06Circular ripple stagger

<main class="stage">
  <div class="ripple is-demo">
    <span></span><span></span><span></span>
    <span></span><span></span><span></span>
    <span></span><span></span><span></span>
  </div>
</main>

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

$duration: $dur-base;                              // 점 하나가 커지는 시간
$easing: $ease-out;                                // 시작 빠르고 끝은 부드럽게
$step: 90ms;                                       // 중심 거리 1당 시차 계수

@include stage($stage-yellow);

.ripple {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: clamp(10px, 3vw, 16px);
  width: min(160px, 55vw);
  aspect-ratio: 1;

  span {
    border-radius: 50%;
    background: $stage-ink;
    animation: ripple-loop $dur-loop $easing infinite;
  }

  // 3×3, 중심(칸 5)까지의 거리 × $step — 코너는 √2, 변은 1, 중심은 0
  span:nth-child(1) { animation-delay: $step * 1.41; }
  span:nth-child(2) { animation-delay: $step * 1; }
  span:nth-child(3) { animation-delay: $step * 1.41; }
  span:nth-child(4) { animation-delay: $step * 1; }
  span:nth-child(5) { animation-delay: 0ms; }
  span:nth-child(6) { animation-delay: $step * 1; }
  span:nth-child(7) { animation-delay: $step * 1.41; }
  span:nth-child(8) { animation-delay: $step * 1; }
  span:nth-child(9) { animation-delay: $step * 1.41; }
}

@keyframes ripple-loop {
  0%, 4%    { opacity: 0; transform: scale(.3); }
  24%, 58%  { opacity: 1; transform: scale(1); }
  84%, 100% { opacity: 0; transform: scale(.6); }
}

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

.ripple {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: clamp(10px, 3vw, 16px);
  width: min(160px, 55vw);
  aspect-ratio: 1;
}
.ripple span {
  border-radius: 50%;
  background: #17141a;
  animation: ripple-loop 2s ease-out infinite;
}
.ripple span:nth-child(1) {
  animation-delay: 126.9ms;
}
.ripple span:nth-child(2) {
  animation-delay: 90ms;
}
.ripple span:nth-child(3) {
  animation-delay: 126.9ms;
}
.ripple span:nth-child(4) {
  animation-delay: 90ms;
}
.ripple span:nth-child(5) {
  animation-delay: 0ms;
}
.ripple span:nth-child(6) {
  animation-delay: 90ms;
}
.ripple span:nth-child(7) {
  animation-delay: 126.9ms;
}
.ripple span:nth-child(8) {
  animation-delay: 90ms;
}
.ripple span:nth-child(9) {
  animation-delay: 126.9ms;
}

@keyframes ripple-loop {
  0%, 4% {
    opacity: 0;
    transform: scale(0.3);
  }
  24%, 58% {
    opacity: 1;
    transform: scale(1);
  }
  84%, 100% {
    opacity: 0;
    transform: scale(0.6);
  }
}
@media (prefers-reduced-motion: reduce) {
  .ripple span {
    animation: none;
    opacity: 1;
    transform: none;
  }
}

import styles from "./CircularRipple.module.scss";

// 3×3, 중심(인덱스 4)까지의 거리 — 코너는 √2, 변은 1, 중심은 0
const DIST = [Math.SQRT2, 1, Math.SQRT2, 1, 0, 1, Math.SQRT2, 1, Math.SQRT2];

export type CircularRippleProps = {
  /** 중심 거리 1당 시차 ms (기본 90ms) */
  step?: number;
};

export default function CircularRipple({ step = 90 }: CircularRippleProps) {
  return (
    <div className={styles.ripple}>
      {DIST.map((d, i) => (
        <span key={i} style={{ animationDelay: `${d * step}ms` }} />
      ))}
    </div>
  );
}