/* ===========================================================
   Navigation (sticky, glass, scroll-aware)
   =========================================================== */

.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: var(--z-nav);
  display: flex;
  justify-content: center;
  padding: var(--space-3) var(--gutter);
  pointer-events: none;
  transition: padding var(--duration) var(--ease-out);
}

.nav__shell {
  pointer-events: auto;
  width: 100%;
  max-width: var(--container);
  height: var(--nav-h);
  padding: 0 22px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-6);
  background: color-mix(in srgb, var(--color-surface) 75%, transparent);
  backdrop-filter: blur(20px) saturate(180%);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  border: 1px solid var(--color-border-soft);
  border-radius: var(--radius-pill);
  box-shadow: var(--shadow-sm);
  transition: max-width var(--duration) var(--ease-out),
              box-shadow var(--duration) var(--ease-out);
}

.nav.is-scrolled .nav__shell {
  max-width: 980px;
  box-shadow: var(--shadow-md);
}

.nav__logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-display);
  font-weight: var(--weight-bold);
  font-size: var(--fs-md);
  letter-spacing: var(--tracking-snug);
  color: var(--color-text);
  flex-shrink: 0;
}
.nav__logo svg { width: 28px; height: 28px; flex-shrink: 0; }

.nav__links {
  display: flex;
  align-items: center;
  gap: var(--space-6);
}
.nav__links a {
  font-size: var(--fs-sm);
  font-weight: var(--weight-medium);
  color: var(--color-text-muted);
  position: relative;
  padding: 8px 4px;
  transition: color var(--duration-fast) var(--ease-out);
}
.nav__links a:hover { color: var(--color-text); }
.nav__links a::after {
  content: '';
  position: absolute;
  left: 50%;
  bottom: 2px;
  transform: translateX(-50%);
  width: 0;
  height: 2px;
  background: var(--color-primary);
  border-radius: 2px;
  transition: width var(--duration) var(--ease-out);
}
.nav__links a:hover::after { width: 16px; }

.nav__actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  flex-shrink: 0;
}

/* Theme toggle button */
.theme-toggle {
  width: 38px;
  height: 38px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  background: var(--color-surface-2);
  border: 1px solid var(--color-border);
  color: var(--color-text-muted);
  transition: background var(--duration) var(--ease-out),
              color var(--duration) var(--ease-out),
              transform var(--duration-fast) var(--ease-spring);
}
.theme-toggle:hover {
  background: var(--color-primary-50);
  color: var(--color-primary);
  transform: rotate(15deg);
}
.theme-toggle svg { width: 18px; height: 18px; }
.theme-toggle .icon-moon { display: none; }
.theme-toggle .icon-sun  { display: block; }
[data-theme="dark"] .theme-toggle .icon-moon { display: block; }
[data-theme="dark"] .theme-toggle .icon-sun  { display: none; }
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .theme-toggle .icon-moon { display: block; }
  :root:not([data-theme="light"]) .theme-toggle .icon-sun  { display: none; }
}

/* Lang switcher */
.lang-switch {
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  font-weight: var(--weight-medium);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  padding: 6px 10px;
  border-radius: var(--radius-pill);
  border: 1px solid var(--color-border);
  background: var(--color-surface-2);
  transition: color var(--duration-fast) var(--ease-out);
}
.lang-switch:hover { color: var(--color-text); border-color: var(--color-border-strong); }

/* Mobile menu toggle */
.nav__toggle {
  display: none;
  width: 40px;
  height: 40px;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  background: var(--color-surface-2);
  border: 1px solid var(--color-border);
  position: relative;
}
.nav__toggle span {
  position: absolute;
  left: 50%;
  width: 18px;
  height: 1.6px;
  background: var(--color-text);
  border-radius: 2px;
  transition: transform var(--duration) var(--ease-out),
              top var(--duration) var(--ease-out),
              opacity var(--duration-fast) var(--ease-out);
}
.nav__toggle span:nth-child(1) { top: 14px; transform: translateX(-50%); }
.nav__toggle span:nth-child(2) { top: 19px; transform: translateX(-50%); }
.nav__toggle span:nth-child(3) { top: 24px; transform: translateX(-50%); }
.nav__toggle[aria-expanded="true"] span:nth-child(1) {
  top: 19px;
  transform: translateX(-50%) rotate(45deg);
}
.nav__toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.nav__toggle[aria-expanded="true"] span:nth-child(3) {
  top: 19px;
  transform: translateX(-50%) rotate(-45deg);
}

/* Mobile drawer */
.nav__mobile {
  pointer-events: auto;
  position: fixed;
  top: calc(var(--nav-h-mobile) + 24px);
  left: var(--gutter);
  right: var(--gutter);
  background: color-mix(in srgb, var(--color-surface) 92%, transparent);
  backdrop-filter: blur(24px) saturate(180%);
  -webkit-backdrop-filter: blur(24px) saturate(180%);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-2);
  display: none;
  flex-direction: column;
  gap: 2px;
  box-shadow: var(--shadow-lg);
  opacity: 0;
  transform: translateY(-8px) scale(0.98);
  transition: opacity var(--duration) var(--ease-out),
              transform var(--duration) var(--ease-out);
  z-index: var(--z-nav);
}
.nav__mobile.is-open {
  display: flex;
  opacity: 1;
  transform: translateY(0) scale(1);
}
.nav__mobile a {
  display: block;
  padding: 12px 14px;
  font-size: var(--fs-md);
  font-weight: var(--weight-medium);
  color: var(--color-text);
  border-radius: var(--radius);
  transition: background var(--duration-fast) var(--ease-out);
}
.nav__mobile a:hover { background: var(--color-surface-2); }
.nav__mobile a:last-child {
  margin-top: 6px;
  padding: 13px 14px;
  text-align: center;
  background: var(--grad-primary);
  color: #fff;
  font-weight: var(--weight-semibold);
  box-shadow: var(--shadow-glow);
}

/* Responsive */
@media (max-width: 960px) {
  .nav__links { display: none; }
}
@media (max-width: 720px) {
  .nav { padding: var(--space-2) var(--space-3); }
  .nav__shell { height: var(--nav-h-mobile); padding: 0 14px; }
  .nav__toggle { display: inline-flex; }
  .nav__actions .btn { display: none; }
}