:root {
  color-scheme: light;
  --ink: #182026;
  --text-2: #4d5c66;
  --muted: #66737f;
  --line: #d9e0e6;
  --line-soft: #e5ebf0;
  --paper: #f6f8f5;
  --surface: #ffffff;
  --surface-2: #fbfcfd;
  --surface-3: #f8fafc;
  --panel: rgba(255, 255, 255, 0.72);
  --blue: #2563eb;
  --blue-soft: #edf4ff;
  --green: #16845b;
  --red: #bd3b31;
  --gold: #a66b00;
  --violet: #6d4ac7;
  --ok-bg: #e4f7ee;
  --bad-bg: #fdeceb;
  --shadow: 0 16px 40px rgba(22, 32, 38, 0.08);
  --code-bg: #101820;
  --code-ink: #eff6ff;
  --chip-bg: #eef2f6;
  --chip-ink: #42505b;
  --note-blue-bg: #eff6ff;
  --note-green-bg: #f0fbf6;
  --audit-bg: #f5f9ff;
  --audit-border: #d7e4f5;
  --tag-mit-ink: #8b1f17;
  --tag-mit-bg: #fff0ee;
  --tag-stanford-ink: #8f2520;
  --tag-stanford-bg: #fff3ef;
  --tag-berkeley-ink: #155e75;
  --tag-berkeley-bg: #ecfeff;
  --tag-princeton-ink: #8a5200;
  --tag-princeton-bg: #fff7e6;
  --tag-advanced-ink: #5b39a8;
  --tag-advanced-bg: #f4f0ff;
  --status-covered-ink: #0f6b4b;
  --status-covered-bg: #dcfce7;
  --status-extended-ink: #6d4ac7;
  --status-extended-bg: #f4f0ff;
  --map-line: #9aa7b1;
  --map-node-fill: #f8fafc;
  --map-node-stroke: #2f3b45;
}

html[data-theme="dark"] {
  color-scheme: dark;
  --ink: #e7edf3;
  --text-2: #b6c2cd;
  --muted: #8d9aa6;
  --line: #2b3644;
  --line-soft: #263140;
  --paper: #0e1319;
  --surface: #151c25;
  --surface-2: #1a2330;
  --surface-3: #1d2836;
  --panel: rgba(21, 28, 37, 0.72);
  --blue: #7aa7f8;
  --blue-soft: rgba(122, 167, 248, 0.16);
  --green: #43c795;
  --red: #f08a80;
  --gold: #e0b45c;
  --violet: #b39df1;
  --ok-bg: rgba(67, 199, 149, 0.15);
  --bad-bg: rgba(240, 138, 128, 0.15);
  --shadow: 0 16px 40px rgba(0, 0, 0, 0.45);
  --code-bg: #0b1118;
  --code-ink: #dbe7f3;
  --chip-bg: #223041;
  --chip-ink: #c2cfda;
  --note-blue-bg: rgba(122, 167, 248, 0.12);
  --note-green-bg: rgba(67, 199, 149, 0.1);
  --audit-bg: rgba(122, 167, 248, 0.08);
  --audit-border: #2b3d55;
  --tag-mit-ink: #f7a9a0;
  --tag-mit-bg: rgba(240, 138, 128, 0.14);
  --tag-stanford-ink: #f7b3a6;
  --tag-stanford-bg: rgba(247, 179, 166, 0.12);
  --tag-berkeley-ink: #7edce9;
  --tag-berkeley-bg: rgba(103, 232, 249, 0.12);
  --tag-princeton-ink: #ecc56f;
  --tag-princeton-bg: rgba(224, 180, 92, 0.14);
  --tag-advanced-ink: #c9b8f5;
  --tag-advanced-bg: rgba(179, 157, 241, 0.14);
  --status-covered-ink: #63d9a7;
  --status-covered-bg: rgba(34, 197, 94, 0.15);
  --status-extended-ink: #c9b8f5;
  --status-extended-bg: rgba(139, 92, 246, 0.16);
  --map-line: #4a5a6a;
  --map-node-fill: #1d2836;
  --map-node-stroke: #9fb2c2;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei", sans-serif;
}

button,
input,
select {
  font: inherit;
}

button {
  cursor: pointer;
}

code,
pre {
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
}

.app-shell {
  display: grid;
  grid-template-columns: 300px minmax(0, 1fr);
  min-height: 100vh;
}

