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

:root {
  --bg: #f0f2f5;
  --surface: #ffffff;
  --border: #d0d5dd;
  --text: #1a1a2e;
  --text-muted: #6b7280;
  --primary: #4f46e5;
  --primary-hover: #4338ca;
  --danger: #ef4444;
  --danger-hover: #dc2626;
  --radius: 8px;
  --shadow: 0 1px 3px rgba(0,0,0,.1), 0 1px 2px rgba(0,0,0,.06);
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  display: flex;
  flex-direction: column;
  height: 100vh;
  overflow: hidden;
}

/* ── Toolbar ─────────────────────────────── */
.toolbar {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 8px 16px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}
.toolbar h1 {
  font-size: 16px;
  font-weight: 600;
  white-space: nowrap;
}
.toolbar-actions {
  display: flex;
  align-items: center;
  gap: 6px;
  margin-left: auto;
  flex-wrap: wrap;
}
.separator {
  width: 1px;
  height: 24px;
  background: var(--border);
  margin: 0 4px;
}

/* ── Buttons ─────────────────────────────── */
button {
  font-size: 13px;
  padding: 6px 14px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--text);
  cursor: pointer;
  white-space: nowrap;
  transition: background .15s, border-color .15s;
}
button:hover { background: #f9fafb; }
button:disabled { opacity: .4; cursor: not-allowed; }
button.active {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
}
button.primary {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
}
button.primary:hover { background: var(--primary-hover); }
button.danger { color: var(--danger); border-color: var(--danger); }
button.danger:hover { background: #fef2f2; }

/* ── Main Layout ─────────────────────────── */
.main-container {
  display: flex;
  flex: 1;
  overflow: hidden;
}

/* ── Sidebar ─────────────────────────────── */
.sidebar {
  width: 160px;
  flex-shrink: 0;
  background: var(--surface);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}
.sidebar-header {
  font-size: 12px;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: .05em;
  padding: 10px 12px 6px;
}
.thumbnail-list {
  flex: 1;
  overflow-y: auto;
  padding: 4px 8px;
  display: flex;
  flex-direction: column;
  gap: 6px;
}
.thumbnail-item {
  border: 2px solid transparent;
  border-radius: 4px;
  cursor: pointer;
  overflow: hidden;
  transition: border-color .15s;
  position: relative;
  background: #f9fafb;
}
.thumbnail-item:hover { border-color: #a5b4fc; }
.thumbnail-item.active { border-color: var(--primary); }
.thumbnail-item canvas {
  display: block;
  width: 100%;
  height: auto;
}
.thumbnail-item .badge {
  position: absolute;
  top: 2px;
  right: 2px;
  background: var(--primary);
  color: #fff;
  font-size: 10px;
  padding: 1px 5px;
  border-radius: 10px;
  pointer-events: none;
}

/* ── Viewer ──────────────────────────────── */
.viewer {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: auto;
  position: relative;
  background: #e5e7eb;
  padding: 16px;
}
.canvas-container {
  position: relative;
  box-shadow: var(--shadow);
}
#pdf-canvas, #overlay-canvas {
  display: block;
}
#overlay-canvas {
  position: absolute;
  top: 0;
  left: 0;
  cursor: crosshair;
  touch-action: none;
}

/* ── Upload Overlay ──────────────────────── */
.upload-overlay {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(255,255,255,.7);
  backdrop-filter: blur(4px);
  z-index: 10;
}
.upload-overlay.hidden { display: none; }
.upload-box {
  text-align: center;
  padding: 48px;
  border: 2px dashed var(--border);
  border-radius: 12px;
  background: var(--surface);
}
.upload-icon { font-size: 48px; margin-bottom: 12px; }
.upload-box p { margin-top: 8px; color: var(--text-muted); }
.upload-hint { font-size: 13px; }
.file-label {
  color: var(--primary);
  cursor: pointer;
  text-decoration: underline;
}

