@charset "UTF-8";
/* ==========================================================================
   WhatsApp 网页版手册 · 样式表
   设计方向：印刷说明书 / 杂志编辑风
   纸色底 + 墨色字 + 砖红强调色，衬线展示字，只有规则线，没有圆角与投影
   所有颜色走变量，暗色模式只覆盖令牌
   ========================================================================== */

/* ---------- 1. 令牌 ---------- */
:root {
  --paper: #f6f2e9;
  --paper-2: #efe9db;
  --card: #fffdf7;
  --ink: #15130f;
  --ink-2: #322d24;
  --muted: #6a6355;
  --faint: #8d8574;
  --rule: #d6cebb;
  --rule-soft: #e3dccb;
  --accent: #9e3413;
  --accent-soft: #f2e2d8;
  --ok: #2f6142;
  --ok-soft: #e2ebdf;
  --no: #8a2c17;

  --font-display: Georgia, "Songti SC", "Source Han Serif SC", "Noto Serif SC", "SimSun", "STSong", serif;
  --font-body: "PingFang SC", "Microsoft YaHei", "Hiragino Sans GB", "Noto Sans SC", system-ui, sans-serif;
  --font-mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;

  --fs-xs: 0.75rem;
  --fs-sm: 0.84rem;
  --fs-base: 1.0625rem;
  --fs-md: 1.19rem;
  --fs-lg: 1.44rem;
  --fs-xl: clamp(1.6rem, 2.6vw, 2.1rem);
  --fs-2xl: clamp(2rem, 4vw, 3.1rem);
  --fs-hero: clamp(2.2rem, 4.4vw, 3.6rem);

  --sp-1: 0.25rem;
  --sp-2: 0.5rem;
  --sp-3: 1rem;
  --sp-4: 1.5rem;
  --sp-5: 2.5rem;
  --sp-6: 4rem;
  --sp-7: 6.5rem;

  --gutter: clamp(1.15rem, 5vw, 4rem);
  --maxw: 74rem;
  --measure: 40em;

  --ease: cubic-bezier(0.16, 1, 0.3, 1);
  --dur-fast: 160ms;
  --dur-base: 320ms;
  --dur-slow: 640ms;
}

@media (prefers-color-scheme: dark) {
  :root {
    --paper: #131210;
    --paper-2: #1b1916;
    --card: #1a1815;
    --ink: #f3ede1;
    --ink-2: #ddd5c5;
    --muted: #a49c8b;
    --faint: #8b8372;
    --rule: #3a352c;
    --rule-soft: #2b2721;
    --accent: #e0703c;
    --accent-soft: #2e1d14;
    --ok: #7fbd93;
    --ok-soft: #1c2a21;
    --no: #e0855f;
  }
}

/* ---------- 2. 重置 ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: var(--fs-base);
  line-height: 1.85;
  letter-spacing: 0.012em;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}
img, svg { max-width: 100%; }
img { height: auto; }
h1, h2, h3, h4, p, ul, ol, dl, figure, blockquote { margin: 0; }
ul, ol { padding: 0; }
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; }
table { border-collapse: collapse; width: 100%; }
code, kbd, samp { font-family: var(--font-mono); font-size: 0.92em; }
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
}
::selection { background: var(--accent); color: var(--paper); }

/* ---------- 3. 版心与纸面 ---------- */
.wrap {
  width: 100%;
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

/* 打样内框 + 四角裁切线：整站的印刷记忆点 */
.sheet { position: relative; overflow-x: clip; }
.sheet::before {
  content: "";
  position: fixed;
  inset: 14px;
  border: 1px solid var(--rule-soft);
  pointer-events: none;
  z-index: 40;
}
.sheet::after {
  content: "";
  position: fixed;
  inset: 4px;
  pointer-events: none;
  z-index: 41;
  --c: var(--rule);
  background:
    linear-gradient(var(--c) 0 0) left 0 top 20px / 1px 14px no-repeat,
    linear-gradient(var(--c) 0 0) left 20px top 0 / 14px 1px no-repeat,
    linear-gradient(var(--c) 0 0) right 0 top 20px / 1px 14px no-repeat,
    linear-gradient(var(--c) 0 0) right 20px top 0 / 14px 1px no-repeat,
    linear-gradient(var(--c) 0 0) left 0 bottom 20px / 1px 14px no-repeat,
    linear-gradient(var(--c) 0 0) left 20px bottom 0 / 14px 1px no-repeat,
    linear-gradient(var(--c) 0 0) right 0 bottom 20px / 1px 14px no-repeat,
    linear-gradient(var(--c) 0 0) right 20px bottom 0 / 14px 1px no-repeat;
}
@media (max-width: 720px) {
  .sheet::before, .sheet::after { display: none; }
}

