:root {
  --bg: #F7F8FA;
  --surface: #FFFFFF;
  --text: #1A1D26;
  --text-secondary: #5C6370;
  --border: #E6E8EC;
  --brand: #1E3A5F;
  --brand-soft: #E8EEF5;
  --accent: #0D9488;
  --accent-soft: #E6F7F5;
  --warn: #B45309;
  --code-bg: #0F172A;
  --code-text: #E2E8F0;
  --radius: 12px;
}
html[data-theme="dark"] {
  --bg: #0B1220;
  --surface: #121A2B;
  --text: #E8ECF4;
  --text-secondary: #9AA3B5;
  --border: #243049;
  --brand: #8BB4E0;
  --brand-soft: #1A2740;
  --accent: #2DD4BF;
  --accent-soft: #0F2A28;
  --code-bg: #060B14;
  --code-text: #E2E8F0;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { transition: none !important; }
}
body {
  font-family: "PingFang SC", "Noto Sans SC", "Source Han Sans SC", "Microsoft YaHei", system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  font-size: 15px;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
a:focus-visible, button:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}
.wrap { max-width: 1120px; margin: 0 auto; padding: 0 24px; width: 100%; }
main { flex: 1; }

/* Header */
.site-header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  height: 56px;
  position: sticky; top: 0; z-index: 50;
}
.nav { display: flex; align-items: center; justify-content: space-between; height: 56px; gap: 16px; }
.logo {
  font-weight: 700; color: var(--brand); font-size: 17px;
  letter-spacing: 0.02em; white-space: nowrap; text-decoration: none;
}
.logo:hover { text-decoration: none; }
.logo span { color: var(--accent); font-weight: 600; margin-left: 2px; }
.nav-links { display: flex; gap: 28px; list-style: none; align-items: center; }
.nav-links a {
  color: var(--text-secondary); font-size: 14px; text-decoration: none;
}
.nav-links a:hover, .nav-links a.active { color: var(--brand); }
.nav-toggle {
  display: none; background: none; border: 1px solid var(--border);
  border-radius: 8px; padding: 8px 12px; color: var(--brand); font-size: 14px; cursor: pointer;
}
@media (max-width: 800px) {
  .nav-toggle { display: inline-flex; }
  .nav-links {
    display: none; position: absolute; top: 56px; left: 0; right: 0;
    background: var(--surface); border-bottom: 1px solid var(--border);
    flex-direction: column; padding: 12px 24px 16px; gap: 12px;
  }
  .nav-links.open { display: flex; }
}

/* Buttons */
.btn {
  display: inline-flex; align-items: center; justify-content: center;
  height: 44px; padding: 0 20px; border-radius: 10px;
  font-size: 14px; font-weight: 600; border: 1px solid transparent;
  cursor: pointer; text-decoration: none; gap: 6px;
  font-family: inherit; transition: background 150ms, border-color 150ms;
}
.btn:hover { text-decoration: none; }
.btn-primary { background: var(--brand); color: #fff; }
.btn-primary:hover { filter: brightness(1.08); }
.btn-accent { background: var(--accent); color: #fff; }
.btn-accent:hover { filter: brightness(1.06); }
.btn-ghost { background: var(--surface); color: var(--brand); border-color: var(--border); }
.btn-ghost:hover { border-color: var(--brand); }
.btn-sm { height: 36px; padding: 0 14px; font-size: 13px; }
.btn:disabled { opacity: 0.5; cursor: not-allowed; }

/* Hero */
.hero { padding: 56px 0 40px; }
.eyebrow {
  display: inline-block; font-size: 12px; color: var(--accent);
  background: var(--accent-soft); padding: 4px 10px; border-radius: 999px;
  margin-bottom: 16px; font-weight: 500;
}
.hero h1 {
  font-size: 32px; line-height: 1.3; color: var(--brand);
  font-weight: 700; max-width: 640px; margin-bottom: 12px;
}
.lead { color: var(--text-secondary); font-size: 16px; max-width: 560px; margin-bottom: 28px; }
.cta-row { display: flex; flex-wrap: wrap; gap: 12px; margin-bottom: 8px; }

section { padding: 28px 0; }
.section-title {
  font-size: 13px; font-weight: 600; color: var(--text-secondary);
  letter-spacing: 0.04em; margin-bottom: 16px;
}

