:root {
  --bg: #f6f7f9;
  --surface: #ffffff;
  --surface-2: #f8fafc;
  --text: #111827;
  --muted: #667085;
  --border: #d9e0e8;
  --green: #12824c;
  --green-dark: #0f6b3e;
  --blue: #2563eb;
  --amber: #b45309;
  --red: #b42318;
  --code-bg: #0f172a;
  --shadow: 0 10px 30px rgba(15, 23, 42, 0.08);
  --topbar-height: 58px;
  --disclaimer-height: 34px;
  --header-offset: calc(var(--topbar-height) + var(--disclaimer-height));
  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(--bg);
  color: var(--text);
  line-height: 1.65;
}

a {
  color: var(--blue);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

img {
  max-width: 100%;
  height: auto;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.topbar {
  position: relative;
  z-index: 1;
  height: var(--topbar-height);
  display: grid;
  grid-template-columns: auto max-content auto minmax(200px, 360px);
  align-items: center;
  gap: 14px;
  padding: 0 18px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  box-shadow: 0 1px 0 rgba(15, 23, 42, 0.04);
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  background: var(--surface);
}

.header-disclaimer {
  margin: 0;
  padding: 7px 16px;
  background: linear-gradient(180deg, #fffbeb 0%, #fef3c7 100%);
  border-bottom: 1px solid #fcd34d;
  color: #92400e;
  font-size: 12px;
  line-height: 1.45;
  text-align: center;
  font-weight: 500;
}

.header-disclaimer strong {
  font-weight: 700;
  color: #78350f;
}

.brand {
  color: var(--text);
  font-weight: 800;
  letter-spacing: 0;
  white-space: nowrap;
}

.top-links {
  display: flex;
  align-items: center;
  gap: 4px;
}

.top-links a {
  color: #273142;
  font-size: 14px;
  font-weight: 650;
  padding: 7px 10px;
  border-radius: 6px;
}

.top-links a:hover,
.top-links a[aria-current="page"] {
  background: #ecfdf5;
  color: var(--green-dark);
  text-decoration: none;
}

.icon-button {
  width: 38px;
  height: 38px;
  border: 1px solid var(--border);
  background: var(--surface);
  border-radius: 6px;
  display: none;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  gap: 4px;
  cursor: pointer;
}

.icon-button span {
  width: 18px;
  height: 2px;
  background: var(--text);
  display: block;
}

.global-search {
  position: relative;
}

.global-search input,
.sidebar-tools input {
  width: 100%;
  height: 38px;
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0 12px;
  background: var(--surface-2);
  color: var(--text);
  font: inherit;
  font-size: 14px;
}

.global-search input:focus,
.sidebar-tools input:focus,
.tool-panel input:focus {
  outline: 2px solid rgba(37, 99, 235, 0.18);
  border-color: var(--blue);
  background: #ffffff;
}

.search-results {
  position: absolute;
  right: 0;
  top: calc(100% + 8px);
  width: min(520px, calc(100vw - 24px));
  max-height: 70vh;
  overflow: auto;
  padding: 8px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  box-shadow: var(--shadow);
}

.search-result {
  display: block;
  padding: 10px;
  border-radius: 6px;
  color: var(--text);
}

.search-result:hover {
  background: #f1f5f9;
  text-decoration: none;
}

.search-result strong {
  display: block;
  font-size: 14px;
}

.search-result small {
  color: var(--muted);
  display: block;
  margin-top: 2px;
}

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

.site-footer {
  border-top: 1px solid var(--border);
  background: var(--surface-2);
  padding: 14px 18px;
  text-align: center;
}

.site-footer p {
  margin: 0;
  max-width: 720px;
  margin-inline: auto;
  font-size: 13px;
  line-height: 1.5;
  color: var(--muted);
}

.footer-legal {
  display: flex;
  justify-content: center;
  gap: 16px;
  margin-top: 10px;
  flex-wrap: wrap;
}

.footer-legal a {
  font-size: 13px;
  color: var(--muted);
  text-decoration: none;
}

