/* Header look-and-feel: modern, sticky, responsive, accessible */

:root {
  --header-bg: color-mix(in oklab, white 70%, transparent);
  --header-border: color-mix(in oklab, #1e293b 15%, transparent);
  --header-text: #0f172a; /* slate-900 */
  --brand-strong: #0ea5e9; /* sky-500 */
  --brand-strong-2: #06b6d4; /* cyan-500 */
  --link: #0f172a;
  --link-hover: #0ea5e9;
  --active-bg: rgba(14, 165, 233, 0.12);
  --active-ring: rgba(14, 165, 233, 0.35);
  --shadow: 0 6px 24px rgba(2, 6, 23, 0.08), 0 1px 1px rgba(2, 6, 23, 0.06);

  /* Header spacing variables */
  --header-py: 16px;         /* increased vertical padding (was 12px) */
  --header-px: 16px;         /* keep horizontal padding the same */
  --header-py-scrolled: 8px; /* desktop shrink matches previous look */
  /* Mobile menu offset = toggle height (≈40px) + 2 * vertical padding */
  --header-mobile-offset: calc(40px + (var(--header-py) * 2));
}

/* Accessibility: skip link */
.skip-link {
  position: absolute;
  top: -40px;
  left: 16px;
  background: #0f172a;
  color: white;
  padding: 8px 12px;
  border-radius: 6px;
  z-index: 10000;
  text-decoration: none;
  transition: top .2s ease;
}
.skip-link:focus { top: 12px; }

/* Screen-reader only utility */
.sr-only {
  position: absolute !important;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0,0,0,0);
  white-space: nowrap; border: 0;
}

.site-header {
  position: sticky;
  top: 0; z-index: 1000;
  background: var(--header-bg);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--header-border);
  transition: background .25s ease, box-shadow .25s ease, transform .2s ease;
}
.site-header.scrolled {
  box-shadow: var(--shadow);
  background: color-mix(in oklab, white 82%, transparent);
}

.header-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: var(--header-py) var(--header-px);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  color: var(--header-text);
  text-decoration: none;
  font-weight: 700;
  letter-spacing: 0.2px;
}
.brand-logo svg {
  display: block;
  filter: drop-shadow(0 2px 6px rgba(14,165,233,.25));
}
.brand-text {
  font-size: 1.05rem;
  line-height: 1;
}

/* Nav base */
.primary-nav ul {
  list-style: none;
  margin: 0; padding: 0;
  display: flex;
  gap: 10px;
}
.primary-nav a {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border-radius: 10px;
  color: var(--link);
  text-decoration: none;
  line-height: 1.2;
  transition: background .2s ease, color .2s ease, transform .15s ease;
  position: relative;
}
.primary-nav a:hover {
  color: var(--link-hover);
  background: rgba(2,6,23,0.04);
}
.primary-nav a:focus-visible {
  outline: 2px solid var(--active-ring);
  outline-offset: 2px;
  background: rgba(14,165,233,0.06);
}
.primary-nav a[aria-current="page"] {
  color: var(--link-hover);
  background: var(--active-bg);
}
.primary-nav { display: block; }

/* Toggle button */
.nav-toggle {
  appearance: none;
  border: 1px solid rgba(2,6,23,0.08);
  background: white;
  color: #0f172a;
  border-radius: 10px;
  padding: 8px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  cursor: pointer;
  transition: transform .1s ease, box-shadow .15s ease, background .2s ease;
}
.nav-toggle:hover { box-shadow: 0 4px 14px rgba(2,6,23,0.08); }
.nav-toggle:active { transform: translateY(1px); }
.nav-toggle .icon-close { display: none; }
.nav-toggle[aria-expanded="true"] .icon-menu { display: none; }
.nav-toggle[aria-expanded="true"] .icon-close { display: block; }

/* Overlay for mobile menu */
.nav-overlay {
  position: fixed;
  inset: 0;
  background: rgba(2,6,23,0.35);
  backdrop-filter: blur(1px);
  -webkit-backdrop-filter: blur(1px);
  opacity: 0;
  pointer-events: none;
  transition: opacity .2s ease;
  z-index: 900;
}
body.nav-open .nav-overlay {
  opacity: 1;
  pointer-events: auto;
}

/* Desktop vs Mobile layout */
@media (min-width: 768px) {
  .nav-toggle { display: none; }
  .primary-nav {
    position: static;
  }
}

@media (max-width: 767.98px) {
  .primary-nav {
    position: fixed;
    top: calc(var(--header-mobile-offset) + env(safe-area-inset-top));
    right: 12px; left: 12px;
    background: white;
    border: 1px solid rgba(2,6,23,0.08);
    border-radius: 14px;
    box-shadow: 0 24px 40px rgba(2,6,23,0.12);
    transform-origin: top right;
    transform: scale(0.98) translateY(-8px);
    opacity: 0;
    pointer-events: none;
    transition: transform .18s ease, opacity .18s ease;
    z-index: 1001;
  }
  .primary-nav ul {
    flex-direction: column;
    padding: 8px;
    gap: 4px;
  }
  .primary-nav a {
    padding: 12px 14px;
    border-radius: 10px;
  }
  body.nav-open .primary-nav {
    opacity: 1;
    pointer-events: auto;
    transform: scale(1) translateY(0);
  }
  body.nav-open {
    overflow: hidden;
    touch-action: none;
  }
}

/* Slight shrink on scroll for header content (desktop only) */
@media (min-width: 768px) {
  .site-header.scrolled .header-inner {
    padding-top: var(--header-py-scrolled);
    padding-bottom: var(--header-py-scrolled);
  }
}