/* Cards */
.cards {
  display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px;
}
@media (max-width: 960px) { .cards { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 520px) { .cards { grid-template-columns: 1fr; } }
.card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 18px 18px 16px;
  border-left: 3px solid var(--brand); transition: border-color 150ms;
  display: flex; flex-direction: column;
}
.card:hover { border-color: var(--brand); }
.card.accent-left { border-left-color: var(--accent); }
.card h3 { font-size: 16px; color: var(--brand); margin-bottom: 6px; }
.card p { font-size: 13px; color: var(--text-secondary); margin-bottom: 12px; flex: 1; }
.meta { font-size: 12px; color: var(--text-secondary); margin-bottom: 14px; font-variant-numeric: tabular-nums; }
.card .link { font-size: 13px; font-weight: 600; color: var(--accent); text-decoration: none; }
.card .link:hover { text-decoration: underline; }
.badge {
  display: inline-block; font-size: 11px; font-weight: 600;
  padding: 2px 8px; border-radius: 999px; margin-left: 6px;
  vertical-align: middle;
}
.badge-open { background: var(--accent-soft); color: var(--accent); }
.badge-soon { background: var(--brand-soft); color: var(--text-secondary); }
.badge-preview { background: #FEF3C7; color: var(--warn); }

/* Beats */
.beats {
  display: flex; flex-wrap: wrap; gap: 8px; align-items: center;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 16px 20px;
}
.beat {
  font-size: 13px; color: var(--brand); background: var(--brand-soft);
  padding: 6px 12px; border-radius: 8px; font-weight: 500;
}
.beat-arrow { color: var(--text-secondary); font-size: 12px; }

/* Chips */
.phases { display: flex; flex-wrap: wrap; gap: 8px; }
.chip {
  font-size: 12px; color: var(--text-secondary);
  background: var(--surface); border: 1px solid var(--border);
  padding: 6px 10px; border-radius: 8px; text-decoration: none;
}
.chip:hover { border-color: var(--brand); color: var(--brand); text-decoration: none; }
.chip strong { color: var(--brand); font-weight: 600; }

.note {
  margin-top: 32px; padding: 16px 18px;
  background: var(--brand-soft); border-radius: 10px;
  font-size: 13px; color: var(--text-secondary);
}

/* About page promotions */
.promo-grid {
  display: grid; grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px; margin: 18px 0;
}
.promo-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 12px; text-align: center;
  display: flex; flex-direction: column; align-items: center;
}
.promo-card img {
  display: block; width: 100%; max-width: 300px; height: auto;
  object-fit: contain; border-radius: 8px; margin-inline: auto;
}
.promo-card p { margin-top: 8px; font-size: 13px; color: var(--text-secondary); }
@media (max-width: 640px) {
  .promo-grid { grid-template-columns: 1fr; }
  .promo-card img { max-width: 280px; }
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--border);
  padding: 24px 0 40px; margin-top: 40px;
  font-size: 12px; color: var(--text-secondary);
}
.footer-inner {
  display: flex; flex-wrap: wrap; gap: 16px; justify-content: space-between;
}
.footer-inner a { color: var(--text-secondary); }
.footer-inner strong { color: var(--brand); font-weight: 600; }

/* Catalog */
.page-head { padding: 36px 0 12px; }
.page-head h1 { font-size: 28px; color: var(--brand); margin-bottom: 8px; }
.page-head .sub { color: var(--text-secondary); font-size: 14px; }
.search-row { display: flex; gap: 12px; margin: 20px 0 8px; flex-wrap: wrap; }
.search-input {
  flex: 1; min-width: 200px; height: 44px; padding: 0 14px;
  border: 1px solid var(--border); border-radius: 10px;
  background: var(--surface); color: var(--text); font-size: 14px; font-family: inherit;
}
.phase-block {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); margin-bottom: 12px; overflow: hidden;
}
.phase-head {
  display: flex; align-items: center; gap: 12px; padding: 14px 18px;
  cursor: pointer; user-select: none; width: 100%;
  background: none; border: none; text-align: left; font-family: inherit; color: inherit;
}
.phase-head:hover { background: var(--bg); }
.phase-head .chev { color: var(--text-secondary); width: 16px; flex-shrink: 0; }
.phase-head h2 { font-size: 15px; color: var(--brand); font-weight: 650; flex: 1; }
.phase-meta { font-size: 12px; color: var(--text-secondary); white-space: nowrap; font-variant-numeric: tabular-nums; }
.phase-progress {
  height: 4px; background: var(--border); border-radius: 99px;
  width: 64px; overflow: hidden; flex-shrink: 0;
}
.phase-progress > i { display: block; height: 100%; background: var(--accent); }
.lesson-list { list-style: none; border-top: 1px solid var(--border); display: none; }
.phase-block.open .lesson-list { display: block; }
.phase-block.open .chev { transform: rotate(90deg); }
.lesson-row {
  display: flex; align-items: center; gap: 12px;
  padding: 10px 18px 10px 42px; border-bottom: 1px solid var(--border);
  color: var(--text); text-decoration: none; font-size: 14px;
}
.lesson-row:last-child { border-bottom: none; }
.lesson-row:hover { background: var(--bg); text-decoration: none; }
.lesson-row .num {
  font-variant-numeric: tabular-nums; color: var(--text-secondary);
  width: 28px; flex-shrink: 0; font-size: 13px;
}
.lesson-row .title { flex: 1; color: var(--brand); }
.lesson-row .time { font-size: 12px; color: var(--text-secondary); }
.lesson-row .done { color: var(--accent); font-size: 14px; width: 18px; text-align: center; }
.lesson-row.disabled { opacity: 0.55; pointer-events: none; }

