06Cursor trail

<main class="stage">
  <div class="trail is-demo" aria-hidden="true">
    <span></span><span></span><span></span><span></span><span></span><span></span>
  </div>
  <div class="cursor is-demo" aria-hidden="true"></div>
</main>

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

$duration: $dur-loop;                                 // 경로를 한 바퀴 도는 시간
$easing: $ease-spring;
$color: $subject-ink;                                  // 점 색

@include stage($stage-yellow);

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

.cursor {
  position: absolute;
  top: 0;
  left: 0;
  width: 10px;
  height: 10px;
  margin: -5px 0 0 -5px;
  border-radius: 50%;
  background: $color;
  pointer-events: none;

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

.trail span {
  position: absolute;
  top: 0;
  left: 0;
  width: 8px;
  height: 8px;
  margin: -4px 0 0 -4px;
  border-radius: 50%;
  background: $color;
  pointer-events: none;
}

// 점마다 같은 경로를 시차(음수 delay)를 두고 돌아 순간마다 서로 다른 위치에 있게 되고, 그게 꼬리로 보인다.
@for $i from 1 through 6 {
  .trail.is-demo span:nth-child(#{$i}) {
    opacity: 1 - $i * .13;
    animation: cursor-path $duration $easing infinite;
    animation-delay: -#{$i * 90}ms;
  }
}

@keyframes cursor-path {
  0%   { transform: translate(40px, 200px); }
  30%  { transform: translate(140px, 60px); }
  60%  { transform: translate(260px, 180px); }
  100% { transform: translate(40px, 200px); }
}

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

@media (prefers-reduced-motion: reduce) {
  .cursor.is-demo { animation: none; transform: translate(40px, 200px); }
  .trail.is-demo span { animation: none; opacity: 0; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

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

.cursor {
  position: absolute;
  top: 0;
  left: 0;
  width: 10px;
  height: 10px;
  margin: -5px 0 0 -5px;
  border-radius: 50%;
  background: #17141a;
  pointer-events: none;
}
.cursor.is-demo {
  animation: cursor-path 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

.trail span {
  position: absolute;
  top: 0;
  left: 0;
  width: 8px;
  height: 8px;
  margin: -4px 0 0 -4px;
  border-radius: 50%;
  background: #17141a;
  pointer-events: none;
}

.trail.is-demo span:nth-child(1) {
  opacity: 0.87;
  animation: cursor-path 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: -90ms;
}

.trail.is-demo span:nth-child(2) {
  opacity: 0.74;
  animation: cursor-path 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: -180ms;
}

.trail.is-demo span:nth-child(3) {
  opacity: 0.61;
  animation: cursor-path 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: -270ms;
}

.trail.is-demo span:nth-child(4) {
  opacity: 0.48;
  animation: cursor-path 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: -360ms;
}

.trail.is-demo span:nth-child(5) {
  opacity: 0.35;
  animation: cursor-path 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: -450ms;
}

.trail.is-demo span:nth-child(6) {
  opacity: 0.22;
  animation: cursor-path 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: -540ms;
}

@keyframes cursor-path {
  0% {
    transform: translate(40px, 200px);
  }
  30% {
    transform: translate(140px, 60px);
  }
  60% {
    transform: translate(260px, 180px);
  }
  100% {
    transform: translate(40px, 200px);
  }
}
@media (pointer: coarse) {
  .cursor, .trail {
    display: none;
  }
  .stage {
    cursor: auto;
  }
}
@media (prefers-reduced-motion: reduce) {
  .cursor.is-demo {
    animation: none;
    transform: translate(40px, 200px);
  }
  .trail.is-demo span {
    animation: none;
    opacity: 0;
  }
}

// 실제 포인터를 움직이면 맨 앞 점이 그 좌표를 따라간다. 꼬리 점들은 같은 경로를 시차를 두고 도는 채로 남는다.
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 "./CursorTrail.module.scss";

export type CursorTrailProps = {
  dots?: number;
  duration?: number;
  easing?: string;
  color?: string;
};

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

export default function CursorTrail({
  dots = 6,
  duration = 2000,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#17141a",
}: CursorTrailProps) {
  const [demo, setDemo] = useState(true);
  const [pos, setPos] = useState({ x: 40, y: 200 });

  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}>
      {demo &&
        Array.from({ length: dots }).map((_, i) => (
          <span
            key={i}
            className={styles.trailDot}
            style={{ opacity: 1 - (i + 1) * 0.13, animationDelay: `${-(i + 1) * 90}ms` }}
          />
        ))}
      <div
        className={demo ? `${styles.cursor} ${styles.isDemo}` : styles.cursor}
        style={demo ? undefined : { transform: `translate(${pos.x}px,${pos.y}px)` }}
        aria-hidden="true"
      />
    </div>
  );
}