:root {
  color-scheme: light;
  --ink: #1f2233;
  --ink-strong: #111527;
  --muted: #636a7d;
  --muted-strong: #43485a;
  --canvas: #f7f8fb;
  --surface: #ffffff;
  --surface-soft: #f2f4f8;
  --line: #d9deea;
  --line-strong: #bdc5d6;
  --lumina-blue: #2f72ea;
  --lumina-blue-dark: #2357b7;
  --lumina-blue-soft: #eaf3ff;
  --lumina-blue-hover: #f4f9ff;
  --lumina-blue-line: #bcd7ff;
  --teal: #1aa884;
  --shadow-subtle: 0 2px 8px rgba(30, 35, 55, 0.08);
  --shadow-panel: 0 8px 22px rgba(30, 35, 55, 0.1);
  font-family:
    Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI",
    sans-serif;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--surface);
  color: var(--ink);
}

a {
  color: inherit;
}

button,
summary,
a {
  -webkit-tap-highlight-color: transparent;
}

.ai-shell {
  min-height: 100vh;
  background:
    linear-gradient(180deg, rgba(247, 248, 251, 0.96), #ffffff 240px),
    var(--surface);
}

.ai-topbar {
  position: sticky;
  top: 0;
  z-index: 30;
  border-bottom: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.96);
  box-shadow: 0 1px 8px rgba(30, 35, 55, 0.06);
  backdrop-filter: blur(14px);
}

.ai-topbar-inner {
  width: min(1240px, calc(100% - 40px));
  min-height: 66px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: auto 1fr auto;
  gap: 18px;
  align-items: center;
}

.ai-brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  color: var(--ink-strong);
  text-decoration: none;
  font-size: 1.02rem;
  font-weight: 800;
}

.brand-mark {
  width: 34px;
  height: 34px;
  display: inline-grid;
  place-items: center;
  border-radius: 6px;
  background: var(--lumina-blue);
  color: #ffffff;
  font-size: 0.9rem;
  font-weight: 900;
}

.ai-tabs {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 2px;
}

.ai-tab {
  display: inline-flex;
  min-height: 38px;
  align-items: center;
  justify-content: center;
  padding: 0 14px;
  border: 1px solid transparent;
  border-radius: 4px;
  color: var(--muted-strong);
  text-decoration: none;
  font-size: 0.95rem;
  font-weight: 650;
  transition:
    background 160ms ease,
    border-color 160ms ease,
    color 160ms ease;
}

.ai-tab:hover,
.ai-tab:focus-visible {
  color: var(--lumina-blue-dark);
  background: var(--lumina-blue-soft);
}

.ai-tab.active {
  color: var(--lumina-blue-dark);
  border-color: var(--lumina-blue-line);
  background: #ffffff;
}

.lesson-drawer-button {
  display: none;
}

.ai-main {
  width: min(1240px, calc(100% - 40px));
  margin: 0 auto;
  padding: 30px 0 56px;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin: 0 0 10px;
  color: var(--lumina-blue-dark);
  font-size: 0.76rem;
  font-weight: 850;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.eyebrow::before {
  content: "";
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--teal);
}

.course-header,
.overview-hero {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 24px;
  align-items: end;
  margin-bottom: 24px;
  padding: 26px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
  box-shadow: var(--shadow-subtle);
}

.overview-hero {
  grid-template-columns: minmax(0, 0.95fr) minmax(360px, 0.75fr);
  align-items: stretch;
}

.course-header h1,
.overview-hero h1 {
  max-width: 780px;
  margin-bottom: 12px;
  color: var(--ink-strong);
  font-size: clamp(2rem, 4.2vw, 3.4rem);
  line-height: 1.05;
  letter-spacing: 0;
}

.course-subtitle,
.hero-copy {
  max-width: 760px;
  margin-bottom: 0;
  color: var(--muted);
  font-size: 1.02rem;
  line-height: 1.62;
}

.course-actions,
.hero-actions,
.page-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: center;
  justify-content: flex-end;
}

.button,
.rail-toggle,
.drawer-close {
  min-height: 40px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 0 14px;
  border: 1px solid var(--line-strong);
  border-radius: 6px;
  background: #ffffff;
  color: var(--ink-strong);
  text-decoration: none;
  font: inherit;
  font-size: 0.95rem;
  font-weight: 780;
  cursor: pointer;
  box-shadow: none;
  transition:
    background 160ms ease,
    border-color 160ms ease,
    color 160ms ease,
    transform 160ms ease,
    box-shadow 160ms ease;
}

