/* ================================== */
/* == Main Application Layout == */
/* ================================== */
.app {
  display: flex;
  height: 100vh;
  width: 100vw;
  overflow: hidden; /* Prevent body scroll */
}

/* ================================== */
/* == Sidebar Layout == */
/* ================================== */
.sidebar {
  width: var(--sidebar-width);
  background-color: var(--color-surface);
  border-right: 1px solid var(--color-card-border);
  display: flex;
  flex-direction: column;
  transition: width var(--duration-normal), transform var(--duration-normal);
  position: relative;
  z-index: 100;
  flex-shrink: 0; /* Prevent sidebar from shrinking */
}

.sidebar.collapsed {
  width: var(--sidebar-collapsed-width);
}

.sidebar.collapsed .logo span,
.sidebar.collapsed .nav-item span,
.sidebar.collapsed .nav-section h3,
.sidebar.collapsed .nav-item .count {
  display: none;
}

/* Sidebar Header */
.sidebar-header {
  padding: var(--space-4);
  border-bottom: 1px solid var(--color-card-border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: var(--topbar-height);
  flex-shrink: 0; /* Prevent header shrinking */
}

.logo {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-weight: var(--font-weight-bold);
  font-size: var(--font-size-lg);
  color: var(--color-primary);
  white-space: nowrap;
  overflow: hidden;
}

.logo i {
  font-size: var(--font-size-xl);
  flex-shrink: 0;
}

.sidebar-toggle {
  background: none;
  border: none;
  color: var(--color-text-secondary);
  cursor: pointer;
  padding: var(--space-2);
  border-radius: var(--radius-sm);
  transition: all var(--duration-fast);
  display: flex; /* Ensure icon is centered */
  align-items: center;
  justify-content: center;
}
.sidebar-toggle:hover {
  background-color: var(--color-secondary);
  color: var(--color-text);
}
.sidebar.collapsed .sidebar-toggle i {
  transform: rotate(180deg);
}

/* Sidebar Navigation */
.sidebar-nav {
  flex-grow: 1; /* Allow nav to fill space */
  overflow-y: auto;
  padding: var(--space-4);
}
.nav-section { margin-bottom: var(--space-6); }
.nav-section h3 {
  font-size: var(--font-size-xs);
  text-transform: uppercase;
  color: var(--color-text-secondary);
  margin-bottom: var(--space-3);
  letter-spacing: 0.5px;
  font-weight: var(--font-weight-semibold);
  padding: 0 var(--space-4);
  white-space: nowrap;
  overflow: hidden;
}

.nav-item {
  display: flex;
  align-items: center;
  width: 100%;
  padding: var(--space-3) var(--space-4);
  border: none;
  background: none;
  color: var(--color-text);
  text-align: left;
  border-radius: var(--radius-base);
  cursor: pointer;
  transition: all var(--duration-fast);
  margin-bottom: var(--space-1);
  font-size: var(--font-size-sm);
  gap: var(--space-3);
  position: relative;
  white-space: nowrap;
  overflow: hidden;
}
.nav-item:hover { background-color: var(--color-secondary); }
.nav-item.active { background-color: var(--color-primary); color: white; }
.nav-item i { width: 16px; text-align: center; flex-shrink: 0; }
.nav-item span { flex-grow: 1; overflow: hidden; text-overflow: ellipsis; } /* Allow text to grow and truncate */

.nav-item .count {
  margin-left: auto;
  background-color: var(--color-secondary);
  color: var(--color-text-secondary);
  padding: 2px 6px;
  border-radius: var(--radius-full);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-medium);
  flex-shrink: 0; /* Prevent count shrinking */
}
.nav-item.active .count { background-color: rgba(255, 255, 255, 0.2); color: white; }

/* Sidebar Footer */
.sidebar-footer {
  padding: var(--space-4);
  border-top: 1px solid var(--color-card-border);
  flex-shrink: 0; /* Prevent footer shrinking */
}
.profile-avatar {
  width: 24px;
  height: 24px;
  border-radius: var(--radius-full);
  background-color: var(--color-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text);
  font-size: var(--font-size-sm);
  flex-shrink: 0;
  overflow: hidden;
}
.profile-avatar img { width: 100%; height: 100%; object-fit: cover; }
.profile-avatar span { font-weight: bold; } /* Initials */

