/* 大模型视觉 — 项目落地实践
   版式：窄栏正文 + 单栏图版（Tufte / Distill 路线）
   配色：石灰岩底 + 瓷白纸面 + 深孔雀绿点缀，字体走系统栈不依赖 CDN */

:root {
  --measure: 44rem;

  --stone: #e8e6e1;          /* 页面底色，纸面之外 */
  --paper: #fcfbf9;          /* 正文纸面 */
  --paper-2: #f4f2ec;        /* 卡片 / 表头底 */
  --ink: #16181a;
  --ink-2: #3d4146;
  --muted: #7b8088;
  --rule: #dfdbd2;
  --rule-2: #16181a;
  --accent: #0d5c55;         /* 深孔雀绿 */
  --accent-soft: rgba(13, 92, 85, .07);
  --amber: #8a6212;
  --danger: #9c3521;

  --serif: "Source Han Serif SC", "Noto Serif SC", "Songti SC", "SimSun", Georgia, serif;
  --sans: "PingFang SC", "Source Han Sans SC", "Noto Sans SC", -apple-system,
    BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei", sans-serif;
  --mono: ui-monospace, "SF Mono", "JetBrains Mono", Menlo, Consolas, monospace;
}

/* ── 英文版排印 ─────────────────────────── */
html[lang="en"] {
  --measure: 46rem;
  --serif: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
}
html[lang="en"] body { letter-spacing: 0; line-height: 1.72; }
/* 英文不做两端对齐：没有连字符会拉出难看的字间距 */
html[lang="en"] p,
html[lang="en"] li,
html[lang="en"] dd,
html[lang="en"] figcaption { text-align: left; }
/* 英文词长，表头和首列不能禁止换行 */
html[lang="en"] thead th,
html[lang="en"] tbody td:first-child { white-space: normal; }
html[lang="en"] .chaps button { font-size: .715rem; }
html[lang="en"] .take::before { content: "THE CORE TENSION"; }
html[lang="en"] .take.plain::before { content: "IN SHORT"; }

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 4.5rem;
}

body {
  margin: 0;
  color: var(--ink);
  font-family: var(--serif);
  font-size: 1.0625rem;
  line-height: 1.9;
  letter-spacing: .012em;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  /* 石灰岩底上压一层极淡的斜向光，纸面浮在上面 */
  background:
    radial-gradient(120% 60% at 50% -10%, #f2f1ed 0%, rgba(242, 241, 237, 0) 60%),
    var(--stone);
  background-attachment: fixed;
}

/* ── 阅读进度 ───────────────────────────── */
#progress {
  position: fixed;
  inset: 0 auto auto 0;
  height: 2px;
  width: 0;
  background: var(--accent);
  z-index: 60;
  transition: width .1s linear;
}

/* ── 章节导航 ───────────────────────────── */
#nav {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(252, 251, 249, .93);
  backdrop-filter: saturate(1.6) blur(10px);
  border-bottom: 1px solid var(--rule);
  opacity: 0;
  pointer-events: none;
  transition: opacity .25s;
}
#nav.on { opacity: 1; pointer-events: auto; }
#nav ol {
  max-width: var(--measure);
  margin: 0 auto;
  padding: .55rem 2.75rem;
  list-style: none;
  display: flex;
  gap: 1.15rem;
  overflow-x: auto;
  scrollbar-width: none;
  font-family: var(--sans);
  font-size: .74rem;
  letter-spacing: .04em;
}
#nav ol::-webkit-scrollbar { display: none; }
#nav a {
  color: var(--muted);
  text-decoration: none;
  white-space: nowrap;
  padding-bottom: 1px;
  border-bottom: 1.5px solid transparent;
}
#nav a:hover { color: var(--ink); }
#nav a.here { color: var(--accent); border-bottom-color: var(--accent); }

