header {
  position: sticky;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 100;
  background-color: rgba(4, 12, 36, 0.96);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.35);
  transition: all 0.3s ease;
}

header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
  padding: 0 20px;
  max-width: 1280px;
  margin: 0 auto;
}

header.scrolled .container {
  height: 56px;
}

/* Logo Design */
.logo {
  display: inline-flex;
  align-items: center;
  text-decoration: none;
  user-select: none;
  transition: transform 0.2s ease;
  flex-shrink: 0;
}

.logo:hover {
  transform: scale(1.02);
}

header .brand-logo-img,
.mobile-nav-header .brand-logo-img {
  height: 44px !important;
  max-height: 48px !important;
  width: auto !important;
  object-fit: contain !important;
  display: block;
}

header.scrolled .brand-logo-img {
  height: 38px !important;
  max-height: 42px !important;
}

/* Nav Links - Desktop */
.nav-menu {
  display: flex;
  align-items: center;
  list-style: none;
  gap: var(--space-xl);
}

.nav-link {
  font-weight: 500;
  color: rgba(255, 255, 255, 0.85);
  font-size: var(--font-size-small);
  transition: opacity var(--transition-fast), color var(--transition-fast);
}

.nav-link:hover {
  opacity: 1;
  color: var(--color-white);
}

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

header.scrolled .nav-link:hover {
  color: var(--color-white);
}

/* Auth Controls & Dynamic Buttons */
.nav-auth {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
}

.nav-auth .btn-primary {
  background-color: var(--color-white);
  color: var(--color-primary);
  border-radius: 999px;
  padding: 10px 22px;
  font-weight: 600;
  font-size: 14px;
  border: none;
  transition: background 0.2s ease, transform 0.18s ease;
}

.nav-auth .btn-primary:hover {
  background-color: var(--color-blue);
  color: var(--color-white);
  transform: translateY(-1px);
}

header.scrolled .nav-auth .btn-enroll {
  background-color: #3b7de8;
  color: var(--color-white);
}

header.scrolled .nav-auth .btn-enroll:hover {
  background-color: #2d6ad4;
}

.user-profile {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
  font-size: var(--font-size-small);
  color: var(--color-primary);
}

.avatar {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background-color: var(--color-sky);
  color: var(--color-primary);
  font-weight: 600;
  display: flex;
  align-items: center;
  justify-content: center;
  text-transform: uppercase;
}

/* Mobile Toggle Hamburger – fully managed in responsive.css */
/* Base style here ensures it stays hidden by default (display:none set in responsive.css) */

header .brand-logo-img,
header .devpath-brand-logo {
  height: 60px !important;
  max-height: 68px !important;
  width: auto !important;
}

header.scrolled .brand-logo-img,
header.scrolled .devpath-brand-logo {
  height: 48px !important;
  max-height: 54px !important;
}