.sidebar {
  position: sticky;
  top: 0;
  height: 100vh;
  overflow: auto;
  padding: 22px;
  background: #101820;
  color: #f3f7f5;
  border-right: 1px solid rgba(255, 255, 255, 0.08);
}

.brand {
  display: flex;
  gap: 12px;
  align-items: center;
  margin-bottom: 20px;
}

.brand strong {
  display: block;
  font-size: 18px;
}

.brand small {
  color: #aeb9c2;
}

.brand-mark {
  width: 42px;
  height: 42px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 4px;
  padding: 7px;
  border: 1px solid rgba(255, 255, 255, 0.24);
  border-radius: 8px;
}

.brand-mark span {
  border-radius: 3px;
  background: #7dd3fc;
}

.brand-mark span:nth-child(2) {
  background: #fbbf24;
}

.brand-mark span:nth-child(3) {
  background: #34d399;
}

.search-box {
  display: flex;
  align-items: center;
  gap: 9px;
  height: 42px;
  padding: 0 12px;
  border: 1px solid rgba(255, 255, 255, 0.14);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.08);
  color: #dbe5ec;
}

.search-box svg {
  width: 18px;
  height: 18px;
  flex: 0 0 auto;
}

.search-box input {
  width: 100%;
  min-width: 0;
  color: #fff;
  border: 0;
  outline: 0;
  background: transparent;
}

.search-box input::placeholder {
  color: #91a1ad;
}

.theme-toggle {
  width: 100%;
  min-height: 36px;
  margin-top: 10px;
  padding: 0 10px;
  color: #dbeafe;
  border: 1px solid rgba(255, 255, 255, 0.14);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.06);
  font-size: 13px;
  font-weight: 700;
}

.theme-toggle:hover {
  background: rgba(255, 255, 255, 0.12);
}

.progress-card {
  margin-top: 12px;
  padding: 12px;
  border: 1px solid rgba(255, 255, 255, 0.14);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.06);
  color: #dbe5ec;
}

.progress-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 8px;
}

.progress-head strong {
  color: #fff;
  font-size: 14px;
}

.progress-head span {
  color: #7dd3fc;
  font-weight: 800;
  font-size: 15px;
}

.progress-track {
  height: 8px;
  margin: 9px 0 7px;
  border-radius: 999px;
  background: rgba(125, 211, 252, 0.18);
  overflow: hidden;
}

.progress-fill {
  width: 0;
  height: 100%;
  border-radius: 999px;
  background: #7dd3fc;
  transition: width 0.3s ease;
}

.progress-card small {
  color: #91a1ad;
}

.nav-list {
  display: grid;
  gap: 6px;
  margin-top: 18px;
}

.site-links {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px;
  margin-top: 14px;
}

.site-links a {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 34px;
  padding: 0 8px;
  color: #dbeafe;
  text-decoration: none;
  border: 1px solid rgba(255, 255, 255, 0.12);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.06);
  font-size: 13px;
  font-weight: 700;
}

.site-links a:hover {
  background: rgba(255, 255, 255, 0.12);
}

.site-links a.active {
  color: #bae6fd;
  border-color: rgba(125, 211, 252, 0.55);
  background: rgba(125, 211, 252, 0.16);
}

.nav-list a {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  padding: 10px 11px;
  color: #e5edf2;
  text-decoration: none;
  border-radius: 8px;
}

.nav-list a:hover {
  background: rgba(255, 255, 255, 0.08);
}

.nav-list small {
  color: #91a1ad;
}

main {
  padding: 28px;
  min-width: 0;
}

.topbar {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 420px;
  gap: 26px;
  align-items: stretch;
  margin-bottom: 18px;
}