/* ── 纸面 ───────────────────────────────── */
.sheet {
  max-width: var(--measure);
  margin: 2.5rem auto 3.5rem;
  padding: 0 2.75rem 4.5rem;
  background: var(--paper);
  border: 1px solid var(--rule);
  box-shadow: 0 1px 2px rgba(22, 24, 26, .04), 0 18px 50px -24px rgba(22, 24, 26, .18);
}

/* ── 报头 ───────────────────────────────── */
.mast {
  padding: 3.6rem 0 2rem;
  border-bottom: 2.5px solid var(--rule-2);
  margin-bottom: 2.5rem;
}
.kicker {
  font-family: var(--sans);
  font-size: .72rem;
  letter-spacing: .17em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 1.4rem;
}
.kicker b { font-weight: 600; }
h1 {
  font-size: clamp(1.75rem, 4.2vw, 2.4rem);
  line-height: 1.28;
  letter-spacing: -.012em;
  font-weight: 700;
  margin: 0 0 1.05rem;
  text-wrap: balance;
}
.nb { white-space: nowrap; }
.subtitle {
  font-size: 1.06rem;
  line-height: 1.78;
  color: var(--ink-2);
  margin: 0 0 1.8rem;
}
.subtitle em {
  font-style: normal;
  background: linear-gradient(transparent 62%, var(--accent-soft) 62%);
  border-bottom: 1.5px solid var(--accent);
  padding-bottom: 1px;
}
.byline {
  font-family: var(--sans);
  font-size: .78rem;
  color: var(--muted);
  display: flex;
  flex-wrap: wrap;
  gap: .5rem 1.5rem;
}
.byline b { color: var(--ink); font-weight: 600; }
.byline a { text-decoration: none; border-bottom: 1px solid var(--rule); padding-bottom: 1px; }
.byline a:hover { border-bottom-color: var(--accent); }

/* ── 章节 ───────────────────────────────── */
section { margin: 3.4rem 0 0; scroll-margin-top: 4.5rem; }

.secno {
  display: flex;
  align-items: center;
  gap: .5rem;
  margin: 0 0 .8rem;
  font-family: var(--sans);
}
.secno b {
  flex: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 1.9rem;
  height: 1.9rem;
  padding: 0 .35rem;
  font-family: var(--mono);
  font-size: .86rem;
  font-weight: 700;
  letter-spacing: 0;
  color: var(--paper);
  background: var(--accent);
}
.secno em {
  font-family: var(--mono);
  font-style: normal;
  font-size: .72rem;
  color: var(--muted);
  margin-left: -.2rem;
}
.secno span {
  font-size: .715rem;
  letter-spacing: .19em;
  font-weight: 600;
  color: var(--muted);
  margin-left: .3rem;
}
.secno.alt b {
  color: var(--accent);
  background: transparent;
  box-shadow: inset 0 0 0 1.5px rgba(13, 92, 85, .45);
}

h2 {
  font-size: 1.5rem;
  line-height: 1.42;
  font-weight: 700;
  letter-spacing: -.005em;
  margin: 0 0 1.3rem;
  padding-bottom: .65rem;
  border-bottom: 1px solid var(--rule);
}
h3 {
  font-size: 1.16rem;
  line-height: 1.52;
  font-weight: 700;
  margin: 2.45rem 0 .85rem;
}
.h3n {
  font-family: var(--mono);
  font-size: .8em;
  color: var(--accent);
  margin-right: .55em;
  font-weight: 600;
}

p { margin: 0 0 1.15rem; }
p, li, dd, figcaption {
  text-align: justify;
  text-justify: inter-ideograph;
  word-break: normal;
  overflow-wrap: break-word;
}
.lede { font-size: 1.1rem; color: var(--ink-2); }
b, strong { font-weight: 700; color: var(--ink); }
ul, ol { margin: 0 0 1.15rem; padding-left: 1.15rem; }
li { margin-bottom: .5rem; }
li::marker { color: var(--accent); }
a { color: var(--accent); text-underline-offset: .2em; text-decoration-thickness: .5px; }

code {
  font-family: var(--mono);
  font-size: .86em;
  background: var(--paper-2);
  border: 1px solid var(--rule);
  padding: .04em .32em;
  border-radius: 2px;
  white-space: nowrap;
}

