.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: calc(var(--z-modal) + 2);
  background-color: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border-color);
  transition: var(--transition);
}

[data-theme="dark"] .header {
  background-color: rgba(17, 24, 39, 0.95);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-lg) 0;
}

.nav-brand {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--primary);
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.nav-menu {
  display: flex;
  align-items: center;
  gap: var(--space-xl);
}

.nav-link {
  font-weight: 500;
  color: var(--text-secondary);
  transition: var(--transition);
  padding: var(--space-sm) var(--space-md);
  border-radius: var(--radius-md);
  position: relative;
  outline: none;
  text-decoration: none;
}

.nav-link:focus {
  outline: none;
  box-shadow: none;
}

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

.nav-link::before {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 50%;
  transform: translateX(-50%);
  width: 0;
  height: 2px;
  background: var(--gradient-primary);
  transition: var(--transition);
}

.nav-link:hover::before,
.nav-link.active::before {
  width: 100%;
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 4px;
  padding: var(--space-sm);
  background: none;
  border: none;
  cursor: pointer;
}

.nav-toggle span {
  width: 24px;
  height: 2px;
  background: var(--text-primary);
  transition: var(--transition);
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: var(--space-md);
}

.theme-toggle {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-full);
  background: var(--bg-tertiary);
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition);
}

.theme-toggle:hover {
  background: var(--primary);
  color: var(--white);
}