.button:hover,
.button:focus-visible,
.rail-toggle:hover,
.rail-toggle:focus-visible,
.drawer-close:hover,
.drawer-close:focus-visible {
  border-color: var(--lumina-blue);
  color: var(--lumina-blue-dark);
  background: var(--lumina-blue-soft);
  box-shadow: var(--shadow-subtle);
}

.button.primary {
  border-color: var(--lumina-blue);
  background: var(--lumina-blue);
  color: #ffffff;
}

.button.primary:hover,
.button.primary:focus-visible {
  border-color: var(--lumina-blue-dark);
  background: var(--lumina-blue-dark);
  color: #ffffff;
}

.button.accent {
  border-color: rgba(26, 168, 132, 0.38);
  background: #eefaf6;
  color: #0f735d;
}

.visual-panel {
  min-height: 0;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--canvas);
  box-shadow: none;
}

.course-meta {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
}

.meta-box {
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: #ffffff;
}

.meta-box strong {
  display: block;
  margin-bottom: 2px;
  color: var(--ink-strong);
  font-size: 1.42rem;
  line-height: 1;
}

.meta-box span {
  color: var(--muted);
  font-size: 0.83rem;
  font-weight: 700;
}

.flow-map {
  display: grid;
  gap: 8px;
  margin-top: 12px;
}

.flow-node {
  display: grid;
  grid-template-columns: 36px 1fr auto;
  gap: 10px;
  align-items: center;
  padding: 11px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: #ffffff;
  transition:
    border-color 160ms ease,
    background 160ms ease,
    transform 160ms ease;
}

.flow-node:hover {
  transform: translateY(-1px);
  border-color: var(--lumina-blue-line);
  background: var(--lumina-blue-hover);
}

.node-index,
.mini-index {
  display: inline-grid;
  place-items: center;
  border-radius: 6px;
  background: var(--surface-soft);
  color: var(--lumina-blue-dark);
  font-weight: 850;
}

.node-index {
  width: 36px;
  height: 36px;
}

.flow-node strong {
  display: block;
  color: var(--ink-strong);
}

.flow-node span {
  color: var(--muted);
  font-size: 0.9rem;
}

.node-tag {
  color: var(--lumina-blue-dark);
  font-size: 0.8rem;
  font-weight: 850;
}

.section {
  margin-top: 34px;
}

.section-heading {
  display: grid;
  grid-template-columns: minmax(0, 0.8fr) minmax(280px, 0.6fr);
  gap: 20px;
  align-items: end;
  margin-bottom: 16px;
}

.section-heading h2 {
  margin-bottom: 0;
  color: var(--ink-strong);
  font-size: clamp(1.7rem, 2.8vw, 2.35rem);
  line-height: 1.12;
}

.section-heading p {
  margin-bottom: 0;
  color: var(--muted);
  line-height: 1.58;
}

.track-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 14px;
}

.course-card,
.content-card,
.callout,
.lesson-step {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
  box-shadow: none;
}

.course-card {
  min-height: 240px;
  padding: 22px;
  text-decoration: none;
  transition:
    transform 160ms ease,
    border-color 160ms ease,
    box-shadow 160ms ease;
}

.course-card:hover,
.course-card:focus-visible {
  transform: translateY(-2px);
  border-color: var(--lumina-blue);
  box-shadow: var(--shadow-panel);
}

.course-card .number {
  display: inline-grid;
  width: 38px;
  height: 38px;
  place-items: center;
  margin-bottom: 16px;
  border-radius: 6px;
  background: var(--lumina-blue-soft);
  color: var(--lumina-blue-dark);
  font-weight: 850;
}

.course-card h3 {
  margin-bottom: 10px;
  color: var(--ink-strong);
  font-size: 1.3rem;
  line-height: 1.2;
}

.course-card p,
.lesson-step p,
.content-card p,
.callout p {
  color: var(--muted);
  line-height: 1.58;
}

.card-link {
  display: inline-flex;
  margin-top: 12px;
  color: var(--lumina-blue-dark);
  font-weight: 820;
}

.curriculum {
  display: grid;
  gap: 10px;
}

.curriculum-row {
  display: grid;
  grid-template-columns: 84px 1fr auto;
  gap: 16px;
  align-items: center;
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #ffffff;
  transition:
    border-color 160ms ease,
    box-shadow 160ms ease;
}

