.portal-grid.single { grid-template-columns: minmax(0, 720px); }
.one-book-portal { max-width: 1040px; }
.brand-mark { font: 800 25px/1 Tahoma, sans-serif; letter-spacing: -.06em; }
.page-tools { display: flex; align-items: center; gap: 6px; min-width: 0; }
.page-tools .panel-page { margin-left: 0; min-width: 122px; text-align: center; }
.page-tool {
  min-width: 34px;
  min-height: 32px;
  padding: 5px 8px;
  color: var(--navy);
  background: #f1f5f7;
  border: 1px solid #cdd9df;
  border-radius: 8px;
  cursor: pointer;
  font-weight: 800;
}
.page-tool:disabled { cursor: default; opacity: .4; }
.page-spacer { flex: 1; }
.page-strip { display: flex; gap: 5px; padding: 7px 10px; overflow-x: auto; border-top: 1px solid var(--line); -webkit-overflow-scrolling: touch; }
.page-chip { flex: 0 0 auto; min-width: 38px; padding: 6px 8px; border: 1px solid #ced9df; border-radius: 8px; color: var(--muted); background: white; cursor: pointer; font-size: 11px; }
.page-chip.active { color: white; background: var(--blue); border-color: var(--blue); font-weight: 800; }
.source-panel.with-strip { grid-template-rows: auto minmax(0,1fr) auto; }
.question-image.zoomed { max-width: none; }
.choices.many { grid-template-columns: repeat(4, 1fr); }
.choice.letter { text-transform: lowercase; }
.source-note { color: var(--muted); font-size: 10px; white-space: nowrap; }

@media (max-width: 760px) {
  .portal-grid.single { grid-template-columns: 1fr; }
  .page-tools .panel-page { min-width: 102px; }
  .source-note { display: none; }
}

@media (max-width: 470px) {
  .panel-bar { padding: 7px 8px; }
  .page-tools { gap: 4px; }
  .page-tool { min-width: 31px; padding: 4px 6px; }
  .page-tools .panel-page { min-width: 91px; font-size: 10px; }
  .choices.many { grid-template-columns: repeat(4, 1fr); }
}