03Magnetic pull with label offset

<main class="stage">
  <div class="mag__field">
    <button class="mag is-demo" type="button"><span class="mag__label">View projects</span></button>
  </div>
</main>

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

// 변형은 이 세 줄만 바꾼다
$duration: $dur-loop;
$easing:   $ease-spring;
$color:    $subject-blue;

@include stage($stage-paper);

.mag__field {
  display: grid;
  place-items: center;
  padding: $sp-8;
}

.mag {
  border: 0;
  cursor: pointer;
  padding: $sp-4 $sp-8;
  border-radius: $r-control;
  background: $color;
  color: $subject-cream;
  font-family: inherit;
  font-size: clamp(15px, 4.5vw, 19px);
  font-weight: 700;
  box-shadow: $shadow-press;
  transition: translate $dur-quick $easing;
}

.mag__label {
  display: inline-block;
  transition: translate $dur-quick $easing;
}

.mag.is-demo { animation: mag-pull $duration $easing infinite; }
.mag.is-demo .mag__label { animation: mag-drift $duration $easing infinite; }

// 네 지점을 돌고 0 0 으로 돌아온다. 마지막 키프레임을 빼면 한 바퀴마다 제자리로 튄다
@keyframes mag-pull {
  0%   { translate: 0 0; }
  25%  { translate: 22px -8px; }
  50%  { translate: 0 6px; }
  75%  { translate: -22px -8px; }
  100% { translate: 0 0; }
}

// 같은 좌표에 -0.4 를 곱한 값. 부호가 반대라 층이 갈라져 보인다
@keyframes mag-drift {
  0%   { translate: 0 0; }
  25%  { translate: -9px 3px; }
  50%  { translate: 0 -2px; }
  75%  { translate: 9px 3px; }
  100% { translate: 0 0; }
}

@media (prefers-reduced-motion: reduce) {
  .mag.is-demo,
  .mag.is-demo .mag__label { animation: none; }
  .mag,
  .mag__label { transition: none; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffffff;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.mag__field {
  display: grid;
  place-items: center;
  padding: 32px;
}

.mag {
  border: 0;
  cursor: pointer;
  padding: 16px 32px;
  border-radius: 12px;
  background: #2f6df6;
  color: #fff7e6;
  font-family: inherit;
  font-size: clamp(15px, 4.5vw, 19px);
  font-weight: 700;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
  transition: translate 220ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.mag__label {
  display: inline-block;
  transition: translate 220ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.mag.is-demo {
  animation: mag-pull 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

.mag.is-demo .mag__label {
  animation: mag-drift 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

@keyframes mag-pull {
  0% {
    translate: 0 0;
  }
  25% {
    translate: 22px -8px;
  }
  50% {
    translate: 0 6px;
  }
  75% {
    translate: -22px -8px;
  }
  100% {
    translate: 0 0;
  }
}
@keyframes mag-drift {
  0% {
    translate: 0 0;
  }
  25% {
    translate: -9px 3px;
  }
  50% {
    translate: 0 -2px;
  }
  75% {
    translate: 9px 3px;
  }
  100% {
    translate: 0 0;
  }
}
@media (prefers-reduced-motion: reduce) {
  .mag.is-demo,
  .mag.is-demo .mag__label {
    animation: none;
  }
  .mag,
  .mag__label {
    transition: none;
  }
}

// 실제 동작: 커서가 감지 영역에 들어오면 버튼은 커서 쪽으로, 라벨은 그 절반만큼 반대로 움직인다.
var field = document.querySelector('.mag__field');
var btn = document.querySelector('.mag');
var label = document.querySelector('.mag__label');
field.addEventListener('pointermove', function (e) {
  var r = btn.getBoundingClientRect();
  var dx = (e.clientX - (r.left + r.width / 2)) * 0.35;
  var dy = (e.clientY - (r.top + r.height / 2)) * 0.35;
  btn.classList.remove('is-demo');
  btn.style.translate = dx + 'px ' + dy + 'px';
  label.style.translate = (-dx * 0.4) + 'px ' + (-dy * 0.4) + 'px';
});
field.addEventListener('pointerleave', function () {
  btn.style.translate = '';
  label.style.translate = '';
  btn.classList.add('is-demo');
});

import { useState } from "react";
import type { CSSProperties, PointerEvent } from "react";
import styles from "./MagnetButton.module.scss";

export type MagnetButtonProps = {
  label?: string;
  duration?: number;
  easing?: string;
  color?: string;
};

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

export default function MagnetButton({
  label = "View projects",
  duration = 2000,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#2f6df6",
}: MagnetButtonProps) {
  const [pull, setPull] = useState<{ x: number; y: number } | null>(null);

  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  function move(e: PointerEvent<HTMLDivElement>) {
    const btn = e.currentTarget.firstElementChild as HTMLElement | null;
    if (!btn) { return; }
    const r = btn.getBoundingClientRect();
    setPull({
      x: (e.clientX - (r.left + r.width / 2)) * 0.35,
      y: (e.clientY - (r.top + r.height / 2)) * 0.35,
    });
  }

  return (
    <div className={styles.field} style={vars} onPointerMove={move} onPointerLeave={() => setPull(null)}>
      <button
        type="button"
        className={`${styles.mag} ${pull ? "" : styles.loop}`}
        style={pull ? { translate: `${pull.x}px ${pull.y}px` } : undefined}
      >
        <span
          className={`${styles.label} ${pull ? "" : styles.labelLoop}`}
          style={pull ? { translate: `${-pull.x * 0.4}px ${-pull.y * 0.4}px` } : undefined}
        >
          {label}
        </span>
      </button>
    </div>
  );
}