/* ============================================================
   MathGyro — Layout: Header, Footer, Nav, Hero, Toast
   ============================================================ */

/* --- Container --- */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--space-6);
}

/* --- Skip link --- */
.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-4);
  background: var(--accent-primary);
  color: var(--text-inverse);
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: var(--text-sm);
  z-index: var(--z-modal);
  transition: top var(--duration-fast) var(--ease-out);
}
.skip-link:focus { top: var(--space-2); color: var(--text-inverse); }

/* --- Header --- */
.site-header {
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  height: var(--header-height);
  background: var(--header-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-subtle);
  transition: background var(--duration-base) ease;
}

/* When mobile nav is open, disable header blur so overlay is fully opaque */
.site-header.nav-is-open {
  background: transparent;
  -webkit-backdrop-filter: none;
  backdrop-filter: none;
  border-bottom-color: transparent;
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
  gap: var(--space-6);
}

/* Logo */
.logo { display: flex; align-items: center; flex-shrink: 0; }
.logo:hover { text-decoration: none; }
.logo img, .logo svg { height: 34px; width: auto; }
.logo-footer img, .logo-footer svg { height: 28px; width: auto; }
.logo-footer:hover { text-decoration: none; }

/* Main nav */
.main-nav {
  display: flex;
  align-items: center;
  gap: var(--space-8);
}

.nav-list {
  display: flex;
  list-style: none;
  gap: var(--space-1);
  padding: 0;
  margin: 0;
}

.nav-list li { margin: 0; }

.nav-list a {
  display: block;
  padding: var(--space-2) var(--space-3);
  color: var(--text-secondary);
  font-size: var(--text-sm);
  font-weight: 500;
  border-radius: var(--radius-md);
  transition: color var(--duration-fast) ease, background var(--duration-fast) ease;
  position: relative;
}

.nav-list a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: var(--space-3);
  right: var(--space-3);
  height: 2px;
  background: var(--accent-primary);
  border-radius: var(--radius-full);
  transform: scaleX(0);
  transition: transform var(--duration-base) var(--ease-out);
}

.nav-list a:hover { color: var(--text-primary); text-decoration: none; }
.nav-list a:hover::after { transform: scaleX(1); }
.nav-list a[aria-current="page"] { color: var(--accent-primary); }
.nav-list a[aria-current="page"]::after { transform: scaleX(1); }

/* Nav actions */
.nav-actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

/* Language switcher */
.lang-switcher { position: relative; }

.lang-btn {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-1) var(--space-3);
  background: var(--bg-tertiary);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-full);
  color: var(--text-secondary);
  font-family: var(--font-body);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: var(--tracking-wide);
  cursor: pointer;
  transition: all var(--duration-fast) ease;
}
.lang-btn:hover { border-color: var(--accent-primary); color: var(--text-primary); }

.lang-dropdown {
  position: absolute;
  top: calc(100% + var(--space-2));
  right: 0;
  background: var(--bg-secondary);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  padding: var(--space-1);
  min-width: 80px;
  list-style: none;
  opacity: 0;
  visibility: hidden;
  transform: translateY(-4px);
  transition: all var(--duration-base) var(--ease-out);
  z-index: var(--z-dropdown);
}

.lang-btn[aria-expanded="true"] + .lang-dropdown {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.lang-dropdown li { margin: 0; }

.lang-dropdown a {
  display: block;
  padding: var(--space-2) var(--space-3);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--text-secondary);
  border-radius: var(--radius-sm);
  transition: all var(--duration-fast) ease;
}
.lang-dropdown a:hover { background: var(--bg-tertiary); color: var(--text-primary); text-decoration: none; }
.lang-dropdown a[aria-current="true"] { color: var(--accent-primary); background: var(--accent-subtle); }

/* Theme toggle */
.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  background: transparent;
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-full);
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--duration-fast) ease;
}
.theme-toggle:hover { border-color: var(--accent-primary); color: var(--accent-primary); }
.theme-toggle svg { width: 18px; height: 18px; }

/* Sun/Moon visibility */
[data-theme="dark"] .icon-sun  { display: block; }
[data-theme="dark"] .icon-moon { display: none; }
[data-theme="light"] .icon-sun  { display: none; }
[data-theme="light"] .icon-moon { display: block; }
/* Default (dark) */
.icon-sun  { display: block; }
.icon-moon { display: none; }

