:root {
  --bg: #f6f3ec;
  --bg-elev: #fffdf8;
  --ink: #1c1917;
  --ink-soft: #44403c;
  --ink-mute: #78716c;
  --line: #e7e0d4;
  --accent: #0f766e;
  --accent-ink: #115e59;
  --accent-dim: #ccfbf1;
  --danger: #9a3412;
  --code-bg: #1c1917;
  --code-ink: #f5f5f4;
  --header: 56px;
  --sidebar: 260px;
  --toc: 230px;
  --font: "IBM Plex Sans", "Segoe UI", system-ui, sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, "SFMono-Regular", monospace;
  --shadow: 0 1px 0 rgba(28, 25, 23, 0.04);
}

[data-theme="dark"] {
  --bg: #121417;
  --bg-elev: #1a1d22;
  --ink: #eceae6;
  --ink-soft: #d6d3cd;
  --ink-mute: #a8a29e;
  --line: #2a2e35;
  --accent: #2dd4bf;
  --accent-ink: #5eead4;
  --accent-dim: #134e4a;
  --danger: #fdba74;
  --code-bg: #0c0d10;
  --code-ink: #e7e5e4;
  --shadow: none;
}

*, *::before, *::after { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.55;
}

a { color: var(--accent-ink); text-decoration-thickness: 1px; text-underline-offset: 3px; }
a:hover { color: var(--accent); }

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  background: var(--accent);
  color: var(--bg);
  padding: 8px 12px;
  z-index: 100;
}
.skip-link:focus { left: 8px; top: 8px; }

.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  height: var(--header);
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 0 20px;
  background: var(--bg-elev);
  border-bottom: 1px solid var(--line);
}
.brand {
  font-family: var(--mono);
  font-size: 0.82rem;
  letter-spacing: 0.04em;
  color: var(--ink);
  text-decoration: none;
  font-weight: 600;
}
.brand:hover { color: var(--accent); }
.nav {
  display: flex;
  gap: 16px;
  margin-left: auto;
  align-items: center;
}
.nav a {
  font-size: 0.9rem;
  color: var(--ink-soft);
  text-decoration: none;
}
.nav a:hover, .nav a[aria-current="page"] { color: var(--accent); }
.icon-btn {
  border: 1px solid var(--line);
  background: transparent;
  color: var(--ink-soft);
  min-width: 36px;
  min-height: 36px;
  cursor: pointer;
  font-family: var(--mono);
  font-size: 0.75rem;
}
.icon-btn:hover { border-color: var(--accent); color: var(--accent); }
.nav-toggle { display: none; }

.wrap {
  width: min(1120px, calc(100% - 40px));
  max-width: 100%;
  margin: 0 auto;
  padding: 32px 0 80px;
  min-width: 0;
}

.hero h1 {
  font-size: clamp(1.8rem, 4vw, 2.6rem);
  font-weight: 600;
  letter-spacing: -0.03em;
  line-height: 1.15;
  margin: 0 0 12px;
}
.lede {
  font-size: 1.08rem;
  color: var(--ink-soft);
  max-width: 40rem;
  margin: 0 0 28px;
}

.progress-panel {
  border: 1px solid var(--line);
  background: var(--bg-elev);
  padding: 14px 16px;
  margin: 0 0 28px;
}
.progress-row {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: baseline;
  flex-wrap: wrap;
  font-family: var(--mono);
  font-size: 0.78rem;
  color: var(--ink-mute);
}
.progress-track {
  height: 4px;
  background: var(--line);
  margin-top: 10px;
  overflow: hidden;
}
.progress-fill {
  height: 100%;
  width: 100%;
  background: var(--accent);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.25s ease;
}
.text-btn {
  background: none;
  border: 0;
  color: var(--accent-ink);
  cursor: pointer;
  font: inherit;
  padding: 0;
}

.section-label {
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 36px 0 12px;
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 12px;
}
.card {
  display: flex;
  flex-direction: column;
  gap: 8px;
  border: 1px solid var(--line);
  background: var(--bg-elev);
  padding: 16px 16px 14px;
  text-decoration: none;
  color: inherit;
  min-height: 148px;
}
.card:hover { border-color: var(--accent); }
.card h2 {
  font-size: 1.05rem;
  margin: 0;
  letter-spacing: -0.02em;
}
.card p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 0.92rem;
  flex: 1;
}
.card .meta {
  font-family: var(--mono);
  font-size: 0.72rem;
  color: var(--accent);
}

.table-scroll {
  width: 100%;
  max-width: 100%;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}
.module-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
}
.module-table th {
  text-align: left;
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-mute);
  border-bottom: 1px solid var(--ink);
  padding: 8px 10px;
}
.module-table td {
  padding: 10px;
  border-bottom: 1px solid var(--line);
  vertical-align: top;
  overflow-wrap: break-word;
}
.dot {
  display: inline-block;
  width: 8px;
  height: 8px;
  border: 1px solid var(--ink-mute);
  border-radius: 50%;
  vertical-align: middle;
  margin-right: 8px;
}
.dot.is-seen {
  background: linear-gradient(135deg, var(--accent) 50%, transparent 50%);
  border-color: var(--accent);
}
.dot.is-done { background: var(--accent); border-color: var(--accent); }