/* 纸面颗粒 */
.sheet > .grain {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  opacity: 0.035;
  mix-blend-mode: multiply;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='180' height='180'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.85' numOctaves='3'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}
@media (prefers-color-scheme: dark) {
  .sheet > .grain { mix-blend-mode: screen; opacity: 0.05; }
}

/* ---------- 4. 报头 ---------- */
.masthead {
  position: sticky;
  top: 0;
  z-index: 30;
  background: var(--paper);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--ink);
}
@supports (background: color-mix(in srgb, #000 50%, #fff)) {
  .masthead { background: color-mix(in srgb, var(--paper) 94%, transparent); }
}
.masthead-in {
  display: flex;
  align-items: center;
  gap: var(--sp-4);
  min-height: 4.2rem;
  padding-block: 0.7rem;
}
.brand { display: flex; align-items: baseline; gap: 0.6rem; margin-right: auto; }
.brand-mark {
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  letter-spacing: 0.16em;
  color: var(--accent);
  border: 1px solid var(--accent);
  padding: 0.2rem 0.34rem;
  line-height: 1;
  align-self: center;
}
.brand-name {
  font-family: var(--font-display);
  font-size: 1.14rem;
  letter-spacing: 0.01em;
  white-space: nowrap;
}
.brand-sub {
  display: none;
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  color: var(--faint);
  letter-spacing: 0.1em;
}
@media (min-width: 900px) { .brand-sub { display: inline; } }

.nav { display: flex; align-items: center; gap: clamp(0.9rem, 1.8vw, 1.7rem); }
.nav a {
  position: relative;
  font-size: var(--fs-sm);
  color: var(--ink-2);
  padding-block: 0.4rem;
  white-space: nowrap;
}
.nav a::after {
  content: "";
  position: absolute;
  left: 0; right: 0; bottom: 0.1rem;
  height: 1px;
  background: var(--accent);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--dur-base) var(--ease);
}
.nav a:hover::after, .nav a:focus-visible::after { transform: scaleX(1); }
.nav a[aria-current="page"] { color: var(--accent); }
.nav a[aria-current="page"]::after { transform: scaleX(1); }

.head-cta { display: none; }
@media (min-width: 1100px) { .head-cta { display: block; } }

/* 移动端菜单：details 实现，零 JS 依赖 */
.mnav { display: block; position: relative; }
.mnav > summary {
  list-style: none;
  cursor: pointer;
  border: 1px solid var(--ink);
  padding: 0.42rem 0.7rem;
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  letter-spacing: 0.12em;
}
.mnav > summary::-webkit-details-marker { display: none; }
.mnav[open] > summary { background: var(--ink); color: var(--paper); }
.mnav-list {
  position: absolute;
  right: 0;
  top: calc(100% + 0.5rem);
  min-width: 13rem;
  background: var(--card);
  border: 1px solid var(--ink);
  padding: 0.4rem 0;
  display: grid;
}
.mnav-list a {
  padding: 0.62rem 1rem;
  font-size: var(--fs-sm);
  border-bottom: 1px solid var(--rule-soft);
}
.mnav-list a:last-child { border-bottom: 0; }
.mnav-list a[aria-current="page"] { color: var(--accent); }
@media (min-width: 900px) { .mnav { display: none; } }
@media (max-width: 899px) { .nav { display: none; } }

