:root { --platform-header-height: 100px; }
body.platform-site { padding-top: var(--platform-header-height); }

header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 999;
  }

/* 导航栏容器样式 */
.navbar {
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    margin-bottom: 0;
    padding-bottom: 0;
    padding-top: 0;
}

.navbar .container {
  width: 100%;
  max-width: 100%;
  padding: 0;
}

.navbar .platform-nav-column {
  min-height: 100px;
  padding: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 0;
}

.navbar .navbar-nav {
  width: 100%;
  justify-content: space-around;
  margin: 0;
}

/* 导航栏样式 */
.navbar-nav .nav-item {
  display: flex;
  align-items: center;
  min-height: 100px;
  position: relative;
  transition: all 0.3s ease;
}

/* 导航链接默认样式 */
.navbar-light .navbar-nav .nav-link {
  color: black;
  font-size: 18px;
  transition: color 0.3s ease;
}

/* 底部边框样式 */
.navbar-nav .nav-item::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100%;
  height: 3px;
  background-color: transparent;
  transition: background-color 0.3s ease;
}

/* 导航栏悬停样式 */
.navbar-nav .nav-item:hover::after {
  background-color: var(--platform-accent);
}

.navbar-nav .nav-item:hover .nav-link {
  color: var(--platform-accent);
}

/* 导航栏激活样式 */
.navbar-nav .nav-item.active::after {
  background-color: var(--platform-accent);
}

.navbar-nav .nav-item.active .nav-link {
  color: var(--platform-accent);
}

/* 导航栏点击状态样式 */
.navbar-nav .nav-item:active::after {
  background-color: var(--platform-accent);
}

.navbar-nav .nav-item:active .nav-link {
  color: var(--platform-accent);
}

.btn-auth {
  padding: 0.5rem 2.5rem;
  font-size: 18px;
  border-radius: 50px;
  text-decoration: none;
  background: var(--platform-brand-gradient);
  color: var(--platform-surface);
  transition: background 0.3s ease;
  min-width: 150px;
  text-align: center;
}

.btn-auth:hover {
  background: linear-gradient(to right, #E08215, #C83E12);
  color: var(--platform-surface);
  text-decoration: none;
}

/* 响应式调整 */
@media (max-width: 768px) {
  .navbar .row {
    margin: 0;
  }
  
  .navbar .col-md-3,
  .navbar .col-md-6 {
    padding: 0;
  }
  
  .btn-auth {
    padding: 0.3rem 1rem;
    font-size: 16px;
  }
}

/* 窄屏导航参与正常文档流，避免堆叠后遮住页面内容。 */
@media (max-width: 767.98px) {
  :root { --platform-header-height: 0px; }
  body.platform-site > header { position: static; flex-shrink: 0; }
  .navbar .platform-nav-column { min-height: 64px; padding: 8px 0; }
  .navbar .platform-nav-links { min-height: 0; padding: 0; }
  .navbar .navbar-nav { flex-direction: row; flex-wrap: wrap; }
  .navbar-nav .nav-item { min-height: 44px; width: 50%; justify-content: center; }
  .navbar-light .navbar-nav .nav-link { font-size: 16px; text-align: center; }
  .navbar .btn-auth { max-width: 100%; white-space: normal; }
}