09Stagger utility

<main class="stage">
  <ul class="list is-demo">
    <li class="list__item" style="--i:0">A new comment was posted</li>
    <li class="list__item" style="--i:1">You have a new follower</li>
    <li class="list__item" style="--i:2">Payment completed</li>
  </ul>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: 400ms;
$easing: ease-out;
$color: $subject-cream;

// ── 데모 무대 ──────────────────────────────────────────
@include stage($stage-ink);

.list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: $sp-2;
  width: min(280px, 88vw);
}

.list__item {
  padding: $sp-2 $sp-4;
  border-radius: $r-sm;
  background: rgba($subject-cream, .08);
  color: $color;
  font-weight: 500;
  font-size: clamp(12px, 3.4vw, 14px);
  line-height: 1.3;
  font-family: inherit;
  opacity: 0;
  transform: translateY(10px);
}

// 실사용: 각 항목의 --i 만 바꿔 [animation-delay:calc(var(--i)*80ms)] 로 순서를 만든다
.list.is-demo .list__item {
  animation: stagger-in-loop 2s $easing infinite;
  animation-delay: calc(var(--i) * 80ms);
}

@keyframes stagger-in-loop {
  0%   { opacity: 0; transform: translateY(10px); }
  20%  { opacity: 1; transform: translateY(0); }
  75%  { opacity: 1; transform: translateY(0); }
  100% { opacity: 0; transform: translateY(10px); }
}

// 실사용 단발 버전
.list.is-appear .list__item {
  animation: stagger-in $duration $easing both;
  animation-delay: calc(var(--i) * 80ms);
}

@keyframes stagger-in {
  from { opacity: 0; transform: translateY(10px); }
  to   { opacity: 1; transform: translateY(0); }
}

// ── 접근성 ──────────────────────────────────────────
@media (prefers-reduced-motion: reduce) {
  .list__item { animation: none !important; opacity: 1; transform: none; }
}

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);
}

.list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: min(280px, 88vw);
}

.list__item {
  padding: 8px 16px;
  border-radius: 8px;
  background: rgba(255, 247, 230, 0.08);
  color: #fff7e6;
  font-weight: 500;
  font-size: clamp(12px, 3.4vw, 14px);
  line-height: 1.3;
  font-family: inherit;
  opacity: 0;
  transform: translateY(10px);
}

.list.is-demo .list__item {
  animation: stagger-in-loop 2s ease-out infinite;
  animation-delay: calc(var(--i) * 80ms);
}

@keyframes stagger-in-loop {
  0% {
    opacity: 0;
    transform: translateY(10px);
  }
  20% {
    opacity: 1;
    transform: translateY(0);
  }
  75% {
    opacity: 1;
    transform: translateY(0);
  }
  100% {
    opacity: 0;
    transform: translateY(10px);
  }
}
.list.is-appear .list__item {
  animation: stagger-in 400ms ease-out both;
  animation-delay: calc(var(--i) * 80ms);
}

@keyframes stagger-in {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}
@media (prefers-reduced-motion: reduce) {
  .list__item {
    animation: none !important;
    opacity: 1;
    transform: none;
  }
}

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

export type StaggerUtilListProps = {
  items?: string[];
  duration?: number;
  /** 항목 사이 지연, ms — [animation-delay:calc(var(--i)*80ms)] 의 80 */
  step?: number;
  easing?: string;
  color?: string;
};

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

export default function StaggerUtilList({
  items = [
    "A new comment was posted",
    "You have a new follower",
    "Payment completed",
  ],
  duration = 400,
  step = 80,
  easing = "ease-out",
  color = "#fff7e6",
}: StaggerUtilListProps) {
  const vars: Vars = {
    "--duration": `${duration}ms`,
    "--step": `${step}ms`,
    "--easing": easing,
    "--color": color,
  };
  return (
    <ul className={styles.list} style={vars}>
      {items.map((text, i) => {
        const itemVars: ItemVars = { "--i": i };
        return (
          <li key={text} className={styles.list__item} style={itemVars}>
            {text}
          </li>
        );
      })}
    </ul>
  );
}