/* ── 摘要卡 ─────────────────────────────── */
.tldr {
  background: var(--paper-2);
  border-left: 3px solid var(--rule-2);
  padding: 1.4rem 1.5rem .6rem;
  margin-bottom: 2.5rem;
}
.tldr h2 {
  font-family: var(--sans);
  font-size: .74rem;
  letter-spacing: .18em;
  border: 0;
  padding: 0;
  margin: 0 0 .9rem;
  color: var(--accent);
}
.tldr ul { margin: 0; padding-left: 1.1rem; }
.tldr li { font-size: .97rem; line-height: 1.78; }

/* ── 一句话 ─────────────────────────────── */
.take {
  border-top: 1.5px solid var(--rule-2);
  border-bottom: 1.5px solid var(--rule-2);
  padding: .95rem 0;
  margin: 1.9rem 0;
  font-size: 1rem;
  line-height: 1.8;
}
.take::before {
  content: "关键矛盾";
  display: block;
  font-family: var(--sans);
  font-size: .66rem;
  letter-spacing: .2em;
  color: var(--accent);
  font-weight: 600;
  margin-bottom: .45rem;
}
.take p { margin: 0; }
.take.plain::before { content: "一句话"; }

/* ── 图版 ───────────────────────────────── */
figure { max-width: 100%; margin: 2.4rem 0; }
figure img, figure video {
  width: 100%;
  display: block;
  border: 1px solid var(--rule);
  background: var(--paper-2);
}
figure img { cursor: zoom-in; }
figcaption {
  font-family: var(--sans);
  font-size: .795rem;
  line-height: 1.7;
  color: var(--muted);
  margin: .8rem 0 0;
  letter-spacing: 0;
}
figcaption b { color: var(--ink-2); font-weight: 600; }
.fno {
  font-family: var(--mono);
  font-size: .74rem;
  color: var(--accent);
  font-weight: 600;
  margin-right: .6em;
  white-space: nowrap;
}

/* ── 算子链 / 步骤链 ────────────────────── */
.chain {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: .35rem;
  list-style: none;
  padding: 0;
  margin: 1.4rem 0 1.6rem;
  font-family: var(--sans);
  letter-spacing: 0;
}
.chain li {
  margin: 0;
  padding: .55rem .65rem;
  background: var(--paper-2);
  border: 1px solid var(--rule);
  border-left: 2.5px solid var(--accent);
}
.chain b { display: block; font-size: .81rem; line-height: 1.45; font-weight: 700; }
.chain span { display: block; font-size: .69rem; color: var(--muted); margin-top: .1rem; }

/* ── 视频章节 ───────────────────────────── */
.chaps {
  list-style: none;
  padding: 0;
  margin: .75rem 0 0;
  display: flex;
  flex-wrap: wrap;
  gap: .35rem;
  font-family: var(--sans);
}
.chaps li { margin: 0; }
.chaps button {
  font: inherit;
  font-size: .735rem;
  letter-spacing: 0;
  color: var(--ink-2);
  background: var(--paper-2);
  border: 1px solid var(--rule);
  padding: .3rem .6rem;
  cursor: pointer;
  transition: color .15s, border-color .15s;
}
.chaps button:hover { color: var(--accent); border-color: var(--accent); }
.chaps b { font-family: var(--mono); font-size: .96em; color: var(--accent); margin-right: .4em; }

/* ── 能做 / 不做 ────────────────────────── */
.limits {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: .5rem;
  margin: 1.6rem 0;
  font-family: var(--sans);
  letter-spacing: 0;
}
.limits > div {
  background: var(--paper-2);
  border: 1px solid var(--rule);
  border-top: 2.5px solid var(--accent);
  padding: .8rem .9rem 1rem;
}
.limits > div.mid { border-top-color: var(--amber); }
.limits > div.no { border-top-color: var(--danger); }
.limits h4 {
  margin: 0 0 .5rem;
  font-size: .72rem;
  letter-spacing: .12em;
  color: var(--muted);
  font-weight: 700;
}
.limits ul { margin: 0; padding-left: .95rem; }
.limits li { font-size: .785rem; line-height: 1.6; margin-bottom: .3rem; color: var(--ink-2); text-align: left; }