/* --- Mobile nav toggle --- */
.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 36px;
  height: 36px;
  background: transparent;
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-md);
  padding: 8px;
  cursor: pointer;
  z-index: calc(var(--z-overlay) + 1);
}
.nav-toggle-bar {
  display: block;
  width: 100%;
  height: 2px;
  background: var(--text-primary);
  border-radius: var(--radius-full);
  transition: all var(--duration-base) var(--ease-out);
}
.nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(1) { transform: rotate(45deg) translate(5px, 5px); }
.nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(3) { transform: rotate(-45deg) translate(5px, -5px); }

/* --- Footer --- */
.site-footer {
  border-top: 1px solid var(--border-primary);
  padding: var(--space-16) 0 var(--space-8);
  margin-top: var(--space-20);
}

.footer-inner {
  display: grid;
  grid-template-columns: 1.5fr 2fr;
  gap: var(--space-12);
}

.footer-brand { display: flex; flex-direction: column; gap: var(--space-3); }
.footer-slogan { color: var(--text-secondary); font-size: var(--text-sm); }

.footer-nav {
  display: flex;
  gap: var(--space-12);
}
.footer-nav ul { list-style: none; padding: 0; margin: 0; }
.footer-nav li { margin-bottom: var(--space-2); }
.footer-nav a {
  color: var(--text-secondary);
  font-size: var(--text-sm);
  transition: color var(--duration-fast) ease;
}
.footer-nav a:hover { color: var(--accent-primary); text-decoration: none; }

.footer-bottom {
  grid-column: 1 / -1;
  padding-top: var(--space-8);
  border-top: 1px solid var(--border-primary);
  margin-top: var(--space-4);
}
.footer-bottom p { font-size: var(--text-sm); color: var(--text-tertiary); margin-bottom: var(--space-1); }
.footer-disc { font-size: var(--text-xs); }

/* --- Hero --- */
.hero {
  padding: var(--space-20) 0 var(--space-16);
  text-align: center;
  background: linear-gradient(
    135deg,
    var(--bg-primary) 0%,
    color-mix(in srgb, var(--accent-primary) 6%, var(--bg-primary)) 50%,
    var(--bg-primary) 100%
  );
  border-bottom: 1px solid var(--border-subtle);
}
.hero h1 { margin-top: 0; margin-bottom: var(--space-4); font-size: var(--text-5xl); letter-spacing: -0.03em; }
.hero p  { font-size: var(--text-lg); max-width: 560px; margin: 0 auto var(--space-8); }

/* --- Breadcrumb --- */
.breadcrumb { padding: var(--space-4) 0 var(--space-2); }
.breadcrumb ol {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1);
  list-style: none;
  padding: 0;
  margin: 0;
  font-size: var(--text-sm);
  color: var(--text-tertiary);
}
.breadcrumb li { display: flex; align-items: center; gap: var(--space-1); margin: 0; }
.breadcrumb li:not(:last-child)::after { content: '/'; color: var(--text-tertiary); margin-left: var(--space-1); opacity: 0.5; }
.breadcrumb a { color: var(--text-secondary); }
.breadcrumb a:hover { color: var(--accent-primary); }
.breadcrumb span[aria-current] { color: var(--text-primary); font-weight: 600; }

/* --- Toast --- */
.toast {
  position: fixed;
  bottom: var(--space-6);
  right: var(--space-6);
  background: var(--bg-secondary);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  padding: var(--space-3) var(--space-5);
  box-shadow: var(--shadow-xl);
  font-size: var(--text-sm);
  font-weight: 500;
  z-index: var(--z-toast);
  display: flex;
  align-items: center;
  gap: var(--space-2);
  transform: translateY(120%);
  opacity: 0;
  transition: all var(--duration-slow) var(--ease-out);
}
.toast.is-visible { transform: translateY(0); opacity: 1; }
.toast--success { border-left: 3px solid var(--success); }
.toast--error   { border-left: 3px solid var(--danger); }
.toast--warning { border-left: 3px solid var(--warning); }
.toast--info    { border-left: 3px solid var(--info); }

/* --- Scroll-to-top --- */
.scroll-top-btn {
  position: fixed;
  bottom: var(--space-6);
  right: var(--space-6);
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-secondary);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-full);
  color: var(--text-secondary);
  box-shadow: var(--shadow-lg);
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(8px);
  transition: all var(--duration-base) var(--ease-out);
  z-index: var(--z-sticky);
}
.scroll-top-btn.is-visible { opacity: 1; visibility: visible; transform: translateY(0); }
.scroll-top-btn:hover { color: var(--accent-primary); border-color: var(--accent-primary); }
.scroll-top-btn svg { width: 20px; height: 20px; }