.footer-legal a:hover {
  color: var(--text);
  text-decoration: underline;
}

.ad-slot {
  margin: 1.5rem 0;
  min-height: 90px;
  border: 1px dashed var(--border);
  border-radius: 8px;
  background: var(--surface-2);
}

.course-hero {
  margin-bottom: 2rem;
}

.course-subtitle {
  font-size: 1.1rem;
  color: var(--muted);
  margin: 0.5rem 0 1rem;
}

.course-lead {
  font-size: 1.05rem;
  line-height: 1.6;
  max-width: 52ch;
}

.course-cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 1.25rem;
}

.course-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 20px;
  margin-bottom: 2rem;
}

.course-card {
  padding: 1.25rem;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--surface);
}

.course-pricing .price-main {
  font-size: 2rem;
  font-weight: 700;
  margin: 0.25rem 0;
  color: var(--accent);
}

.course-pricing .price-compare {
  color: var(--muted);
  margin: 0;
}

.course-pricing .small {
  font-size: 12px;
  margin-top: 1rem;
}

.sidebar {
  position: sticky;
  top: var(--header-offset);
  align-self: start;
  height: calc(100vh - var(--header-offset));
  overflow: auto;
  background: var(--surface);
  border-right: 1px solid var(--border);
}

.sidebar-tools {
  position: sticky;
  top: 0;
  z-index: 2;
  padding: 12px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}

.sidebar-nav {
  padding: 8px 8px 28px;
}

.part-group {
  border-bottom: 1px solid #edf1f5;
}

.part-group summary {
  list-style: none;
  cursor: pointer;
  padding: 10px 8px;
  display: flex;
  align-items: center;
  gap: 8px;
  color: #273142;
  font-weight: 750;
  font-size: 14px;
  border-radius: 6px;
}

.part-group summary::-webkit-details-marker {
  display: none;
}

.part-group summary span {
  color: var(--green-dark);
  font-variant-numeric: tabular-nums;
}

.part-group summary:hover {
  background: #f1f5f9;
}

.chapter-link {
  display: grid;
  grid-template-columns: 34px minmax(0, 1fr);
  gap: 8px;
  align-items: baseline;
  padding: 8px 8px 8px 18px;
  color: #344054;
  border-radius: 6px;
  font-size: 13px;
  line-height: 1.35;
}

.chapter-link span {
  color: var(--muted);
  font-size: 12px;
  font-variant-numeric: tabular-nums;
}

.chapter-link:hover,
.chapter-link.active {
  background: #ecfdf5;
  color: var(--green-dark);
  text-decoration: none;
}

.chapter-link.completed::after {
  content: "Done";
  color: var(--green-dark);
  font-size: 11px;
  justify-self: end;
}

.chapter-link.overview,
.chapter-link.lab {
  grid-template-columns: minmax(0, 1fr);
  padding-left: 18px;
  font-weight: 650;
}

.content-shell {
  display: grid;
  grid-template-columns: minmax(0, 880px) 250px;
  gap: 30px;
  width: min(100%, 1230px);
  margin: 0 auto;
  padding: 28px 24px 56px;
}

.lesson {
  min-width: 0;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 32px;
  box-shadow: 0 1px 1px rgba(15, 23, 42, 0.04);
}

.lesson h1,
.lesson h2,
.lesson h3,
.lesson h4 {
  line-height: 1.25;
  letter-spacing: 0;
}

.lesson h1 {
  margin: 8px 0 18px;
  font-size: clamp(30px, 4vw, 42px);
}

.lesson h2 {
  margin: 38px 0 14px;
  padding-top: 6px;
  font-size: 24px;
}

.lesson h3 {
  margin: 28px 0 10px;
  font-size: 19px;
}

.lesson h4 {
  margin: 22px 0 8px;
  font-size: 16px;
}

.lesson p {
  margin: 14px 0;
}

.lesson ul,
.lesson ol {
  padding-left: 24px;
}

.lesson li {
  margin: 6px 0;
}

.lesson hr {
  border: 0;
  border-top: 1px solid #e6ebf1;
  margin: 24px 0;
}

.lesson blockquote {
  margin: 18px 0;
  padding: 14px 16px;
  border-left: 4px solid var(--green);
  background: #f0fdf4;
  color: #214232;
  border-radius: 0 6px 6px 0;
}

