/* Knowledge tree: the directory and notes share the site's study palette. */
body[data-learning-page="knowledge"] .lt-page {
  --lt-ink: var(--ink, var(--fg, #1a2822));
  --lt-accent: var(--accent, var(--a, #2f7a56));
  --lt-surface: var(--surface, var(--card, #fff));
  color: var(--lt-ink);
}
.lt-page [hidden] { display: none !important; }
.lt-page a:not(.btn) { color: var(--lt-accent); }
.lt-page :focus-visible { outline: 3px solid var(--lt-accent); outline-offset: 3px; }
.lt-heading { margin: 24px 0 28px; }
.lt-heading h1 { margin: 0 0 5px; font-size: clamp(27px, 3vw, 34px); line-height: 1.35; }
.lt-heading p { margin: 0; color: var(--muted, #5e6b64); }
.lt-context { display: flex; gap: 12px; flex-wrap: wrap; justify-content: space-between; padding: 12px 0; margin: -8px 0 24px; border-block: 1px solid var(--line, #e2dcd0); font-size: 14px; }
.lt-context a { font-weight: 600; }
.lt-layout { display: grid; grid-template-columns: minmax(230px, 285px) minmax(0, 1fr); align-items: start; gap: clamp(22px, 3vw, 42px); }
.lt-sidebar { position: sticky; top: 20px; max-height: calc(100dvh - 40px); overflow-y: auto; padding: 0 5px 16px 0; scrollbar-width: thin; }
.lt-filters label:not(.lt-check) { display: block; font-size: 14px; font-weight: 600; margin: 0 0 5px; }
.lt-search-row { display: flex; align-items: center; gap: 3px; }
.lt-search-row input, .lt-filters select { width: 100%; min-width: 0; min-height: 44px; padding: 9px 10px; color: var(--lt-ink); background: var(--lt-surface); border: 1px solid var(--line, #e2dcd0); border-radius: 7px; font: inherit; font-size: 14px; }
.lt-search-row input::placeholder { color: var(--muted, #5e6b64); opacity: 1; }
.lt-text-button { min-height: 44px; padding: 6px 8px; border: 0; background: none; color: var(--lt-accent); font: inherit; font-size: 14px; cursor: pointer; text-decoration: underline; text-underline-offset: 3px; }
.lt-selects { display: grid; gap: 12px; margin-top: 14px; }
.lt-selects > div { min-width: 0; }
.lt-check { display: flex; gap: 8px; align-items: center; margin-top: 9px; font-size: 14px; min-height: 44px; cursor: pointer; }
.lt-check input { width: 18px; height: 18px; margin: 0; accent-color: var(--lt-accent); }
.lt-directory { margin-top: 17px; border-top: 1px solid var(--line, #e2dcd0); }
.lt-directory > summary { padding: 12px 0 3px; min-height: 44px; font-size: 16px; font-weight: 650; cursor: pointer; }
.lt-directory > summary > span { color: var(--muted, #5e6b64); margin-left: 6px; font-size: 14px; font-weight: 400; white-space: nowrap; }
.lt-hint { color: var(--muted, #5e6b64); font-size: 14px; margin: 2px 0 10px; }
.lt-topic { border-bottom: 1px solid var(--line, #e2dcd0); }
.lt-topic > summary, .lt-group > summary { position: relative; cursor: pointer; list-style: none; display: flex; gap: 7px; align-items: baseline; padding: 10px 0 10px 16px; min-height: 44px; line-height: 1.65; }
.lt-topic > summary::-webkit-details-marker, .lt-group > summary::-webkit-details-marker { display: none; }
.lt-topic > summary::before, .lt-group > summary::before { content: "+"; position: absolute; left: 0; width: 12px; color: var(--muted, #5e6b64); font-weight: 400; }
.lt-topic[open] > summary::before, .lt-group[open] > summary::before { content: "−"; }
.lt-topic > summary > span, .lt-group > summary > span { flex: 1; min-width: 0; overflow-wrap: anywhere; }
