07--i変数とcalc()一行

<main class="stage">
  <ul class="i-list is-demo">
    <li style="--i:0">項目1</li>
    <li style="--i:1">項目2</li>
    <li style="--i:2">項目3</li>
    <li style="--i:3">項目4</li>
  </ul>
</main>

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

$duration: $dur-quick;                             // 항목 하나가 나타나는 시간
$easing: $ease-out;                                // 시작 빠르고 끝은 부드럽게
$stagger: 80ms;                                    // --i 1당 시차

@include stage($stage-orange);

.i-list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 8px;
  max-width: min(360px, 88vw);
  font-weight: 600; font-size: clamp(12px, 3.4vw, 15px); line-height: 1.2; font-family: inherit;

  li {
    padding: clamp(8px, 2.6vw, 11px) clamp(12px, 3.4vw, 16px);
    border-radius: $r-control;
    background: $subject-cream;
    color: $stage-ink;
    box-shadow: $shadow-raised;
    animation: i-loop $dur-loop $easing infinite;
    animation-delay: calc(var(--i) * #{$stagger});   // ← --i 변수 + calc 한 줄
  }
}

@keyframes i-loop {
  0%, 6%    { opacity: 0; transform: translateY(10px); }
  22%, 68%  { opacity: 1; transform: translateY(0); }
  88%, 100% { opacity: 0; transform: translateY(6px); }
}

@media (prefers-reduced-motion: reduce) {
  .i-list li { animation: none; 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: #ff4d1f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.i-list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 8px;
  max-width: min(360px, 88vw);
  font-weight: 600;
  font-size: clamp(12px, 3.4vw, 15px);
  line-height: 1.2;
  font-family: inherit;
}
.i-list li {
  padding: clamp(8px, 2.6vw, 11px) clamp(12px, 3.4vw, 16px);
  border-radius: 12px;
  background: #fff7e6;
  color: #17141a;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  animation: i-loop 2s ease-out infinite;
  animation-delay: calc(var(--i) * 80ms);
}

@keyframes i-loop {
  0%, 6% {
    opacity: 0;
    transform: translateY(10px);
  }
  22%, 68% {
    opacity: 1;
    transform: translateY(0);
  }
  88%, 100% {
    opacity: 0;
    transform: translateY(6px);
  }
}
@media (prefers-reduced-motion: reduce) {
  .i-list li {
    animation: none;
    opacity: 1;
    transform: none;
  }
}

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

type Vars = CSSProperties & { "--i"?: number };

export type CustomPropertyListProps = {
  items: string[];
  /** --i 1당 시차 ms (기본 80ms) — CSS 쪽 calc(var(--i) * 80ms) 한 줄이 실제 계산을 한다 */
  stagger?: number;
};

export default function CustomPropertyList({ items }: CustomPropertyListProps) {
  return (
    <ul className={styles.list}>
      {items.map((label, i) => (
        <li key={label} style={{ "--i": i } as Vars}>
          {label}
        </li>
      ))}
    </ul>
  );
}