/* Header styles (builds on base.css) */
.site-header {
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  background: linear-gradient(180deg, rgba(10,14,20,0.95) 0%, rgba(10,14,20,0.85) 100%);
  border-bottom: 1px solid var(--color-gray-800);
  box-shadow: var(--shadow-base);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  min-height: 64px;
  width: 100%;
}

@media (max-width: 640px) {
  .header-inner {
    gap: var(--space-2);
  }
}

/* Brand */
.site-brand {
  display: inline-flex;
  align-items: center;
  gap: var(--space-3);
  color: var(--color-text-primary);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.02em;
}
.brand-mark {
  width: 10px;
  height: 10px;
  border-radius: var(--radius-full);
  background: radial-gradient(circle at 30% 30%, var(--color-primary), var(--color-accent));
  box-shadow: var(--shadow-glow);
}
.brand-text { font-family: var(--font-heading); }

/* Navigation */
.primary-nav {
  /* Desktop default */
}
.nav-list {
  display: flex;
  align-items: center;
  gap: var(--space-6);
}

.nav-link {
  color: var(--color-text-secondary);
  font-weight: var(--font-weight-medium);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-lg);
  transition: color var(--transition-base) var(--ease-out), background-color var(--transition-base) var(--ease-out);
}

.nav-link:hover,
.nav-link:focus-visible {
  color: var(--color-text-primary);
  background-color: var(--color-bg-tertiary);
}

/* Mobile toggle */
.menu-toggle {
  display: none;
  color: var(--color-text-primary);
  gap: var(--space-2);
  align-items: center;
  padding: var(--space-2) var(--space-3);
  border: 1px solid var(--color-gray-800);
  border-radius: var(--radius-lg);
}
.menu-toggle:hover {
  background-color: var(--color-bg-tertiary);
}
.menu-toggle .toggle-text { font-size: var(--font-size-sm); }

/* Progressive enhancement: only collapse nav on small screens when JS is available */
@media (max-width: 768px) {
  .menu-toggle { display: inline-flex; }
  .nav-list { gap: var(--space-4); }

  html.js .primary-nav {
    position: fixed;
    inset: 0;
    background: var(--color-bg-overlay);
    -webkit-backdrop-filter: blur(6px);
    backdrop-filter: blur(6px);
    display: none; /* hidden until opened */
    align-items: center;
    justify-content: center;
  }
  html.js .site-header.is-open .primary-nav { display: flex; }

  html.js .primary-nav .nav-list {
    flex-direction: column;
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-gray-800);
    border-radius: var(--radius-2xl);
    padding: var(--space-8);
    box-shadow: var(--shadow-xl);
    min-width: min(85vw, 420px);
    max-width: 90vw;
  }
  html.js .primary-nav .nav-link { font-size: var(--font-size-lg); }
}

/* Prevent background scroll when menu open */
body.no-scroll { overflow: hidden; }

/* Reduced motion */
@media (prefers-reduced-motion: no-preference) {
  html.js .primary-nav { animation: fadeIn var(--transition-slower) var(--ease-out); }
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}