/* ---------- 5. 首屏 ---------- */
.hero { padding-block: clamp(2.6rem, 6vw, 5rem) clamp(2.2rem, 4vw, 3.6rem); }
.hero-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.18fr) minmax(0, 0.82fr);
  gap: clamp(2rem, 5vw, 4.5rem);
  align-items: start;
}
@media (max-width: 899px) {
  .hero-grid { grid-template-columns: minmax(0, 1fr); }
  .fig { max-width: 30rem; }
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--muted);
}
.eyebrow::before {
  content: "";
  width: 1.6rem;
  height: 1px;
  background: var(--accent);
}
.hero h1 {
  font-family: var(--font-display);
  font-size: var(--fs-hero);
  font-weight: 700;
  line-height: 1.12;
  letter-spacing: -0.01em;
  margin-block: 1.1rem 1.4rem;
}
.hero h1 em {
  font-style: italic;
  color: var(--accent);
}
.hero-lead {
  font-size: var(--fs-md);
  line-height: 1.82;
  max-width: 34em;
  color: var(--ink-2);
}
.hero-lead code {
  background: var(--accent-soft);
  border: 1px solid color-mix(in srgb, var(--accent) 22%, transparent);
  padding: 0.04em 0.32em;
}
.hero-lead::first-letter { color: var(--accent); }
.hero-acts {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 2rem;
  padding-top: 1.6rem;
  border-top: 1px solid var(--rule);
}
.hero-foot {
  margin-top: 1.2rem;
  font-size: var(--fs-sm);
  color: var(--muted);
  display: flex;
  gap: 0.5rem;
  align-items: flex-start;
}
.hero-foot b { color: var(--ink-2); font-weight: 600; }

/* 竖排书脊：只在宽屏出现 */
.spine {
  display: none;
  position: fixed;
  left: 1.5rem;
  top: 50%;
  transform: translateY(-50%);
  writing-mode: vertical-rl;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.34em;
  text-transform: uppercase;
  color: var(--faint);
  z-index: 5;
  pointer-events: none;
}
@media (min-width: 1400px) { .spine { display: block; } }

/* ---------- 6. 按钮 ---------- */
.btn {
  position: relative;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  min-height: 2.9rem;
  padding: 0.72rem 1.35rem;
  border: 1px solid var(--ink);
  background: var(--ink);
  color: var(--paper);
  font-size: var(--fs-sm);
  letter-spacing: 0.04em;
  overflow: hidden;
  transition: color var(--dur-base) var(--ease), border-color var(--dur-base) var(--ease);
}
.btn::before {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--accent);
  transform: translateY(101%);
  transition: transform var(--dur-base) var(--ease);
}
.btn > * { position: relative; }
.btn:hover::before, .btn:focus-visible::before { transform: translateY(0); }
.btn:hover, .btn:focus-visible { color: var(--paper); border-color: var(--accent); }
.btn:active { transform: translateY(1px); }

.btn-ghost { background: transparent; color: var(--ink); }
.btn-ghost:hover, .btn-ghost:focus-visible { color: var(--paper); }
.btn-sm { min-height: 2.3rem; padding: 0.42rem 0.9rem; font-size: var(--fs-xs); }

.link-more {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-size: var(--fs-sm);
  color: var(--accent);
  border-bottom: 1px solid color-mix(in srgb, var(--accent) 40%, transparent);
  padding-bottom: 1px;
  transition: gap var(--dur-fast) var(--ease), border-color var(--dur-fast);
}
.link-more:hover { gap: 0.68rem; border-bottom-color: var(--accent); }

/* ---------- 7. 登录示意插图 ---------- */
.fig {
  border: 1px solid var(--ink);
  background: var(--card);
  padding: 0.55rem;
  position: relative;
}
.fig::before {
  content: "图 1";
  position: absolute;
  top: -0.72rem;
  left: 0.6rem;
  background: var(--paper);
  padding-inline: 0.4rem;
  font-family: var(--font-mono);
  font-size: 0.66rem;
  letter-spacing: 0.12em;
  color: var(--muted);
}
.fig-bar {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  border-bottom: 1px solid var(--rule);
  padding: 0.3rem 0.35rem 0.5rem;
}
.fig-dots { display: flex; gap: 0.22rem; }
.fig-dots i { width: 0.42rem; height: 0.42rem; border: 1px solid var(--ink); display: block; }
.fig-url {
  flex: 1;
  text-align: center;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  color: var(--muted);
  letter-spacing: 0.04em;
}
.fig-body { padding: 1.4rem 1rem 1rem; }
.qr-wrap { display: grid; place-items: center; gap: 0.9rem; }
.qr {
  width: min(12rem, 52%);
  aspect-ratio: 1;
  background: #fff;
  border: 1px solid var(--ink);
  padding: 0.5rem;
}
.qr svg { display: block; width: 100%; height: 100%; }
.qr-cap {
  font-size: 0.72rem;
  text-align: center;
  color: var(--muted);
  line-height: 1.6;
  max-width: 15rem;
}
.fig-note {
  margin-top: 1rem;
  padding-top: 0.8rem;
  border-top: 1px dashed var(--rule);
  font-family: var(--font-mono);
  font-size: 0.66rem;
  letter-spacing: 0.08em;
  color: var(--faint);
  display: flex;
  justify-content: space-between;
  gap: 0.6rem;
}

