/* YSY Learning Journal — shared reading and reference components. */
:root {
  --study-bg: #f5f3ed;
  --study-paper: #fffefa;
  --study-ink: #243e35;
  --study-muted: #6b766e;
  --study-line: #dddfd4;
  --study-accent: #24634d;
  --study-tint: #eaf0e7;
  --study-serif: "Noto Serif CJK SC", "Source Han Serif SC", "Songti SC", "STSong", serif;
  --study-sans: "Inter", "Noto Sans CJK SC", "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  --study-mono: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
}
.learning-page {
  --bg: var(--study-bg); --paper: var(--study-paper); --panel: var(--study-paper); --panel2: #f0f2e9;
  --ink: var(--study-ink); --text: var(--study-ink); --muted: var(--study-muted); --line: var(--study-line);
  --blue: #3b6589; --cyan: #23716e; --green: #37714c; --yellow: #9a742d;
  --orange: #ab6535; --red: #a74449; --purple: #765692;
  --shadow: 0 4px 18px rgb(36 62 53 / 4%);
  margin: 0;
  background: var(--study-bg);
  color: var(--study-ink);
  font: 16px/1.85 var(--study-sans);
  -webkit-font-smoothing: antialiased;
  overflow-wrap: anywhere;
}
.learning-page *, .learning-page *::before, .learning-page *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 105px; }
.learning-page a { color: var(--study-accent); text-decoration-thickness: 1px; text-underline-offset: .22em; }
.learning-page a:hover { color: #123f2f; }
.learning-page button, .learning-page input { font: inherit; }
.learning-page :focus-visible { outline: 2px solid var(--study-accent); outline-offset: 4px; }
.learning-page ::selection { background: #dce8d7; color: #18392a; }

/* One identity and one navigation across all courses. */
.learning-page .site-header {
  position: sticky; top: 0; z-index: 30;
  display: flex; align-items: center; gap: 32px;
  min-height: 85px; padding: 16px max(28px, calc((100vw - 1376px) / 2));
  border-bottom: 1px solid var(--study-line);
  background: rgb(245 243 237 / 96%);
}
.learning-page .site-brand { display: flex; align-items: center; gap: 12px; flex-shrink: 0; color: var(--study-ink); text-decoration: none; font-size: 17px; font-weight: 700; line-height: 1.45; }
.learning-page .site-mark { display: grid; place-items: center; width: 40px; height: 44px; background: var(--study-ink); color: #fffefa; border-radius: 3px 9px 3px 3px; font: 23px var(--study-serif); letter-spacing: -.07em; }
.learning-page .site-brand small { display: block; font: 9px/1.8 var(--study-mono); color: var(--study-muted); letter-spacing: .14em; }
.learning-page .site-nav { display: flex; gap: 6px; margin: 0 0 0 auto; }
.learning-page .site-nav a { display: block; margin: 0; padding: 7px 13px; border-radius: 5px; color: var(--study-muted); font-size: 13px; font-weight: 500; text-decoration: none; white-space: nowrap; }
.learning-page .site-nav a[aria-current="page"], .learning-page .site-nav a:hover { color: var(--study-accent); background: var(--study-tint); }
.learning-page .print-action, .learning-page .quiet-action { flex-shrink: 0; border: 1px solid #cdd3c6; border-radius: 5px; background: transparent; padding: 7px 12px; font-size: 12px; color: var(--study-ink); cursor: pointer; text-decoration: none; }
.learning-page .print-action:hover, .learning-page .quiet-action:hover { background: var(--study-paper); border-color: var(--study-accent); }
.learning-page .lesson-shell { display: grid; grid-template-columns: 226px minmax(0, 1fr); gap: 0; max-width: 1376px; margin: 0 auto; min-height: calc(100vh - 85px); }
.learning-page .lesson-sidebar { position: sticky; display: block; top: 85px; height: calc(100vh - 85px); overflow: auto; min-width: 0; padding: 37px 22px 36px 12px; border: 0; border-right: 1px solid var(--study-line); background: transparent; backdrop-filter: none; }
.learning-page .lesson-sidebar .brand { margin: 8px 0; font: 700 18px/1.6 var(--study-serif); letter-spacing: 0; }
.learning-page .lesson-sidebar .small, .learning-page .subbrand { font-size: 12px; color: var(--study-muted); }
