/* 返回顶部按钮样式 - 固定在右下角，现代简洁设计 */
  .go-top-btn {
    position: fixed;
    bottom: 24px;
    right: 24px;
    z-index: 9999;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 10px 18px;
    background-color: #1e40af; /* 深蓝色，稳重专业 */
    color: white;
    font-size: 14px;
    font-weight: 600;
    font-family: system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', sans-serif;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    border-radius: 40px;
    box-shadow: 0 6px 16px rgba(0, 0, 0, 0.12), 0 2px 4px rgba(0, 0, 0, 0.05);
    cursor: pointer;
    transition: all 0.25s ease-in-out;
    opacity: 0;
    visibility: hidden;
    backdrop-filter: blur(0px);
    border: none;
    text-decoration: none;
    line-height: 1;
    white-space: nowrap;
  }

  /* 显示状态 */
  .go-top-btn.show {
    opacity: 1;
    visibility: visible;
  }

  /* 悬停/聚焦效果 */
  .go-top-btn:hover,
  .go-top-btn:focus-visible {
    background-color: #1e3a8a; /* 更深蓝 */
    transform: translateY(-3px);
    box-shadow: 0 12px 24px rgba(0, 0, 0, 0.18);
    outline: none;
  }

  /* 点击反馈 */
  .go-top-btn:active {
    transform: translateY(2px);
    transition-duration: 0.05s;
  }

  /* 移动端适配：稍微缩小间距，保持点击区域舒适 */
  @media (max-width: 640px) {
    .go-top-btn {
      bottom: 18px;
      right: 18px;
      padding: 8px 16px;
      font-size: 13px;
      gap: 6px;
    }
  }

  /* 针对深色模式/高对比度不影响原有设计，仅做优雅降级 */
  @media (prefers-reduced-motion: reduce) {
    .go-top-btn {
      transition: none;
    }
  }