.lesson code {
  background: #eef2f7;
  border: 1px solid #dbe3ee;
  border-radius: 5px;
  padding: 2px 5px;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 0.92em;
}

.lesson pre {
  position: relative;
  overflow: auto;
  background: var(--code-bg);
  color: #e5e7eb;
  border-radius: 8px;
  padding: 16px;
  margin: 18px 0;
}

.lesson pre code {
  background: transparent;
  border: 0;
  color: inherit;
  padding: 0;
}

.copy-button {
  position: absolute;
  top: 8px;
  right: 8px;
  border: 1px solid rgba(255, 255, 255, 0.18);
  background: rgba(255, 255, 255, 0.1);
  color: #ffffff;
  border-radius: 5px;
  padding: 4px 8px;
  font-size: 12px;
  cursor: pointer;
}

.table-wrap {
  overflow-x: auto;
  margin: 18px 0;
  border: 1px solid var(--border);
  border-radius: 8px;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
}

th,
td {
  padding: 10px 12px;
  border-bottom: 1px solid #e6ebf1;
  vertical-align: top;
}

th {
  text-align: left;
  background: #f1f5f9;
  color: #253044;
  font-weight: 750;
}

tr:last-child td {
  border-bottom: 0;
}

figure {
  margin: 20px 0;
  padding: 14px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: #ffffff;
}

.diagram-block {
  margin: 18px 0;
  padding: 14px;
  border: 1px solid #c7d2fe;
  border-radius: 8px;
  background: #f8fbff;
  overflow-x: auto;
}

.right-rail {
  position: sticky;
  top: calc(var(--header-offset) + 24px);
  align-self: start;
  max-height: calc(100vh - var(--header-offset) - 48px);
  overflow: auto;
}

.rail-section {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 16px;
  margin-bottom: 16px;
}

.rail-section h2 {
  margin: 0 0 10px;
  font-size: 14px;
  text-transform: uppercase;
  letter-spacing: 0;
  color: #344054;
}

.toc,
.rail-section {
  display: grid;
  gap: 8px;
}

.toc a,
.rail-section a {
  color: #475467;
  font-size: 13px;
}

.toc a:hover,
.rail-section a:hover {
  color: var(--green-dark);
}

.toc-level-3 {
  padding-left: 12px;
}

.breadcrumbs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
  color: var(--muted);
  font-size: 13px;
  margin-bottom: 14px;
}

.breadcrumbs a {
  color: var(--green-dark);
  font-weight: 650;
}

.breadcrumbs .sep {
  color: #98a2b3;
}

.completion-panel {
  margin-top: 34px;
  padding: 16px;
  border: 1px solid #bbf7d0;
  background: #f0fdf4;
  border-radius: 8px;
  display: flex;
  gap: 12px;
  align-items: center;
  flex-wrap: wrap;
}

.primary-button,
.secondary-button,
.tool-panel button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 38px;
  padding: 8px 14px;
  border-radius: 6px;
  border: 1px solid transparent;
  font-weight: 750;
  font-size: 14px;
  cursor: pointer;
}

.primary-button,
.tool-panel button {
  background: var(--green);
  color: #ffffff;
}

.primary-button:hover,
.tool-panel button:hover {
  background: var(--green-dark);
  text-decoration: none;
}

.secondary-button {
  background: #eff6ff;
  color: #1d4ed8;
  border-color: #bfdbfe;
}

.secondary-button:hover {
  background: #dbeafe;
  text-decoration: none;
}

.prev-next {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
  margin-top: 28px;
}

.prev-next a {
  display: grid;
  gap: 4px;
  border: 1px solid var(--border);
  background: #ffffff;
  border-radius: 8px;
  padding: 14px;
  color: var(--text);
}

.prev-next a:hover {
  border-color: var(--green);
  text-decoration: none;
}

.prev-next span {
  color: var(--muted);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0;
}

.prev-next .next {
  text-align: right;
}

.dashboard-hero {
  border-bottom: 1px solid var(--border);
  padding-bottom: 24px;
  margin-bottom: 28px;
}

