/* ベーススタイル */
      *,
      *::before,
      *::after {
        box-sizing: border-box;
      }

      :root {
        /* 配色パレット（デザイン改善版を維持） */
        --primary-color: #1e293b;
        --text-secondary: #64748b;
        --accent-color: #4f46e5;
        --accent-light: #e0e7ff;
        --bg-color: #f8fafc;
        --card-bg: #ffffff;
      }

      body {
        margin: 0;
        padding: 0;
        font-family: "Helvetica Neue", Arial, "Hiragino Kaku Gothic ProN",
          "Hiragino Sans", Meiryo, sans-serif;
        background-color: var(--bg-color);
        color: var(--primary-color);
        line-height: 1.8;
        overflow-x: hidden;
        letter-spacing: 0.03em;
      }

      header {
        height: 100vh;
        display: flex;
        flex-direction: column;
        justify-content: center;
        align-items: center;
        background: radial-gradient(circle at top left, #eef2ff, #ffffff);
        text-align: center;
        position: relative;
      }

      h1 {
        font-size: 3rem;
        margin-bottom: 1rem;
        background: linear-gradient(135deg, #4f46e5 0%, #06b6d4 100%);
        -webkit-background-clip: text;
        -webkit-text-fill-color: transparent;
        font-weight: 800;
      }

      header p {
        color: var(--text-secondary);
        font-weight: bold;
      }

      .scroll-indicator {
        margin-top: 3rem;
        font-size: 0.9rem;
        color: var(--accent-color);
        font-weight: bold;
        animation: bounce 2s infinite;
      }

      @keyframes bounce {
        0%,
        20%,
        50%,
        80%,
        100% {
          transform: translateY(0);
        }
        40% {
          transform: translateY(-10px);
        }
        60% {
          transform: translateY(-5px);
        }
      }

      section {
        padding: 120px 20px;
        max-width: 1000px;
        margin: 0 auto;
      }

      /* 偶数セクションの背景 */
      section:nth-child(even) {
        background-color: #f1f5f9;
        margin-left: calc(50% - 50vw);
        margin-right: calc(50% - 50vw);
        padding-left: calc(50vw - 500px + 20px);
        padding-right: calc(50vw - 500px + 20px);
        width: 100vw;
        max-width: 100vw;
      }
      @media (max-width: 1040px) {
        section:nth-child(even) {
          padding-left: 20px;
          padding-right: 20px;
        }
      }

      h2 {
        font-size: 2rem;
        margin-bottom: 1rem;
        text-align: center;
        color: var(--primary-color);
      }

      h2 + p {
        text-align: center;
        margin-bottom: 60px;
        color: var(--text-secondary);
      }

      h3 {
        margin-top: 4rem;
        margin-bottom: 1.5rem;
        font-size: 1.3rem;
        color: var(--primary-color);
        display: flex;
        align-items: center;
      }

      h3::before {
        content: "";
        display: inline-block;
        width: 6px;
        height: 24px;
        background-color: var(--accent-color);
        margin-right: 12px;
        border-radius: 3px;
      }

      h4 {
        font-size: 1rem;
        color: var(--text-secondary);
        margin-bottom: 1rem;
        text-align: center;
        margin-top: 2rem;
        font-weight: normal;
      }

      /* --- 共通カードスタイル --- */
      .card,
      .box,
      .fade-item,
      .demo-box-large,
      .demo-box-small {
        background-color: var(--card-bg);
        border-radius: 16px;
        box-shadow: 0 10px 30px -10px rgba(0, 0, 0, 0.08);
        border: 1px solid rgba(255, 255, 255, 0.5);
      }

      /* --- ポップアップ系 --- */
      .cardWrap {
        display: grid;
        grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
        gap: 24px;
        margin-bottom: 40px;
      }

      .card {
        height: 150px;
        display: flex;
        align-items: center;
        justify-content: center;
        font-weight: bold;
        color: var(--text-secondary);
        font-size: 1.1rem;
      }

      .box {
        padding: 40px;
        margin: 40px auto;
        max-width: 600px;
        color: var(--primary-color);
      }

      .buttonWrap {
        display: flex;
        justify-content: center;
        gap: 20px;
        margin-top: 40px;
      }

      .button {
        padding: 16px 48px;
        background-color: var(--accent-color);
        color: white;
        border-radius: 50px;
        font-weight: bold;
        cursor: pointer;
        box-shadow: 0 4px 15px rgba(79, 70, 229, 0.4);
        letter-spacing: 0.05em;
      }

      /* --- フェードイン系 --- */
      .fade-grid {
        display: grid;
        grid-template-columns: repeat(2, 1fr);
        gap: 32px;
        margin-bottom: 40px;
      }

      .fade-grid-3 {
        display: grid;
        grid-template-columns: repeat(3, 1fr);
        gap: 24px;
        margin-bottom: 40px;
      }

      .fade-item {
        padding: 32px;
      }

      .fade-item p {
        font-size: 0.95rem;
        color: var(--text-secondary);
        margin: 0;
      }

      .fade-list {
        list-style: none;
        padding: 0;
        max-width: 600px;
        margin: 0 auto;
      }
      .fade-list li {
        background: white;
        padding: 24px;
        margin-bottom: 16px;
        border-radius: 12px;
        box-shadow: 0 4px 6px rgba(0, 0, 0, 0.02);
        border: 1px solid #f1f5f9;
        display: flex;
        align-items: center;
        color: var(--primary-color);
        font-weight: bold;
      }
      .fade-list li::before {
        content: "✓";
        color: var(--accent-color);
        margin-right: 16px;
        font-weight: 900;
      }

      /* 画像プレースホルダー */
      .img-placeholder {
        width: 100%;
        height: 180px;
        background-color: #f1f5f9;
        border-radius: 8px;
        display: flex;
        align-items: center;
        justify-content: center;
        color: #94a3b8;
        margin-bottom: 1.5rem;
        font-weight: bold;
        font-size: 1.2rem;
      }

      /* デモ用ボックス */
      .demo-box-large {
        height: 220px;
        display: flex;
        align-items: center;
        justify-content: center;
        font-size: 1.4rem;
        font-weight: bold;
        color: var(--accent-color);
        margin-bottom: 20px;
        background: white;
      }

      .demo-box-small {
        height: 120px;
        display: flex;
        align-items: center;
        justify-content: center;
        font-size: 1rem;
        font-weight: bold;
        color: var(--accent-color);
        background: white;
      }

      .perspective-container {
        perspective: 1000px;
      }

      @media (max-width: 768px) {
        .fade-grid,
        .fade-grid-3,
        .cardWrap {
          grid-template-columns: 1fr;
        }
        section:nth-child(even) {
          margin-left: 0;
          margin-right: 0;
          padding-left: 20px;
          padding-right: 20px;
          width: auto;
          max-width: none;
        }
        h1 {
          font-size: 2rem;
        }
      }