/* === 固定导航栏 === */
.header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: var(--header-height);
  z-index: 1000;
  transition: all var(--transition-base);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: var(--max-width-content);
  margin: 0 auto;
  padding: 0 var(--space-lg);
  height: 100%;
}

/* 首屏透明态 */
.header-logo .logo-text {
  font-size: 1.5rem;
  font-weight: 700;
  font-family: var(--font-accent);
  color: #fff;
  letter-spacing: 2px;
  transition: color var(--transition-base);
}

.header-nav .nav-link {
  color: rgba(255,255,255,0.85);
  font-size: var(--text-sm);
  font-weight: 400;
  padding: 0.5rem 1.25rem;
  transition: color var(--transition-base);
  position: relative;
}

.header-nav .nav-link:hover,
.header-nav .nav-link.active {
  color: #fff;
}

.header-nav .nav-link::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 50%;
  transform: translateX(-50%) scaleX(0);
  width: 20px;
  height: 2px;
  background-color: var(--color-accent);
  transition: transform var(--transition-base);
}

.header-nav .nav-link:hover::after,
.header-nav .nav-link.active::after {
  transform: translateX(-50%) scaleX(1);
}

.nav-cta {
  background-color: var(--color-accent);
  border-radius: var(--radius-sm);
  padding: 0.5rem 1.5rem !important;
  color: #fff !important;
  font-weight: 500 !important;
}

.nav-cta::after {
  display: none;
}

.nav-cta:hover {
  background-color: var(--color-accent-hover);
}

/* 滚动后红底态 */
.header.scrolled {
  background-color: var(--color-primary);
  box-shadow: var(--shadow-nav);
}

.header.scrolled .logo-text {
  color: #fff;
}

.header.scrolled .nav-link {
  color: rgba(255,255,255,0.85);
}

.header.scrolled .nav-link:hover,
.header.scrolled .nav-link.active {
  color: #fff;
}

.header.scrolled .nav-cta {
  color: #fff !important;
}

/* 桌面端菜单布局 */
.nav-list {
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

/* 移动端菜单按钮 */
.header-menu-btn {
  display: none;
  flex-direction: column;
  gap: 5px;
  padding: 4px;
  z-index: 1001;
}

.header-menu-btn span {
  display: block;
  width: 24px;
  height: 2px;
  background-color: #fff;
  transition: all var(--transition-base);
}

.header.scrolled .header-menu-btn span {
  background-color: #fff;
}

/* 移动端菜单打开态 */
.header-menu-btn.open span:nth-child(1) {
  transform: rotate(45deg) translate(5px, 5px);
}

.header-menu-btn.open span:nth-child(2) {
  opacity: 0;
}

.header-menu-btn.open span:nth-child(3) {
  transform: rotate(-45deg) translate(5px, -5px);
}