06Noise grain overlay

<main class="stage">
  <p class="hint">Premium card</p>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: $dur-loop;                                // 그레인 지글거림이 한 바퀴 도는 시간
$easing: steps(40);                                   // 프레임을 건너뛰어야 그레인처럼 보인다 (부드러운 이징 금지)
$color: $stage-ink;                                    // 그레인 점 색

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

.stage {
  position: relative;
  overflow: hidden;
}

// 아주 작은 conic-gradient 타일을 반복시키고 background-position 을 steps() 로 매 프레임 건너뛴다
.stage::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: repeating-conic-gradient(from 0deg, rgba($color, .55) 0deg 90deg, transparent 90deg 180deg);
  background-size: 3px 3px;
  opacity: .35;
  animation: grain $duration $easing infinite;
}

.hint {
  position: relative;
  margin: 0;
  padding: 10px 20px;
  border-radius: $r-pill;
  background: rgba($stage-ink, .12);
  color: $stage-ink;
  font: 700 clamp(14px, 4vw, 18px)/1.3 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

@keyframes grain {
  from { background-position: 0 0; }
  to   { background-position: 117px 69px; }
}

@media (prefers-reduced-motion: reduce) {
  .stage::before { animation: 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);
}

.stage {
  position: relative;
  overflow: hidden;
}

.stage::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: repeating-conic-gradient(from 0deg, rgba(23, 20, 26, 0.55) 0deg 90deg, transparent 90deg 180deg);
  background-size: 3px 3px;
  opacity: 0.35;
  animation: grain 2s steps(40) infinite;
}

.hint {
  position: relative;
  margin: 0;
  padding: 10px 20px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.12);
  color: #17141a;
  font: 700 clamp(14px, 4vw, 18px)/1.3 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

@keyframes grain {
  from {
    background-position: 0 0;
  }
  to {
    background-position: 117px 69px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .stage::before {
    animation: none;
  }
}

import type { CSSProperties, ReactNode } from "react";
import styles from "./NoiseGrainBg.module.scss";

export type NoiseGrainBgProps = {
  children?: ReactNode;
  /** 그레인 지글거림이 한 바퀴 도는 시간 (기본 2000ms) */
  duration?: number;
  /** 그레인 점 색 */
  color?: string;
  className?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--color"?: string };

export default function NoiseGrainBg({
  children,
  duration = 2000,
  color = "#17141a",
  className = "",
}: NoiseGrainBgProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--color": color };
  return (
    <div className={`${styles.stage} ${className}`} style={vars}>
      <div className={styles.grain} aria-hidden="true" />
      {children}
    </div>
  );
}