.learning-page .lesson-sidebar .badge { max-width: 100%; margin-top: 12px; border: 0; background: var(--study-tint); padding: 5px 9px; color: var(--study-accent); font-size: 11px; }
.learning-page .lesson-sidebar .kicker { font-size: 9px; }
.learning-page .lesson-toc { margin: 25px 0 0; padding: 0; background: none; border: none; border-radius: 0; }
.learning-page .lesson-toc summary { font: 600 11px/1.8 var(--study-sans); color: var(--study-muted); letter-spacing: .1em; }
.learning-page .lesson-toc nav { display: grid; gap: 2px; margin: 12px 0 0; }
.learning-page .lesson-toc nav a { display: block; margin: 0; padding: 7px 10px; border: 0; border-left: 2px solid transparent; border-radius: 0 5px 5px 0; background: transparent; color: var(--study-muted); font-size: 12px; line-height: 1.65; text-decoration: none; }
.learning-page .lesson-toc nav a:hover, .learning-page .lesson-toc nav a[aria-current="location"] { color: var(--study-accent); border-left-color: var(--study-accent); background: var(--study-tint); }
.learning-page .lesson-main { min-width: 0; padding: 22px 46px 72px; }
.learning-page.collection-page .lesson-main { max-width: 1152px; padding: 28px 28px 72px; margin: 0 auto; }
.learning-page nav.lesson-breadcrumbs { display: flex; align-items: center; flex-wrap: wrap; gap: 4px 10px; width: auto; max-width: 1376px; margin: 0 auto 12px; padding: 0; }
.learning-page > nav.lesson-breadcrumbs { padding: 15px 28px 0; margin-bottom: 0; }
.learning-page nav.lesson-breadcrumbs a { display: inline; padding: 0; margin: 0; background: none; border: 0; border-radius: 0; color: var(--study-muted); font-size: 11px; line-height: 1.8; text-decoration: none; }
.learning-page nav.lesson-breadcrumbs a + a::before { content: "/"; color: #a6ae9e; margin-right: 10px; }
.learning-page nav.lesson-breadcrumbs a:hover { color: var(--study-accent); }

/* Editorial page opening, quiet surfaces, semantic accents. */
.learning-page .hero { position: relative; margin: 0 0 32px; padding: 24px 0 30px; background: none; color: var(--study-ink); border: 0; border-bottom: 1px solid #cdd2c5; border-radius: 0; box-shadow: none; overflow: visible; }
.learning-page .hero::after { content: none; }
.learning-page .hero :is(.kicker, .eyebrow), .learning-page .kicker, .learning-page .eyebrow { color: #847046; font: 600 11px/1.8 var(--study-mono); text-transform: uppercase; letter-spacing: .12em; opacity: 1; }
.learning-page .hero h1 { position: relative; max-width: 1020px; margin: 12px 0 18px; color: var(--study-ink); font: 700 clamp(29px, 3.1vw, 43px)/1.5 var(--study-serif); letter-spacing: -.025em; text-wrap: pretty; }
.learning-page .hero p { max-width: 900px; margin: 0 0 12px; color: #647168; opacity: 1; font-size: 15px; line-height: 1.95; }
.learning-page .hero-grid { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 0; margin: 24px 0 0; border-top: 1px solid var(--study-line); }
.learning-page .metric { background: none; border: 0; border-right: 1px solid var(--study-line); border-radius: 0; padding: 16px 15px 0; font-size: 12px; }
.learning-page .metric:first-child { padding-left: 0; }
.learning-page .metric:last-child { border-right: 0; }
.learning-page .metric b { display: block; color: var(--study-accent); font: 29px/1.6 var(--study-serif); }
.learning-page .metric .small { font-size: 11px; }
.learning-page .chips { display: flex; flex-wrap: wrap; gap: 7px; margin-top: 18px; }
.learning-page .chip, .learning-page .tag { display: inline-block; background: var(--study-tint); color: var(--study-accent); border: 1px solid #dce3d6; border-radius: 4px; padding: 3px 8px; font-size: 11px; }
.learning-page main > section:not(.hero), .learning-page main > .section { margin-top: 44px; scroll-margin-top: 108px; }
.learning-page h2 { margin: 0 0 17px; color: var(--study-ink); font: 700 25px/1.65 var(--study-serif); letter-spacing: -.025em; }
.learning-page .section h2 { font: 700 25px/1.65 var(--study-serif); }
.learning-page h3 { color: #314a40; font-size: 17px; line-height: 1.75; }
.learning-page h4 { color: #42584b; }
.learning-page .section-head { gap: 16px; }
