.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  padding: 0 40px;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: rgba(10, 10, 10, 0.8);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border-subtle);
  transition: background var(--transition-slow), border-color var(--transition-slow);
}

[data-theme="light"] .header {
  background: rgba(248, 248, 246, 0.85);
}

.header-logo {
  font-family: var(--font-mono);
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--accent);
  letter-spacing: -0.02em;
  display: flex;
  align-items: center;
  gap: 8px;
}

.header-logo .logo-slash {
  color: var(--text-muted);
  font-weight: 400;
}

.header-nav {
  display: flex;
  align-items: center;
  gap: 32px;
}

.header-nav a {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-secondary);
  transition: color var(--transition);
  position: relative;
}

.header-nav a::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  right: 0;
  height: 1px;
  background: var(--accent);
  transform: scaleX(0);
  transition: transform var(--transition);
}

.header-nav a:hover,
.header-nav a.active {
  color: var(--accent);
}

.header-nav a:hover::after,
.header-nav a.active::after {
  transform: scaleX(1);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 12px;
}

.theme-toggle {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-sm);
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  transition: all var(--transition);
}

.theme-toggle:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.lang-toggle {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-secondary);
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 6px 12px;
  cursor: pointer;
  transition: all var(--transition);
}

.lang-toggle:hover {
  border-color: var(--accent);
  color: var(--accent);
}

/* Mobile */
.mobile-menu-btn {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.mobile-menu-btn span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text-primary);
  transition: all var(--transition);
}

@media (max-width: 768px) {
  .header {
    padding: 0 20px;
  }

  .header-nav {
    display: none;
    position: fixed;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--bg-surface);
    border-bottom: 1px solid var(--border);
    flex-direction: column;
    padding: 24px 20px;
    gap: 20px;
    align-items: flex-start;
  }

  .header-nav.open {
    display: flex;
  }

  .mobile-menu-btn {
    display: flex;
  }
}