08Mouse-move parallax

<main class="stage is-demo">
  <div class="mousepar">
    <div class="mousepar__layer mousepar__layer--a" style="--depth:.3" aria-hidden="true"></div>
    <div class="mousepar__layer mousepar__layer--b" style="--depth:.6" aria-hidden="true"></div>
    <div class="mousepar__layer mousepar__layer--c" style="--depth:1" aria-hidden="true"></div>
    <p class="mousepar__label">Follows your cursor</p>
  </div>
</main>

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

// ── 변수 3개. 변형은 이것만 바꾼다 ──────────────────────────
$amp: 22px;                                      // 커서 정규화값 1당 이동량
$duration: $dur-loop;                            // 데모 왕복 주기
$color: $subject-blue;                           // 레이어 색 (paper 무대라 blue)

@include stage($stage-paper);

.mousepar {
  position: relative;
  width: 100%;
  height: 100%;
  display: grid;
  place-items: center;
}
.mousepar__layer {
  position: absolute;
  width: 46px;
  height: 46px;
  border-radius: 50%;
  background: rgba($color, .5);
  transition: transform 120ms $ease-out;

  // ── 실제 사용 코드: pointermove 로 받은 --mx·--my 에 레이어별 --depth 를 곱해 이동한다 ──
  &--a { left: 18%; top: 24%; transform: translate(calc(var(--mx, 0) * var(--depth) * #{$amp}), calc(var(--my, 0) * var(--depth) * #{$amp})); }
  &--b { left: 62%; top: 54%; transform: translate(calc(var(--mx, 0) * var(--depth) * #{$amp}), calc(var(--my, 0) * var(--depth) * #{$amp})); }
  &--c { left: 40%; top: 68%; transform: translate(calc(var(--mx, 0) * var(--depth) * #{$amp}), calc(var(--my, 0) * var(--depth) * #{$amp})); }
}
.mousepar__label {
  position: relative;
  z-index: 1;
  margin: 0;
  padding: 12px 20px;
  border-radius: $r-pill;
  background: $stage-ink;
  color: #fff;
  font: 700 clamp(13px, 4.2vw, 16px)/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

// ── 데모(.is-demo): 커서 대신 2초 루프로 흉내 ────────
.stage.is-demo .mousepar__layer--a { animation: loop-a $duration ease-in-out infinite; }
.stage.is-demo .mousepar__layer--b { animation: loop-b $duration ease-in-out infinite; }
.stage.is-demo .mousepar__layer--c { animation: loop-c $duration ease-in-out infinite; }
@keyframes loop-a { 0%, 100% { transform: translate(-10px, -6px); }  50% { transform: translate(10px, 6px); } }
@keyframes loop-b { 0%, 100% { transform: translate(16px, 10px); }   50% { transform: translate(-16px, -10px); } }
@keyframes loop-c { 0%, 100% { transform: translate(-24px, -14px); } 50% { transform: translate(24px, 14px); } }

@media (prefers-reduced-motion: reduce) {
  .mousepar__layer,
  .stage.is-demo .mousepar__layer--a, .stage.is-demo .mousepar__layer--b, .stage.is-demo .mousepar__layer--c {
    animation: none !important;
    transform: none !important;
    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);
}

.mousepar {
  position: relative;
  width: 100%;
  height: 100%;
  display: grid;
  place-items: center;
}

.mousepar__layer {
  position: absolute;
  width: 46px;
  height: 46px;
  border-radius: 50%;
  background: rgba(47, 109, 246, 0.5);
  transition: transform 120ms ease-out;
}
.mousepar__layer--a {
  left: 18%;
  top: 24%;
  transform: translate(calc(var(--mx, 0) * var(--depth) * 22px), calc(var(--my, 0) * var(--depth) * 22px));
}
.mousepar__layer--b {
  left: 62%;
  top: 54%;
  transform: translate(calc(var(--mx, 0) * var(--depth) * 22px), calc(var(--my, 0) * var(--depth) * 22px));
}
.mousepar__layer--c {
  left: 40%;
  top: 68%;
  transform: translate(calc(var(--mx, 0) * var(--depth) * 22px), calc(var(--my, 0) * var(--depth) * 22px));
}