.learning-page .section-head .num { color: #8b7955; font: 12px var(--study-mono); }
.learning-page .lead { color: var(--study-muted); font-size: 15px; line-height: 1.9; }
.learning-page .grid2 { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 18px; }
.learning-page .grid3 { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px; }
.learning-page .grid4 { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 14px; }
.learning-page :is(.card, .box) { min-width: 0; background: var(--study-paper); color: var(--study-ink); border: 1px solid var(--study-line); border-radius: 9px; padding: 21px 23px; box-shadow: 0 2px 4px rgb(36 62 53 / 2%); }
.learning-page .card h3 { margin: 0 0 10px; }
.learning-page .card h4 { color: #42584b; }
.learning-page .card p { line-height: 1.9; }
.learning-page .card.key { border-left: 3px solid var(--blue); }
.learning-page .card.theorem { border-left: 3px solid var(--purple); }
.learning-page .card.alg { border-left: 3px solid var(--green); }
.learning-page .icon { width: 37px; height: 37px; border: 0; border-radius: 5px; background: var(--study-tint); font-size: 20px; }
.learning-page :is(.callout, .warn, .danger, .memory) { padding: 16px 18px; border: 1px solid #d9e3d3; border-left: 3px solid var(--study-accent); border-radius: 0 7px 7px 0; background: #edf2e9; color: var(--study-ink); box-shadow: none; }
.learning-page :is(.warn, .memory) { border-color: #eadfc5; border-left-color: #b78b3f; background: #faf4e6; }
.learning-page .danger { border-color: #ecd7d4; border-left-color: var(--red); background: #fbefed; }
.learning-page .callout { margin: 18px 0; font-size: 14px; }
.learning-page .formula, .learning-page .formula-big, .learning-page .matrix { max-width: 100%; overflow-x: auto; border: 1px solid #dde2d6; border-radius: 6px; background: #f0f3eb; color: #2d503e; padding: 15px 18px; font-family: "Cambria Math", "STIX Two Math", var(--study-serif); }
.learning-page .formula { font-size: 18px; text-align: center; margin: 16px 0; }
.learning-page .formula strong { color: var(--study-accent); }
.learning-page .code, .learning-page pre { max-width: 100%; overflow-x: auto; white-space: pre; overflow-wrap: normal; padding: 20px; border: 1px solid var(--study-line); border-radius: 7px; background: #edf0e9; color: #2d453b; font: 13px/1.8 var(--study-mono); }
.learning-page code { font-family: var(--study-mono); font-size: .88em; }
.learning-page .diagram { max-width: 100%; background: #f9faf5; border-color: var(--study-line); border-radius: 7px; }
.learning-page div.diagram { overflow-x: auto; padding: 18px; margin: 20px 0; }
.learning-page svg.diagram { display: block; height: auto; }
.learning-page img, .learning-page svg { max-width: 100%; }
.learning-page .table-scroll, .learning-page .table-wrap { max-width: 100%; overflow-x: auto; margin: 18px 0; border-radius: 7px; border: 1px solid var(--study-line); }
.learning-page table { width: 100%; border-collapse: collapse; background: var(--study-paper); color: var(--study-ink); font-size: 13px; border-color: var(--study-line); }
.learning-page th, .learning-page td { padding: 12px 15px; text-align: left; vertical-align: top; border-bottom: 1px solid var(--study-line); }
.learning-page th { background: #eef1e8; color: #435d4e; font-weight: 600; }
.learning-page tr:last-child td { border-bottom: 0; }
.learning-page details:not(.lesson-toc) { margin: 12px 0; padding: 15px 18px; border: 1px solid var(--study-line); background: var(--study-paper); border-radius: 7px; }
.learning-page summary { cursor: pointer; color: var(--study-ink); font-weight: 600; }
.learning-page details[open]:not(.lesson-toc) summary { margin-bottom: 12px; }
.learning-page .small { color: var(--study-muted); font-size: 12px; }
.learning-page .topmap { gap: 12px; }
.learning-page .topmap a { background: #fffefa; border: 1px solid var(--study-line); border-radius: 7px; box-shadow: none; padding: 14px 16px; }
.learning-page .topmap b { color: var(--study-accent); }
.learning-page .flow .step { border-color: var(--study-line); background: var(--study-paper); color: var(--study-ink); }
