:root {
  color-scheme: light;
  --ink: #0d1813;
  --ink-soft: #304139;
  --paper: #f6f7f3;
  --surface: #ffffff;
  --forest: #0b1d16;
  --jade: #2c805e;
  --jade-light: #dbece3;
  --muted: #66756c;
  --line: rgba(18, 51, 38, 0.16);
  --accent: #a64734;
  --accent-soft: #f0dfda;
  --serif: "Songti SC", "STSong", "Noto Serif CJK SC", serif;
  --sans: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; min-width: 320px; overflow-x: hidden; color: var(--ink); background: var(--paper); font-family: var(--sans); line-height: 1.78; -webkit-font-smoothing: antialiased; }
body.ai-course { --accent: #247656; --accent-soft: #dcebe3; }
a { color: inherit; text-decoration: none; }
button { font: inherit; }
img, svg { display: block; max-width: 100%; }
h1, h2, h3, p, blockquote, figure { margin-top: 0; }
h1, h2, h3 { letter-spacing: 0; text-wrap: balance; }
p, li { text-wrap: pretty; }
:focus-visible { outline: 3px solid #4eb187; outline-offset: 4px; }
.course-shell { width: min(1180px, calc(100% - 56px)); margin-inline: auto; }
.skip-link { position: fixed; top: 10px; left: 10px; z-index: 100; padding: 10px 14px; color: #fff; background: var(--forest); transform: translateY(-150%); }
.skip-link:focus { transform: none; }
.reading-progress { position: fixed; inset: 0 0 auto; z-index: 90; height: 3px; }
.reading-progress span { display: block; width: 100%; height: 100%; background: var(--accent); transform: scaleX(0); transform-origin: left; }
.course-header { position: absolute; inset: 0 0 auto; z-index: 20; color: #f5f8f6; }
.course-header-inner { min-height: 80px; display: flex; justify-content: space-between; align-items: center; gap: 24px; }
.brand { display: inline-flex; align-items: center; gap: 11px; }
.brand-mark { width: 40px; height: 46px; display: grid; place-items: center; overflow: hidden; flex: 0 0 auto; border-radius: 8px; background: #fff; }
.brand-mark img { width: 90%; height: 90%; object-fit: contain; }
.brand > span:last-child { display: grid; line-height: 1.2; }
.brand strong { font-size: 14px; }.brand small { margin-top: 4px; color: rgba(241,247,243,0.62); font-size: 10px; }
.course-header nav { display: flex; gap: 26px; }
.course-header nav a { min-height: 44px; display: inline-flex; align-items: center; color: rgba(241,247,243,0.72); font-size: 13px; }
.course-header nav a:hover { color: #fff; }
.course-hero { position: relative; overflow: hidden; min-height: 720px; display: grid; align-items: end; color: #f4f8f5; background: var(--forest); }
.course-hero::before { content: ""; position: absolute; width: 620px; height: 620px; right: -120px; top: 60px; border: 1px solid rgba(255,255,255,0.14); border-radius: 50%; }
.course-hero::after { content: ""; position: absolute; width: 390px; height: 390px; right: -5px; top: 172px; border: 1px solid rgba(255,255,255,0.09); border-radius: 50%; }
.hero-symbol { position: absolute; right: 8%; top: 21%; color: rgba(255,255,255,0.06); font-family: var(--serif); font-size: clamp(11rem, 24vw, 22rem); line-height: 1; }
.course-hero-inner { position: relative; z-index: 2; display: grid; grid-template-columns: 1.4fr 0.6fr; gap: 78px; align-items: end; padding: 158px 0 84px; }
.course-meta { display: flex; flex-wrap: wrap; gap: 8px 20px; margin-bottom: 26px; color: rgba(237,245,240,0.66); font-size: 12px; font-weight: 700; }
.course-meta span:first-child { color: #70c69f; }
.course-hero h1 { max-width: 850px; margin-bottom: 24px; font-family: var(--serif); font-size: clamp(3.6rem, 7.4vw, 6rem); line-height: 1.04; }
.course-thesis { max-width: 760px; margin: 0; color: rgba(238,246,241,0.72); font-family: var(--serif); font-size: clamp(1.3rem, 2.6vw, 2rem); line-height: 1.65; }
.hero-brief { border-top: 1px solid rgba(255,255,255,0.22); }
.hero-brief div { padding: 18px 0; border-bottom: 1px solid rgba(255,255,255,0.22); }
.hero-brief small { display: block; color: #75c9a3; font-size: 11px; font-weight: 800; }
