.reading-progress {
  position: fixed;
  inset: 0 0 auto;
  z-index: 70;
  height: 3px;
  background: transparent;
}

.reading-progress span {
  display: block;
  width: 0;
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--gold));
}

.lecture {
  width: min(calc(100% - 22rem), 980px);
  margin-left: calc(max(1rem, calc((100vw - 1360px) / 2)) + 17.5rem);
  margin-right: auto;
  padding-right: 0;
  overflow-x: clip;
}

.lecture-toc {
  position: fixed;
  top: 4.7rem;
  left: max(1rem, calc((100vw - 1360px) / 2));
  right: auto;
  z-index: 40;
  width: 15.5rem;
  max-height: calc(100vh - 6rem);
  padding: 0.9rem;
  overflow: auto;
  border: 1px solid var(--line);
  background: rgba(251, 250, 246, 0.96);
  box-shadow: var(--shadow);
}

html[data-theme="dark"] .lecture-toc {
  background: rgba(16, 18, 19, 0.88);
}

.lecture-toc p {
  margin: 0 0 0.55rem;
  color: var(--accent-deep);
  font-family: var(--mono);
  font-size: 0.78rem;
  font-weight: 850;
}

.lecture-toc nav {
  display: grid;
  gap: 0.16rem;
}

.lecture-toc a {
  display: block;
  padding: 0.36rem 0.45rem;
  color: var(--muted);
  font-size: 0.85rem;
  line-height: 1.3;
  text-decoration: none;
  border-left: 3px solid transparent;
}

.lecture-toc a.active,
.lecture-toc a:hover,
.lecture-toc a:focus-visible {
  color: var(--ink);
  background: rgba(15, 111, 104, 0.07);
  border-left-color: var(--accent);
  outline: none;
}

html[data-theme="dark"] .lecture-toc a.active,
html[data-theme="dark"] .lecture-toc a:hover,
html[data-theme="dark"] .lecture-toc a:focus-visible {
  background: rgba(81, 184, 200, 0.12);
}

.toc-toggle {
  display: none;
  position: fixed;
  right: 0.85rem;
  bottom: 0.85rem;
  z-index: 65;
  padding: 0.58rem 0.74rem;
  color: var(--accent-deep);
  font-weight: 850;
  border: 1px solid var(--line);
  background: var(--panel-strong);
  box-shadow: var(--shadow);
}

.chapter-header {
  padding: 1.25rem 0 1.05rem;
  border-bottom: 1px solid var(--line);
}

.chapter-summary {
  max-width: 820px;
  margin: 0.75rem 0 0;
  color: var(--ink);
  font-family: var(--serif);
  font-size: 1.12rem;
  line-height: 1.55;
}

.prereq-card,
.intuition-section,
.notation-box,
.misconception-card,
.chapter-checkpoints,
.judgement-card,
.advanced-derivation,
.summary-matrix,
.roadmap-grid article {
  margin-top: 1rem;
  padding: 1rem;
  border: 1px solid var(--line);
  background: var(--panel);
  box-shadow: var(--shadow);
}

.prereq-card strong {
  display: block;
  color: var(--accent-deep);
  font-family: var(--mono);
  font-size: 0.8rem;
  text-transform: uppercase;
}

.prereq-card a {
  display: inline-block;
  margin-top: 0.6rem;
  color: var(--accent-deep);
  font-weight: 800;
}

.notation-box {
  overflow-x: auto;
}

.notation-box table,
.summary-matrix table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92rem;
}

.notation-box th,
.notation-box td,
.summary-matrix th,
.summary-matrix td {
  padding: 0.62rem;
  text-align: left;
  vertical-align: top;
  border: 1px solid var(--line);
}

.notation-box th,
.summary-matrix th {
  color: var(--accent-deep);
  font-family: var(--mono);
  font-size: 0.78rem;
  background: rgba(15, 111, 104, 0.06);
}

.derivation-steps {
  display: grid;
  gap: 0.9rem;
  margin: 1rem 0 0;
  padding: 0;
  list-style: none;
}

.derivation-steps li {
  min-width: 0;
  padding: 1rem;
  border: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.76);
}

.step-label {
  margin: 0 0 0.55rem !important;
  color: var(--accent-deep) !important;
  font-family: var(--mono);
  font-size: 0.78rem !important;
  font-weight: 850;
}

