/* ============================================================
   navbar.css — Navigation Bar
   Fixed header, desktop links, theme switcher,
   hamburger button, and mobile slide-down drawer.
============================================================ */

/* ── Header wrapper ─────────────────────────────────────────── */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 50;
  transition: background 0.5s, border-color 0.5s, backdrop-filter 0.5s;
  border-bottom: 1px solid transparent;
}

/* Frosted-glass effect on scroll */
.site-header.scrolled {
  background: color-mix(in srgb, var(--color-paper) 85%, transparent);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom-color: var(--color-line);
}

/* ── Inner row ──────────────────────────────────────────────── */
.nav-inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1.5rem;
  height: 68px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
}
@media (min-width: 64rem) {
  .nav-inner { padding: 0 2.5rem; }
}

/* ── Logo ───────────────────────────────────────────────────── */
.nav-logo {
  font-family: var(--font-display);
  font-size: 1.2rem;
  font-weight: 600;
  letter-spacing: -0.025em;
  color: var(--color-ink);
  flex-shrink: 0;
}
.logo-dot { color: var(--color-accent); }

/* ── Desktop nav links (hidden on mobile) ───────────────────── */
.nav-links {
  display: none;
  align-items: center;
  gap: 2rem;
}
@media (min-width: 48rem) {
  .nav-links { display: flex; }
}

.nav-link {
  font-size: 0.875rem;
  color: var(--color-ink-soft);
  transition: color 0.2s;
  position: relative;
}
/* Animated underline indicator */
.nav-link::after {
  content: "";
  position: absolute;
  bottom: -4px;
  left: 0;
  height: 1px;
  width: 0;
  background: var(--color-accent);
  transition: width 0.3s cubic-bezier(0, 0, 0.2, 1);
}
.nav-link.active,
.nav-link:hover               { color: var(--color-ink); }
.nav-link.active::after,
.nav-link:hover::after        { width: 100%; }

/* ── Theme switcher (pill group) ────────────────────────────── */
.theme-switcher {
  display: flex;
  align-items: center;
  gap: 2px;
  background: var(--color-sand);
  border: 1px solid var(--color-line);
  border-radius: 999px;
  padding: 2px;
}
.theme-btn {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  font-size: 0.875rem;
  color: var(--color-ink-soft);
  display: grid;
  place-items: center;
  transition: background 0.3s, color 0.3s;
}
.theme-btn.active,
.theme-btn[aria-pressed="true"] {
  background: var(--color-accent);
  color: var(--color-paper);
}

/* ── CTA button ─────────────────────────────────────────────── */
.nav-cta {
  background: var(--color-ink);
  color: var(--color-paper);
  border-radius: 999px;
  padding: 0.5rem 1.25rem;
  font-size: 0.875rem;
  transition: background 0.3s, transform 0.3s;
  flex-shrink: 0;
}
.nav-cta:hover {
  background: var(--color-accent);
  transform: translateY(-2px);
}

/* ── Mobile controls (visible only on small screens) ────────── */
.nav-mobile-controls {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}
@media (min-width: 48rem) {
  .nav-mobile-controls { display: none; }
}

/* ── Hamburger button ───────────────────────────────────────── */
.hamburger {
  width: 36px;
  height: 36px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 6px;
}
.ham-bar {
  display: block;
  width: 24px;
  height: 1.5px;
  background: var(--color-ink);
  border-radius: 2px;
  transition: transform 0.3s, opacity 0.3s;
}
/* Animate into × when open */
.hamburger[aria-expanded="true"] .ham-bar:nth-child(1) {
  transform: translateY(3.75px) rotate(45deg);
}
.hamburger[aria-expanded="true"] .ham-bar:nth-child(2) {
  transform: translateY(-3.75px) rotate(-45deg);
}

/* ── Mobile slide-down drawer ───────────────────────────────── */
.mobile-drawer {
  display: none;            /* hidden by default */
  flex-direction: column;
  gap: 0.25rem;
  background: var(--color-paper);
  border-top: 1px solid var(--color-line);
  padding: 1rem 1.5rem;
}
/* Shown when JS removes the `hidden` attribute */
.mobile-drawer:not([hidden]) {
  display: flex;
}

.mobile-link {
  display: block;
  padding: 0.625rem 0;
  color: var(--color-ink-soft);
  font-size: 0.95rem;
  transition: color 0.2s;
}
.mobile-link:hover { color: var(--color-ink); }

.mobile-cta {
  display: inline-block;
  margin-top: 0.5rem;
  background: var(--color-ink);
  color: var(--color-paper);
  border-radius: 999px;
  padding: 0.5rem 1.25rem;
  font-size: 0.875rem;
}