $color, $stage-orange, $subject-ink, $subject-cream;

.cr-wrap {
  position: relative;
  width: min(320px, 88vw);
  height: min(220px, 62vh);
  overflow: hidden;
  border-radius: $r-card;
  background: rgba(23, 20, 26, .06);
}

.cr-banner {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  padding: $sp-4;
  box-sizing: border-box;
  text-align: center;
  color: $subject-ink;
  font: 700 18px/1.3 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

.cr-piece {
  position: absolute;
  top: -220px;
  width: 9px;
  height: 16px;
  border-radius: $r-xs;
  opacity: .95;
  animation-duration: $duration;
}

// 조각 18개가 카드 높이 전체에 걸쳐 서로 다른 top 시작값을 갖는다 — delay 만 다르면 전부 위쪽에서
// 한 줄로 뭉쳐 같이 출발해 버린다 (실측). top 순서를 왼쪽 순서(left%)와 다르게 섞어야 대각선 한 줄이
// 아니라 흩뿌린 비처럼 보인다 (실측: left·top 을 같은 $i 로 선형 배치하면 완벽한 대각선이 된다)
$tops: -40px, 160px, -180px, 20px, 100px, -120px, 60px, -200px, 140px, -20px, 180px, -100px, 40px, -160px, 120px, -60px, 200px, -140px;
@for $i from 1 through 18 {
  .cr-piece:nth-child(#{$i + 1}) {
    left: percentage($i / 19);
    top: nth($tops, $i);
    background: nth($piece-colors, $i % 4 + 1);
    animation-duration: #{1700ms + ($i % 5) * 140ms};
  }
}

@keyframes cr-fall {
  0%   { transform: translateY(0) rotate(0deg); }
  100% { transform: translateY(520px) rotate(300deg); }
}

// duration 은 shorthand 로 주지 않는다 — 그러면 specificity 가 더 높아 항목마다 다른 animation-duration(위) 을
// 덮어써 18개가 전부 같은 박자로 떨어져 버린다 (실측). name·timing·iteration 만 여기서, duration 은 조각마다
.cr-wrap.is-demo .cr-piece { animation-name: cr-fall; animation-timing-function: $easing; animation-iteration-count: infinite; }

@media (prefers-reduced-motion: reduce) {
  .cr-wrap.is-demo .cr-piece { 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: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.cr-wrap {
  position: relative;
  width: min(320px, 88vw);
  height: min(220px, 62vh);
  overflow: hidden;
  border-radius: 16px;
  background: rgba(23, 20, 26, 0.06);
}

.cr-banner {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  padding: 16px;
  box-sizing: border-box;
  text-align: center;
  color: #17141a;
  font: 700 18px/1.3 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

.cr-piece {
  position: absolute;
  top: -220px;
  width: 9px;
  height: 16px;
  border-radius: 4px;
  opacity: 0.95;
  animation-duration: 2s;
}

.cr-piece:nth-child(2) {
  left: 5.2631578947%;
  top: -40px;
  background: #ff4d1f;
  animation-duration: 1840ms;
}

.cr-piece:nth-child(3) {
  left: 10.5263157895%;
  top: 160px;
  background: #17141a;
  animation-duration: 1980ms;
}

.cr-piece:nth-child(4) {
  left: 15.7894736842%;
  top: -180px;
  background: #fff7e6;
  animation-duration: 2120ms;
}

.cr-piece:nth-child(5) {
  left: 21.0526315789%;
  top: 20px;
  background: #2f6df6;
  animation-duration: 2260ms;
}

.cr-piece:nth-child(6) {
  left: 26.3157894737%;
  top: 100px;
  background: #ff4d1f;
  animation-duration: 1700ms;
}

.cr-piece:nth-child(7) {
  left: 31.5789473684%;
  top: -120px;
  background: #17141a;
  animation-duration: 1840ms;
}

.cr-piece:nth-child(8) {
  left: 36.8421052632%;
  top: 60px;
  background: #fff7e6;
  animation-duration: 1980ms;
}

.cr-piece:nth-child(9) {
  left: 42.1052631579%;
  top: -200px;
  background: #2f6df6;
  animation-duration: 2120ms;
}

.cr-piece:nth-child(10) {
  left: 47.3684210526%;
  top: 140px;
  background: #ff4d1f;
  animation-duration: 2260ms;
}

.cr-piece:nth-child(11) {
  left: 52.6315789474%;
  top: -20px;
  background: #17141a;
  animation-duration: 1700ms;
}

.cr-piece:nth-child(12) {
  left: 57.8947368421%;
  top: 180px;
  background: #fff7e6;
  animation-duration: 1840ms;
}

.cr-piece:nth-child(13) {
  left: 63.1578947368%;
  top: -100px;
  background: #2f6df6;
  animation-duration: 1980ms;
}

.cr-piece:nth-child(14) {
  left: 68.4210526316%;
  top: 40px;
  background: #ff4d1f;
  animation-duration: 2120ms;
}

.cr-piece:nth-child(15) {
  left: 73.6842105263%;
  top: -160px;
  background: #17141a;
  animation-duration: 2260ms;
}

.cr-piece:nth-child(16) {
  left: 78.9473684211%;
  top: 120px;
  background: #fff7e6;
  animation-duration: 1700ms;
}

.cr-piece:nth-child(17) {
  left: 84.2105263158%;
  top: -60px;
  background: #2f6df6;
  animation-duration: 1840ms;
}

.cr-piece:nth-child(18) {
  left: 89.4736842105%;
  top: 200px;
  background: #ff4d1f;
  animation-duration: 1980ms;
}

.cr-piece:nth-child(19) {
  left: 94.7368421053%;
  top: -140px;
  background: #17141a;
  animation-duration: 2120ms;
}

@keyframes cr-fall {
  0% {
    transform: translateY(0) rotate(0deg);
  }
  100% {
    transform: translateY(520px) rotate(300deg);
  }
}
.cr-wrap.is-demo .cr-piece {
  animation-name: cr-fall;
  animation-timing-function: linear;
  animation-iteration-count: infinite;
}

@media (prefers-reduced-motion: reduce) {
  .cr-wrap.is-demo .cr-piece {
    animation: none !important;
    opacity: 0 !important;
  }
}

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

type Vars = CSSProperties & Record<string, string>;

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

const COLORS = ["var(--color)", "#ff4d1f", "#17141a", "#fff7e6"];
// top 을 left% 순서와 다르게 섞는다 — 둘을 같은 인덱스로 선형 배치하면 낙하가 아니라 대각선 한 줄로 보인다
const TOPS = [-40, 160, -180, 20, 100, -120, 60, -200, 140, -20, 180, -100, 40, -160, 120, -60, 200, -140];

export default function ConfettiRain({
  duration = "2s",
  easing = "linear",
  color = "#2f6df6",
}: ConfettiRainProps) {
  const style: Vars = { "--duration": duration, "--easing": easing, "--color": color };
  return (
    <div className={styles.wrap} style={style}>
      <span className={styles.banner}>당첨을 축하드려요</span>
      {TOPS.map((top, i) => {
        const pieceStyle: Vars = {
          left: `${((i + 1) / (TOPS.length + 1)) * 100}%`,
          top: `${top}px`,
          background: COLORS[i % COLORS.length],
          animationDuration: `${1700 + (i % 5) * 140}ms`,
        };
        return <span key={i} className={styles.piece} style={pieceStyle} />;
      })}
    </div>
  );
}