.hero-brief strong { font-family: var(--serif); font-size: 17px; }
.course-layout { display: grid; grid-template-columns: 230px minmax(0, 1fr); gap: clamp(50px, 8vw, 110px); align-items: start; padding-block: 96px 132px; }
.toc { position: sticky; top: 32px; min-width: 0; }
.toc p { margin-bottom: 16px; color: var(--accent); font-size: 12px; font-weight: 800; }
.toc ol { margin: 0; padding: 0; list-style: none; }
.toc li { border-top: 1px solid var(--line); }
.toc li:last-child { border-bottom: 1px solid var(--line); }
.toc a { min-height: 46px; display: flex; align-items: center; gap: 10px; color: var(--muted); font-size: 13px; transition: color 180ms ease, transform 180ms var(--ease); }
.toc a::before { content: ""; width: 10px; height: 1px; flex: 0 0 auto; background: var(--line); }
.toc a:hover, .toc a.is-active { color: var(--ink); transform: translateX(4px); }
.toc a.is-active::before { background: var(--accent); }
.article { min-width: 0; max-width: 860px; }
.lead { margin-bottom: 78px; }
.lead > p:first-child { margin-bottom: 28px; color: var(--accent); font-size: 13px; font-weight: 800; }
.lead h2 { margin-bottom: 28px; font-family: var(--serif); font-size: clamp(2.6rem, 5vw, 4.6rem); line-height: 1.14; }
.lead > p:last-child { max-width: 760px; margin: 0; color: var(--ink-soft); font-size: 19px; line-height: 1.95; }
.course-section { padding: 74px 0; border-top: 1px solid var(--line); scroll-margin-top: 34px; }
.course-section > header { display: grid; grid-template-columns: 80px 1fr; gap: 26px; margin-bottom: 34px; }
.section-number { color: var(--accent); font-family: var(--serif); font-size: 24px; }
.course-section h2 { margin: 0; font-family: var(--serif); font-size: clamp(2.1rem, 4vw, 3.4rem); line-height: 1.2; }
.course-section > p, .course-section > div > p { max-width: 760px; color: var(--ink-soft); font-size: 17px; line-height: 1.95; }
.concepts { display: grid; grid-template-columns: repeat(2, minmax(0,1fr)); border-top: 1px solid var(--line); border-left: 1px solid var(--line); }
.concept { min-width: 0; padding: 28px; border-right: 1px solid var(--line); border-bottom: 1px solid var(--line); background: var(--surface); }
.concept small { color: var(--accent); font-size: 11px; font-weight: 800; }
.concept h3 { margin: 8px 0 12px; font-family: var(--serif); font-size: 25px; }
.concept p { margin: 0; color: var(--muted); font-size: 14px; line-height: 1.78; }
.causal-chain { margin: 42px 0; padding: 36px; color: #eef6f1; background: var(--forest); }
.causal-chain > p { margin: 0 0 24px; color: #77c9a4; font-size: 12px; font-weight: 800; }
.chain-items { display: flex; flex-wrap: wrap; align-items: center; gap: 10px; }
.chain-items span { display: inline-flex; min-height: 42px; align-items: center; padding: 0 12px; border: 1px solid rgba(255,255,255,0.18); font-size: 13px; }
.chain-items i { color: #77c9a4; font-style: normal; }
.pullquote { margin: 42px 0; padding: 34px 0; border-top: 1px solid var(--accent); border-bottom: 1px solid var(--accent); color: var(--ink); font-family: var(--serif); font-size: clamp(1.55rem, 3vw, 2.25rem); line-height: 1.65; }
.comparison { display: grid; grid-template-columns: 1fr 1fr; gap: 1px; margin-top: 34px; background: var(--line); }
.comparison section { min-width: 0; padding: 30px; background: var(--surface); }
.comparison h3 { margin-bottom: 16px; font-family: var(--serif); font-size: 24px; }
.comparison ul, .principles, .checklist { margin: 0; padding: 0; list-style: none; }
.comparison li, .principles li, .checklist li { position: relative; padding: 11px 0 11px 24px; color: var(--ink-soft); border-top: 1px solid var(--line); }
.comparison li::before, .principles li::before { content: ""; position: absolute; left: 2px; top: 23px; width: 8px; height: 1px; background: var(--accent); }
.framework { margin-top: 32px; overflow-x: auto; border-top: 2px solid var(--ink); }
