/* ========================================
   SITE HEADER LAYOUT
   ======================================== */

.site-header {
  position: sticky;
  top: 0;
  z-index: var(--z-index-sticky);
  background-color: var(--color-background-primary);
  border-bottom: var(--border-width-thin) solid var(--color-border-light);
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition-duration-fast) var(--transition-timing-out);
}

.site-header.scrolled {
  box-shadow: var(--shadow-md);
}

.header-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 80px;
  transition: height var(--transition-duration-fast) var(--transition-timing-out);
}

/* Logo */
.site-logo {
  font-family: var(--font-family-heading);
  font-size: var(--font-size-2xl);
  font-weight: var(--font-weight-bold);
  color: var(--color-primary);
  text-decoration: none;
  letter-spacing: var(--letter-spacing-tight);
  line-height: var(--line-height-tight);
  transition: color var(--transition-duration-fast) var(--transition-timing-out);
  flex-shrink: 0;
}

.site-logo span {
  color: var(--color-secondary);
}

.site-logo:hover {
  color: var(--color-primary-dark);
  text-decoration: none;
}

.site-logo:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 4px;
  border-radius: var(--border-radius-sm);
}

/* Desktop Navigation */
@media (min-width: 769px) {
  .header-container {
    height: 90px;
  }
  
  .nav-menu {
    display: flex;
    align-items: center;
    gap: var(--spacing-2);
  }
  
  .nav-link {
    position: relative;
    padding: var(--spacing-2) var(--spacing-3);
    color: var(--color-text-primary);
    font-weight: var(--font-weight-medium);
    font-size: var(--font-size-base);
    border-radius: var(--border-radius-md);
    transition: color var(--transition-duration-fast) var(--transition-timing-out);
    white-space: nowrap;
  }
  
  .nav-link::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 0;
    height: 2px;
    background-color: var(--color-primary);
    transition: width var(--transition-duration-fast) var(--transition-timing-out);
  }
  
  .nav-link:hover {
    color: var(--color-primary);
    text-decoration: none;
  }
  
  .nav-link:hover::after {
    width: calc(100% - (var(--spacing-3) * 2));
  }
  
  .nav-link.active {
    color: var(--color-primary);
    font-weight: var(--font-weight-semibold);
  }
  
  .nav-link.active::after {
    width: calc(100% - (var(--spacing-3) * 2));
  }
}

/* Mobile Menu Toggle */
.mobile-menu-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 44px;
  height: 44px;
  padding: var(--spacing-2);
  background: transparent;
  border: none;
  border-radius: var(--border-radius-md);
  cursor: pointer;
  transition: background-color var(--transition-duration-fast) var(--transition-timing-out);
}

.mobile-menu-toggle:hover {
  background-color: var(--color-background-tertiary);
}

.mobile-menu-toggle:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

.mobile-menu-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background-color: var(--color-primary);
  margin: 3px 0;
  transition: transform var(--transition-duration-fast) var(--transition-timing-out),
              opacity var(--transition-duration-fast) var(--transition-timing-out);
  border-radius: var(--border-radius-full);
}

.mobile-menu-toggle.active span:nth-child(1) {
  transform: translateY(8px) rotate(45deg);
}

.mobile-menu-toggle.active span:nth-child(2) {
  opacity: 0;
}

.mobile-menu-toggle.active span:nth-child(3) {
  transform: translateY(-8px) rotate(-45deg);
}

/* Mobile Navigation */
@media (max-width: 768px) {
  .mobile-menu-toggle {
    display: flex;
  }
  
  .nav-menu {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background-color: var(--color-background-primary);
    border-top: var(--border-width-thin) solid var(--color-border-light);
    border-bottom: var(--border-width-thin) solid var(--border-light);
    box-shadow: var(--shadow-lg);
    padding: var(--spacing-2);
    display: none;
    flex-direction: column;
    gap: var(--spacing-1);
    max-height: calc(100vh - 80px);
    overflow-y: auto;
  }
  
  .nav-menu.active {
    display: flex;
    animation: slideDown var(--transition-duration-normal) var(--transition-timing-out);
  }
  
  .nav-link {
    display: block;
    padding: var(--spacing-3) var(--spacing-4);
    color: var(--color-text-primary);
    font-weight: var(--font-weight-medium);
    font-size: var(--font-size-lg);
    border-radius: var(--border-radius-md);
    transition: background-color var(--transition-duration-fast) var(--transition-timing-out),
                color var(--transition-duration-fast) var(--transition-timing-out);
    text-align: left;
  }
  
  .nav-link:hover {
    background-color: var(--color-background-tertiary);
    color: var(--color-primary);
    text-decoration: none;
  }
  
  .nav-link.active {
    background-color: var(--color-primary-50);
    color: var(--color-primary);
    font-weight: var(--font-weight-semibold);
  }
  
  @keyframes slideDown {
    from {
      opacity: 0;
      transform: translateY(-10px);
    }
    to {
      opacity: 1;
      transform: translateY(0);
    }
  }
}

/* Tablet adjustments */
@media (min-width: 769px) and (max-width: 1024px) {
  .nav-link {
    padding: var(--spacing-2) var(--spacing-2);
    font-size: var(--font-size-sm);
  }
}