:root {
        --bg-dark: #0f172a;
        --bg-deep: #020617;
        --neon-blue: #0ea5e9;
        --neon-purple: #8b5cf6;
        --glass-bg: rgba(255, 255, 255, 0.05);
        --glass-border: rgba(255, 255, 255, 0.1);
        --section-height: 50vh;
      }

      body {
        margin: 0;
        padding: 0;
        background-color: var(--bg-deep);
        font-family: "Inter", sans-serif;
        color: white;
        overflow-x: hidden;
      }

      /* 共通セクションスタイル */
      section {
        position: relative;
        width: 100vw;
        height: var(--section-height);
        display: flex;
        justify-content: center;
        align-items: center;
        border-bottom: 1px solid rgba(255, 255, 255, 0.1);
        overflow: hidden;
      }

      .section-label {
        position: absolute;
        top: 20px;
        left: 20px;
        font-family: "Orbitron", sans-serif;
        font-size: 1.2rem;
        color: rgba(255, 255, 255, 0.5);
        z-index: 20;
        background: rgba(0, 0, 0, 0.3);
        padding: 5px 15px;
        border-radius: 4px;
        border: 1px solid rgba(255, 255, 255, 0.1);
      }

      /* 背景グリッド (共通) */
      .bg-grid {
        position: absolute;
        width: 200%;
        height: 200%;
        top: -50%;
        left: -50%;
        background-image: linear-gradient(
            rgba(255, 255, 255, 0.03) 1px,
            transparent 1px
          ),
          linear-gradient(90deg, rgba(255, 255, 255, 0.03) 1px, transparent 1px);
        background-size: 50px 50px;
        opacity: 0.2;
        pointer-events: none;
      }

      /* 3Dの方だけパースをつける */
      .section-3d .bg-grid {
        transform: perspective(500px) rotateX(60deg) translateY(-100px)
          translateZ(-200px);
      }

      /* 軌道SVG (共通) */
      .orbit-svg {
        position: absolute;
        top: 50%;
        left: 50%;
        transform: translate(-50%, -50%);
        width: 90%;
        max-width: 1000px;
        height: auto;
        aspect-ratio: 1000 / 400;
        overflow: visible;
        pointer-events: none;
        z-index: 1;
      }

      .orbit-path {
        fill: none;
        stroke-width: 2;
        stroke-linecap: round;
      }

      /* 2D用のパススタイル */
      .section-2d .orbit-path {
        stroke: rgba(255, 255, 255, 0.2);
      }

      /* 3D用のパススタイル (光る) */
      .section-3d .orbit-path {
        stroke: url(#gradientStroke);
        opacity: 0.5;
        filter: drop-shadow(0 0 8px var(--neon-blue));
      }

      /* コア (共通) */
      .core-wrapper {
        position: absolute;
        z-index: 5;
        top: 50%;
        left: 50%;
        transform: translate(-50%, -50%);
        display: flex;
        justify-content: center;
        align-items: center;
      }

      .core {
        border-radius: 50%;
        display: flex;
        justify-content: center;
        align-items: center;
        font-family: "Orbitron", sans-serif;
        font-weight: 700;
      }

      /* 2Dのコア: シンプル */
      .section-2d .core {
        width: 100px;
        height: 100px;
        background: rgba(255, 255, 255, 0.1);
        border: 1px solid rgba(255, 255, 255, 0.3);
        color: rgba(255, 255, 255, 0.8);
        letter-spacing: 2px;
      }

      /* 3Dのコア: 豪華 */
      .section-3d .core {
        width: 140px;
        height: 140px;
        background: radial-gradient(
          circle,
          rgba(14, 165, 233, 0.15) 0%,
          transparent 70%
        );
        border: 1px solid rgba(14, 165, 233, 0.2);
        box-shadow: 0 0 40px rgba(14, 165, 233, 0.15),
          inset 0 0 20px rgba(14, 165, 233, 0.1);
        backdrop-filter: blur(4px);
        color: var(--neon-blue);
        text-shadow: 0 0 15px var(--neon-blue);
        letter-spacing: 4px;
        animation: pulse 4s ease-in-out infinite;
      }
      .section-3d .core::after {
        content: "";
        position: absolute;
        width: 80%;
        height: 80%;
        border-radius: 50%;
        border: 1px dashed rgba(255, 255, 255, 0.15);
        animation: spin 15s linear infinite;
      }

      /* アイコン (共通ベース) */
      .icon-item {
        position: absolute;
        width: 60px;
        height: 60px;
        margin-top: -30px;
        margin-left: -30px;
        border-radius: 50%;
        display: flex;
        justify-content: center;
        align-items: center;
        top: 50%;
        left: 50%;
        z-index: 10;
      }

      .icon-inner {
        width: 24px;
        height: 24px;
        stroke-width: 1.5;
      }

      /* 2Dアイコンスタイル: フラット */
      .section-2d .icon-item {
        background: #1e293b;
        border: 1px solid rgba(255, 255, 255, 0.2);
        color: rgba(255, 255, 255, 0.6);
        /* 影も控えめ */
        box-shadow: 0 2px 10px rgba(0, 0, 0, 0.2);
      }

      /* 3Dアイコンスタイル: グラスモーフィズム */
      .section-3d .icon-item {
        background: var(--glass-bg);
        backdrop-filter: blur(12px);
        -webkit-backdrop-filter: blur(12px);
        border: 1px solid var(--glass-border);
        color: rgba(255, 255, 255, 0.7);
        box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
        will-change: transform, opacity, filter, border-color, box-shadow, color;
      }

      /* アニメーション定義 */
      @keyframes pulse {
        0%,
        100% {
          transform: scale(1);
          opacity: 0.8;
        }
        50% {
          transform: scale(1.05);
          opacity: 1;
        }
      }
      @keyframes spin {
        0% {
          transform: rotate(0deg);
        }
        100% {
          transform: rotate(360deg);
        }
      }

      /* レスポンシブ調整 */
      @media (max-width: 768px) {
        .section-label {
          font-size: 0.9rem;
          padding: 4px 10px;
        }
        .section-2d .core,
        .section-3d .core {
          width: 90px;
          height: 90px;
          font-size: 0.9rem;
        }
        .icon-item {
          width: 44px;
          height: 44px;
          margin-top: -22px;
          margin-left: -22px;
        }
        .icon-inner {
          width: 20px;
          height: 20px;
        }
      }