.ce-student-shell {
  --ce-surface: #ffffff;
  --ce-surface-soft: #f8fafc;
  --ce-ink: #111827;
  --ce-muted: #64748b;
  --ce-line: #dbe3ed;
  --ce-accent: #2563eb;
  --ce-good: #047857;
  --ce-warn: #b45309;
  color: var(--ce-ink);
  display: grid;
  gap: 28px;
  grid-template-columns: minmax(220px, 280px) minmax(0, 1fr);
  margin: 0 auto;
  max-width: 1180px;
  padding: 24px;
}

.ce-student-shell--notice {
  grid-template-columns: minmax(0, 1fr);
}

.ce-student-sidebar {
  align-self: start;
  display: grid;
  gap: 18px;
  position: sticky;
  top: 24px;
}

.ce-student-topic,
.ce-student-toc,
.ce-student-section,
.ce-student-notice {
  background: var(--ce-surface);
  border: 1px solid var(--ce-line);
  border-radius: 8px;
}

.ce-student-topic {
  display: grid;
  gap: 6px;
  padding: 14px;
}

.ce-student-topic p,
.ce-student-summary,
.ce-student-section-header p,
.ce-student-rich-text p,
.ce-student-step-note {
  color: var(--ce-muted);
  line-height: 1.65;
  margin: 0;
}

.ce-student-toc {
  max-height: calc(100vh - 140px);
  overflow: auto;
  padding: 14px;
}

.ce-student-toc h2,
.ce-student-toc h3 {
  font-size: 14px;
  margin: 0 0 8px;
}

.ce-student-toc h3 {
  color: var(--ce-muted);
  font-weight: 700;
}

.ce-student-toc ol {
  display: grid;
  gap: 4px;
  list-style: none;
  margin: 0 0 14px;
  padding: 0;
}

.ce-student-toc a {
  border-radius: 6px;
  color: var(--ce-ink);
  display: block;
  padding: 7px 8px;
  text-decoration: none;
}

.ce-student-toc .is-active a,
.ce-student-toc a:hover {
  background: #eff6ff;
  color: var(--ce-accent);
}

.ce-student-shell :where(a[href], button, [tabindex]:not([tabindex="-1"])):focus-visible {
  outline: 2px solid var(--ce-accent);
  outline-offset: 3px;
}

.ce-student-main {
  min-width: 0;
}

.ce-student-lesson {
  display: grid;
  gap: 18px;
}

.ce-student-hero {
  display: grid;
  gap: 12px;
  padding: 8px 0 10px;
}

.ce-student-breadcrumb,
.ce-student-meta,
.ce-student-source-chip,
.ce-student-formula-complexity > span {
  color: var(--ce-muted);
  font-size: 13px;
}

.ce-student-hero h1 {
  font-size: 36px;
  line-height: 1.15;
  margin: 0;
}

.ce-student-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.ce-student-meta span,
.ce-student-source-chip span,
.ce-student-source-chip a {
  background: var(--ce-surface-soft);
  border: 1px solid var(--ce-line);
  border-radius: 999px;
  color: var(--ce-muted);
  padding: 4px 8px;
  text-decoration: none;
}

.ce-student-section {
  content-visibility: auto;
  contain-intrinsic-size: 360px;
  display: grid;
  gap: 14px;
  padding: 20px;
}

.ce-student-section:focus-within {
  content-visibility: visible;
}

.ce-student-section[data-ce-layout-width] {
  box-sizing: border-box;
  justify-self: var(--ce-section-align, stretch);
  width: min(var(--ce-section-width, 100%), 100%);
}

.ce-student-section-header {
  display: grid;
  gap: 6px;
}

.ce-student-section h2 {
  font-size: 23px;
  line-height: 1.25;
  margin: 0;
}

.ce-student-rich-text {
  display: grid;
  gap: 10px;
}

.ce-student-rich-text h3 {
  font-size: 18px;
  margin: 0;
}

.ce-student-rich-text ul {
  margin: 0;
  padding-left: 22px;
}

.ce-student-rich-text blockquote {
  border-left: 4px solid #60a5fa;
  color: #334155;
  margin: 0;
  padding: 4px 0 4px 12px;
}