.lt-topic > summary { font-size: 14px; font-weight: 600; }
.lt-topic summary > small { color: var(--muted, #5e6b64); font-size: 14px; font-weight: 400; }
.lt-groups { padding: 0 0 7px 15px; }
.lt-group > summary { font-size: 14px; color: var(--muted, #5e6b64); }
.lt-points { border-left: 1px solid var(--line, #e2dcd0); margin-left: 5px; padding-left: 8px; }
.lt-point-link { display: flex; gap: 6px; align-items: baseline; padding: 10px 9px; min-height: 44px; font-size: 14px; line-height: 1.65; border-left: 3px solid transparent; text-decoration: none; overflow-wrap: anywhere; }
.lt-page .lt-point-link { color: var(--lt-ink); }
.lt-point-link > span { flex: 1; min-width: 0; }
.lt-point-link > small { color: var(--muted, #5e6b64); font-size: 14px; white-space: nowrap; }
.lt-point-link:hover, .lt-point-link[aria-current="page"] { background: var(--lt-surface); color: var(--lt-accent); }
.lt-point-link[aria-current="page"] { border-color: var(--lt-accent); font-weight: 600; }
.lt-detail { min-width: 0; scroll-margin-top: 20px; }
.lt-back { display: inline-flex; align-items: center; min-height: 44px; font-size: 14px; margin: -5px 0 10px; text-underline-offset: 4px; }
.lt-overview h2 { margin: 0 0 9px; font-size: 25px; line-height: 1.5; }
.lt-overview-intro { margin: 0 0 26px; max-width: 46em; font-size: 15px; color: var(--muted, #5e6b64); }
.lt-primary-topics { display: grid; gap: 0; border-top: 2px solid var(--lt-accent); }
.lt-topic-card { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 6px 20px; padding: 21px 0 22px; border-bottom: 1px solid var(--line, #e2dcd0); }
.lt-topic-card h3 { grid-column: 1; margin: 0; font-size: 22px; line-height: 1.5; }
.lt-topic-card h3 a { text-decoration: none; display: inline-block; min-height: 36px; }
.lt-topic-card h3 a:hover { text-decoration: underline; text-underline-offset: 5px; }
.lt-topic-card p { grid-column: 1; margin: 0; color: var(--muted, #5e6b64); font-size: 14px; }
.lt-topic-card > span { grid-column: 2; grid-row: 1 / 3; align-self: center; color: var(--muted, #5e6b64); font-size: 14px; }
.lt-more-topics { margin-top: 29px; }
.lt-more-topics > h3 { margin: 0 0 9px; font-size: 16px; }
.lt-topic-list { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); column-gap: 24px; }
.lt-topic-list > a { display: flex; align-items: baseline; gap: 12px; padding: 11px 0; border-bottom: 1px solid var(--line, #e2dcd0); min-height: 44px; font-size: 14px; text-decoration: none; }
.lt-topic-list > a > span { flex: 1; min-width: 0; }
.lt-topic-list > a > small { font-size: 14px; color: var(--muted, #5e6b64); }
.lt-topic-list > a:hover > span { text-decoration: underline; text-underline-offset: 4px; }
.lt-overview-domain { margin-top: 24px; }
.lt-overview-domain > h3 { font-size: 18px; margin: 0 0 9px; }
.lt-overview-group { border-top: 1px solid var(--line, #e2dcd0); }
.lt-overview-group > summary { padding: 12px 0; min-height: 44px; cursor: pointer; font-weight: 600; font-size: 15px; }
.lt-overview-group > summary > span { font-size: 14px; color: var(--muted, #5e6b64); font-weight: 400; margin-left: 10px; }
.lt-overview-group > div { padding: 0 0 10px 14px; }
.lt-section-browser { margin-top: 28px; border-top: 1px solid var(--line); }
.lt-section-browser > summary { min-height: 44px; padding: 12px 0; cursor: pointer; font-size: 15px; }