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

.dashboard-actions {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin-top: 18px;
}

.continue-box {
  margin-top: 18px;
  padding: 12px;
  border: 1px solid #bfdbfe;
  background: #eff6ff;
  border-radius: 8px;
}

.path-grid,
.part-grid,
.tool-grid {
  display: grid;
  gap: 14px;
}

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

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

.path-card,
.part-card,
.tool-panel {
  display: grid;
  gap: 8px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  padding: 16px;
  color: var(--text);
}

.path-card:hover,
.part-card:hover {
  border-color: var(--green);
  text-decoration: none;
}

.path-card span,
.part-card span,
.part-card small {
  color: var(--muted);
  font-size: 13px;
}

.part-card span {
  color: var(--green-dark);
  font-weight: 800;
}

.lesson-list-block {
  margin-top: 30px;
}

.lesson-list {
  display: grid;
  gap: 10px;
}

.lesson-list a {
  display: grid;
  grid-template-columns: 48px minmax(0, 1fr);
  gap: 6px 12px;
  align-items: start;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 12px;
  color: var(--text);
}

.lesson-list a:hover {
  border-color: var(--green);
  text-decoration: none;
}

.lesson-list span {
  grid-row: span 2;
  color: var(--green-dark);
  font-weight: 800;
  font-variant-numeric: tabular-nums;
}

.lesson-list small {
  color: var(--muted);
}

.quality-note {
  border: 1px solid #fed7aa;
  background: #fff7ed;
  color: #7c2d12;
  padding: 12px 14px;
  border-radius: 8px;
  margin-bottom: 18px;
}

.tool-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
  align-items: start;
}

.tool-panel h2 {
  margin: 0 0 4px;
}

.tool-panel label {
  display: grid;
  gap: 5px;
  color: #344054;
  font-size: 14px;
  font-weight: 650;
}

.tool-panel input {
  height: 38px;
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0 10px;
  font: inherit;
}

.tool-panel output {
  display: block;
  min-height: 52px;
  border: 1px solid #bbf7d0;
  background: #f0fdf4;
  border-radius: 6px;
  padding: 10px;
  color: #14532d;
}

.muted {
  color: var(--muted);
}

body.sidebar-open {
  overflow: hidden;
}

@media (max-width: 1180px) {
  .content-shell {
    grid-template-columns: minmax(0, 1fr);
    max-width: 920px;
  }

  .right-rail {
    display: none;
  }
}

@media (max-width: 900px) {
  .topbar {
    grid-template-columns: auto minmax(0, 1fr) auto minmax(0, 1fr);
  }

  .icon-button {
    display: flex;
  }

  .top-links {
    display: none;
  }

  .app-shell {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: fixed;
    left: 0;
    top: var(--header-offset);
    bottom: 0;
    width: min(88vw, 330px);
    height: auto;
    transform: translateX(-105%);
    transition: transform 180ms ease;
    z-index: 30;
    box-shadow: var(--shadow);
  }

  body.sidebar-open .sidebar {
    transform: translateX(0);
  }

  .content-shell {
    padding: 18px 14px 42px;
  }

  .lesson {
    padding: 22px;
  }

  .path-grid,
  .part-grid,
  .tool-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 620px) {
  .topbar {
    grid-template-columns: auto minmax(0, 1fr);
    gap: 10px;
  }

  .global-search {
    grid-column: 1 / -1;
    width: 100%;
  }

  .topbar {
    height: auto;
    padding: 10px 12px;
  }

  :root {
    --topbar-height: 104px;
    --disclaimer-height: 48px;
  }

  .lesson h1 {
    font-size: 30px;
  }

  .lesson {
    padding: 18px;
  }

  .prev-next {
    grid-template-columns: 1fr;
  }
}

@media print {
  .site-header,
  .topbar,
  .sidebar,
  .right-rail,
  .completion-panel,
  .prev-next {
    display: none;
  }

  .app-shell,
  .content-shell {
    display: block;
    padding: 0;
  }

  .lesson {
    border: 0;
    box-shadow: none;
    padding: 0;
  }
}