.derivation-note {
  padding: 0.56rem 0.7rem;
  border-left: 3px solid var(--accent);
  background: var(--code);
  font-family: var(--mono);
  font-size: 0.86rem !important;
}

.equation {
  max-width: 100%;
  width: 100%;
  overflow-x: auto;
  overflow-y: hidden;
  padding: 0.9rem;
  contain: inline-size;
}

.equation mjx-container {
  display: block;
  max-width: 100%;
  overflow-x: auto;
  overflow-y: hidden;
  contain: paint;
}

.eq-number {
  display: block;
  margin-top: 0.4rem;
  color: var(--muted);
  font-family: var(--mono);
  font-size: 0.75rem;
  text-align: right;
}

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

.algorithm-grid article {
  min-width: 0;
}

.advanced-derivation summary {
  color: var(--accent-deep);
  font-weight: 850;
  cursor: pointer;
}

.advanced-derivation[open] summary {
  margin-bottom: 0.75rem;
}

.judgement-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.85rem;
}

.judgement-grid > div {
  min-width: 0;
  padding: 0.85rem;
  border: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.7);
}

.judgement-grid strong {
  color: var(--accent-deep);
}

.roadmap-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}

.interface-table {
  margin-top: 1rem;
}

.interface-table .interface-row {
  display: grid;
  grid-template-columns: 0.95fr 0.72fr 1.25fr 1.2fr 0.95fr 1fr;
}

.interface-table .interface-row span {
  min-width: 0;
}

.overview-diagram {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr) auto minmax(0, 1fr);
  gap: 0.7rem;
  align-items: stretch;
  margin-top: 0.9rem;
}

.flow-node,
.flow-arrow {
  display: grid;
  place-items: center;
  min-width: 0;
  padding: 0.78rem;
  text-align: center;
  border: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.78);
}

.flow-node {
  color: var(--accent-deep);
  font-family: var(--mono);
  font-weight: 850;
}

.flow-node small {
  display: block;
  margin-top: 0.35rem;
  color: var(--muted);
  font-family: var(--sans);
  font-weight: 500;
}

.flow-arrow {
  color: var(--muted);
  font-size: 0.82rem;
}

.page-footer {
  display: flex;
  justify-content: center;
  gap: 1rem;
  padding: 2rem 1rem 3rem;
  border-top: 1px solid var(--line);
}

@media (max-width: 1220px) {
  .lecture {
    margin-right: auto;
    margin-left: auto;
    padding-right: 0;
  }

  .lecture-toc {
    display: none;
  }

  .toc-toggle {
    display: inline-flex;
  }

  .lecture-toc.open {
    display: block;
    top: auto;
    right: 0.75rem;
    bottom: 3.8rem;
    left: 0.75rem;
    width: auto;
    max-height: 60vh;
  }
}

@media (max-width: 860px) {
  .lecture {
    width: min(100% - 1rem, 980px);
  }

  .roadmap-grid,
  .judgement-grid,
  .algorithm-grid {
    grid-template-columns: 1fr;
  }

  .overview-diagram {
    grid-template-columns: 1fr;
  }

  .flow-arrow {
    min-height: 2rem;
  }

  .interface-table .interface-row {
    display: block;
    padding: 0.7rem 0;
  }

  .interface-table .interface-head {
    display: none;
  }

  .interface-table .interface-row span {
    display: grid;
    grid-template-columns: 7.2rem minmax(0, 1fr);
    gap: 0.6rem;
    padding: 0.36rem 0.75rem;
    border: 0;
  }

  .interface-table .interface-row span::before {
    color: var(--accent-deep);
    font-family: var(--mono);
    font-size: 0.74rem;
    font-weight: 850;
  }

  .interface-table .interface-row span:nth-child(1)::before { content: "模型族"; }
  .interface-table .interface-row span:nth-child(2)::before { content: "显式密度"; }
  .interface-table .interface-row span:nth-child(3)::before { content: "可计算对象"; }
  .interface-table .interface-row span:nth-child(4)::before { content: "训练目标"; }
  .interface-table .interface-row span:nth-child(5)::before { content: "采样入口"; }
  .interface-table .interface-row span:nth-child(6)::before { content: "主要代价"; }
}