/* --- Responsive --- */
@media (max-width: 768px) {
  .nav-toggle { display: flex; }

  .main-nav {
    position: fixed;
    inset: 0;
    background: #0f172a;
    background: var(--bg-primary);
    -webkit-backdrop-filter: none;
    backdrop-filter: none;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    gap: var(--space-8);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-8px);
    transition: opacity var(--duration-slow) var(--ease-out),
                visibility var(--duration-slow) var(--ease-out),
                transform var(--duration-slow) var(--ease-out);
    z-index: var(--z-overlay);
  }
  .main-nav.is-open {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
  }

  /* Ensure header doesn't clip or bleed into fullscreen nav */
  .site-header { overflow: visible; }
  .main-nav.is-open ~ *,
  .site-header:has(.main-nav.is-open) {
    -webkit-backdrop-filter: none;
    backdrop-filter: none;
  }

  .nav-list { flex-direction: column; align-items: center; gap: var(--space-4); }
  .nav-list a { font-size: var(--text-xl); padding: var(--space-3) var(--space-6); }
  .nav-list a::after { display: none; }

  .nav-actions { gap: var(--space-4); }

  .hero h1 { font-size: var(--text-3xl); }
  .hero { padding: var(--space-12) 0 var(--space-10); }

  .footer-inner { grid-template-columns: 1fr; gap: var(--space-8); }
  .footer-nav { flex-direction: column; gap: var(--space-6); }

  .container { padding: 0 var(--space-4); }
}

/* === Nav dropdown === */
.nav-has-dropdown { position: relative; }
.nav-has-dropdown > a { display: inline-flex; align-items: center; gap: var(--space-1); }
.nav-chevron { transition: transform var(--duration-base) var(--ease-out); }

.nav-dropdown {
  position: absolute;
  top: calc(100% + var(--space-3));
  left: 50%;
  transform: translateX(-50%) translateY(-4px);
  background: var(--bg-secondary);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-xl);
  padding: var(--space-4);
  min-width: 260px;
  opacity: 0;
  visibility: hidden;
  transition: all var(--duration-base) var(--ease-out);
  z-index: var(--z-dropdown);
}

.nav-has-dropdown:hover > .nav-dropdown,
.nav-has-dropdown:focus-within > .nav-dropdown {
  opacity: 1;
  visibility: visible;
  transform: translateX(-50%) translateY(0);
}
.nav-has-dropdown:hover .nav-chevron { transform: rotate(180deg); }

.nav-dropdown-group { margin-bottom: var(--space-3); }
.nav-dropdown-group:last-child { margin-bottom: 0; }

.nav-dropdown-label {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-xs);
  font-weight: 600;
  color: var(--text-tertiary);
  text-transform: uppercase;
  letter-spacing: var(--tracking-wide);
  padding: var(--space-1) var(--space-2);
  margin-bottom: var(--space-1);
}
.nav-dropdown-label svg { width: 14px; height: 14px; }

.nav-dropdown ul { list-style: none; padding: 0; margin: 0; }
.nav-dropdown li { margin: 0; }

.nav-dropdown a {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  font-size: var(--text-sm);
  color: var(--text-secondary);
  border-radius: var(--radius-md);
  transition: all var(--duration-fast) ease;
}
.nav-dropdown a:hover { background: var(--bg-tertiary); color: var(--text-primary); text-decoration: none; }

.nav-dropdown-icon { display: flex; color: var(--accent-primary); }
.nav-dropdown-icon svg { width: 16px; height: 16px; }

/* Footer email */
.footer-email {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  color: var(--text-secondary);
  font-size: var(--text-sm);
  transition: color var(--duration-fast) ease;
}
.footer-email:hover { color: var(--accent-primary); text-decoration: none; }
.footer-email svg { width: 16px; height: 16px; }

.footer-nav-col ul { list-style: none; padding: 0; margin: 0; }

/* Mobile dropdown behavior */
@media (max-width: 768px) {
  .nav-dropdown { display: none; }
  .nav-chevron { display: none; }
}

/* Light theme mobile nav solid background */
@media (max-width: 768px) {
  [data-theme="light"] .main-nav {
    background: #fafbfd;
    background: var(--bg-primary);
  }
}