/* === App Shell & Navigation === */

.app-shell {
  display: flex;
  flex-direction: column;
  min-height: 100dvh;
}

/* Top Navigation */
.top-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--nav-height);
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow-sm);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 var(--space-md);
}

.nav-brand {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 18px;
  font-weight: 700;
  color: var(--accent);
  white-space: nowrap;
}

.nav-brand-icon {
  width: 28px;
  height: 28px;
  display: block;
  border-radius: 8px;
}

.nav-links {
  display: flex;
  gap: var(--space-xs);
}

.nav-link {
  padding: 8px 16px;
  border-radius: var(--btn-radius);
  font-size: 15px;
  font-weight: 500;
  color: var(--text-secondary);
  transition: background-color var(--transition-hover),
              color var(--transition-hover);
}

.nav-link:hover {
  background: var(--accent-subtle);
  color: var(--accent);
}

.nav-link.active {
  background: var(--accent-subtle);
  color: var(--accent);
  font-weight: 600;
}

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

.theme-toggle {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-secondary);
}

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

/* Main Content Area */
.app-content {
  flex: 1;
  display: flex;
  flex-direction: column;
}

.page {
  flex: 1;
  display: flex;
  flex-direction: column;
  min-height: 0;
  overflow: hidden;
  padding: var(--space-md);
  max-width: var(--content-max-w);
  width: 100%;
  margin: 0 auto;
}

.page.hidden {
  display: none;
}

/* Responsive Utility Classes */
.show-mobile  { display: block; }
.hide-mobile  { display: none; }

@media (min-width: 640px) {
  .show-mobile  { display: none; }
  .hide-mobile  { display: block; }

  .top-nav {
    padding: 0 var(--space-lg);
  }

  .nav-brand {
    font-size: 20px;
  }

  .page {
    padding: var(--space-lg);
  }
}

@media (min-width: 1024px) {
  .top-nav {
    padding: 0 var(--space-xl);
  }

  .page {
    padding: var(--space-xl);
  }
}