/* ==========================================================================
   Nexus Mastering — Navigation
   Sticky header, transparent-to-glass transition, dropdowns, mobile menu
   ========================================================================== */

.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 900;
  height: var(--nav-height);
  display: flex;
  align-items: center;
  background: transparent;
  border-bottom: 1px solid transparent;
  transition: background-color var(--duration-base) var(--ease-smooth),
    border-color var(--duration-base) var(--ease-smooth),
    backdrop-filter var(--duration-base) var(--ease-smooth);
}

.site-header.is-scrolled {
  background: rgba(5, 5, 6, 0.65);
  border-bottom: 1px solid var(--border-hairline);
  backdrop-filter: var(--blur-glass);
  -webkit-backdrop-filter: var(--blur-glass);
}

.nav-inner {
  width: 100%;
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--space-md);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

/* Primary nav list */
.nav-menu {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
}

.nav-link {
  position: relative;
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  font-size: 0.94rem;
  font-weight: 500;
  color: var(--text-secondary);
  padding: 0.4rem 0.1rem;
  transition: color var(--duration-fast) var(--ease-smooth);
}

.nav-link::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -2px;
  width: 100%;
  height: 1px;
  background: var(--text-primary);
  transform: scaleX(0);
  transform-origin: right;
  transition: transform var(--duration-base) var(--ease-apple);
}

.nav-link:hover {
  color: var(--text-primary);
}

.nav-link:hover::after {
  transform: scaleX(1);
  transform-origin: left;
}

.nav-link.active {
  color: var(--text-primary);
}

.nav-caret {
  width: 9px;
  height: 9px;
  border-right: 1.5px solid currentColor;
  border-bottom: 1.5px solid currentColor;
  transform: rotate(45deg) translateY(-2px);
  transition: transform var(--duration-fast) var(--ease-smooth);
  margin-left: 2px;
}

.nav-item.has-dropdown:hover .nav-caret {
  transform: rotate(225deg) translateY(2px);
}

/* Dropdown */
.nav-item {
  position: relative;
}

.nav-dropdown {
  position: absolute;
  top: 100%;
  left: 50%;
  transform: translateX(-50%) translateY(8px);
  min-width: 220px;
  padding: 0.6rem;
  background: rgba(10, 10, 12, 0.85);
  border: 1px solid var(--border-hairline-strong);
  border-radius: var(--radius-md);
  backdrop-filter: var(--blur-glass);
  -webkit-backdrop-filter: var(--blur-glass);
  box-shadow: var(--shadow-lg);
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transition: opacity var(--duration-base) var(--ease-apple),
    transform var(--duration-base) var(--ease-apple),
    visibility var(--duration-base);
}

.nav-item.has-dropdown:hover .nav-dropdown,
.nav-item.has-dropdown:focus-within .nav-dropdown {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
  transform: translateX(-50%) translateY(0);
}

.nav-dropdown-link {
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
  padding: 0.65rem 0.9rem;
  border-radius: var(--radius-sm);
  transition: background var(--duration-fast) var(--ease-smooth);
}

.nav-dropdown-link:hover {
  background: var(--surface-glass-strong);
}

.nav-dropdown-link .dd-title {
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--text-primary);
}

.nav-dropdown-link .dd-desc {
  font-size: 0.78rem;
  color: var(--text-tertiary);
}

/* Nav actions (right side) */
.nav-actions {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.nav-cta {
  padding: 0.6rem 1.35rem;
  font-size: 0.88rem;
}

/* Mobile toggle */
.nav-toggle {
  display: none;
  width: 40px;
  height: 40px;
  position: relative;
  z-index: 1001;
}

.nav-toggle span {
  position: absolute;
  left: 8px;
  right: 8px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: transform var(--duration-base) var(--ease-apple),
    opacity var(--duration-fast) var(--ease-smooth);
}

.nav-toggle span:nth-child(1) {
  top: 14px;
}

.nav-toggle span:nth-child(2) {
  top: 20px;
}

.nav-toggle span:nth-child(3) {
  top: 26px;
}

.nav-toggle.is-open span:nth-child(1) {
  transform: translateY(6px) rotate(45deg);
}

.nav-toggle.is-open span:nth-child(2) {
  opacity: 0;
}

.nav-toggle.is-open span:nth-child(3) {
  transform: translateY(-6px) rotate(-45deg);
}

/* Mobile menu panel */
.nav-mobile-panel {
  position: fixed;
  inset: 0;
  z-index: 999;
  background: rgba(5, 5, 6, 0.98);
  backdrop-filter: var(--blur-glass);
  -webkit-backdrop-filter: var(--blur-glass);
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: var(--space-xl) var(--space-lg);
  opacity: 0;
  visibility: hidden;
  transform: translateY(-12px);
  transition: opacity var(--duration-base) var(--ease-apple),
    transform var(--duration-base) var(--ease-apple),
    visibility var(--duration-base);
}

.nav-mobile-panel.is-open {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.nav-mobile-list {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}

.nav-mobile-link {
  font-size: 1.6rem;
  font-weight: 600;
  padding: 0.6rem 0;
  color: var(--text-primary);
  letter-spacing: -0.02em;
}

.nav-mobile-sub {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
  padding-left: var(--space-md);
  max-height: 0;
  overflow: hidden;
  transition: max-height var(--duration-base) var(--ease-apple);
}

.nav-mobile-group.is-open .nav-mobile-sub {
  max-height: 200px;
}

.nav-mobile-sub a {
  font-size: 1.05rem;
  color: var(--text-secondary);
  padding: 0.4rem 0;
}

.nav-mobile-group-toggle {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
}

.nav-mobile-footer {
  margin-top: var(--space-xl);
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}