/* ==========================================================================
   VORTEX-SDN Application Layout Structure
   Architecture:
   BODY -> APP-CONTAINER
            ├── SIDEBAR-BACKDROP (Mobile overlay)
            ├── SIDEBAR (position: fixed; top: 0; left: 0; height: 100vh; NO SCROLLBAR)
            └── MAIN-WRAPPER (margin-left: 260px; height: 100vh)
                 ├── TOPBAR (height: 60px; fixed header)
                 └── CONTENT-VIEWPORT (flex: 1; ONLY area that scrolls)
   ========================================================================== */

#app-container {
  display: flex;
  width: 100vw;
  height: 100vh;
  overflow: hidden;
  position: relative;
  background-color: var(--bg-primary);
}

/* Mobile Sidebar Backdrop */
#sidebar-backdrop {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background: rgba(3, 7, 18, 0.75);
  backdrop-filter: blur(4px);
  z-index: calc(var(--z-sidebar) - 5);
  opacity: 0;
  transition: opacity var(--transition-normal);
  pointer-events: none;
}

#sidebar-backdrop.active {
  display: block;
  opacity: 1;
  pointer-events: auto;
}

/* Fixed Desktop Sidebar */
#sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: var(--sidebar-width);
  height: 100vh;
  background-color: var(--bg-secondary);
  border-right: 1px solid var(--border-subtle);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  z-index: var(--z-sidebar);
  transition: width var(--transition-speed), transform var(--transition-speed);
  overflow: hidden; /* STRICT: No internal scrollbar */
}

/* Collapsed Sidebar State */
#sidebar.collapsed {
  width: var(--sidebar-collapsed-width);
}

/* Main Content Column (Takes rest of viewport) */
#main-wrapper {
  margin-left: var(--sidebar-width);
  width: calc(100vw - var(--sidebar-width));
  height: 100vh;
  display: flex;
  flex-direction: column;
  min-width: 0;
  overflow: hidden;
  transition: margin-left var(--transition-speed), width var(--transition-speed);
}

/* Main wrapper adjusts when sidebar is collapsed */
#sidebar.collapsed ~ #main-wrapper {
  margin-left: var(--sidebar-collapsed-width);
  width: calc(100vw - var(--sidebar-collapsed-width));
}

/* Topbar Header (Fixed in place at top of main wrapper) */
#topbar {
  height: var(--topbar-height);
  min-height: var(--topbar-height);
  background-color: var(--bg-surface);
  border-bottom: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 var(--space-lg);
  gap: var(--space-md);
  z-index: var(--z-topbar);
  flex-shrink: 0;
  box-sizing: border-box;
}

/* Scrollable Viewport (ONLY region that scrolls) */
#content-viewport {
  flex: 1;
  overflow-y: auto;
  overflow-x: hidden;
  padding: var(--space-lg);
  background-color: var(--bg-primary);
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
}

/* View Sections */
.view-section {
  display: none;
  animation: fadeIn 0.15s ease-in-out;
  width: 100%;
}

.view-section.active {
  display: block;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(2px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Subtle Global App Footer */
.app-footer {
  margin-top: auto;
  padding-top: var(--space-lg);
  border-top: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 11px;
  color: var(--text-muted);
}