.lt-course-link { display: inline-block; min-height: 44px; padding: 10px 9px; font-size: 14px; }
.lt-empty, .lt-loading { color: var(--muted, #5e6b64); font-size: 14px; }
.lt-empty-state { border: 1px solid var(--line, #e2dcd0); border-radius: 10px; background: var(--lt-surface, var(--surface, #fff)); padding: 24px; }
.lt-empty-state h1, .lt-empty-state h2, .lt-empty-state h3 { margin-top: 0; line-height: 1.5; }
.lt-empty-state a { display: inline-block; min-height: 44px; padding: 8px 0; margin-right: 12px; }
.lt-empty-state p { color: var(--muted, #5e6b64); }
.lt-detail .k-point { --fg: var(--lt-ink); --card: var(--lt-surface); --a: var(--lt-accent); border-radius: 10px; }
.lt-detail .k-point-title { overflow-wrap: anywhere; }
.lt-detail .k-lesson-links a { white-space: normal; }
@media (max-width: 1000px) {
  .lt-layout { grid-template-columns: minmax(210px, 245px) minmax(0, 1fr); gap: 24px; }
  .lt-detail .k-point { padding-inline: 22px; }
  .lt-topic-list { grid-template-columns: minmax(0, 1fr); }
}
@media (max-width: 760px) {
  .lt-heading { margin: 18px 0 22px; }
  .lt-heading p { font-size: 14px; }
  .lt-layout { display: block; }
  .lt-sidebar { position: static; max-height: none; overflow: visible; padding: 0; margin-bottom: 25px; }
  .lt-selects { grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 10px; }
  .lt-directory { border: 1px solid var(--line, #e2dcd0); border-radius: 7px; padding: 0 12px; margin-top: 10px; }
  .lt-directory > summary { padding: 11px 0; }
  .lt-directory[open] > summary { padding-bottom: 5px; }
  #learning-tree { max-height: 54dvh; overflow-y: auto; padding: 0 3px 5px 0; }
  .lt-overview h2 { font-size: 23px; }
  .lt-overview-intro { margin-bottom: 21px; font-size: 14px; }
  .lt-topic-card { grid-template-columns: minmax(0, 1fr); gap: 4px; padding: 17px 0 18px; }
  .lt-topic-card h3 { font-size: 21px; }
  .lt-topic-card > span { grid-column: 1; grid-row: auto; margin-top: 3px; font-size: 14px; }
  .lt-topic-card p { line-height: 1.8; }
  .lt-context { display: block; margin-bottom: 21px; }
  .lt-context > span { display: block; }
  .lt-context > a { display: inline-block; min-height: 44px; padding-top: 8px; }
  .lt-detail .k-point { padding: 20px 17px 24px; }
  .lt-detail .k-point-title { font-size: 24px; }
  .lt-empty-state { padding: 20px 17px; }
}

/* Primary keeps the familiar grade tabs and shows one textbook unit at a time. */
.pk-library { max-width: 850px; margin: auto; font-size: 16px; overflow-wrap: anywhere; }
.pk-library .cc-filter { margin: 20px 0; }
.pk-selects { display: grid; grid-template-columns: 1fr 2fr; gap: 16px; }
.pk-selects > div { min-width: 0; }
.pk-library select { width: 100%; min-height: 44px; color: var(--fg); background: var(--card); border: 1px solid var(--muted); border-radius: 8px; font: inherit; padding: 8px; }
.pk-library .cc-card { font-size: 16px; }
.pk-library .cc-card h2 { font-size: 23px; }
.pk-library .cc-low { font-size: 20px; }
.pk-library .cc-low rt { font-size: 14px; }
.pk-library .cc-links a { font-size: 16px; }
.pk-card .cc-answer { border-top: 1px solid var(--line); }
.pk-note { color: var(--muted); font-size: 14px; }
.pk-card:target, .pk-card:focus { outline: 2px solid var(--a); outline-offset: 3px; }
@media (max-width: 620px) { .pk-selects { grid-template-columns: 1fr; gap: 0; } }
.pk-library .cc-grades a[aria-current] { color: var(--bg); }