/* ═══════════════════════════════════════════════
   NABLA — Shared Components
   Header · Footer · Theme Toggle
   Desktop-only: mobile/tablet intercepted by app.js
   Import after theme.css
═══════════════════════════════════════════════ */

/* ── RESET (shared baseline) ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
}

body {
  background-color: var(--void);
  color: var(--text-primary);
  font-family: var(--font-sans);
  line-height: 1.6;
  min-height: 100vh;
  overflow-x: hidden;
}

::selection { background: var(--orange-dim); color: var(--text-primary); }

::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--void); }
::-webkit-scrollbar-thumb { background: var(--scrollbar-thumb); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--orange); }

/* ── HEADER ── */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--header-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
}

.header-inner {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 2rem;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 2rem;
}

/* Brand */
.brand {
  display: flex;
  align-items: center;
  text-decoration: none;
  flex-shrink: 0;
}

.logo-wrap {
  display: flex;
  align-items: center;
  gap: 0.65rem;
}

.nabla-logo {
  width: 32px;
  height: 32px;
  flex-shrink: 0;
}

.brand-name {
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 1.15rem;
  letter-spacing: -0.02em;
  background: var(--grad-brand);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* Desktop nav */
.header-nav {
  display: flex;
  align-items: center;
  gap: 1.75rem;
  flex: 1;
  justify-content: center;
}

.nav-link {
  font-size: 0.875rem;
  color: var(--text-secondary);
  text-decoration: none;
  font-family: var(--font-mono);
  transition: color 0.18s;
  position: relative;
  padding: 0.25rem 0;
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  right: 0;
  height: 1px;
  background: var(--orange-bright);
  transform: scaleX(0);
  transition: transform 0.2s ease;
}

.nav-link:hover { color: var(--text-primary); }
.nav-link:hover::after { transform: scaleX(1); }
.nav-link.active { color: var(--orange-bright); }
.nav-link.active::after { transform: scaleX(1); }

/* Header actions — theme toggle only */
.header-actions {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  flex-shrink: 0;
}

/* Theme toggle button */
.theme-toggle-btn {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--surface-raised);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.18s;
  flex-shrink: 0;
}

.theme-toggle-btn:hover {
  color: var(--orange-bright);
  border-color: var(--border-hover);
  background: var(--surface-hover);
}

.theme-toggle-btn svg {
  width: 16px;
  height: 16px;
}

/* ── FOOTER ── */
.site-footer {
  background: var(--void);
  border-top: 1px solid var(--border);
  padding: 5rem 2rem 0;
  position: relative;
  overflow: hidden;
}

.footer-glow {
  position: absolute;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 60%;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--orange-glow), transparent);
  pointer-events: none;
}

.footer-inner {
  max-width: 1280px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: 4rem;
  padding-bottom: 4rem;
}

.footer-col {
  display: flex;
  flex-direction: column;
  gap: 0.9rem;
}

.footer-col--brand { gap: 1.25rem; }

.footer-brand {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  font-family: var(--font-mono);
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--text-primary);
}

.footer-brand .nabla-logo { width: 28px; height: 28px; }

.footer-tagline {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.7;
  max-width: 340px;
}

.footer-col-title {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--orange-bright);
  margin-bottom: 0.25rem;
}

.footer-link-sm {
  font-family: var(--font-mono);
  font-size: 0.88rem;
  color: var(--text-secondary);
  text-decoration: none;
  transition: color 0.18s, transform 0.18s;
  display: inline-block;
}

.footer-link-sm:hover {
  color: var(--orange-bright);
  transform: translateX(3px);
}

.footer-cta {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  width: fit-content;
  font-family: var(--font-mono);
  font-size: 0.84rem;
  font-weight: 700;
  color: #fff;
  background: var(--grad-brand);
  padding: 0.6rem 1.2rem;
  border-radius: var(--radius-pill);
  text-decoration: none;
  transition: box-shadow 0.22s, transform 0.22s;
}

[data-theme="light"] .footer-cta { color: #fff; }

.footer-cta:hover {
  box-shadow: 0 0 20px var(--orange-glow);
  transform: translateY(-2px);
}

.footer-cta-arrow { transition: transform 0.18s; }
.footer-cta:hover .footer-cta-arrow { transform: translateX(4px); }

.footer-bottom {
  border-top: 1px solid var(--border);
  padding: 1.75rem 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1rem;
  max-width: 1280px;
  margin: 0 auto;
}

.footer-copy {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--text-muted);
}

.footer-copy--muted { opacity: 0.7; }

/* ── REDUCED MOTION ── */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}