.topbar h1 {
  max-width: 920px;
  margin: 4px 0 12px;
  font-size: clamp(32px, 5vw, 56px);
  line-height: 1.05;
  letter-spacing: 0;
}

.lead {
  max-width: 850px;
  margin: 0;
  color: var(--text-2);
  font-size: 18px;
  line-height: 1.7;
}

.eyebrow {
  margin: 0 0 6px;
  color: var(--red);
  font-size: 12px;
  font-weight: 800;
  letter-spacing: 0;
  text-transform: uppercase;
}

.concept-map {
  margin: 0;
  min-height: 220px;
  padding: 20px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
  box-shadow: var(--shadow);
}

.concept-map svg {
  width: 100%;
  height: 100%;
}

.concept-map line {
  stroke: var(--map-line);
  stroke-width: 2;
}

.concept-map circle {
  fill: var(--map-node-fill);
  stroke: var(--map-node-stroke);
  stroke-width: 2;
}

.concept-map text {
  text-anchor: middle;
  font-size: 18px;
  font-weight: 800;
  fill: var(--ink);
}

.stats-grid,
.source-grid,
.knowledge-grid,
.deploy-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 12px;
}

.stats-grid {
  margin-bottom: 18px;
}

.stats-grid div,
.source-card,
.knowledge-card,
.deploy-grid div {
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
}

.stats-grid strong {
  display: block;
  margin-bottom: 4px;
  font-size: 28px;
}

.stats-grid span,
.source-card p,
.knowledge-card p,
.deploy-grid p {
  color: var(--muted);
  line-height: 1.6;
}

.panel {
  margin-top: 18px;
  padding: 20px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
}

.section-head {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 16px;
}

.section-head h2 {
  margin: 0;
  font-size: 26px;
  letter-spacing: 0;
}

.segmented,
.toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.segmented button,
.toolbar select {
  min-height: 38px;
  padding: 0 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
  color: var(--ink);
}

.segmented button.active {
  border-color: var(--blue);
  color: var(--blue);
  background: var(--blue-soft);
}

.source-card h3,
.knowledge-card h3,
.deploy-grid h3 {
  margin: 0 0 8px;
}

.source-card a,
.knowledge-card a {
  color: var(--blue);
  font-weight: 700;
}

.knowledge-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.knowledge-card {
  display: flex;
  flex-direction: column;
  min-height: 280px;
}

.knowledge-card h3 {
  font-size: 18px;
  line-height: 1.35;
}

.knowledge-card ul {
  margin: 8px 0 0;
  padding-left: 18px;
}

.knowledge-card li {
  color: var(--text-2);
  line-height: 1.55;
}

.knowledge-card .cpp-note {
  margin-top: auto;
  padding-top: 12px;
  color: var(--text-2);
  font-size: 14px;
}

.knowledge-card .source-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-top: 10px;
}

.module-list,
.textbook-list,
.exercise-list,
.set-list {
  display: grid;
  gap: 12px;
}

.module-card,
.textbook-card,
.exercise-card,
.set-card {
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
}

.module-card {
  display: grid;
  grid-template-columns: 1fr 320px;
  gap: 18px;
}

.module-card h3,
.textbook-card h3,
.exercise-card h3,
.set-card h3 {
  margin: 0 0 8px;
  font-size: 20px;
}

.module-card p,
.textbook-card p,
.exercise-card p,
.set-card p,
.module-card li,
.textbook-card li,
.set-card li {
  color: var(--text-2);
  line-height: 1.65;
}

.textbook-card {
  display: grid;
  gap: 14px;
}

.textbook-intro {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 260px;
  gap: 16px;
  align-items: start;
}

.textbook-side {
  padding: 12px;
  border-left: 3px solid var(--blue);
  border-radius: 8px;
  background: var(--note-blue-bg);
}

.textbook-section-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 10px;
}

.textbook-section {
  padding: 12px;
  border: 1px solid var(--line-soft);
  border-radius: 8px;
  background: var(--surface-2);
}