/* ================================== */
/* == Main Content Area Layout == */
/* ================================== */
.main-content {
  flex-grow: 1; /* Allow main content to fill remaining width */
  display: flex;
  flex-direction: column;
  overflow: hidden; /* Prevent main content area itself from scrolling */
  background-color: var(--color-background); /* Background for the area behind pages */
}

/* Top Bar */
.top-bar {
  height: var(--topbar-height);
  background-color: var(--color-surface);
  border-bottom: 1px solid var(--color-card-border);
  display: flex;
  align-items: center;
  padding: 0 var(--space-6);
  gap: var(--space-4);
  flex-shrink: 0; /* Prevent top bar shrinking */
  position: relative; /* For z-index context if needed */
  z-index: 50;
}

.top-bar-left { display: flex; align-items: center; gap: var(--space-4); }
.mobile-menu-btn {
  display: none; /* Hidden by default, shown via media query */
  background: none;
  border: none;
  color: var(--color-text);
  cursor: pointer;
  padding: var(--space-2);
  border-radius: var(--radius-base);
  font-size: var(--font-size-lg);
  transition: background-color var(--duration-fast);
}
.mobile-menu-btn:hover { background-color: var(--color-secondary); }

.breadcrumb {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.top-bar-center {
  flex-grow: 1;
  display: flex;
  justify-content: center;
  max-width: 500px;
  margin: 0 auto; /* Center horizontally */
}
.quick-search { position: relative; width: 100%; max-width: 400px; }
.quick-search input {
  width: 100%;
  padding: var(--space-2) var(--space-4) var(--space-2) 36px; /* Space for icon */
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  background-color: var(--color-background);
  color: var(--color-text);
  font-size: var(--font-size-sm);
  transition: all var(--duration-fast);
}
.quick-search input:focus { outline: none; border-color: var(--color-primary); box-shadow: var(--focus-ring); }
.quick-search i { position: absolute; left: 12px; top: 50%; transform: translateY(-50%); color: var(--color-text-secondary); pointer-events: none; }

.top-bar-right { display: flex; align-items: center; gap: var(--space-2); }
.action-btn {
  width: 36px;
  height: 36px;
  border: none;
  background-color: transparent;
  color: var(--color-text-secondary);
  border-radius: var(--radius-base);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--duration-fast);
}
.action-btn:hover { background-color: var(--color-secondary); color: var(--color-text); }

/* Page Container */
.page-container {
  flex-grow: 1; /* Allow page container to fill remaining vertical space */
  overflow: hidden; /* Contains the pages */
  position: relative; /* For absolute positioning of pages */
}

.page {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  padding: var(--space-6);
  overflow-y: auto; /* Allow individual pages to scroll */
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--duration-normal), transform var(--duration-normal);
  transform: translateY(10px);
  background-color: var(--color-background); /* Ensure page background matches */
}
.page.active { opacity: 1; visibility: visible; transform: translateY(0); }

.page-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-6);
  flex-shrink: 0; /* Prevent shrinking if page content is flex */
}
.page-header h1 { font-size: var(--font-size-3xl); margin: 0; }

/* ================================== */
/* == Responsive Layout Adjustments == */
/* ================================== */
@media (max-width: 768px) {
  :root { --sidebar-width: 80%; } /* Adjust sidebar width for mobile */

  .sidebar {
    position: fixed;
    top: 0;
    left: 0;
    bottom: 0;
    transform: translateX(-100%);
    z-index: 200; /* Ensure sidebar is above overlay */
    box-shadow: var(--shadow-lg);
    border-right: 1px solid var(--color-card-border);
  }
  .sidebar.open { transform: translateX(0); }

  /* Add an overlay for when mobile sidebar is open */
  .sidebar-overlay {
      position: fixed;
      top: 0;
      left: 0;
      right: 0;
      bottom: 0;
      background-color: rgba(0, 0, 0, 0.4);
      z-index: 199; /* Below sidebar */
      opacity: 0;
      visibility: hidden;
      transition: opacity var(--duration-normal), visibility var(--duration-normal);
  }
  .sidebar.open + .sidebar-overlay {
      opacity: 1;
      visibility: visible;
  }

  .mobile-menu-btn { display: flex; align-items: center; justify-content: center; }
  .top-bar-center { display: none; } /* Hide center search on small screens */

  .page { padding: var(--space-4); } /* Reduce page padding */
}

@media (max-width: 480px) {
  .page-header h1 { font-size: var(--font-size-2xl); }
}