/* ---------- 8. 数据条 ---------- */
.strip {
  border-block: 1px solid var(--ink);
  display: grid;
  grid-template-columns: repeat(4, 1fr);
}
.strip > div {
  padding: 1.5rem 1.2rem;
  border-right: 1px solid var(--rule);
}
.strip > div:last-child { border-right: 0; }
.strip b {
  display: block;
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 3vw, 2.3rem);
  font-weight: 700;
  line-height: 1;
  font-variant-numeric: tabular-nums;
}
.strip span {
  display: block;
  margin-top: 0.55rem;
  font-size: var(--fs-xs);
  color: var(--muted);
  line-height: 1.6;
}
@media (max-width: 720px) {
  .strip { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .strip > div:nth-child(2) { border-right: 0; }
  .strip > div:nth-child(-n+2) { border-bottom: 1px solid var(--rule); }
}

/* ---------- 9. 章节 ---------- */
.sec { padding-block: clamp(2.8rem, 6vw, 5.2rem); }
.sec + .sec { border-top: 1px solid var(--rule); }
.sec-tint { background: var(--paper-2); }

.chapter {
  display: grid;
  grid-template-columns: 5.2rem minmax(0, 1fr);
  gap: clamp(0.8rem, 2.5vw, 2.2rem);
}
@media (max-width: 760px) {
  .chapter { grid-template-columns: minmax(0, 1fr); gap: 0.6rem; }
}
.chapter-num {
  font-family: var(--font-display);
  font-style: italic;
  font-size: clamp(1.5rem, 2.4vw, 2rem);
  color: var(--accent);
  line-height: 1;
  padding-top: 2.15rem;
  border-top: 2px solid var(--accent);
  font-variant-numeric: lining-nums;
}
@media (max-width: 760px) {
  .chapter-num { border-top-width: 1px; padding-top: 0.3rem; font-size: 1.15rem; display: inline-block; }
}

.sec-head { margin-bottom: clamp(1.6rem, 3vw, 2.6rem); }
.sec-tag {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 0.7rem;
}
h2.sec-title {
  font-family: var(--font-display);
  font-size: var(--fs-2xl);
  font-weight: 700;
  line-height: 1.14;
  letter-spacing: -0.01em;
  max-width: 22em;
  text-wrap: balance;
}
.sec-sub {
  margin-top: 0.95rem;
  color: var(--muted);
  max-width: 40em;
  font-size: var(--fs-base);
}

h3 { font-size: var(--fs-lg); font-weight: 600; line-height: 1.4; letter-spacing: 0; }
h4 {
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--muted);
  font-weight: 400;
}

.prose { max-width: var(--measure); }
.prose p + p { margin-top: 1.05em; }
.prose h2 { margin-top: 2.4rem; }
.prose h3 { margin-top: 2rem; margin-bottom: 0.7rem; }
.prose ul, .prose ol { margin-block: 1rem; padding-left: 1.15rem; }
.prose li { margin-block: 0.45rem; }
.prose li::marker { color: var(--accent); }
.prose strong { font-weight: 600; }
.prose code {
  background: var(--accent-soft);
  padding: 0.1em 0.35em;
  color: var(--ink);
  border: 1px solid color-mix(in srgb, var(--accent) 22%, transparent);
}

/* 首字下沉：只在长文首段使用 */
.dropcap::first-letter {
  float: left;
  font-family: var(--font-display);
  font-size: 3.6em;
  line-height: 0.82;
  padding: 0.08em 0.12em 0 0;
  color: var(--accent);
}

