05Con trỏ mix-blend-mode

<main class="stage">
  <div class="half half--left"></div>
  <div class="half half--right"></div>
  <p class="banner">Đảo màu</p>
  <div class="cursor is-demo" aria-hidden="true"></div>
</main>

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

$duration: $dur-loop;                                 // 원이 두 영역을 오가는 한 바퀴
$easing: $ease-spring;
$color: $stage-paper;                                  // 블렌드 원은 흰색이어야 difference 가 또렷하다

@include stage($stage-ink);

.stage { position: relative; overflow: hidden; cursor: none; }

.half {
  position: absolute;
  top: 0;
  bottom: 0;
  width: 50%;
  z-index: 0;
}
.half--left  { left: 0; background: $stage-ink; }
.half--right { right: 0; background: $subject-blue; }

.banner {
  position: relative;
  z-index: 1;
  margin: 0;
  font-weight: 800; font-size: clamp(34px, 11vw, 56px); line-height: 1; font-family: inherit;
  color: $subject-cream;
  letter-spacing: -.02em;
}

.cursor {
  position: absolute;
  top: 0;
  left: 0;
  z-index: 2;
  width: 70px;
  height: 70px;
  margin: -35px 0 0 -35px;
  border-radius: 50%;
  background: $color;
  mix-blend-mode: difference;                          // 지나가는 배경 색을 반전시킨다
  pointer-events: none;

  &.is-demo { animation: cursor-path $duration $easing infinite; }
}

@keyframes cursor-path {
  0%   { transform: translate(80px, 60px); }
  35%  { transform: translate(280px, 150px); }          // 오른쪽 영역으로 넘어간다
  70%  { transform: translate(120px, 200px); }
  100% { transform: translate(80px, 60px); }
}

@media (pointer: coarse) {
  .cursor { display: none; }
  .stage { cursor: auto; }
}

@media (prefers-reduced-motion: reduce) {
  .cursor.is-demo { animation: none; transform: translate(80px, 60px); }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.stage {
  position: relative;
  overflow: hidden;
  cursor: none;
}

.half {
  position: absolute;
  top: 0;
  bottom: 0;
  width: 50%;
  z-index: 0;
}

.half--left {
  left: 0;
  background: #17141a;
}

.half--right {
  right: 0;
  background: #2f6df6;
}

.banner {
  position: relative;
  z-index: 1;
  margin: 0;
  font-weight: 800;
  font-size: clamp(34px, 11vw, 56px);
  line-height: 1;
  font-family: inherit;
  color: #fff7e6;
  letter-spacing: -0.02em;
}

.cursor {
  position: absolute;
  top: 0;
  left: 0;
  z-index: 2;
  width: 70px;
  height: 70px;
  margin: -35px 0 0 -35px;
  border-radius: 50%;
  background: #ffffff;
  mix-blend-mode: difference;
  pointer-events: none;
}
.cursor.is-demo {
  animation: cursor-path 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

@keyframes cursor-path {
  0% {
    transform: translate(80px, 60px);
  }
  35% {
    transform: translate(280px, 150px);
  }
  70% {
    transform: translate(120px, 200px);
  }
  100% {
    transform: translate(80px, 60px);
  }
}
@media (pointer: coarse) {
  .cursor {
    display: none;
  }
  .stage {
    cursor: auto;
  }
}
@media (prefers-reduced-motion: reduce) {
  .cursor.is-demo {
    animation: none;
    transform: translate(80px, 60px);
  }
}

// 실제 포인터가 움직이면 블렌드 원이 그 좌표를 따라가며 지나는 배경 색을 반전시킨다.
if (matchMedia('(pointer: fine)').matches) {
  var stage = document.querySelector('.stage'), cur = document.querySelector('.cursor');
  stage.addEventListener('pointermove', function (e) {
    cur.classList.remove('is-demo');
    var r = stage.getBoundingClientRect();
    cur.style.transform = 'translate(' + (e.clientX - r.left) + 'px,' + (e.clientY - r.top) + 'px)';
  });
}

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

export type BlendModeCursorProps = {
  text?: string;
  duration?: number;
  easing?: string;
  color?: string;
};

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

export default function BlendModeCursor({
  text = "반전",
  duration = 2000,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#ffffff",
}: BlendModeCursorProps) {
  const [demo, setDemo] = useState(true);
  const [pos, setPos] = useState({ x: 80, y: 60 });

  const move = (e: PointerEvent<HTMLDivElement>) => {
    const r = e.currentTarget.getBoundingClientRect();
    setDemo(false);
    setPos({ x: e.clientX - r.left, y: e.clientY - r.top });
  };

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

  return (
    <div className={styles.stage} style={vars} onPointerMove={move}>
      <div className={`${styles.half} ${styles.halfLeft}`} />
      <div className={`${styles.half} ${styles.halfRight}`} />
      <p className={styles.banner}>{text}</p>
      <div
        className={demo ? `${styles.cursor} ${styles.isDemo}` : styles.cursor}
        style={demo ? undefined : { transform: `translate(${pos.x}px,${pos.y}px)` }}
        aria-hidden="true"
      />
    </div>
  );
}