.clone {
  font-family: var(--mono);
  font-size: 0.82rem;
  background: var(--code-bg);
  color: var(--code-ink);
  padding: 14px 16px;
  overflow-x: auto;
  margin: 16px 0 0;
}

/* Module layout */
.lesson-layout {
  display: flex;
  min-height: calc(100vh - var(--header));
  padding-top: 0;
}
.lesson-sidebar {
  width: var(--sidebar);
  flex-shrink: 0;
  border-right: 1px solid var(--line);
  padding: 20px 0 40px;
  position: sticky;
  top: var(--header);
  height: calc(100vh - var(--header));
  overflow: auto;
  background: var(--bg);
}
.sidebar-kicker {
  padding: 8px 18px 4px;
  font-family: var(--mono);
  font-size: 0.68rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--ink-mute);
}
.sidebar-link {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 7px 18px;
  color: var(--ink-soft);
  text-decoration: none;
  font-size: 0.92rem;
  border-left: 2px solid transparent;
}
.sidebar-link:hover { background: var(--accent-dim); color: var(--ink); }
.sidebar-link.active {
  color: var(--accent);
  border-left-color: var(--accent);
  background: var(--accent-dim);
}
.lesson-main {
  flex: 1;
  min-width: 0;
  padding: 32px 36px 80px;
}
.lesson-content { max-width: 46rem; }
.toc {
  display: none;
  width: var(--toc);
  flex-shrink: 0;
  position: sticky;
  top: var(--header);
  height: calc(100vh - var(--header));
  overflow: auto;
  padding: 32px 18px 40px 8px;
}
@media (min-width: 1280px) {
  .toc { display: block; }
}
.toc-header {
  font-family: var(--mono);
  font-size: 0.68rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 10px;
}
.toc-nav { list-style: none; margin: 0; padding: 0; border-left: 1px solid var(--line); }
.toc-nav a {
  display: block;
  padding: 4px 12px;
  color: var(--ink-mute);
  text-decoration: none;
  font-size: 0.82rem;
  border-left: 2px solid transparent;
  margin-left: -1px;
}
.toc-nav a:hover, .toc-nav a.active { color: var(--accent); border-left-color: var(--accent); }
.toc-h3 a { padding-left: 22px; font-size: 0.78rem; }

.band-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 0;
  border: 1px solid var(--line);
  margin: 0 0 20px;
}
.band-tabs a {
  padding: 8px 12px;
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  text-decoration: none;
  color: var(--ink-soft);
  border-right: 1px solid var(--line);
}
.band-tabs a:last-child { border-right: 0; }
.band-tabs a.active, .band-tabs a:hover { color: var(--accent); background: var(--accent-dim); }

.study-chrome {
  border: 1px solid var(--accent);
  background: var(--accent-dim);
  padding: 14px 16px;
  margin: 0 0 24px;
}
.study-chrome h2 {
  font-size: 0.95rem;
  margin: 0 0 8px;
}
.lab-prereq {
  font-size: 0.88rem;
  color: var(--ink-soft);
  margin: 0 0 10px;
}
.checks {
  display: grid;
  gap: 6px;
}
.checks label {
  display: flex;
  gap: 8px;
  align-items: flex-start;
  font-size: 0.9rem;
  cursor: pointer;
}

.crumb {
  font-family: var(--mono);
  font-size: 0.75rem;
  color: var(--ink-mute);
  margin: 0 0 10px;
}
.page-title {
  font-size: clamp(1.6rem, 3vw, 2.1rem);
  letter-spacing: -0.03em;
  margin: 0 0 8px;
  line-height: 1.15;
}

.prose h1 { font-size: 1.9rem; letter-spacing: -0.03em; }
.prose h2 {
  font-size: 1.25rem;
  margin-top: 2.2rem;
  padding-top: 0.4rem;
  border-top: 1px solid var(--line);
}
.prose h3 { font-size: 1.02rem; margin-top: 1.5rem; }
.prose h1, .prose h2, .prose h3 { scroll-margin-top: calc(var(--header) + 16px); }
.prose p, .prose li { color: var(--ink); }
.prose table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92rem;
  margin: 16px 0;
}
.prose th, .prose td {
  text-align: left;
  padding: 8px 10px;
  border-bottom: 1px solid var(--line);
  vertical-align: top;
}
.prose th {
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}
.prose blockquote {
  margin: 16px 0;
  padding: 8px 14px;
  border-left: 3px solid var(--accent);
  background: var(--accent-dim);
  color: var(--ink-soft);
}
.prose code {
  font-family: var(--mono);
  font-size: 0.86em;
  background: var(--bg-elev);
  border: 1px solid var(--line);
  padding: 0 4px;
}
.prose pre code {
  background: none;
  border: 0;
  padding: 0;
  color: var(--code-ink);
  font-size: 0.82rem;
  line-height: 1.55;
}
.code-block {
  position: relative;
  margin: 16px 0;
  background: var(--code-bg);
  border: 1px solid var(--line);
}
.code-block pre {
  margin: 0;
  padding: 36px 16px 16px;
  overflow-x: auto;
}
.code-copy {
  position: absolute;
  top: 0;
  right: 0;
  border: 0;
  border-left: 1px solid #3f3f46;
  background: transparent;
  color: #a8a29e;
  font-family: var(--mono);
  font-size: 0.68rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 8px 12px;
  cursor: pointer;
}
.code-copy:hover { color: #fff; }