.mousepar__label {
  position: relative;
  z-index: 1;
  margin: 0;
  padding: 12px 20px;
  border-radius: 999px;
  background: #17141a;
  color: #fff;
  font: 700 clamp(13px, 4.2vw, 16px)/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

.stage.is-demo .mousepar__layer--a {
  animation: loop-a 2s ease-in-out infinite;
}

.stage.is-demo .mousepar__layer--b {
  animation: loop-b 2s ease-in-out infinite;
}

.stage.is-demo .mousepar__layer--c {
  animation: loop-c 2s ease-in-out infinite;
}

@keyframes loop-a {
  0%, 100% {
    transform: translate(-10px, -6px);
  }
  50% {
    transform: translate(10px, 6px);
  }
}
@keyframes loop-b {
  0%, 100% {
    transform: translate(16px, 10px);
  }
  50% {
    transform: translate(-16px, -10px);
  }
}
@keyframes loop-c {
  0%, 100% {
    transform: translate(-24px, -14px);
  }
  50% {
    transform: translate(24px, 14px);
  }
}
@media (prefers-reduced-motion: reduce) {
  .mousepar__layer,
  .stage.is-demo .mousepar__layer--a, .stage.is-demo .mousepar__layer--b, .stage.is-demo .mousepar__layer--c {
    animation: none !important;
    transform: none !important;
    transition: none;
  }
}

// 실제 사용: 커서 위치를 -0.5~0.5 로 정규화해 CSS 변수로 넘긴다. 레이어는 --depth 로 배율만 다르게 받는다.
var el = document.querySelector('.mousepar');
el.addEventListener('pointermove', function (e) {
  var r = el.getBoundingClientRect();
  el.style.setProperty('--mx', ((e.clientX - r.left) / r.width - 0.5).toFixed(3));
  el.style.setProperty('--my', ((e.clientY - r.top) / r.height - 0.5).toFixed(3));
});

import { useCallback, useRef } from "react";
import type { CSSProperties, PointerEvent, ReactNode } from "react";
import styles from "./MouseParallax.module.scss";

export type MouseParallaxProps = {
  children: ReactNode;
  /** 커서 정규화값 1당 이동량 (기본 22px) */
  amp?: number;
  /** 레이어 색 */
  color?: string;
  className?: string;
};

type Vars = CSSProperties & { "--amp"?: string; "--color"?: string; "--mx"?: string; "--my"?: string };

export default function MouseParallax({ children, amp = 22, color = "#2f6df6", className = "" }: MouseParallaxProps) {
  const ref = useRef<HTMLDivElement>(null);

  const handle = useCallback((e: PointerEvent<HTMLDivElement>) => {
    const r = e.currentTarget.getBoundingClientRect();
    ref.current?.style.setProperty("--mx", `${(e.clientX - r.left) / r.width - 0.5}`);
    ref.current?.style.setProperty("--my", `${(e.clientY - r.top) / r.height - 0.5}`);
  }, []);

  const vars: Vars = { "--amp": `${amp}px`, "--color": color };

  return (
    <div ref={ref} className={`${styles.wrap} ${className}`} style={vars} onPointerMove={handle}>
      <div className={styles.layer} style={{ "--depth": ".3", left: "18%", top: "24%" } as Vars} aria-hidden="true" />
      <div className={styles.layer} style={{ "--depth": ".6", left: "62%", top: "54%" } as Vars} aria-hidden="true" />
      <div className={styles.layer} style={{ "--depth": "1", left: "40%", top: "68%" } as Vars} aria-hidden="true" />
      <p className={styles.label}>{children}</p>
    </div>
  );
}