07Gradient border reveal

<main class="stage">
  <article class="card is-demo" tabindex="0">
    <span class="card__border" aria-hidden="true"></span>
    <div class="card__inner">
      <h3 class="card__title">Recommended plan</h3>
      <p class="card__meta">Most popular choice</p>
    </div>
  </article>
</main>

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

$duration: $dur-base;                                 // 테두리가 나타나는 시간
$easing: $ease-out;
$color: $subject-blue;                                 // 그라데이션 시작 색

@include stage($stage-orange);
.stage { padding: clamp(6px, 2.4vw, 16px); }

@property --mx { syntax: "<percentage>"; inherits: true; initial-value: 50%; }
@property --my { syntax: "<percentage>"; inherits: true; initial-value: 50%; }
@property --sp { syntax: "<number>"; inherits: true; initial-value: 0; }
@property --rx { syntax: "<angle>"; inherits: true; initial-value: 0deg; }
@property --ry { syntax: "<angle>"; inherits: true; initial-value: 0deg; }

.card {
  position: relative;
  width: min(190px, 58vw);
  border-radius: $r-card;
  padding: 2px;
  outline: none;
  cursor: pointer;
  isolation: isolate;
  transform: perspective(800px) rotateX(var(--rx, 0deg)) rotateY(var(--ry, 0deg));
  transition: transform $duration $easing;
}
.card::after {
  content: '';
  position: absolute;
  inset: 0;
  border-radius: inherit;
  pointer-events: none;
  background: radial-gradient(120px circle at var(--mx) var(--my), rgba(255, 255, 255, .32), transparent 70%);
  opacity: var(--sp);
}
.card__border {
  position: absolute;
  inset: 0;
  border-radius: $r-card;
  padding: 2px;
  background: linear-gradient(135deg, $color, $subject-cream);
  -webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  -webkit-mask-composite: xor;
  mask-composite: exclude;
  opacity: 0;
  transition: opacity $duration $easing;
}
.card__inner {
  position: relative;
  border: 2px solid rgba($stage-ink, .12);
  border-radius: $r-card - 2px;
  background: $stage-paper;
  padding: 14px 12px;
}
.card__title { margin: 0 0 4px; font-weight: 700; font-size: clamp(12px, 3.4vw, 14px); line-height: 1.3; font-family: inherit; color: $stage-ink; }
.card__meta { margin: 0; font-weight: 500; font-size: clamp(11px, 3vw, 12px); line-height: 1.3; font-family: inherit; color: rgba($stage-ink, .6); }

.card:hover .card__border,
.card:focus-visible .card__border,
.card:active .card__border,
.card.is-demo .card__border {
  opacity: 1;
}
.card.is-demo .card__border { animation: glow-loop $dur-loop $easing infinite; }
.card.is-demo { animation: spot-loop $dur-loop $easing infinite, tilt-loop $dur-loop $easing infinite; }

@keyframes glow-loop {
  0%, 20%  { opacity: 0; }
  50%, 75% { opacity: 1; }
  100%     { opacity: 0; }
}
@keyframes spot-loop {
  0%, 15%   { --sp: 0; --mx: 15%; --my: 20%; }
  30%       { --sp: 1; }
  50%       { --mx: 85%; --my: 30%; }
  70%       { --mx: 50%; --my: 80%; }
  85%, 100% { --sp: 0; }
}
@keyframes tilt-loop {
  0%, 15%   { --rx: 0deg; --ry: 0deg; }
  35%       { --rx: -4deg; --ry: 5deg; }
  65%       { --rx: 3deg; --ry: -5deg; }
  85%, 100% { --rx: 0deg; --ry: 0deg; }
}

@media (hover: none) {
  .card:active .card__border { opacity: 1; }
}
@media (prefers-reduced-motion: reduce) {
  .card__border { transition: none; }
  .card.is-demo .card__border { animation: none; }
  .card { transition: none; }
  .card.is-demo { animation: none; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ff4d1f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.stage {
  padding: clamp(6px, 2.4vw, 16px);
}

@property --mx {
  syntax: "<percentage>";
  inherits: true;
  initial-value: 50%;
}
@property --my {
  syntax: "<percentage>";
  inherits: true;
  initial-value: 50%;
}
@property --sp {
  syntax: "<number>";
  inherits: true;
  initial-value: 0;
}
@property --rx {
  syntax: "<angle>";
  inherits: true;
  initial-value: 0deg;
}
@property --ry {
  syntax: "<angle>";
  inherits: true;
  initial-value: 0deg;
}
.card {
  position: relative;
  width: min(190px, 58vw);
  border-radius: 16px;
  padding: 2px;
  outline: none;
  cursor: pointer;
  isolation: isolate;
  transform: perspective(800px) rotateX(var(--rx, 0deg)) rotateY(var(--ry, 0deg));
  transition: transform 300ms ease-out;
}

.card::after {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: inherit;
  pointer-events: none;
  background: radial-gradient(120px circle at var(--mx) var(--my), rgba(255, 255, 255, 0.32), transparent 70%);
  opacity: var(--sp);
}