/* ── 表格 ───────────────────────────────── */
.tbl {
  margin: 1.8rem 0;
  overflow-x: auto;
  border: 1px solid var(--rule);
  background: var(--paper);
}
table {
  width: 100%;
  border-collapse: collapse;
  font-family: var(--sans);
  font-size: .82rem;
  line-height: 1.65;
  letter-spacing: 0;
}
thead th {
  background: var(--paper-2);
  color: var(--ink);
  font-weight: 700;
  font-size: .74rem;
  letter-spacing: .06em;
  text-align: left;
  padding: .7rem .9rem;
  border-bottom: 1.5px solid var(--rule-2);
  white-space: nowrap;
}
tbody td {
  padding: .68rem .9rem;
  border-bottom: 1px solid var(--rule);
  color: var(--ink-2);
  vertical-align: top;
}
tbody tr:last-child td { border-bottom: 0; }
tbody td:first-child { color: var(--ink); font-weight: 600; white-space: nowrap; }
tbody td b { color: var(--ink); }

/* ── 落款 ───────────────────────────────── */
.colophon {
  margin-top: 4.5rem;
  padding-top: 2rem;
  border-top: 2.5px solid var(--rule-2);
  display: grid;
  grid-template-columns: 7rem 1fr;
  gap: 2rem;
  font-family: var(--sans);
  font-size: .845rem;
  line-height: 1.78;
  color: var(--ink-2);
  letter-spacing: 0;
}
.sig {
  font-family: var(--serif);
  font-size: 1.05rem;
  font-weight: 700;
  line-height: 1.3;
  letter-spacing: .05em;
  color: var(--accent);
  display: block;
  padding-top: .2rem;
}
.who { font-weight: 700; color: var(--ink); margin: 0 0 .45rem; font-size: .95rem; }
.colophon p { margin: 0 0 .8rem; }
.colophon p:last-child { margin: 0; }

/* ── 灯箱 ───────────────────────────────── */
#lb {
  position: fixed;
  inset: 0;
  background: rgba(14, 15, 16, .94);
  z-index: 100;
  display: none;
  place-items: center;
  padding: 1.5rem;
  cursor: zoom-out;
}
#lb.on { display: grid; }
#lb img { max-width: 100%; max-height: 88vh; object-fit: contain; }
#lb p {
  position: absolute;
  bottom: 1.1rem;
  left: 0;
  right: 0;
  text-align: center;
  color: #c9c5bd;
  font-family: var(--sans);
  font-size: .76rem;
  margin: 0;
  padding: 0 1.5rem;
}

/* ── 窄屏 ───────────────────────────────── */
@media (max-width: 46rem) {
  body { font-size: 1.02rem; line-height: 1.84; background: var(--paper); }
  .sheet {
    margin: 0;
    padding: 0 1.05rem 3.5rem;
    border: 0;
    box-shadow: none;
    max-width: 100%;
  }
  #nav ol { padding: .55rem 1.05rem; }
  .mast { padding-top: 2.6rem; }
  figure { margin: 1.9rem -1.05rem; }
  figure img, figure video { border-left: 0; border-right: 0; }
  figcaption { padding: 0 1.05rem; }
  .tldr { padding: 1.15rem 1.15rem .4rem; }
  .chain { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .limits { grid-template-columns: 1fr; }
  .colophon { grid-template-columns: 1fr; gap: .8rem; }
  .tbl { margin: 1.6rem -1.05rem; border-left: 0; border-right: 0; }
}

@media print {
  body { background: #fff; }
  #nav, #progress, #lb { display: none; }
  .sheet { border: 0; box-shadow: none; margin: 0; padding: 0; }
  figure { break-inside: avoid; }
}