.ce-student-rich-text code,
.ce-student-code {
  font-family: Consolas, Monaco, monospace;
}

.ce-student-definition-list {
  display: grid;
  gap: 8px 14px;
  grid-template-columns: minmax(120px, 0.35fr) minmax(0, 1fr);
  margin: 0;
}

.ce-student-definition-list dt {
  font-weight: 700;
}

.ce-student-definition-list dd {
  margin: 0;
}

.ce-student-table-wrap {
  overflow-x: auto;
}

.ce-student-table {
  border-collapse: collapse;
  min-width: 520px;
  width: 100%;
}

.ce-student-table th,
.ce-student-table td {
  border: 1px solid var(--ce-line);
  padding: 8px 10px;
  text-align: left;
  vertical-align: top;
}

.ce-student-table th {
  background: #eef2f7;
}

.ce-student-code {
  background: #0f172a;
  border-radius: 8px;
  color: #e5e7eb;
  font-size: 14px;
  line-height: 1.55;
  margin: 0;
  overflow: auto;
  padding: 12px;
}

.ce-student-code-line {
  display: grid;
  gap: 10px;
  grid-template-columns: 3em minmax(0, 1fr);
}

.ce-student-code--no-lines .ce-student-code-line {
  grid-template-columns: minmax(0, 1fr);
}

.ce-student-code-line.is-active {
  background: rgba(37, 99, 235, 0.28);
}

.ce-student-code-line-number {
  color: #94a3b8;
  text-align: right;
}

.ce-student-code-line-text {
  overflow-wrap: anywhere;
  white-space: pre-wrap;
}

.ce-student-code-compare,
.ce-student-cards,
.ce-student-gallery {
  display: grid;
  gap: 12px;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
}

.ce-student-code-pane,
.ce-student-card,
.ce-student-formula-reference,
.ce-student-fallback-card {
  background: var(--ce-surface-soft);
  border: 1px solid var(--ce-line);
  border-radius: 8px;
  display: grid;
  gap: 10px;
  padding: 12px;
}

.ce-student-step-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.ce-student-step-tabs button,
.ce-student-visual-steps button,
.ce-student-quiz button {
  border: 1px solid var(--ce-line);
  border-radius: 6px;
  cursor: pointer;
  min-height: 40px;
  padding: 8px 10px;
  touch-action: manipulation;
}

.ce-student-step-tabs button[aria-selected="true"],
.ce-student-visual-steps button[aria-selected="true"] {
  background: #eff6ff;
  border-color: #93c5fd;
  color: var(--ce-accent);
}

.ce-student-quiz {
  display: grid;
  gap: 12px;
}

.ce-student-quiz ol {
  display: grid;
  gap: 8px;
  list-style-position: inside;
  margin: 0;
  padding: 0;
}

.ce-student-quiz li {
  display: grid;
  gap: 8px;
}

.ce-student-quiz button {
  background: var(--ce-surface-soft);
  text-align: left;
}

.ce-student-quiz button.is-correct {
  border-color: #86efac;
  color: var(--ce-good);
}

.ce-student-quiz button.is-incorrect {
  border-color: #fca5a5;
  color: #b91c1c;
}

.ce-student-timeline {
  display: grid;
  gap: 12px;
  margin: 0;
  padding-left: 22px;
}

.ce-student-timeline li {
  border-left: 3px solid #60a5fa;
  display: grid;
  gap: 4px;
  padding-left: 10px;
}

.ce-student-timeline span {
  color: var(--ce-muted);
  font-size: 13px;
}

.ce-student-media,
.ce-student-gallery-item {
  display: grid;
  gap: 8px;
  margin: 0;
}

.ce-student-media img,
.ce-student-gallery-item img,
.ce-student-media video,
.ce-student-gallery-item video,
.ce-student-media iframe,
.ce-student-gallery-item iframe {
  border: 1px solid var(--ce-line);
  border-radius: 8px;
  max-width: 100%;
}

.ce-student-media audio,
.ce-student-gallery-item audio {
  width: 100%;
}

.ce-student-media iframe,
.ce-student-gallery-item iframe {
  aspect-ratio: 16 / 9;
  width: 100%;
}