.textbook-section strong {
  display: block;
  margin-bottom: 6px;
}

.textbook-section ul,
.textbook-section ol {
  margin: 0;
  padding-left: 18px;
}

.code-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
}

.code-card {
  display: flex;
  flex-direction: column;
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
}

.code-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
}

.code-card h3 {
  margin: 0;
  font-size: 17px;
  line-height: 1.4;
}

.code-card pre {
  margin: 12px 0 0;
  font-size: 13px;
  line-height: 1.55;
}

.code-note {
  margin: 10px 0 0;
  color: var(--muted);
  font-size: 14px;
  line-height: 1.6;
}

.copy-btn {
  flex: 0 0 auto;
  min-height: 32px;
  padding: 0 10px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface-2);
  color: var(--text-2);
  font-size: 12px;
  font-weight: 700;
  white-space: nowrap;
}

.copy-btn:hover {
  border-color: var(--blue);
  color: var(--blue);
}

.copy-btn.copied {
  border-color: var(--green);
  color: var(--green);
}

.quiz-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
}

.quiz-card {
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
}

.quiz-card h3 {
  margin: 0;
  font-size: 17px;
  line-height: 1.5;
}

.quiz-options {
  display: grid;
  gap: 8px;
  margin-top: 12px;
}

.quiz-option {
  display: flex;
  gap: 8px;
  align-items: baseline;
  padding: 9px 12px;
  text-align: left;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface-2);
  color: var(--text-2);
  line-height: 1.5;
}

.quiz-letter {
  font-weight: 800;
  color: var(--muted);
}

.quiz-option:hover:not(:disabled) {
  border-color: var(--blue);
  color: var(--ink);
}

.quiz-option:disabled {
  cursor: default;
  opacity: 0.7;
}

.quiz-option.correct,
.quiz-option.wrong {
  opacity: 1;
  font-weight: 600;
}

.quiz-option.correct {
  border-color: var(--green);
  background: var(--ok-bg);
  color: var(--green);
}

.quiz-option.correct .quiz-letter,
.quiz-option.wrong .quiz-letter {
  color: inherit;
}

.quiz-option.wrong {
  border-color: var(--red);
  background: var(--bad-bg);
  color: var(--red);
}

.quiz-explain {
  margin-top: 12px;
  padding: 12px;
  border-left: 3px solid var(--blue);
  border-radius: 8px;
  background: var(--note-blue-bg);
  color: var(--text-2);
  line-height: 1.6;
}

.quiz-explain p {
  margin: 0 0 8px;
}

.quiz-reset {
  padding: 0;
  border: 0;
  background: none;
  color: var(--blue);
  font-weight: 700;
}

.audit-note {
  margin-bottom: 14px;
  padding: 14px;
  color: var(--text-2);
  line-height: 1.65;
  border: 1px solid var(--audit-border);
  border-radius: 8px;
  background: var(--audit-bg);
}

.coverage-table-wrap {
  overflow-x: auto;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
}

.coverage-table {
  width: 100%;
  min-width: 980px;
  border-collapse: collapse;
}

.coverage-table.plan-table {
  min-width: 760px;
}

.coverage-table th,
.coverage-table td {
  padding: 10px 12px;
  text-align: left;
  vertical-align: top;
  border-bottom: 1px solid var(--line-soft);
}

.coverage-table th {
  position: sticky;
  top: 0;
  z-index: 1;
  background: var(--surface-3);
  color: var(--ink);
  font-size: 13px;
}

.coverage-table td {
  color: var(--text-2);
  line-height: 1.45;
  font-size: 14px;
}

.coverage-status {
  display: inline-flex;
  align-items: center;
  min-height: 24px;
  padding: 0 8px;
  border-radius: 999px;
  font-weight: 800;
  font-size: 12px;
}

.coverage-status.covered {
  color: var(--status-covered-ink);
  background: var(--status-covered-bg);
}

.coverage-status.extended {
  color: var(--status-extended-ink);
  background: var(--status-extended-bg);
}