.framework-row { min-width: 680px; display: grid; grid-template-columns: 0.6fr 1fr 1.5fr; }
.framework-row > * { min-width: 0; padding: 17px 18px; border-bottom: 1px solid var(--line); }
.framework-row > * + * { border-left: 1px solid var(--line); }
.framework-row.header { color: var(--surface); background: var(--ink); font-size: 12px; font-weight: 800; }
.framework-row:not(.header) span { color: var(--accent); font-weight: 800; }
.framework-row:not(.header) p { margin: 0; color: var(--muted); font-size: 14px; }
.practice { display: grid; gap: 0; margin-top: 36px; border-top: 1px solid var(--line); }
.practice li { display: grid; grid-template-columns: 54px 1fr minmax(180px,0.7fr); gap: 22px; padding: 24px 0; border-bottom: 1px solid var(--line); list-style: none; }
.practice span { color: var(--accent); font-size: 12px; font-weight: 800; }
.practice strong { font-family: var(--serif); font-size: 20px; }
.practice p { margin: 0; color: var(--muted); font-size: 14px; }
.boundary { padding: 34px; background: var(--accent-soft); }
.boundary h3 { margin-bottom: 14px; font-family: var(--serif); font-size: 24px; }
.boundary p { margin-bottom: 12px; color: var(--ink-soft); }
.boundary p:last-child { margin-bottom: 0; }
.source-note { color: var(--muted); font-size: 13px; }
.course-next { display: grid; grid-template-columns: 1fr auto; gap: 34px; align-items: center; margin-top: 78px; padding: 38px; color: #f1f6f3; background: var(--forest); }
.course-next small { color: #78c8a3; font-size: 11px; font-weight: 800; }
.course-next h2 { margin: 6px 0 0; font-family: var(--serif); font-size: 30px; }
.course-next a { min-height: 48px; display: inline-flex; align-items: center; padding: 0 18px; border: 1px solid rgba(255,255,255,0.3); border-radius: 8px; font-weight: 750; }
.course-next a:hover { color: var(--forest); background: #fff; }
.course-footer { color: rgba(239,246,241,0.68); background: #050e09; }
.course-footer div { min-height: 100px; display: flex; justify-content: space-between; align-items: center; gap: 24px; }
.course-footer a { min-height: 44px; display: inline-flex; align-items: center; }
.course-footer a:hover { color: #fff; }
.js .reveal { transform: translateY(22px); transition: transform 450ms var(--ease); }
.js .reveal.is-visible { transform: none; }
@media (max-width: 900px) {
  .course-shell { width: min(100% - 40px, 760px); }
  .course-hero-inner { grid-template-columns: 1fr; gap: 52px; }
  .course-layout { grid-template-columns: 1fr; }
  .toc { position: static; }
  .toc ol { display: flex; gap: 8px; overflow-x: auto; padding-bottom: 12px; }
  .toc li { flex: 0 0 auto; border: 1px solid var(--line); }
  .toc li:last-child { border-bottom: 1px solid var(--line); }
  .toc a { padding: 0 14px; }
  .course-section { scroll-margin-top: 18px; }
}
@media (max-width: 620px) {
  .course-shell { width: min(100% - 24px, 560px); }
  .course-header nav a:first-child { display: none; }
  .course-hero { min-height: 720px; }
  .course-hero-inner { padding: 126px 0 60px; }
  .course-hero h1 { font-size: 50px; }
  .course-thesis { font-size: 20px; }
  .course-layout { padding-block: 62px 90px; gap: 58px; }
  .lead { margin-bottom: 60px; }
  .lead h2 { font-size: 38px; }
  .lead > p:last-child { font-size: 17px; }
  .course-section { padding: 56px 0; }
  .course-section > header { grid-template-columns: 1fr; gap: 8px; }
  .course-section h2 { font-size: 34px; }
  .concepts, .comparison { grid-template-columns: 1fr; }
  .causal-chain { padding: 26px 20px; }
  .practice li { grid-template-columns: 42px 1fr; }
  .practice p { grid-column: 2; }
  .boundary { padding: 26px 20px; }
  .course-next { grid-template-columns: 1fr; padding: 28px 22px; }
  .course-next a { justify-content: center; }
  .course-footer div { display: grid; align-content: center; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; }
  .js .reveal { opacity: 1; transform: none; }
}