.card__border {
  position: absolute;
  inset: 0;
  border-radius: 16px;
  padding: 2px;
  background: linear-gradient(135deg, #2f6df6, #fff7e6);
  -webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  -webkit-mask-composite: xor;
  mask-composite: exclude;
  opacity: 0;
  transition: opacity 300ms ease-out;
}

.card__inner {
  position: relative;
  border: 2px solid rgba(23, 20, 26, 0.12);
  border-radius: 14px;
  background: #ffffff;
  padding: 14px 12px;
}

.card__title {
  margin: 0 0 4px;
  font-weight: 700;
  font-size: clamp(12px, 3.4vw, 14px);
  line-height: 1.3;
  font-family: inherit;
  color: #17141a;
}

.card__meta {
  margin: 0;
  font-weight: 500;
  font-size: clamp(11px, 3vw, 12px);
  line-height: 1.3;
  font-family: inherit;
  color: rgba(23, 20, 26, 0.6);
}

.card:hover .card__border,
.card:focus-visible .card__border,
.card:active .card__border,
.card.is-demo .card__border {
  opacity: 1;
}

.card.is-demo .card__border {
  animation: glow-loop 2s ease-out infinite;
}

.card.is-demo {
  animation: spot-loop 2s ease-out infinite, tilt-loop 2s ease-out infinite;
}

@keyframes glow-loop {
  0%, 20% {
    opacity: 0;
  }
  50%, 75% {
    opacity: 1;
  }
  100% {
    opacity: 0;
  }
}
@keyframes spot-loop {
  0%, 15% {
    --sp: 0;
    --mx: 15%;
    --my: 20%;
  }
  30% {
    --sp: 1;
  }
  50% {
    --mx: 85%;
    --my: 30%;
  }
  70% {
    --mx: 50%;
    --my: 80%;
  }
  85%, 100% {
    --sp: 0;
  }
}
@keyframes tilt-loop {
  0%, 15% {
    --rx: 0deg;
    --ry: 0deg;
  }
  35% {
    --rx: -4deg;
    --ry: 5deg;
  }
  65% {
    --rx: 3deg;
    --ry: -5deg;
  }
  85%, 100% {
    --rx: 0deg;
    --ry: 0deg;
  }
}
@media (hover: none) {
  .card:active .card__border {
    opacity: 1;
  }
}
@media (prefers-reduced-motion: reduce) {
  .card__border {
    transition: none;
  }
  .card.is-demo .card__border {
    animation: none;
  }
  .card {
    transition: none;
  }
  .card.is-demo {
    animation: none;
  }
}

// 커서 위치로 스포트라이트(반사광)와 미세 3D 틸트를 함께 만든다.
var card = document.querySelector('.card');
card.addEventListener('pointermove', function (e) {
  card.classList.remove('is-demo');
  var r = card.getBoundingClientRect();
  var px = (e.clientX - r.left) / r.width, py = (e.clientY - r.top) / r.height;
  card.style.setProperty('--mx', (px * 100) + '%');
  card.style.setProperty('--my', (py * 100) + '%');
  card.style.setProperty('--sp', 1);
  card.style.setProperty('--rx', (-(py - .5) * 8) + 'deg');
  card.style.setProperty('--ry', ((px - .5) * 9) + 'deg');
});
card.addEventListener('pointerleave', function () {
  card.style.setProperty('--sp', 0);
  card.style.setProperty('--rx', '0deg');
  card.style.setProperty('--ry', '0deg');
});

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

export type GradientBorderCardProps = {
  title: string;
  meta: string;
  /** 테두리가 나타나는 시간 (기본 300ms) */
  duration?: number;
  easing?: string;
  /** 그라데이션 시작 색 */
  color?: string;
};

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

export default function GradientBorderCard({
  title,
  meta,
  duration = 300,
  easing = "ease-out",
  color = "#2f6df6",
}: GradientBorderCardProps) {
  const ref = useRef<HTMLElement>(null);

  const move = useCallback((e: PointerEvent<HTMLElement>) => {
    const el = ref.current;
    if (!el) return;
    const r = el.getBoundingClientRect();
    const px = (e.clientX - r.left) / r.width, py = (e.clientY - r.top) / r.height;
    el.style.setProperty("--mx", `${px * 100}%`);
    el.style.setProperty("--my", `${py * 100}%`);
    el.style.setProperty("--sp", "1");
    el.style.setProperty("--rx", `${-(py - 0.5) * 8}deg`);
    el.style.setProperty("--ry", `${(px - 0.5) * 9}deg`);
  }, []);

  const leave = useCallback(() => {
    const el = ref.current;
    if (!el) return;
    el.style.setProperty("--sp", "0");
    el.style.setProperty("--rx", "0deg");
    el.style.setProperty("--ry", "0deg");
  }, []);

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

  return (
    <article ref={ref} className={styles.card} style={vars} tabIndex={0} onPointerMove={move} onPointerLeave={leave}>
      <span className={styles.border} aria-hidden="true" />
      <div className={styles.inner}>
        <h3 className={styles.title}>{title}</h3>
        <p className={styles.meta}>{meta}</p>
      </div>
    </article>
  );
}