.tag-row {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin: 10px 0;
}

.tag {
  display: inline-flex;
  align-items: center;
  min-height: 26px;
  padding: 0 8px;
  border-radius: 999px;
  background: var(--chip-bg);
  color: var(--chip-ink);
  font-size: 12px;
  font-weight: 700;
}

.tag.mit {
  color: var(--tag-mit-ink);
  background: var(--tag-mit-bg);
}

.tag.stanford {
  color: var(--tag-stanford-ink);
  background: var(--tag-stanford-bg);
}

.tag.berkeley {
  color: var(--tag-berkeley-ink);
  background: var(--tag-berkeley-bg);
}

.tag.princeton {
  color: var(--tag-princeton-ink);
  background: var(--tag-princeton-bg);
}

.tag.advanced {
  color: var(--tag-advanced-ink);
  background: var(--tag-advanced-bg);
}

.detail-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
}

.detail-box {
  padding: 12px;
  border: 1px solid var(--line-soft);
  border-radius: 8px;
  background: var(--surface-2);
}

.detail-box strong {
  display: block;
  margin-bottom: 6px;
}

.detail-box ul {
  margin: 0;
  padding-left: 18px;
}

.module-side {
  padding: 14px;
  border-left: 3px solid var(--green);
  background: var(--note-green-bg);
  border-radius: 8px;
}

.module-side strong {
  display: block;
  margin-bottom: 8px;
}

.exercise-card {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 210px;
  gap: 18px;
}

.exercise-meta {
  display: grid;
  gap: 8px;
  align-content: start;
}

.level {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-weight: 800;
}

.checkline {
  display: flex;
  gap: 8px;
  align-items: flex-start;
  color: var(--text-2);
}

.checkline input {
  width: 18px;
  height: 18px;
  margin-top: 3px;
  accent-color: var(--blue);
  flex: 0 0 auto;
}

.set-tasks {
  display: grid;
  gap: 8px;
  margin: 0;
  padding-left: 18px;
}

.set-tasks li::marker {
  color: var(--muted);
  font-weight: 700;
}

details {
  margin-top: 10px;
}

summary {
  color: var(--blue);
  font-weight: 800;
  cursor: pointer;
}

pre {
  overflow: auto;
  padding: 12px;
  border-radius: 8px;
  background: var(--code-bg);
  color: var(--code-ink);
}

html[data-theme="dark"] pre {
  border: 1px solid var(--line-soft);
}

.empty {
  padding: 24px;
  color: var(--muted);
  text-align: center;
  border: 1px dashed var(--line);
  border-radius: 8px;
  background: var(--surface);
}

.back-to-top {
  position: fixed;
  right: 22px;
  bottom: 22px;
  z-index: 50;
  min-height: 40px;
  padding: 0 14px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--surface);
  color: var(--text-2);
  font-weight: 700;
  box-shadow: var(--shadow);
  opacity: 0;
  transform: translateY(8px);
  pointer-events: none;
  transition: opacity 0.25s ease, transform 0.25s ease;
}

.back-to-top.visible {
  opacity: 1;
  transform: none;
  pointer-events: auto;
}

.back-to-top:hover {
  color: var(--blue);
  border-color: var(--blue);
}

@media (max-width: 1120px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: relative;
    height: auto;
  }

  .nav-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .topbar,
  .module-card,
  .textbook-intro,
  .exercise-card,
  .code-grid,
  .quiz-grid {
    grid-template-columns: 1fr;
  }

  .stats-grid,
  .source-grid,
  .knowledge-grid,
  .textbook-section-grid,
  .deploy-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 680px) {
  main,
  .sidebar {
    padding: 16px;
  }

  .topbar h1 {
    font-size: 34px;
  }

  .lead {
    font-size: 16px;
  }

  .stats-grid,
  .source-grid,
  .knowledge-grid,
  .textbook-section-grid,
  .deploy-grid,
  .detail-grid,
  .nav-list {
    grid-template-columns: 1fr;
  }

  .section-head {
    display: grid;
    align-items: start;
  }

  .back-to-top {
    right: 14px;
    bottom: 14px;
  }
}