/* ── Upload Loading ──────────────────────── */
.upload-loading {
  display: none;
  margin-top: 20px;
}
.upload-box.loading .upload-loading {
  display: block;
}
.upload-box.loading .upload-icon,
.upload-box.loading > p {
  display: none;
}
.spinner {
  width: 32px;
  height: 32px;
  margin: 0 auto 8px;
  border: 3px solid var(--border);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin .7s linear infinite;
}
@keyframes spin {
  to { transform: rotate(360deg); }
}
.upload-loading p {
  font-size: 14px;
  color: var(--text-muted);
}

.canvas-container { display: none; }
.canvas-container.visible { display: block; }

/* ── Status Bar ──────────────────────────── */
.status-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 6px 16px;
  background: var(--surface);
  border-top: 1px solid var(--border);
  font-size: 13px;
  color: var(--text-muted);
  flex-shrink: 0;
}
.page-nav {
  display: flex;
  align-items: center;
  gap: 8px;
}
#page-indicator {
  font-variant-numeric: tabular-nums;
}
.zoom-controls {
  display: flex;
  align-items: center;
  gap: 4px;
}
.zoom-controls button {
  width: 28px;
  height: 28px;
  padding: 0;
  font-size: 16px;
  font-weight: 600;
  line-height: 1;
  text-align: center;
}
#zoom-level {
  min-width: 44px;
  text-align: center;
  font-variant-numeric: tabular-nums;
}

/* ── Sidebar Toggle ──────────────────────── */
.sidebar-toggle {
  display: none;
  font-size: 18px;
  padding: 4px 10px;
  line-height: 1;
}
.sidebar-backdrop {
  display: none;
}

/* ── Toolbar row (for mobile header) ─────── */
.toolbar-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

/* ── Mobile (≤ 768px) ────────────────────── */
@media (max-width: 768px) {
  body {
    height: 100dvh;
  }

  /* Toolbar */
  .toolbar {
    flex-direction: column;
    align-items: stretch;
    gap: 6px;
    padding: 6px 8px;
  }
  .toolbar-row {
    width: 100%;
  }
  .toolbar h1 {
    font-size: 15px;
  }
  .toolbar-actions {
    margin-left: 0;
    gap: 4px;
  }
  .toolbar-actions button {
    flex: 1;
    min-width: 0;
    font-size: 12px;
    padding: 8px 4px;
  }
  .separator {
    display: none;
  }
  .sidebar-toggle {
    display: block;
    min-width: 44px;
    min-height: 44px;
  }

  /* Sidebar — off-screen by default, slides in */
  .sidebar {
    position: fixed;
    top: 0;
    left: 0;
    width: 220px;
    height: 100dvh;
    z-index: 100;
    transform: translateX(-100%);
    transition: transform .25s ease;
    box-shadow: 2px 0 8px rgba(0,0,0,.15);
  }
  .sidebar.open {
    transform: translateX(0);
  }
  .sidebar-backdrop {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,.35);
    z-index: 99;
  }
  .sidebar-backdrop.visible {
    display: block;
  }

  /* Viewer */
  .viewer {
    padding: 8px;
  }

  /* Upload box */
  .upload-box {
    padding: 24px 16px;
  }
  .upload-icon {
    font-size: 36px;
  }

  /* Status bar */
  .status-bar {
    flex-direction: column;
    gap: 6px;
    padding: 6px 8px;
    font-size: 12px;
  }
  .page-nav button,
  .zoom-controls button {
    min-height: 36px;
    min-width: 36px;
  }
}

/* ── Small Mobile (≤ 400px) ──────────────── */
@media (max-width: 400px) {
  .toolbar-actions {
    flex-wrap: wrap;
  }
  .toolbar-actions button {
    flex: 1 1 calc(50% - 2px);
  }
  #btn-export {
    flex: 1 1 100%;
  }
  .status-bar {
    font-size: 11px;
  }
}