.ce-student-media-placeholder {
  background: var(--ce-surface-soft);
  border: 1px dashed var(--ce-line);
  border-radius: 8px;
  color: var(--ce-muted);
  padding: 18px;
}

.ce-student-formula,
.ce-student-formula-steps,
.ce-student-formula-complexity,
.ce-student-formula-references {
  display: grid;
  gap: 10px;
}

.ce-student-formula-expression {
  background: var(--ce-surface-soft);
  border: 1px solid var(--ce-line);
  border-radius: 6px;
  font-family: Cambria Math, Georgia, serif;
  font-size: 18px;
  line-height: 1.45;
  overflow-wrap: anywhere;
  padding: 10px 12px;
}

.ce-student-formula-expression--inline {
  display: inline-block;
  font-size: 1em;
  padding: 2px 6px;
}

.ce-student-formula-expression.is-fallback {
  font-family: Consolas, Monaco, monospace;
  white-space: pre-wrap;
}

.ce-student-formula-steps {
  margin: 0;
  padding-left: 22px;
}

.ce-student-formula-steps li {
  display: grid;
  gap: 8px;
}

.ce-student-formula-complexity,
.ce-student-formula-reference {
  background: var(--ce-surface);
  border: 1px solid var(--ce-line);
  border-radius: 8px;
  padding: 10px;
}

.ce-student-visual {
  display: grid;
  gap: 10px;
}

.ce-student-visual-steps {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.ce-student-visual-canvas:empty {
  display: none;
}

.ce-student-visual.is-rendered .ce-student-visual-canvas {
  display: block;
}

.ce-student-fallback-card span {
  color: var(--ce-warn);
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
}

.ce-student-fallback-card dl {
  display: grid;
  gap: 4px 10px;
  grid-template-columns: max-content minmax(0, 1fr);
  margin: 0;
}

.ce-student-fallback-card dt {
  color: var(--ce-muted);
}

.ce-student-fallback-card dd {
  margin: 0;
}

.ce-student-fallback-card pre {
  background: #0f172a;
  border-radius: 6px;
  color: #e5e7eb;
  margin: 0;
  max-height: 260px;
  overflow: auto;
  padding: 10px;
}

.ce-student-callout {
  border-left: 4px solid #60a5fa;
  background: var(--ce-surface-soft);
  border-radius: 8px;
  padding: 12px;
}

.ce-student-source-list {
  display: grid;
  gap: 8px;
  margin: 0;
  padding-left: 22px;
}

.ce-student-source-list li {
  display: grid;
  gap: 4px;
}

.ce-student-caption,
.ce-student-explanation {
  color: var(--ce-muted);
}

.ce-student-notice {
  padding: 20px;
}

@media (max-width: 860px) {
  .ce-student-shell {
    grid-template-columns: minmax(0, 1fr);
    padding: 16px;
  }

  .ce-student-sidebar {
    position: static;
  }

  .ce-student-toc {
    max-height: none;
  }

  .ce-student-hero h1 {
    font-size: 29px;
  }

  .ce-student-definition-list {
    grid-template-columns: minmax(0, 1fr);
  }

  .ce-student-section {
    padding: 16px;
  }

  .ce-student-section[data-ce-layout-width] {
    justify-self: stretch;
    width: 100%;
  }
}

@media (max-width: 480px) {
  .ce-student-shell {
    gap: 18px;
    padding: 12px;
  }

  .ce-student-hero h1 {
    font-size: 26px;
  }

  .ce-student-section {
    padding: 14px;
  }

  .ce-student-code-compare,
  .ce-student-cards,
  .ce-student-gallery {
    grid-template-columns: minmax(0, 1fr);
  }

  .ce-student-code-line {
    grid-template-columns: 2.4em minmax(0, 1fr);
  }

  .ce-student-source-chip,
  .ce-student-meta {
    gap: 6px;
  }
}

@media (pointer: coarse) {
  .ce-student-step-tabs button,
  .ce-student-visual-steps button,
  .ce-student-quiz button,
  .ce-student-toc a {
    min-height: 44px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .ce-student-shell *,
  .ce-student-shell *::before,
  .ce-student-shell *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    scroll-behavior: auto !important;
    transition-duration: 0.001ms !important;
  }
}