/* ---------- 10. 目录 ---------- */
.toc {
  border-top: 2px solid var(--ink);
  margin-top: 2rem;
}
.toc ol { list-style: none; }
.toc li { border-bottom: 1px solid var(--rule); }
.toc a {
  display: grid;
  grid-template-columns: 3.2rem 1fr auto;
  align-items: baseline;
  gap: 0.8rem;
  padding: 0.95rem 0.2rem;
  transition: padding-left var(--dur-fast) var(--ease), color var(--dur-fast);
}
.toc a:hover { padding-left: 0.7rem; color: var(--accent); }
.toc .toc-n {
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  color: var(--faint);
}
.toc .toc-t {
  font-family: var(--font-display);
  font-size: var(--fs-md);
}
.toc .toc-p {
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  color: var(--faint);
}

/* ---------- 11. 卡片网格 ---------- */
.grid { display: grid; gap: clamp(1rem, 2vw, 1.5rem); }
.g2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.g3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.g4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
@media (max-width: 980px) { .g4 { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
@media (max-width: 760px) {
  .g2, .g3, .g4 { grid-template-columns: minmax(0, 1fr); }
}

.card {
  border: 1px solid var(--rule);
  background: var(--card);
  padding: clamp(1.1rem, 2vw, 1.6rem);
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
  transition: border-color var(--dur-fast) var(--ease), transform var(--dur-base) var(--ease);
}
.card:hover { border-color: var(--ink); transform: translateY(-2px); }
.card h3 { font-family: var(--font-display); font-size: 1.16rem; }
.card p { font-size: var(--fs-sm); color: var(--ink-2); line-height: 1.78; }
.card .num {
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  color: var(--accent);
  letter-spacing: 0.12em;
}

/* ---------- 12. 步骤 ---------- */
.steps { list-style: none; display: grid; gap: 0; border-top: 1px solid var(--ink); }
.steps li {
  display: grid;
  grid-template-columns: 4.6rem minmax(0, 1fr);
  gap: 1.2rem;
  padding: 1.5rem 0;
  border-bottom: 1px solid var(--rule);
}
@media (max-width: 600px) {
  .steps li { grid-template-columns: 3rem minmax(0, 1fr); gap: 0.8rem; }
}
.steps .n {
  font-family: var(--font-display);
  font-style: italic;
  font-size: 2.1rem;
  line-height: 1;
  color: var(--accent);
  font-variant-numeric: lining-nums;
}
.steps h3 { margin-bottom: 0.4rem; font-size: var(--fs-md); font-family: var(--font-display); }
.steps p { color: var(--ink-2); font-size: var(--fs-sm); max-width: 42em; }

/* ---------- 13. 表格 ---------- */
.tbl-wrap { overflow-x: auto; max-width: 100%; margin-block: 1.2rem; }
.tbl { font-size: var(--fs-sm); min-width: 34rem; }
.tbl caption {
  caption-side: top;
  text-align: left;
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  color: var(--muted);
  letter-spacing: 0.1em;
  padding-bottom: 0.6rem;
}
.tbl th {
  text-align: left;
  font-weight: 600;
  font-size: var(--fs-xs);
  letter-spacing: 0.08em;
  padding: 0.7rem 0.8rem;
  border-top: 1.5px solid var(--ink);
  border-bottom: 1px solid var(--ink);
  white-space: nowrap;
}
.tbl td {
  padding: 0.78rem 0.8rem;
  border-bottom: 1px solid var(--rule);
  vertical-align: top;
  line-height: 1.7;
}
.tbl tbody tr:hover { background: color-mix(in srgb, var(--accent) 5%, transparent); }
.tbl .num-cell { font-family: var(--font-mono); font-variant-numeric: tabular-nums; white-space: nowrap; }

.badge {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.06em;
  padding: 0.12rem 0.42rem;
  border: 1px solid currentColor;
  white-space: nowrap;
}
.badge.ok { color: var(--ok); background: var(--ok-soft); }
.badge.no { color: var(--no); background: transparent; }
.badge.part { color: var(--muted); }

