body {
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.header {
  height: var(--header-height);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.5rem;
  border-bottom: 1px solid var(--border-color);
  background: var(--bg-primary);
  flex-shrink: 0;
  z-index: 10;
}

.header-brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.header-brand h1 {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--accent);
}

.header-subtitle {
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

#theme-toggle {
  font-size: 1.25rem;
  padding: 0.5rem;
  border-radius: var(--radius);
  transition: background 0.2s;
  line-height: 1;
}

#theme-toggle:hover {
  background: var(--bg-tertiary);
}

.app-layout {
  display: grid;
  grid-template-columns: var(--sidebar-width) 1fr;
  flex: 1;
  overflow: hidden;
}

.sidebar {
  border-right: 1px solid var(--border-color);
  background: var(--bg-secondary);
  overflow-y: auto;
  display: flex;
  flex-direction: column;
}

.sidebar-search {
  padding: 1rem;
  position: sticky;
  top: 0;
  background: var(--bg-secondary);
  z-index: 5;
  border-bottom: 1px solid var(--border-color);
}

#search-input {
  width: 100%;
  padding: 0.625rem 0.875rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  background: var(--bg-primary);
  color: var(--text-primary);
  font-size: 0.875rem;
  outline: none;
  transition: border-color 0.2s;
}

#search-input:focus {
  border-color: var(--accent);
}

#search-input::placeholder {
  color: var(--text-muted);
}

.sidebar-nav {
  padding: 0.5rem 0;
  flex: 1;
}

.content {
  overflow-y: auto;
  padding: 2rem;
  background: var(--bg-primary);
}

.content:has(.tool-container) {
  padding: 1.5rem;
}

.welcome {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 100%;
  text-align: center;
  color: var(--text-secondary);
}

.welcome h2 {
  font-size: 2rem;
  color: var(--text-primary);
  margin-bottom: 0.5rem;
}

.welcome p {
  font-size: 1.125rem;
  max-width: 400px;
}