.first-success {
  border: 1px solid var(--accent);
  padding: 4px 16px 12px;
  margin: 20px 0 28px;
  background: var(--bg-elev);
}
.first-success > h2 {
  border-top: 0;
  margin-top: 12px;
  color: var(--accent);
}

.mermaid-wrap {
  margin: 20px 0;
  border: 1px solid var(--line);
  background: var(--bg-elev);
  padding: 16px;
  overflow-x: auto;
}

.pager {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  margin-top: 36px;
  border: 1px solid var(--line);
}
.pager a {
  padding: 14px 16px;
  text-decoration: none;
  color: inherit;
  min-height: 72px;
}
.pager a:hover { background: var(--accent-dim); }
.pager a + a { border-left: 1px solid var(--line); }
.pager .kicker {
  display: block;
  font-family: var(--mono);
  font-size: 0.68rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 4px;
}
.pager .next { text-align: right; }

.site-footer {
  border-top: 1px solid var(--line);
  padding: 20px;
  font-size: 0.85rem;
  color: var(--ink-mute);
}
.site-footer .wrap { padding: 0; width: min(1120px, calc(100% - 40px)); }

.sidebar-toggle {
  display: none;
  position: fixed;
  right: 16px;
  bottom: 16px;
  z-index: 50;
  background: var(--bg-elev);
  color: var(--accent);
  border: 1px solid var(--accent);
  min-height: 44px;
  padding: 0 14px;
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  cursor: pointer;
}

.note {
  font-size: 0.88rem;
  color: var(--ink-mute);
}

.quiz {
  border: 1px solid var(--line);
  background: var(--bg-elev);
  padding: 16px 18px 20px;
  margin: 28px 0 8px;
}
.quiz h2 {
  font-size: 1.15rem;
  margin: 0 0 8px;
}
.quiz-q {
  border-top: 1px solid var(--line);
  padding: 14px 0;
  margin: 0;
}
.quiz-q legend {
  font-weight: 600;
  padding: 0 0 8px;
}
.quiz-q label {
  display: flex;
  gap: 8px;
  align-items: flex-start;
  margin: 6px 0;
  cursor: pointer;
}
.quiz-q.is-right {
  border-left: 3px solid var(--accent);
  padding-left: 12px;
}
.quiz-q.is-wrong {
  border-left: 3px solid var(--danger);
  padding-left: 12px;
}
.quiz-why {
  font-size: 0.9rem;
  color: var(--ink-soft);
  margin: 8px 0 0;
}
.quiz-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
  margin-top: 12px;
}
.quiz-submit {
  background: var(--accent);
  color: #f6f3ec;
  border: 0;
  min-height: 40px;
  padding: 0 16px;
  font-family: var(--mono);
  font-size: 0.78rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  cursor: pointer;
}
.quiz-submit:hover { filter: brightness(1.08); }
.quiz-q input:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.search-row {
  margin: 0 0 20px;
}
.search-row label {
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-mute);
}
.search-row input {
  width: 100%;
  max-width: 28rem;
  padding: 10px 12px;
  border: 1px solid var(--line);
  background: var(--bg-elev);
  color: var(--ink);
  font: inherit;
}

@media (max-width: 480px) {
  .wrap { width: min(1120px, calc(100% - 24px)); }
  .module-table { font-size: 0.88rem; }
  .module-table th,
  .module-table td { padding: 8px 6px; }
}

@media (max-width: 900px) {
  .nav-toggle { display: inline-flex; align-items: center; justify-content: center; }
  .nav {
    display: none;
    position: absolute;
    top: var(--header);
    left: 0;
    right: 0;
    background: var(--bg-elev);
    border-bottom: 1px solid var(--line);
    flex-direction: column;
    align-items: stretch;
    padding: 12px 16px 16px;
    gap: 10px;
  }
  body.nav-open .nav { display: flex; }
  .lesson-sidebar {
    position: fixed;
    z-index: 45;
    transform: translateX(-100%);
    transition: transform 0.2s ease;
    background: var(--bg-elev);
  }
  body.sidebar-open .lesson-sidebar { transform: translateX(0); }
  .sidebar-toggle { display: inline-flex; align-items: center; }
  .lesson-main { padding: 24px 16px 96px; }
  .pager { grid-template-columns: 1fr; }
  .pager a + a { border-left: 0; border-top: 1px solid var(--line); }
  .pager .next { text-align: left; }
}

@media (prefers-reduced-motion: reduce) {
  .progress-fill, .lesson-sidebar { transition: none; }
}

.hljs { background: transparent; color: var(--code-ink); }