04Magnetic

<main class="stage">
  <span class="cursor is-demo" aria-hidden="true"></span>
  <button class="btn is-demo" type="button">Get started</button>
</main>

// ── 변수 3개 (JS 가 --radius --strength 를 읽는다) ─────────
$radius: 120px;                                  // 이 안에 들어오면 끌린다
$strength: .35;                                  // 1 이면 커서에 붙는다
$duration: 160ms;

html, body { margin: 0; overflow: hidden; }          // iframe 안에서 스크롤바가 생기지 않게 (실측 2026-09-09: body 여백 8px 이 100vh 를 넘겼다)
.stage { min-height: 100vh; display: grid; place-items: center; margin: 0; background: #17141a; font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif; position: relative; }

.btn {
  --radius: #{$radius};
  --strength: #{$strength};
  border: 0;
  border-radius: 999px;
  padding: 22px 56px;
  font-weight: 800;
  font-size: 20px;
  line-height: 1;
  font-family: inherit;
  color: #17141a;
  background: #fff7e6;
  cursor: pointer;
  will-change: transform;
  transition: transform $duration ease-out;      // 커서를 따라가는 부드러움

  &.is-demo { animation: magnet-loop 2s ease-in-out infinite; }
}

// 데모용 가짜 커서. zip 에서는 지운다
.cursor {
  position: absolute;
  left: 50%; top: 50%;
  width: 14px; height: 14px;
  border-radius: 50%;
  background: #d2c7a4;
  pointer-events: none;
  &.is-demo { animation: cursor-loop 2s ease-in-out infinite; }
}

@keyframes magnet-loop {
  0%   { transform: translate(0, 0); }
  30%  { transform: translate(18px, -10px); }
  60%  { transform: translate(-14px, 12px); }
  100% { transform: translate(0, 0); }
}
@keyframes cursor-loop {
  0%   { transform: translate(-50%, -50%) translate(0, 0); }
  30%  { transform: translate(-50%, -50%) translate(52px, -28px); }
  60%  { transform: translate(-50%, -50%) translate(-40px, 34px); }
  100% { transform: translate(-50%, -50%) translate(0, 0); }
}

@media (prefers-reduced-motion: reduce) {
  .btn, .btn.is-demo, .cursor.is-demo { transition: none; animation: none; transform: none !important; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  position: relative;
}

.btn {
  --radius: 120px;
  --strength: 0.35;
  border: 0;
  border-radius: 999px;
  padding: 22px 56px;
  font-weight: 800;
  font-size: 20px;
  line-height: 1;
  font-family: inherit;
  color: #17141a;
  background: #fff7e6;
  cursor: pointer;
  will-change: transform;
  transition: transform 160ms ease-out;
}
.btn.is-demo {
  animation: magnet-loop 2s ease-in-out infinite;
}

.cursor {
  position: absolute;
  left: 50%;
  top: 50%;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: #d2c7a4;
  pointer-events: none;
}
.cursor.is-demo {
  animation: cursor-loop 2s ease-in-out infinite;
}

@keyframes magnet-loop {
  0% {
    transform: translate(0, 0);
  }
  30% {
    transform: translate(18px, -10px);
  }
  60% {
    transform: translate(-14px, 12px);
  }
  100% {
    transform: translate(0, 0);
  }
}
@keyframes cursor-loop {
  0% {
    transform: translate(-50%, -50%) translate(0, 0);
  }
  30% {
    transform: translate(-50%, -50%) translate(52px, -28px);
  }
  60% {
    transform: translate(-50%, -50%) translate(-40px, 34px);
  }
  100% {
    transform: translate(-50%, -50%) translate(0, 0);
  }
}
@media (prefers-reduced-motion: reduce) {
  .btn, .btn.is-demo, .cursor.is-demo {
    transition: none;
    animation: none;
    transform: none !important;
  }
}

// 커서가 반경(radius) 안에 오면 버튼이 커서 쪽으로 strength 만큼 끌려온다. 값은 CSS 변수로 읽는다.
var btn = document.querySelector('.btn'), cur = document.querySelector('.cursor');
var cs = getComputedStyle(btn);
var radius = parseFloat(cs.getPropertyValue('--radius')) || 120;
var strength = parseFloat(cs.getPropertyValue('--strength')) || 0.35;
document.addEventListener('pointermove', function (e) {
  btn.classList.remove('is-demo'); cur.classList.remove('is-demo'); cur.style.display = 'none';
  var r = btn.getBoundingClientRect();
  var dx = e.clientX - (r.left + r.width / 2), dy = e.clientY - (r.top + r.height / 2);
  var d = Math.hypot(dx, dy);
  if (d < radius) btn.style.transform = 'translate(' + dx * strength + 'px,' + dy * strength + 'px)';
  else btn.style.transform = '';
});

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

export type MagneticButtonProps = { children: ReactNode; radius?: number; strength?: number; duration?: number; onClick?: () => void };

export default function MagneticButton({ children, radius = 120, strength = 0.35, duration = 160, onClick }: MagneticButtonProps) {
  const ref = useRef<HTMLButtonElement>(null);
  useEffect(() => {
    const el = ref.current;
    if (!el) return;
    const move = (e: PointerEvent) => {
      const r = el.getBoundingClientRect();
      const dx = e.clientX - (r.left + r.width / 2), dy = e.clientY - (r.top + r.height / 2);
      el.style.transform = Math.hypot(dx, dy) < radius ? `translate(${dx * strength}px, ${dy * strength}px)` : "";
    };
    document.addEventListener("pointermove", move);
    return () => document.removeEventListener("pointermove", move);
  }, [radius, strength]);
  const vars = { "--duration": `${duration}ms` } as CSSProperties;
  return (
    <button ref={ref} type="button" className={styles.btn} style={vars} onClick={onClick}>
      {children}
    </button>
  );
}