.learning-page .steps .step { background: var(--study-paper); border-color: var(--study-line); border-radius: 7px; }
.learning-page .steps .step::before { background: var(--study-tint); color: var(--study-accent); }
.learning-page .mistake { background: #fcf1ee; border-color: #eddbd5; border-radius: 6px; }
.learning-page .quiz button { background: var(--study-paper); border: 1px solid var(--study-line); border-radius: 6px; color: var(--study-ink); }
.learning-page .quiz button:hover { background: var(--study-tint); border-color: var(--study-accent); }
.learning-page .answer { color: #264734; background: #edf3e9; border-color: #cbdcc2; }
.learning-page .progress { position: fixed; top: 0; left: 0; z-index: 60; width: 0; height: 2px; background: var(--study-accent); }

/* Future lessons: compact recall and immediate feedback. */
.learning-page .lesson-meta { display: flex; flex-wrap: wrap; gap: 7px 20px; margin-top: 21px; color: var(--study-muted); font-size: 12px; }
.learning-page .lesson-meta span + span::before { content: "·"; margin-right: 20px; color: #abaf9f; }
.learning-page .hero .template-tools { margin-top: 22px; }
.learning-page .recall summary { color: var(--study-accent); }
.learning-page [data-quiz] { margin: 22px 0; padding: 23px; background: var(--study-paper); border: 1px solid var(--study-line); border-radius: 8px; }
.learning-page [data-quiz] fieldset { padding: 0; margin: 0; border: 0; }
.learning-page [data-quiz] legend { margin-bottom: 14px; font-weight: 600; }
.learning-page [data-quiz] label { display: flex; align-items: baseline; gap: 10px; padding: 10px 12px; margin: 7px 0; background: #f8f8f1; border: 1px solid var(--study-line); border-radius: 5px; cursor: pointer; }
.learning-page [data-quiz] input { accent-color: var(--study-accent); }
.learning-page [data-quiz] button { margin-top: 15px; padding: 9px 17px; background: var(--study-accent); color: white; border: 0; border-radius: 5px; cursor: pointer; font-size: 13px; }
.learning-page [data-feedback] { margin: 12px 0 0; color: var(--study-accent); font-size: 14px; }
.learning-page [data-feedback]:empty { display: none; }
.learning-page .source-list { padding-left: 22px; font-size: 14px; }
.learning-page .source-list li { padding: 5px 0; }
.learning-page :is(.footer, .site-footer, .lesson-footer, .source-note) { margin: 45px 0 0; padding: 24px 0 0; border-top: 1px solid var(--study-line); color: var(--study-muted); font-size: 12px; line-height: 1.9; background: none; }
.learning-page .site-footer { max-width: 1320px; margin: 24px auto; padding: 24px 28px; }
.learning-page .lesson-footer p { margin: 6px 0; }
.learning-page .chapter-end, .learning-page .site-footer nav { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 22px; }
.learning-page .chapter-end a, .learning-page .site-footer nav a { border: 1px solid var(--study-line); background: var(--study-paper); color: var(--study-accent); border-radius: 5px; padding: 7px 12px; font-size: 12px; text-decoration: none; }
.learning-page.collection-page .hero { padding: 33px 0; }
.learning-page.collection-page .hero h1 { font-size: clamp(30px, 4vw, 48px); }
.learning-page.collection-page a.card { border-radius: 8px; transition: border-color .15s, transform .15s; text-decoration: none; }
.learning-page.collection-page a.card:hover { border-color: #859c86; transform: translateY(-2px); box-shadow: 0 6px 16px rgb(36 62 53 / 5%); }
.learning-page.collection-page .card h2 { font-family: var(--study-serif); font-size: 20px; }
.learning-page.collection-page .card .num { background: #edf1e7; color: #48634b; border: 1px solid #dfe4d6; border-radius: 5px; font: 20px var(--study-serif); }
.learning-page.collection-page .flow { background: none; border: 1px solid var(--study-line); color: var(--study-muted); border-radius: 5px; font-size: 12px; line-height: 2; }
.learning-page.collection-page input[type="search"] { border: 1px solid #ccd4c6; background: var(--study-paper); color: var(--study-ink); border-radius: 5px; padding: 12px 15px; }
