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

    body {
      font-family: "Microsoft YaHei", sans-serif;
      background: radial-gradient(circle at top, #16213e 0%, #0a0f1f 40%, #050816 100%);
      color: #ffffff;
      min-height: 100vh;
      overflow-x: hidden;

      display: flex;
      flex-direction: column;
    }

    /* 星空背景 */
    body::before {
      content: "";
      position: fixed;
      inset: 0;
      background-image:
        radial-gradient(2px 2px at 20% 30%, rgba(255,255,255,0.7), transparent),
        radial-gradient(2px 2px at 80% 20%, rgba(0,255,255,0.8), transparent),
        radial-gradient(1px 1px at 50% 80%, rgba(255,255,255,0.6), transparent),
        radial-gradient(2px 2px at 70% 60%, rgba(0,200,255,0.8), transparent);
      z-index: -1;
    }

    header {
      padding: 40px 20px 20px;
      text-align: center;
    }

    header h1 {
      font-size: 2rem;
      letter-spacing: 4px;
      color: #00eaff;
      text-shadow: 0 0 15px #00eaff;
    }

    .container {
      width: 90%;
      max-width: 1200px;
      margin: 10px auto;

      display: flex;
      flex-wrap: wrap;

      gap: 20px;

      align-items: flex-start;

      flex: 1;
    }

    .menu-card {
      background: rgba(18, 28, 48, 0.85);
      border: 1px solid rgba(0, 234, 255, 0.25);
      border-radius: 18px;
      padding: 24px;
      backdrop-filter: blur(12px);
      box-shadow:
        0 0 20px rgba(0, 234, 255, 0.08),
        inset 0 0 10px rgba(255,255,255,0.03);
      transition: all 0.3s ease;
      /* 新增 */
      flex: 1 1 260px;
      min-width: 260px;
    }

    .menu-card:hover {
      transform: translateY(-6px);
      box-shadow:
        0 0 28px rgba(0, 234, 255, 0.25),
        inset 0 0 12px rgba(255,255,255,0.05);
    }

    .menu-title {
      display: flex;
      justify-content: space-between;
      align-items: center;
      cursor: pointer;
      font-size: 1.5rem;
      font-weight: bold;
      color: #00eaff;
    }

    .arrow {
      transition: transform 0.3s ease;
    }

    .menu-card.active .arrow {
      transform: rotate(180deg);
    }

    .submenu {
      margin-top: 20px;
      display: none;
      flex-direction: column;
      gap: 12px;
    }

    .menu-card.active .submenu {
      display: flex;
    }

    .submenu a {
      text-decoration: none;
      color: #d8e6f2;
      padding: 14px 16px;
      border-radius: 12px;
      background: rgba(255,255,255,0.04);
      border: 1px solid rgba(0,234,255,0.1);
      transition: all 0.25s ease;
    }

    .submenu a:hover {
      background: rgba(0,234,255,0.15);
      color: #00ffff;
      transform: translateX(5px);
      box-shadow: 0 0 12px rgba(0,234,255,0.25);
    }

    footer {
      text-align: center;
      padding: 40px 20px;
      color: #6f87a5;
      font-size: 0.95rem;
    }

    /* 响应式 */
    @media (max-width: 768px) {
      header h1 {
        font-size: 2.2rem;
      }

      header p {
        font-size: 1rem;
      }

      .menu-title {
        font-size: 1.3rem;
      }

      .container {
        width: 94%;
        gap: 20px;
      }
    }

    @media (max-width: 480px) {
      header {
        padding-top: 30px;
      }

      header h1 {
        font-size: 1.8rem;
        letter-spacing: 2px;
      }

      .menu-card {
        padding: 20px;
      }

      .submenu a {
        padding: 12px;
        font-size: 0.95rem;
      }
    }