:root {
  --bg: #f6f8f7;
  --panel: #ffffff;
  --soft: #eef7f4;
  --ink: #17211d;
  --muted: #60706a;
  --line: #d9e5e0;
  --teal: #0f766e;
  --teal-dark: #0b534e;
  --rose: #b23b59;
  --gold: #8a6508;
  --blue: #285f9f;
  --shadow: 0 18px 42px rgba(16, 34, 29, 0.09);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  color: var(--ink);
  background: linear-gradient(180deg, #fbfdfc 0, var(--bg) 340px);
}
* { box-sizing: border-box; }
body { margin: 0; min-height: 100vh; color: var(--ink); background: var(--bg); }
a { color: inherit; }
p, li { line-height: 1.62; }
.topbar { width: min(1240px, calc(100% - 32px)); margin: 0 auto; padding: 16px 0; display: flex; align-items: center; justify-content: space-between; gap: 14px; }
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; }
.brand span { width: 42px; height: 42px; display: grid; place-items: center; border-radius: 8px; color: #fff; background: var(--ink); font-weight: 900; }
.navlinks { display: flex; flex-wrap: wrap; gap: 8px; justify-content: flex-end; }
.navlinks a, .button { border: 1px solid var(--line); background: var(--panel); border-radius: 8px; text-decoration: none; min-height: 40px; padding: 9px 12px; display: inline-flex; align-items: center; justify-content: center; font-weight: 800; }
.navlinks a.is-active, .button.primary { background: var(--teal); color: #fff; border-color: var(--teal); }
.page-shell { width: min(1240px, calc(100% - 32px)); margin: 0 auto; padding-bottom: 48px; }
.hero { border: 1px solid var(--line); background: linear-gradient(180deg, #fff, #fbfdfc); border-radius: 8px; box-shadow: var(--shadow); padding: clamp(20px, 4vw, 42px); margin: 10px 0 18px; }
.hero.split { display: grid; grid-template-columns: minmax(0, 1fr) minmax(320px, 0.62fr); gap: 18px; align-items: stretch; }
.eyebrow { margin: 0 0 8px; text-transform: uppercase; letter-spacing: 0; color: var(--teal-dark); font-size: 0.78rem; font-weight: 900; }
h1 { margin: 0; font-size: clamp(2.2rem, 5vw, 4.7rem); line-height: 0.98; letter-spacing: 0; }
h2, h3 { letter-spacing: 0; }
.lead { max-width: 820px; font-size: clamp(1rem, 1.5vw, 1.22rem); color: var(--ink); }
.hero-actions, .tag-row, .filter-row { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }
.tag-row span { border-radius: 8px; background: var(--soft); color: var(--teal-dark); padding: 5px 8px; font-size: 0.78rem; font-weight: 850; }
.tag-row.mini span { font-size: 0.72rem; }
.band, .card, .side-card, .question-topic, .pattern-card { border: 1px solid var(--line); background: var(--panel); border-radius: 8px; box-shadow: var(--shadow); padding: 18px; margin-bottom: 16px; }
.band.compact { padding: 12px; }
.section-heading, .question-topic-head { display: flex; justify-content: space-between; gap: 12px; align-items: center; margin-bottom: 14px; }
.metric-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); gap: 10px; }
.metric-grid article { border: 1px solid var(--line); border-radius: 8px; padding: 16px; background: #fbfdfc; }
.metric-grid strong { display: block; font-size: 2rem; color: var(--teal-dark); }
.course-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(310px, 1fr)); gap: 12px; }
.course-card { display: grid; grid-template-columns: 110px minmax(0, 1fr); gap: 12px; border: 1px solid var(--line); border-radius: 8px; background: #fff; text-decoration: none; overflow: hidden; min-height: 160px; }
.course-card img { width: 110px; height: 100%; object-fit: cover; background: var(--soft); }
.course-card div { padding: 12px 12px 12px 0; }
.course-card span, .resource-link small, .source-note { color: var(--muted); font-size: 0.85rem; }
.course-card h3 { margin: 4px 0; }
.video-panel { margin: 0; display: grid; gap: 8px; }
.video-panel iframe { width: 100%; min-height: 320px; border: 0; border-radius: 8px; background: #000; }
