/* === App Shell === */
.app-shell {
  display: grid;
  grid-template:
    "sidebar topbar" auto
    "sidebar content" 1fr / 240px 1fr;
  min-height: 100dvh;
}

/* === Sidebar === */
.sidebar {
  grid-area: sidebar;
  background: var(--color-surface-1);
  border-right: 1px solid var(--color-border);
  overflow-y: auto;
  padding: var(--space-4);
}

.sidebar-header {
  padding: var(--space-4) 0;
  border-bottom: 1px solid var(--color-border);
}

.sidebar-nav {
  list-style: none;
  padding: 0;
}

.sidebar-nav li a {
  display: block;
  padding: var(--space-2) var(--space-3);
  color: var(--color-text);
  text-decoration: none;
  border-radius: 8px;
  transition: background var(--transition-fast), color var(--transition-fast);
}

.sidebar-nav li a:hover {
  background: var(--color-surface-2);
}

.sidebar-nav li a:active {
  background: var(--color-surface-3);
}

.sidebar-nav li a[aria-current="page"] {
  background: var(--color-surface-2);
  color: var(--color-primary);
  font-weight: 500;
}

/* === Topbar === */
.topbar {
  grid-area: topbar;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-2) var(--space-5);
  border-bottom: 1px solid var(--color-border);
  background: var(--color-surface-0);
}

/* === Content === */
.content {
  grid-area: content;
  overflow-y: auto;
  padding: var(--space-5);
}

/* === Responsive === */

/* Below 768px: sidebar hidden, single column */
@media (max-width: 767px) {
  .app-shell {
    grid-template:
      "topbar" auto
      "content" 1fr / 1fr;
  }

  .sidebar {
    position: fixed;
    inset-block: 0;
    inset-inline-start: 0;
    width: 280px;
    z-index: 50;
    transform: translateX(-100%);
    transition: transform var(--transition-fast);
  }

  .sidebar.open {
    transform: translateX(0);
  }

  .topbar {
    grid-area: topbar;
  }
}

/* 768px - 1024px */
@media (min-width: 768px) and (max-width: 1023px) {
  .app-shell {
    grid-template-columns: 200px 1fr;
  }
}

/* 1024px - 1440px: default 240px (no override needed) */

/* 1440px+ */
@media (min-width: 1440px) {
  .app-shell {
    grid-template-columns: 280px 1fr;
  }
}

/* 2560px+ (QHD / 4K) */
@media (min-width: 2560px) {
  .app-shell {
    grid-template-columns: 300px 1fr;
  }
}

@media (min-width: 3840px) {
  .app-shell {
    grid-template-columns: 320px 1fr;
  }
}

/* Hamburger button: visible only on mobile */
.hamburger-btn {
  display: none;
}

@media (max-width: 767px) {
  .hamburger-btn {
    display: flex;
  }
}

/* Sidebar close button: visible only on mobile */
.sidebar-close {
  display: none;
}

@media (max-width: 767px) {
  .sidebar-close {
    display: flex;
    margin-left: auto;
    font-size: 1.25rem;
  }
  .sidebar-header {
    display: flex;
    align-items: center;
  }
}

/* Sidebar backdrop for mobile overlay */
@media (max-width: 767px) {
  .sidebar.open::before {
    content: "";
    position: fixed;
    inset: 0;
    background: oklch(0 0 0 / 0.3);
    z-index: -1;
  }
}

/* === App Shell Loading State === */
.app-shell.loading .sidebar,
.app-shell.loading .topbar {
  opacity: 0.5;
  pointer-events: none;
}

.app-shell-loading {
  grid-column: 1 / -1;
  grid-row: 1 / -1;
  display: grid;
  place-items: center;
  z-index: 10;
}

.app-shell-error {
  grid-column: 1 / -1;
  grid-row: 1 / -1;
  display: grid;
  place-items: center;
  text-align: center;
  padding: var(--space-6);
  color: var(--color-error);
}