/* App shell layout */

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html, body {
  height: 100%;
  background: var(--window-bg);
  color: var(--text-1);
  font-family: var(--font-ui);
  font-size: var(--text-base);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  overflow: hidden;
}

/* ── Top-level grid ── */
#app {
  display: grid;
  grid-template-rows: var(--header-h) 1fr;
  height: 100vh;
}

/* ── Header bar ── */
#header {
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  padding: 0 var(--sp-4);
  background: var(--sidebar-bg);
  border-bottom: 1px solid var(--border);
  z-index: 10;
}

#header .logo {
  display: flex;
  align-items: center;
  gap: var(--sp-2);
  font-size: var(--text-md);
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--text-1);
  user-select: none;
}

#header .logo svg { flex-shrink: 0; }

#header .spacer { flex: 1; }

/* ── Body: sidebar + content ── */
#body {
  display: grid;
  grid-template-columns: var(--sidebar-w) 1fr;
  overflow: hidden;
}

/* ── Sidebar ── */
#sidebar {
  background: var(--sidebar-bg);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

#sidebar-scroll {
  flex: 1;
  overflow-y: auto;
  overflow-x: hidden;
  padding-bottom: var(--sp-5);
}

#sidebar-scroll::-webkit-scrollbar { width: 6px; }
#sidebar-scroll::-webkit-scrollbar-track { background: transparent; }
#sidebar-scroll::-webkit-scrollbar-thumb {
  background: rgba(255,255,255,0.12);
  border-radius: 3px;
}

/* ── Content area ── */
#content {
  display: flex;
  flex-direction: column;
  background: var(--window-bg);
  overflow: hidden;
}

/* ── Canvas region ── */
#preview-area {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
  padding: var(--sp-4);
}

/* ── Nav overlay (floats over preview area) ── */
#nav-overlay {
  position: absolute;
  bottom: var(--sp-4);
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  align-items: center;
  gap: var(--sp-2);
  background: rgba(20, 20, 20, 0.72);
  backdrop-filter: blur(8px);
  border: 1px solid var(--border);
  border-radius: var(--r-l);
  padding: 4px var(--sp-2);
  z-index: 5;
}

#nav-overlay #page-counter {
  font-size: var(--text-sm);
  color: var(--text-2);
  font-variant-numeric: tabular-nums;
  min-width: 56px;
  text-align: center;
}

/* ── Sidebar sections ── */
.section {
  border-bottom: 1px solid var(--border);
}

.section-header {
  display: flex;
  align-items: center;
  gap: var(--sp-2);
  padding: var(--sp-2) var(--sp-3);
  font-size: var(--text-sm);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-2);
  user-select: none;
  cursor: pointer;
}

.section-header .chevron {
  margin-left: auto;
  transition: transform var(--dur-fast) var(--ease);
  color: var(--text-3);
}

.section.collapsed .chevron { transform: rotate(-90deg); }
.section.collapsed .section-body { display: none; }

.section-body {
  padding: var(--sp-1) 0 var(--sp-2);
}

/* ── Empty state ── */
#empty-state {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: var(--sp-3);
  color: var(--text-2);
  pointer-events: none;
}

#empty-state svg { opacity: 0.3; }
#empty-state p { font-size: var(--text-md); }