#app {
  display: grid;
  grid-template-columns: var(--sidebar-width) 1fr;
  grid-template-rows: var(--topbar-height) 1fr;
  grid-template-areas:
    "sidebar topbar"
    "sidebar main";
  min-height: 100vh;
}

#app-topbar {
  grid-area: topbar;
  background: var(--color-card-bg);
  border-bottom: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  padding: 0 var(--space-lg);
  gap: var(--space-md);
}

#app-sidebar {
  grid-area: sidebar;
  background: var(--color-bg-paper);
  border-right: 1px solid var(--color-border);
  padding: var(--space-lg) 0;
  overflow-y: auto;
}

#app-main {
  grid-area: main;
  padding: var(--space-xl);
  overflow-y: auto;
}

@media (max-width: 768px) {
  #app {
    grid-template-columns: 1fr;
    grid-template-areas:
      "topbar"
      "main";
  }
  #app-sidebar { display: none; }
}