/* header.css */
header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: var(--z-index-header);
  transition: all var(--transition-normal);
  /* Frosted glass effect so text is always readable */
  background-color: rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  box-shadow: 0 1px 5px rgba(0, 0, 0, 0.05);
  padding: var(--space-4) 0;
}

html.dark-mode header {
  background-color: rgba(9, 9, 11, 0.9);
  box-shadow: 0 1px 5px rgba(0, 0, 0, 0.5);
}

header.scrolled {
  background-color: rgba(255, 255, 255, 0.98);
  box-shadow: var(--shadow-sm);
  padding: var(--space-3) 0;
}

html.dark-mode header.scrolled {
  background-color: rgba(9, 9, 11, 0.98);
}

.header-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  text-decoration: none;
  display: flex;
  align-items: center;
}

.site-logo {
  max-height: 40px;
  width: auto;
}

.nav-links {
  display: flex;
  gap: var(--space-6);
  align-items: center;
}

.nav-links a {
  color: var(--theme-text);
  font-weight: 500;
  text-decoration: none;
  transition: color var(--transition-fast);
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--theme-heading);
}

.mobile-cta {
  display: none;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-4);
}

.theme-toggle {
  background: none;
  border: none;
  color: var(--theme-heading);
  cursor: pointer;
  font-size: 1.25rem;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-full);
  transition: background-color var(--transition-fast), transform var(--transition-normal);
}

.theme-toggle:hover {
  background-color: rgba(128, 128, 128, 0.1);
}

.mobile-menu-btn {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  width: 30px;
  height: 24px;
  position: relative;
  z-index: calc(var(--z-index-overlay) + 1);
}

.mobile-menu-btn span {
  display: block;
  position: absolute;
  height: 2px;
  width: 100%;
  background: var(--theme-heading);
  border-radius: 2px;
  opacity: 1;
  left: 0;
  transform: rotate(0deg);
  transition: .25s ease-in-out;
}

.mobile-menu-btn span:nth-child(1) { top: 0px; }
.mobile-menu-btn span:nth-child(2) { top: 11px; }
.mobile-menu-btn span:nth-child(3) { top: 22px; }

.mobile-menu-btn.open span:nth-child(1) {
  top: 11px;
  transform: rotate(135deg);
}

.mobile-menu-btn.open span:nth-child(2) {
  opacity: 0;
  left: -60px;
}

.mobile-menu-btn.open span:nth-child(3) {
  top: 11px;
  transform: rotate(-135deg);
}

@media (max-width: 768px) {
  .nav-links {
    position: fixed;
    top: 0;
    right: -100%;
    width: 80%;
    max-width: 400px;
    height: 100vh;
    background-color: var(--theme-bg-card);
    flex-direction: column;
    justify-content: center;
    padding: var(--space-8);
    transition: right var(--transition-normal);
    z-index: var(--z-index-overlay);
    box-shadow: var(--shadow-lg);
  }

  .nav-links.active {
    right: 0;
  }
  
  .header-actions .btn {
    display: none; /* Hide primary CTA on mobile header to save space */
  }

  .nav-links .btn {
    display: flex;
    width: 100%;
    margin-top: var(--space-6);
  }

  .mobile-menu-btn {
    display: block;
  }
}