.video-panel figcaption { color: var(--muted); font-size: 0.9rem; }
.learning-layout { display: grid; grid-template-columns: minmax(220px, 270px) minmax(0, 1fr); gap: 18px; align-items: start; }
.sidebar { position: sticky; top: 12px; display: grid; gap: 10px; max-height: calc(100vh - 24px); overflow: auto; }
.lecture-nav { display: grid; gap: 7px; }
.lecture-nav a { display: grid; grid-template-columns: 34px 1fr; gap: 8px; text-decoration: none; border: 1px solid var(--line); border-radius: 8px; padding: 8px; align-items: center; }
.lecture-nav a.current { border-color: var(--teal); background: var(--soft); }
.lecture-nav span { color: var(--teal-dark); font-weight: 900; }
.content { min-width: 0; }
.problem-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 12px; }
.problem-grid article, .answer-block { border-left: 4px solid var(--teal); background: #f8fbfa; border-radius: 8px; padding: 12px; }
.timeline-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 12px; }
.timeline-card { border: 1px solid var(--line); border-radius: 8px; padding: 14px; background: linear-gradient(180deg, #fbfdfc, #fff); }
.timeline-card h3 { margin: 10px 0 6px; }
.time-pill { display: inline-flex; min-height: 32px; align-items: center; border-radius: 8px; padding: 6px 9px; color: #fff; background: var(--ink); text-decoration: none; font-weight: 850; }
.answer-hint { color: var(--muted); font-size: 0.92rem; }
.concept-block { border-left: 4px solid var(--blue); padding: 4px 0 4px 14px; margin: 14px 0; }
.concept-block h3 { margin-bottom: 4px; }
.answer-template { display: grid; gap: 10px; }
.answer-template article { display: grid; grid-template-columns: 150px 1fr; gap: 12px; border: 1px solid var(--line); border-radius: 8px; padding: 12px; background: #fbfdfc; }
.answer-template strong { color: var(--teal-dark); }
.method-list { display: grid; gap: 8px; }
.agent-canvas { width: 100%; min-height: 320px; border: 1px solid var(--line); border-radius: 8px; background: #fbfdfc; }
.agent-canvas.large { min-height: 380px; }
.question-card { border: 1px solid var(--line); border-radius: 8px; background: #fbfdfc; margin: 10px 0; }
.question-card summary { cursor: pointer; padding: 13px; font-weight: 850; }
.question-card summary span { display: inline-flex; margin-right: 8px; color: var(--rose); }
.question-card ol { margin: 0; padding: 0 18px 16px 34px; }
.resource-list { display: grid; gap: 9px; }
.resource-link { display: grid; gap: 3px; border: 1px solid var(--line); border-radius: 8px; padding: 11px; text-decoration: none; background: #fbfdfc; overflow-wrap: anywhere; }
.filter-row input { flex: 1 1 260px; min-height: 42px; padding: 10px 12px; border: 1px solid var(--line); border-radius: 8px; font: inherit; }
.question-stack { display: grid; gap: 14px; }
.table-wrap { overflow-x: auto; border: 1px solid var(--line); border-radius: 8px; }
table { width: 100%; min-width: 680px; border-collapse: collapse; background: #fff; }
th, td { padding: 12px; border-bottom: 1px solid var(--line); text-align: left; vertical-align: top; }
th { background: var(--soft); color: var(--teal-dark); text-transform: uppercase; font-size: 0.8rem; }
.pattern-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(290px, 1fr)); gap: 12px; }
@media (max-width: 860px) {
  .topbar, .section-heading, .question-topic-head { align-items: stretch; flex-direction: column; }
  .hero.split, .learning-layout { grid-template-columns: 1fr; }
  .sidebar { position: static; max-height: none; }
  .course-card { grid-template-columns: 1fr; }
  .course-card img { width: 100%; height: 170px; }
  .course-card div { padding: 12px; }
  .video-panel iframe { min-height: 220px; }
  .answer-template article { grid-template-columns: 1fr; gap: 4px; }
}