/* Paths detail */
.path-list { display: flex; flex-direction: column; gap: 12px; }
.path-item {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 20px 22px; border-left: 3px solid var(--brand);
}
.path-item.recommended { border-left-color: var(--accent); }
.path-item h2 { font-size: 18px; color: var(--brand); margin-bottom: 6px; }
.path-item p { font-size: 14px; color: var(--text-secondary); margin-bottom: 10px; }

/* Progress page */
.stat-grid {
  display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; margin: 20px 0;
}
@media (max-width: 640px) { .stat-grid { grid-template-columns: 1fr; } }
.stat-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 18px;
}
.stat-card .label { font-size: 12px; color: var(--text-secondary); margin-bottom: 6px; }
.stat-card .value { font-size: 28px; font-weight: 700; color: var(--brand); font-variant-numeric: tabular-nums; }
.bar-wide {
  height: 6px; background: var(--border); border-radius: 99px; overflow: hidden; margin: 8px 0 4px;
}
.bar-wide > i { display: block; height: 100%; background: var(--accent); }

/* Lesson reader */
.lesson-top {
  max-width: 1200px; margin: 0 auto; padding: 0 20px;
  height: 52px; display: flex; align-items: center; justify-content: space-between; gap: 12px;
}
.crumb { font-size: 13px; color: var(--text-secondary); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.crumb strong { color: var(--brand); font-weight: 600; }
.lesson-layout {
  max-width: 1200px; margin: 0 auto; padding: 20px 20px 80px;
  display: grid; grid-template-columns: 220px minmax(0, 1fr) 200px;
  gap: 24px; align-items: start;
}
@media (max-width: 960px) {
  .lesson-layout { grid-template-columns: 1fr; }
  .toc, .side { display: none; }
  .mobile-bar {
    display: flex !important; position: fixed; bottom: 0; left: 0; right: 0;
    background: var(--surface); border-top: 1px solid var(--border);
    padding: 10px 16px; gap: 8px; z-index: 40;
  }
}
.mobile-bar { display: none; }
.panel {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 14px;
}
.toc { position: sticky; top: 68px; max-height: calc(100vh - 88px); overflow-y: auto; }
.toc h2 { font-size: 12px; color: var(--text-secondary); margin-bottom: 10px; font-weight: 600; }
.toc ol { list-style: none; }
.toc li a {
  display: block; padding: 7px 10px; border-radius: 8px;
  font-size: 13px; color: var(--text-secondary); line-height: 1.4; text-decoration: none;
}
.toc li a:hover { background: var(--bg); color: var(--brand); text-decoration: none; }
.toc li.done a::before { content: "✓ "; color: var(--accent); }
.toc li.current a {
  background: var(--brand-soft); color: var(--brand); font-weight: 600;
}
.reader {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 32px 40px 40px;
}
@media (max-width: 640px) { .reader { padding: 24px 18px 32px; } }
.reader-badge { font-size: 12px; color: var(--accent); font-weight: 600; margin-bottom: 8px; }
.reader h1 {
  font-size: 28px; color: var(--brand); line-height: 1.3;
  margin-bottom: 8px; font-weight: 700;
}
.reader .meta { margin-bottom: 24px; }
.reader .md-body { max-width: 42em; }
.reader .md-body h1 { display: none; } /* title already shown */
.reader .md-body h2 {
  font-size: 18px; color: var(--brand); margin: 28px 0 10px;
  padding-top: 8px; border-top: 1px solid var(--border); font-weight: 650;
}
.reader .md-body h2:first-child { border-top: none; padding-top: 0; }
.reader .md-body h3 { font-size: 16px; color: var(--brand); margin: 20px 0 8px; font-weight: 600; }
.reader .md-body p { margin-bottom: 12px; }
.reader .md-body ul, .reader .md-body ol { margin: 0 0 12px 1.2em; }
.reader .md-body li { margin-bottom: 4px; }
.reader .md-body blockquote {
  border-left: 3px solid var(--accent); background: var(--accent-soft);
  padding: 12px 16px; border-radius: 0 8px 8px 0; margin: 0 0 20px;
  color: var(--brand); font-size: 14px;
}
.reader .md-body code {