/* ---------- 14. 提示块 ---------- */
.note {
  border-left: 3px solid var(--accent);
  background: color-mix(in srgb, var(--accent) 6%, var(--paper));
  padding: 1.05rem 1.2rem;
  margin-block: 1.4rem;
  font-size: var(--fs-sm);
  color: var(--ink-2);
}
.note strong { color: var(--ink); }
.note p + p { margin-top: 0.6rem; }
.note-title {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 0.35rem;
}

.tip {
  font-size: var(--fs-sm);
  color: var(--muted);
  margin-top: 1.1rem;
  line-height: 1.8;
}

/* 引言块 */
.pull {
  font-family: var(--font-display);
  font-size: clamp(1.25rem, 2.4vw, 1.7rem);
  line-height: 1.55;
  letter-spacing: -0.005em;
  border-top: 1px solid var(--ink);
  border-bottom: 1px solid var(--ink);
  padding-block: 1.3rem;
  margin-block: 2rem;
  color: var(--ink);
}
.pull cite {
  display: block;
  margin-top: 0.8rem;
  font-family: var(--font-mono);
  font-style: normal;
  font-size: var(--fs-xs);
  letter-spacing: 0.1em;
  color: var(--muted);
}

/* ---------- 15. FAQ ---------- */
.faq { border-top: 2px solid var(--ink); }
.faq details { border-bottom: 1px solid var(--rule); }
.faq summary {
  cursor: pointer;
  list-style: none;
  display: flex;
  align-items: flex-start;
  gap: 1rem;
  padding: 1.15rem 0.1rem;
  font-family: var(--font-display);
  font-size: var(--fs-md);
  line-height: 1.6;
  transition: color var(--dur-fast);
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after {
  content: "+";
  margin-left: auto;
  font-family: var(--font-mono);
  font-size: 1.1rem;
  color: var(--accent);
  line-height: 1.4;
}
.faq details[open] summary { color: var(--accent); }
.faq details[open] summary::after { content: "\2212"; }
.faq summary:hover { color: var(--accent); }
.faq .ans { padding: 0 0.1rem 1.4rem; max-width: var(--measure); color: var(--ink-2); font-size: var(--fs-sm); }
.faq .ans p + p { margin-top: 0.7rem; }
.faq .ans ul { margin-top: 0.6rem; padding-left: 1.1rem; }
.faq .ans li { margin-block: 0.35rem; }

/* ---------- 16. 面包屑 ---------- */
.crumb {
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  color: var(--faint);
  padding-block: 1.1rem 0;
  letter-spacing: 0.04em;
}
.crumb ol { list-style: none; display: flex; flex-wrap: wrap; gap: 0.45rem; }
.crumb li { display: flex; gap: 0.45rem; }
.crumb li:not(:last-child)::after { content: "/"; color: var(--rule); }
.crumb a { border-bottom: 1px solid transparent; }
.crumb a:hover { color: var(--accent); border-bottom-color: var(--accent); }
.crumb [aria-current="page"] { color: var(--muted); }

/* ---------- 17. 页内页头 ---------- */
.page-head { padding-block: clamp(1.6rem, 4vw, 3rem) clamp(1.8rem, 4vw, 3.2rem); }
.page-head h1 {
  font-family: var(--font-display);
  font-size: clamp(1.95rem, 3.7vw, 2.9rem);
  line-height: 1.16;
  letter-spacing: -0.012em;
  max-width: 20em;
  text-wrap: balance;
  margin-block: 0.8rem 1.1rem;
}
.page-head .lead {
  font-size: var(--fs-md);
  color: var(--ink-2);
  max-width: 36em;
}
.meta-line {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem 1.2rem;
  margin-top: 1.5rem;
  padding-top: 0.9rem;
  border-top: 1px solid var(--rule);
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  color: var(--faint);
  letter-spacing: 0.06em;
}

/* ---------- 18. 相关链接 ---------- */
.related {
  border-top: 1px solid var(--ink);
  padding-top: 1.4rem;
  margin-top: clamp(2rem, 4vw, 3.4rem);
}
.related h2 {
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted);
  font-weight: 400;
  margin-bottom: 1rem;
}
.related ul { list-style: none; display: grid; gap: 0; }
.related li { border-bottom: 1px solid var(--rule-soft); }
.related a {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: baseline;
  padding: 0.85rem 0.1rem;
  transition: color var(--dur-fast), padding-left var(--dur-fast) var(--ease);
}
.related a:hover { color: var(--accent); padding-left: 0.5rem; }
.related .rt { font-size: var(--fs-sm); }
.related .rd { font-size: var(--fs-xs); color: var(--faint); white-space: nowrap; }