.curriculum-row:hover {
  border-color: var(--lumina-blue);
  box-shadow: var(--shadow-subtle);
}

.curriculum-row .code {
  color: var(--lumina-blue-dark);
  font-weight: 850;
}

.curriculum-row strong {
  display: block;
  margin-bottom: 4px;
  color: var(--ink-strong);
}

.curriculum-row span {
  color: var(--muted);
}

.layout {
  display: grid;
  grid-template-columns: 286px minmax(0, 1fr);
  gap: 22px;
  align-items: start;
  transition: grid-template-columns 180ms ease;
}

.lesson-rail {
  position: sticky;
  top: 88px;
  z-index: 10;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #ffffff;
  box-shadow: var(--shadow-subtle);
  overflow: hidden;
  transition:
    width 180ms ease,
    padding 180ms ease,
    transform 180ms ease;
}

.lesson-rail-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  margin-bottom: 12px;
}

.lesson-rail h2 {
  margin-bottom: 0;
  color: var(--ink-strong);
  font-size: 1rem;
  line-height: 1.2;
}

.rail-toggle {
  width: 34px;
  min-height: 34px;
  padding: 0;
  color: var(--muted-strong);
}

.rail-toggle-icon {
  display: inline-block;
  transition: transform 180ms ease;
}

.lesson-list {
  display: grid;
  gap: 7px;
}

.lesson-list a {
  display: grid;
  grid-template-columns: 34px 1fr;
  gap: 10px;
  align-items: center;
  min-height: 48px;
  padding: 7px 9px;
  border: 1px solid transparent;
  border-radius: 6px;
  color: var(--muted-strong);
  text-decoration: none;
  font-weight: 720;
  transition:
    background 160ms ease,
    border-color 160ms ease,
    color 160ms ease;
}

.lesson-list a:hover,
.lesson-list a:focus-visible {
  border-color: var(--lumina-blue-line);
  background: var(--lumina-blue-hover);
  color: var(--lumina-blue-dark);
}

.lesson-list a.active {
  border-color: var(--lumina-blue-line);
  background: var(--lumina-blue-soft);
  color: var(--lumina-blue-dark);
}

.mini-index {
  width: 34px;
  height: 34px;
  font-size: 0.82rem;
}

.lesson-title {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.lesson-content {
  display: grid;
  gap: 14px;
}

.lesson-step {
  padding: 22px;
  scroll-margin-top: 92px;
}

.lesson-step:hover {
  border-color: var(--line-strong);
}

.lesson-step h2 {
  margin-bottom: 8px;
  color: var(--ink-strong);
  font-size: clamp(1.45rem, 2.4vw, 2.05rem);
  line-height: 1.18;
}

.step-label {
  display: inline-flex;
  margin-bottom: 12px;
  padding: 5px 8px;
  border: 1px solid var(--lumina-blue-line);
  border-radius: 4px;
  background: var(--lumina-blue-soft);
  color: var(--lumina-blue-dark);
  font-size: 0.74rem;
  font-weight: 850;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.checklist,
.prompt-list {
  display: grid;
  gap: 8px;
  margin: 16px 0 0;
  padding: 0;
  list-style: none;
}

.checklist li,
.prompt-list li {
  position: relative;
  padding: 11px 12px 11px 40px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: var(--canvas);
  color: var(--muted-strong);
  line-height: 1.48;
}

.checklist li::before,
.prompt-list li::before {
  content: "+";
  position: absolute;
  left: 12px;
  top: 12px;
  width: 18px;
  height: 18px;
  display: inline-grid;
  place-items: center;
  border-radius: 4px;
  background: var(--teal);
  color: #ffffff;
  font-size: 0.78rem;
  font-weight: 850;
}

.prompt-list li::before {
  content: "#";
  background: var(--lumina-blue);
}

.prompt-box {
  margin-top: 16px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #ffffff;
  overflow: hidden;
}

.prompt-box summary {
  position: relative;
  cursor: pointer;
  padding: 14px 44px 14px 16px;
  color: var(--ink-strong);
  font-weight: 800;
  list-style: none;
}

.prompt-box summary::-webkit-details-marker {
  display: none;
}

.prompt-box summary::after {
  content: "+";
  position: absolute;
  right: 16px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--lumina-blue-dark);
  font-size: 1.2rem;
  font-weight: 850;
}