  font-family: "JetBrains Mono", "SF Mono", Menlo, Consolas, monospace;
  font-size: 0.9em; background: var(--brand-soft); padding: 1px 5px; border-radius: 4px;
}
.reader .md-body pre {
  background: var(--code-bg); color: var(--code-text);
  border-radius: 8px; padding: 14px 16px; overflow-x: auto;
  font-family: "JetBrains Mono", "SF Mono", Menlo, Consolas, monospace;
  font-size: 13px; line-height: 1.55; margin: 12px 0 16px; position: relative;
}
.reader .md-body pre code { background: none; padding: 0; color: inherit; font-size: inherit; }
.reader .md-body table { border-collapse: collapse; width: 100%; margin: 12px 0 16px; font-size: 13px; }
.reader .md-body th, .reader .md-body td {
  border: 1px solid var(--border); padding: 8px 10px; text-align: left;
}
.reader .md-body th { background: var(--brand-soft); }
.reader .md-body img { max-width: 100%; border-radius: 8px; }
.reader .md-body hr { border: none; border-top: 1px solid var(--border); margin: 24px 0; }
.code-wrap { position: relative; margin: 12px 0 16px; }
.code-wrap .copy-btn {
  position: absolute; top: 8px; right: 8px; z-index: 2;
  font-size: 11px; padding: 4px 8px; border-radius: 6px;
  background: #1e293b; color: #94a3b8; border: 1px solid #334155;
  cursor: pointer; font-family: inherit;
}
.code-wrap pre { margin: 0; }
.quiz-card {
  margin-top: 32px; background: var(--accent-soft);
  border: 1px solid #B6E6E0; border-radius: var(--radius); padding: 18px 20px;
}
html[data-theme="dark"] .quiz-card { border-color: #1A4A45; }
.quiz-card h3 { font-size: 15px; color: var(--brand); margin-bottom: 6px; }
.quiz-card p { font-size: 13px; color: var(--text-secondary); margin-bottom: 12px; }
.quiz-q { margin: 14px 0; font-size: 14px; }
.quiz-q .opts { list-style: none; margin: 8px 0 0; }
.quiz-q .opts li {
  margin: 4px 0; padding: 8px 12px; border: 1px solid var(--border);
  border-radius: 8px; cursor: pointer; background: var(--surface);
}
.quiz-q .opts li:hover { border-color: var(--accent); }
.quiz-q .opts li.selected { border-color: var(--accent); background: var(--accent-soft); }
.quiz-q .opts li.correct { border-color: var(--accent); background: var(--accent-soft); }
.quiz-q .opts li.wrong { border-color: #DC2626; background: #FEF2F2; }
.nav-lessons {
  display: flex; justify-content: space-between; gap: 12px; margin-top: 28px; flex-wrap: wrap;
}
.side { position: sticky; top: 68px; }
.side .stat { font-size: 12px; color: var(--text-secondary); margin-bottom: 8px; }
.bar { height: 4px; background: var(--border); border-radius: 99px; overflow: hidden; margin-bottom: 14px; }
.bar > i { display: block; height: 100%; background: var(--accent); }
.side .btn { width: 100%; justify-content: center; margin-bottom: 8px; }
.side-note { font-size: 12px; color: var(--text-secondary); margin-top: 12px; line-height: 1.5; }
.loading { padding: 40px; text-align: center; color: var(--text-secondary); }
.error-box {
  padding: 24px; background: #FEF2F2; border: 1px solid #FECACA;
  border-radius: 10px; color: #991B1B; margin: 20px 0;
}


/* LF figure theme aliases */
:root {
  --blueprint: var(--accent, #0D9488);
  --blueprint-tint: var(--accent-soft, rgba(13,148,136,.12));
  --rule-soft: var(--border, #E6E8EC);
  --ink: var(--text, #1A1D26);
  --ink-soft: var(--text-secondary, #5C6370);
  --ink-mute: var(--text-secondary, #5C6370);
  --font-body: "PingFang SC", "Noto Sans SC", "Source Han Sans SC", "Microsoft YaHei", system-ui, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --ease-out: cubic-bezier(.23,1,.32,1);
  --warn: var(--warn, #B45309);
}
html[data-theme="dark"] {
  --blueprint: var(--accent, #2DD4BF);
  --blueprint-tint: var(--accent-soft, rgba(45,212,191,.12));
  --rule-soft: var(--border, #243049);
  --ink: var(--text, #E8ECF4);
  --ink-soft: var(--text-secondary, #9AA3B5);
  --ink-mute: var(--text-secondary, #9AA3B5);
}