03Scale pop-in

<main class="stage">
  <h2 class="sp-text is-demo">LAUNCHING SOON</h2>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: $dur-loop;
$easing: $ease-pop;
$color: $subject-cream;

@include stage($stage-orange);

.sp-text {
  margin: 0;
  font: 800 clamp(22px, 7vw, 34px)/1.2 -apple-system, "Segoe UI", sans-serif;
  color: $color;
  text-align: center;
  opacity: 0;
  transform: scale(.4);
}

// 데모 루프: 작게 눌려 있다가 살짝 커졌다 제자리로 돌아오며 튕기듯 나타난다
// 한 겹: 관성 lerp — 등장 구간(0→18%)을 $ease-lerp-settle 로 목표를 12.6% 넘겼다 되돌아오게 한다.
@keyframes sp-pop {
  0% { opacity: 0; transform: scale(.4); animation-timing-function: $ease-lerp-settle; }
  18% { opacity: 1; transform: scale(1.1); }
  30% { transform: scale(.96); }
  40%, 78% { transform: scale(1); opacity: 1; }
  100% { opacity: 0; transform: scale(.4); }
}

.sp-text.is-demo { animation: sp-pop $duration $easing infinite; }

@media (prefers-reduced-motion: reduce) {
  .sp-text,
  .sp-text.is-demo {
    animation: none !important;
    opacity: 1 !important;
    transform: none !important;
  }
}

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);
}

.sp-text {
  margin: 0;
  font: 800 clamp(22px, 7vw, 34px)/1.2 -apple-system, "Segoe UI", sans-serif;
  color: #fff7e6;
  text-align: center;
  opacity: 0;
  transform: scale(0.4);
}

@keyframes sp-pop {
  0% {
    opacity: 0;
    transform: scale(0.4);
    animation-timing-function: linear(0, 0.051, 0.176, 0.341, 0.518, 0.685, 0.831, 0.947, 1.032, 1.087, 1.117, 1.126, 1.121, 1.105, 1.085, 1.062, 1.041, 1.022, 1.008, 0.997, 1);
  }
  18% {
    opacity: 1;
    transform: scale(1.1);
  }
  30% {
    transform: scale(0.96);
  }
  40%, 78% {
    transform: scale(1);
    opacity: 1;
  }
  100% {
    opacity: 0;
    transform: scale(0.4);
  }
}
.sp-text.is-demo {
  animation: sp-pop 2s cubic-bezier(0.2, 1.4, 0.4, 1) infinite;
}

@media (prefers-reduced-motion: reduce) {
  .sp-text,
  .sp-text.is-demo {
    animation: none !important;
    opacity: 1 !important;
    transform: none !important;
  }
}

import { CSSProperties, useEffect, useRef, useState } from "react";
import styles from "./ScalePopIn.module.scss";

export interface ScalePopInProps {
  text?: string;
  duration?: string;
  easing?: string;
}

// 실사용: 뷰포트에 들어오면 작게 눌려 있던 글자가 한 번 튕기듯 커지며 자리 잡는다.
export default function ScalePopIn({
  text = "LAUNCHING SOON",
  duration = "550ms",
  easing = "cubic-bezier(.2, 1.4, .4, 1)",
}: ScalePopInProps) {
  const ref = useRef<HTMLHeadingElement>(null);
  const [inView, setInView] = useState(false);

  useEffect(() => {
    const el = ref.current;
    if (!el) return;
    const io = new IntersectionObserver((entries) => {
      entries.forEach((e) => { if (e.isIntersecting) { setInView(true); io.unobserve(e.target); } });
    }, { threshold: 0.3 });
    io.observe(el);
    return () => io.disconnect();
  }, []);

  const style = { "--duration": duration, "--easing": easing } as CSSProperties;

  return (
    <h2 className={`${styles.text} ${inView ? styles.in : ""}`} style={style} ref={ref}>
      {text}
    </h2>
  );
}