/* ---------- 19. 页脚版权页 ---------- */
.colophon {
  border-top: 2px solid var(--ink);
  margin-top: clamp(2rem, 5vw, 4rem);
  padding-block: clamp(2rem, 4vw, 3rem) 2rem;
  font-size: var(--fs-sm);
}
.colo-grid {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr;
  gap: clamp(1.5rem, 4vw, 3rem);
}
@media (max-width: 760px) { .colo-grid { grid-template-columns: minmax(0, 1fr); } }
.colo-col h2 {
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted);
  font-weight: 400;
  margin-bottom: 0.8rem;
}
.colo-col ul { list-style: none; display: grid; gap: 0.5rem; }
.colo-col a { font-size: var(--fs-sm); border-bottom: 1px solid transparent; }
.colo-col a:hover { color: var(--accent); border-bottom-color: var(--accent); }
.colo-col p { color: var(--muted); font-size: var(--fs-sm); line-height: 1.8; }
.colo-foot {
  margin-top: 2.2rem;
  padding-top: 1rem;
  border-top: 1px solid var(--rule);
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem 1.5rem;
  justify-content: space-between;
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  color: var(--faint);
  letter-spacing: 0.06em;
}

/* ---------- 20. 404 ---------- */
.err {
  min-height: 62vh;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  align-content: center;
  gap: 1.2rem;
  padding-block: 4rem;
}
.err-code {
  font-family: var(--font-display);
  font-size: clamp(4rem, 14vw, 9rem);
  line-height: 0.9;
  letter-spacing: -0.04em;
  color: var(--accent);
}
.err h1 { font-family: var(--font-display); font-size: var(--fs-2xl); }
.err p { color: var(--muted); max-width: 34em; }

/* ---------- 21. 入场动效 ---------- */
@media (prefers-reduced-motion: no-preference) {
  @keyframes rise {
    from { opacity: 0; transform: translateY(16px); }
    to { opacity: 1; transform: none; }
  }
  .anim { animation: rise var(--dur-slow) var(--ease) both; }
  .anim-2 { animation-delay: 90ms; }
  .anim-3 { animation-delay: 180ms; }
  .anim-4 { animation-delay: 270ms; }

  /* 只有 JS 生效后才隐藏，无 JS 时内容照常可见 */
  .js .reveal { opacity: 0; transform: translateY(18px); }
  .reveal.in {
    opacity: 1;
    transform: none;
    transition: opacity var(--dur-slow) var(--ease), transform var(--dur-slow) var(--ease);
  }
  .reveal:nth-child(2) { transition-delay: 70ms; }
  .reveal:nth-child(3) { transition-delay: 140ms; }
  .reveal:nth-child(4) { transition-delay: 210ms; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; }
  .reveal { opacity: 1; transform: none; }
}

/* ---------- 22. 打印 ---------- */
@media print {
  .masthead, .head-cta, .related, .sheet::before, .sheet::after, .spine, .grain { display: none !important; }
  body { background: #fff; color: #000; font-size: 11pt; }
  .sec { padding-block: 1.2rem; }
  a[href^="http"]::after { content: " (" attr(href) ")"; font-size: 8pt; color: #555; }
}

/* ---------- 23. 小屏微调 ---------- */
@media (max-width: 480px) {
  .brand-name { font-size: 0.98rem; }
  .brand { min-width: 0; }
  .mnav { flex: none; }
  @supports (background: color-mix(in srgb, #000 50%, #fff)) {
  .masthead { background: color-mix(in srgb, var(--paper) 94%, transparent); }
}
.masthead-in { gap: 0.6rem; }
  .hero h1 { letter-spacing: -0.02em; }
  .toc a { grid-template-columns: 2.4rem 1fr; }
  .toc .toc-p { display: none; }
  .hero-acts { gap: 0.55rem; }
  .hero-acts .btn { flex: 1 1 auto; justify-content: center; padding-inline: 0.9rem; }
  .hero-acts .btn:first-child { flex: 1 1 100%; }
}