.prompt-box[open] summary {
  border-bottom: 1px solid var(--line);
  background: var(--canvas);
}

.prompt-box[open] summary::after {
  content: "-";
}

.prompt-box pre {
  margin: 0;
  padding: 16px;
  overflow-x: auto;
  white-space: pre-wrap;
  color: #283047;
  background: #ffffff;
  font: 0.91rem/1.58 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

.split-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin-top: 16px;
}

.content-card {
  padding: 16px;
}

.content-card h3 {
  margin-bottom: 7px;
  color: var(--ink-strong);
  font-size: 1.05rem;
}

.callout {
  padding: 16px;
  border-color: rgba(26, 168, 132, 0.34);
  background: #f2fbf8;
}

.callout h3 {
  margin-bottom: 7px;
  color: #0f735d;
}

.page-footer {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  margin-top: 18px;
}

.fineprint {
  margin-top: 42px;
  color: var(--muted);
  font-size: 0.9rem;
  text-align: center;
}

.lesson-drawer-overlay {
  display: none;
}

html.lesson-rail-collapsed .layout {
  grid-template-columns: 76px minmax(0, 1fr);
}

html.lesson-rail-collapsed .lesson-rail {
  padding: 12px 10px;
}

html.lesson-rail-collapsed .rail-title,
html.lesson-rail-collapsed .lesson-title {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}

html.lesson-rail-collapsed .lesson-list a {
  grid-template-columns: 34px;
  justify-content: center;
  padding: 7px;
}

html.lesson-rail-collapsed .lesson-rail-header {
  justify-content: center;
}

html.lesson-rail-collapsed .rail-toggle-icon {
  transform: rotate(180deg);
}

@media (max-width: 980px) {
  .ai-topbar-inner {
    width: min(100% - 28px, 1240px);
    grid-template-columns: 1fr auto;
    min-height: 62px;
  }

  .ai-tabs {
    grid-column: 1 / -1;
    justify-content: flex-start;
    overflow-x: auto;
    padding-bottom: 10px;
  }

  .lesson-drawer-button {
    display: inline-flex;
  }

  .ai-main {
    width: min(100% - 28px, 1240px);
    padding-top: 22px;
  }

  .overview-hero,
  .course-header,
  .section-heading,
  .layout,
  .track-grid,
  .split-grid {
    grid-template-columns: 1fr;
  }

  .course-header,
  .overview-hero {
    padding: 20px;
  }

  .course-actions,
  .hero-actions,
  .page-actions {
    justify-content: flex-start;
  }

  .lesson-rail {
    position: fixed;
    top: 0;
    bottom: 0;
    left: 0;
    width: min(340px, calc(100vw - 48px));
    padding: 18px;
    border-radius: 0;
    transform: translateX(-105%);
    z-index: 60;
    overflow-y: auto;
  }

  .lesson-drawer-overlay {
    position: fixed;
    inset: 0;
    z-index: 50;
    display: block;
    background: rgba(17, 21, 39, 0.34);
    opacity: 0;
    pointer-events: none;
    transition: opacity 180ms ease;
  }

  html.lesson-drawer-open .lesson-rail {
    transform: translateX(0);
  }

  html.lesson-drawer-open .lesson-drawer-overlay {
    opacity: 1;
    pointer-events: auto;
  }

  html.lesson-rail-collapsed .layout {
    grid-template-columns: 1fr;
  }

  html.lesson-rail-collapsed .lesson-rail {
    padding: 18px;
  }

  html.lesson-rail-collapsed .rail-title,
  html.lesson-rail-collapsed .lesson-title {
    position: static;
    width: auto;
    height: auto;
    overflow: visible;
    clip: auto;
    white-space: normal;
  }

  html.lesson-rail-collapsed .lesson-list a {
    grid-template-columns: 34px 1fr;
    justify-content: start;
    padding: 7px 9px;
  }
}

@media (max-width: 640px) {
  .course-header h1,
  .overview-hero h1 {
    font-size: clamp(1.9rem, 9vw, 2.45rem);
  }

  .course-meta,
  .curriculum-row {
    grid-template-columns: 1fr;
  }

  .button {
    width: 100%;
  }

  .ai-topbar .button {
    width: auto;
  }

  .course-actions,
  .hero-actions,
  .page-actions,
  .page-footer {
    align-items: stretch;
    flex-direction: column;
  }
}