.learning-page.collection-page .pill { background: var(--study-tint); color: var(--study-accent); border-color: #dce3d6; border-radius: 5px; }

@media (max-width: 1080px) {
  .learning-page .lesson-shell { grid-template-columns: 196px minmax(0, 1fr); }
  .learning-page .lesson-sidebar { padding-left: 18px; padding-right: 14px; }
  .learning-page .lesson-main { padding: 20px 26px 60px; }
  .learning-page .site-header { gap: 20px; padding: 15px 24px; }
  .learning-page .site-nav a { padding: 6px 9px; }
  .learning-page .hero-grid, .learning-page .grid4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .learning-page .metric:nth-child(2) { border-right: 0; }
}
@media (max-width: 800px) {
  html { scroll-padding-top: 135px; }
  .learning-page .site-header { flex-wrap: wrap; gap: 12px; padding: 12px 18px 10px; min-height: 0; }
  .learning-page .site-brand { margin-right: auto; font-size: 15px; }
  .learning-page .site-mark { width: 32px; height: 37px; font-size: 20px; }
  .learning-page .site-nav { order: 3; width: 100%; justify-content: space-between; gap: 0; }
  .learning-page .site-nav a { padding: 5px 11px; font-size: 12px; }
  .learning-page .lesson-shell { display: block; }
  .learning-page .lesson-sidebar { display: block; position: static; height: auto; padding: 16px 20px; border-right: 0; border-bottom: 1px solid var(--study-line); overflow: visible; }
  .learning-page .lesson-sidebar > :not(.lesson-toc) { display: none; }
  .learning-page .lesson-toc { margin: 0; }
  .learning-page .lesson-toc summary { font-size: 12px; }
  .learning-page .lesson-toc nav { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .learning-page .lesson-main { padding: 20px 20px 50px; }
  .learning-page.collection-page .lesson-main { padding: 20px 20px 50px; }
  .learning-page .hero { padding-top: 18px; }
  .learning-page .hero h1 { font-size: 29px; line-height: 1.6; }
  .learning-page .hero p { font-size: 14px; }
  .learning-page .hero-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .learning-page .metric { padding: 13px 12px; }
  .learning-page .metric:first-child { padding-left: 12px; }
  .learning-page .grid2, .learning-page .grid3, .learning-page .grid4 { grid-template-columns: minmax(0, 1fr); }
  .learning-page :is(.card, .box) { padding: 18px; }
  .learning-page main > section:not(.hero), .learning-page main > .section { margin-top: 35px; }
  .learning-page h2, .learning-page .section h2 { font-size: 23px; }
  .learning-page .section-head { align-items: baseline; gap: 10px; }
  .learning-page .site-footer { padding: 20px; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .learning-page * { transition: none !important; }
}
@media print {
  @page { margin: 16mm 14mm; }
  html { scroll-padding: 0; }
  .learning-page { background: white; color: #152c21; font-size: 10pt; }
  .learning-page :is(.site-header, .lesson-sidebar, .lesson-breadcrumbs, .chapter-end, .progress, .printbtn, .site-footer nav, .template-tools) { display: none !important; }
  .learning-page .lesson-shell { display: block; }
  .learning-page .lesson-main, .learning-page.collection-page .lesson-main { width: 100%; max-width: none; margin: 0; padding: 0; }
  .learning-page .hero { margin: 0 0 18px; padding: 0 0 14px; }
  .learning-page .hero h1, .learning-page.collection-page .hero h1 { font-size: 24pt; }
  .learning-page h2 { font-size: 16pt; break-after: avoid; }
  .learning-page h3 { break-after: avoid; }
  .learning-page :is(.card, .box, .callout, .formula, .diagram, details, pre, tr) { break-inside: avoid; box-shadow: none; }
  .learning-page .table-scroll, .learning-page .table-wrap, .learning-page .diagram { overflow: visible; }
  .learning-page .diagram svg, .learning-page table { min-width: 0; }
  .learning-page .code, .learning-page pre { white-space: pre-wrap; overflow-wrap: anywhere; font-size: 8pt; }
  .learning-page .grid2, .learning-page .grid3, .learning-page .grid4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .learning-page a { color: inherit; }
  .learning-page [data-quiz] button { display: none; }
}