回転グラデーションボーダー

<!-- Sakura：回転グラデボーダーで縁を発光させるメンバーカード -->
<section class="sg-stage">
  <header class="sg-head">
    <span class="sg-eyebrow">MEMBER</span>
    <h1 class="sg-title">桜のメンバー</h1>
  </header>

  <div class="sg-cards">
    <!-- ★主役：縁が回転発光するメンバーカード -->
    <article class="sg-card">
      <div class="sg-card__photo" style="--n:71"></div>
      <span class="sg-card__color" style="--c:#ff8fb3">桜ピンク</span>
      <h2 class="sg-card__name">花村 みお</h2>
      <p class="sg-card__role">センター / リードボーカル</p>
    </article>

    <article class="sg-card">
      <div class="sg-card__photo" style="--n:72"></div>
      <span class="sg-card__color" style="--c:#b39cff">ラベンダー</span>
      <h2 class="sg-card__name">星野 あかり</h2>
      <p class="sg-card__role">ダンス / ラップ</p>
    </article>

    <article class="sg-card">
      <div class="sg-card__photo" style="--n:73"></div>
      <span class="sg-card__color" style="--c:#7fd6ff">スカイ</span>
      <h2 class="sg-card__name">小川 ゆい</h2>
      <p class="sg-card__role">サブボーカル / MC</p>
    </article>
  </div>
</section>

/* Sakura：淡い背景に、縁が回転発光するメンバーカード */
@property --sg-angle {
  syntax: "<angle>";
  inherits: false;
  initial-value: 0deg;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

.sg-stage {
  min-height: 400px;
  height: 400px;
  overflow: hidden;
  padding: 24px 26px;
  background: linear-gradient(160deg, #fff5f9 0%, #ffe3ee 100%);
  font-family: "Hiragino Kaku Gothic ProN", "Segoe UI", system-ui, sans-serif;
  color: #6a2740;
}

.sg-eyebrow {
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.26em;
  color: #d65e8c;
}
.sg-title {
  margin-top: 4px;
  font-size: 24px;
  font-weight: 800;
  letter-spacing: 0.04em;
  color: #b23a6a;
}

.sg-cards {
  margin-top: 18px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
}

/* ★主役：conic-gradient のボーダーを @property の角度で回転発光 */
.sg-card {
  position: relative;
  border-radius: 18px;
  padding: 3px; /* この余白がグラデボーダーの太さ */
  background:
    conic-gradient(from var(--sg-angle),
      #ff8fb3, #ffd1e0, #b39cff, #7fd6ff, #ff8fb3);
  animation: sgRotate 5s linear infinite;
  box-shadow: 0 10px 26px rgba(214,94,140,0.25);
  transition: transform 0.25s ease;
}
.sg-card:hover { transform: translateY(-4px); }

@keyframes sgRotate {
  to { --sg-angle: 360deg; }
}

/* 中身（白カード）。ボーダーだけ光らせる */
.sg-card::after {
  content: "";
  position: absolute;
  inset: 3px;
  border-radius: 15px;
  background: #fff;
  z-index: 0;
}
.sg-card > * { position: relative; z-index: 1; }

.sg-card__photo {
  height: 96px;
  border-radius: 15px 15px 0 0;
  background: #ffd9e6 center/cover no-repeat;
  position: relative;
}
/* メンバーごとに別写真（CSS変数では URL 連結できないため個別指定） */
.sg-card:nth-child(1) .sg-card__photo { background-image: url("https://picsum.photos/240/200?random=71"); }
.sg-card:nth-child(2) .sg-card__photo { background-image: url("https://picsum.photos/240/200?random=72"); }
.sg-card:nth-child(3) .sg-card__photo { background-image: url("https://picsum.photos/240/200?random=73"); }
.sg-card__photo::after {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: 15px 15px 0 0;
  background: linear-gradient(180deg, transparent, rgba(255,209,224,0.45));
  mix-blend-mode: multiply;
}

.sg-card__color {
  display: inline-block;
  margin: 10px 12px 0;
  font-size: 10px;
  font-weight: 700;
  padding: 3px 9px;
  border-radius: 999px;
  color: #fff;
  background: var(--c, #ff8fb3);
}
.sg-card__name {
  margin: 8px 12px 2px;
  font-size: 15px;
  font-weight: 800;
  color: #b23a6a;
}
.sg-card__role {
  margin: 0 12px 14px;
  font-size: 10.5px;
  color: #9a6076;
  line-height: 1.5;
}

@media (prefers-reduced-motion: reduce) {
  .sg-card { animation: none; }
}

// メンバーカードのホバーで回転速度を少し上げ、推し感を出す
(() => {
  const cards = document.querySelectorAll(".sg-card");
  if (!cards.length) return; // null安全

  const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
  if (reduce) return;

  cards.forEach((card) => {
    // ホバー中は発光ボーダーを速く回す
    card.addEventListener("pointerenter", () => {
      card.style.animationDuration = "2s";
    });
    card.addEventListener("pointerleave", () => {
      card.style.animationDuration = "5s";
    });
  });
})();

<!-- 回転グラデーションボーダー: conic-gradient を回し、カードの縁を発光させる -->
<div class="gb-stage">
  <div class="gb-card">
    <div class="gb-inner">
      <span class="gb-badge">PRO</span>
      <h1 class="gb-title">Glowing Border</h1>
      <p class="gb-sub">@property で角度を回転させる conic-gradient ボーダー。価格表やバッジカードに。</p>
      <button class="gb-cta" type="button">アップグレード</button>
    </div>
  </div>
</div>

/* @property で角度をアニメーション可能にし、conic-gradient ボーダーを回す */
* { box-sizing: border-box; margin: 0; padding: 0; }

/* カスタムプロパティを角度型として登録(回転アニメに必須) */
@property --gb-angle {
  syntax: "<angle>";
  initial-value: 0deg;
  inherits: false;
}

.gb-stage {
  min-height: 360px;
  display: grid;
  place-items: center;
  padding: 24px;
  font-family: "Segoe UI", "Hiragino Sans", system-ui, sans-serif;
  background:
    radial-gradient(120% 120% at 50% 0%, #1a1030 0%, #0a0716 70%);
}

/* カード外枠 = グラデボーダー本体 */
.gb-card {
  position: relative;
  border-radius: 22px;
  padding: 2px; /* この余白が枠の太さ */
  background: conic-gradient(
    from var(--gb-angle),
    #ff5f6d, #ffc371, #5ee7df, #7b88ff, #c479ff, #ff5f6d
  );
  animation: gb-spin 6s linear infinite;
  box-shadow: 0 0 40px rgba(124, 136, 255, 0.35);
}

@keyframes gb-spin {
  to { --gb-angle: 360deg; }
}

/* 内側パネル */
.gb-inner {
  border-radius: 20px;
  background: #120c24;
  padding: 34px 40px;
  text-align: center;
  color: #f4f1ff;
  max-width: 420px;
}

.gb-badge {
  display: inline-block;
  font-size: 11px;
  font-weight: 800;
  letter-spacing: 0.2em;
  padding: 5px 14px;
  border-radius: 999px;
  background: linear-gradient(90deg, #7b88ff, #c479ff);
  color: #fff;
}

.gb-title {
  margin: 14px 0 10px;
  font-size: 32px;
  font-weight: 800;
  letter-spacing: 0.01em;
}

.gb-sub {
  font-size: 13.5px;
  line-height: 1.8;
  color: rgba(244, 241, 255, 0.78);
}

.gb-cta {
  margin-top: 22px;
  font: inherit;
  font-size: 13px;
  font-weight: 700;
  color: #120c24;
  padding: 12px 28px;
  border: none;
  border-radius: 999px;
  cursor: pointer;
  background: linear-gradient(90deg, #5ee7df, #ffc371);
  transition: transform 0.2s ease, filter 0.2s ease;
}

.gb-cta:hover {
  transform: translateY(-2px);
  filter: brightness(1.08);
}

/* 回転を止めても虹色の枠は残る */
@media (prefers-reduced-motion: reduce) {
  .gb-card { animation: none; }
}