/* =========================================================
   期权方法论 · 全站样式 (Institutional Research Style)
   配色：白底 · Navy · Orange · Gold (统一全项目)
   ========================================================= */

:root {
  /* 纸面层 */
  --paper:        #ffffff;
  --paper-soft:   #fafafa;
  --paper-pale:   #f3f4f6;
  --paper-tint:   #e8eef3;     /* navy tinted */
  --paper-warm:   #fef3e2;     /* orange tinted */

  /* 文字层 */
  --ink:          #111827;     /* 主文字 */
  --ink-soft:     #374151;     /* 正文 */
  --ink-muted:    #6b7280;     /* 说明 / caption */
  --ink-faint:    #9ca3af;     /* placeholder */

  /* 分割线 */
  --rule:         #e5e7eb;
  --rule-strong:  #d1d5db;

  /* 主色（机构研报标准） */
  --navy:         #1a3a52;
  --navy-soft:    #2e5a7a;
  --navy-pale:    #e8eef3;

  --orange:       #d97706;
  --orange-soft:  #f59e0b;
  --orange-pale:  #fef3e2;

  --gold:         #a87f1d;
  --red:          #9d2c2c;
  --green:        #1f7a4a;
  --gray:         #6b7280;

  /* 字体 */
  --font-sans: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI",
               "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei",
               sans-serif;
  --font-mono: "JetBrains Mono", "SF Mono", "Menlo", Consolas, monospace;
  --font-num:  "JetBrains Mono", "SF Mono", "Menlo", monospace;

  /* 度量 */
  --radius-md: 4px;
  --radius-sm: 2px;
  --shadow-xs: 0 1px 2px rgba(15, 23, 42, 0.04);
  --shadow-sm: 0 2px 6px rgba(15, 23, 42, 0.06);
  --shadow-md: 0 4px 12px rgba(15, 23, 42, 0.08);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
html, body { min-height: 100%; }
html {
  -webkit-text-size-adjust: 100%;
  overflow-x: clip; /* 不建立 scroll container，sticky header 不受影响 */
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink-soft);
  font-family: var(--font-sans);
  font-size: 15.5px;
  line-height: 1.7;
  font-feature-settings: "kern" 1, "tnum" 0;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a {
  color: var(--navy);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color 0.12s, color 0.12s;
}
a:hover {
  color: var(--navy-soft);
  border-bottom-color: var(--navy);
}

::selection { background: var(--paper-tint); color: var(--ink); }

/* =========================================================
   章节布局：左 TOC + 主内容 + 右锚点
   ========================================================= */

.book-layout {
  display: grid;
  grid-template-columns: 240px minmax(0, 1fr) 200px;
  max-width: 1320px;
  margin: 0 auto;
  gap: 40px;
  padding: 0 32px;
}

@media (max-width: 1100px) {
  .book-layout { grid-template-columns: 220px 1fr; }
  .book-layout .chapter-anchors { display: none; }
}
@media (max-width: 800px) {
  .book-layout { grid-template-columns: 1fr; padding: 0 18px; }
  .book-layout .book-toc { display: none; }
}

@media (max-width: 600px) {
  .book-layout { padding: 0 16px; gap: 0; }
  .chapter-main { padding: 36px 0 64px; }
  h1.chapter-title { font-size: 28px; line-height: 1.18; }
  .chapter-subtitle { font-size: 15px; margin-bottom: 24px; }
  p.lede {
    font-size: 14.5px;
    padding: 14px 16px;
    margin: 0 0 28px;
  }
  .chapter-main h2 { font-size: 19px; margin: 40px 0 12px; }
  .chapter-main h2 .num { font-size: 14px; margin-right: 8px; }
  .chapter-main h3 { font-size: 14.5px; margin: 22px 0 8px; }
  .chapter-main p { font-size: 14.5px; }
  .chapter-main li { font-size: 14.5px; }
  .chapter-main table { font-size: 12.5px; display: block; overflow-x: auto; }
  .chapter-main th, .chapter-main td { padding: 8px 10px; }
  .callout { padding: 12px 14px; margin: 18px 0; font-size: 13.5px; }
  pre { padding: 14px 16px; font-size: 12px; }
  .katex-display { font-size: 0.95em !important; padding: 14px 0; overflow-x: auto; }
  .chapter-nav { flex-direction: column; gap: 10px; margin-top: 48px; }
  .chapter-nav a { padding: 12px 14px; }
  details.derivation summary { padding: 10px 14px; font-size: 12px; }
  details.derivation > *:not(summary) { padding: 0 14px; }
}

/* =========================================================
   顶部 sticky header
   ========================================================= */

.book-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--rule);
}

.book-header-inner {
  max-width: 1320px;
  margin: 0 auto;
  padding: 14px 32px;
  display: flex;
  align-items: center;
  gap: 24px;
  min-width: 0;
}

.book-header .crumbs {
  font-size: 12px;
  color: var(--ink-muted);
  letter-spacing: 0.04em;
  min-width: 0;
  flex: 1 1 auto;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.book-header .crumbs a {
  color: var(--ink-muted);
  border-bottom: none;
}
.book-header .crumbs a:hover { color: var(--navy); }
.book-header .crumbs strong {
  color: var(--ink);
  font-weight: 600;
}
.book-header .crumbs .sep {
  margin: 0 8px;
  color: var(--ink-faint);
}

.book-header .home-link {
  margin-left: auto;
  font-size: 12px;
  letter-spacing: 0.04em;
  color: var(--ink-muted);
  border-bottom: none;
  white-space: nowrap;
  flex: 0 0 auto;
}
.book-header .home-link:hover { color: var(--navy); }

@media (max-width: 600px) {
  .book-header-inner { padding: 11px 18px; gap: 14px; }
  .book-header .crumbs { font-size: 11.5px; }
  .book-header .home-link { font-size: 11.5px; }
}

#scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  height: 3px;
  width: 0;
  background: var(--orange);
  z-index: 200;
  transition: width 0.08s linear;
  pointer-events: none;
}

/* =========================================================
   左侧 TOC 侧栏
   ========================================================= */

.book-toc {
  position: sticky;
  top: 64px;
  align-self: start;
  padding: 32px 0;
  max-height: calc(100vh - 64px);
  overflow-y: auto;
  font-size: 12.5px;
}

.book-toc::-webkit-scrollbar { width: 4px; }
.book-toc::-webkit-scrollbar-thumb { background: var(--rule-strong); border-radius: 2px; }

.book-toc .toc-part { margin-bottom: 22px; }

.book-toc .toc-part-label {
  font-size: 10px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--ink-muted);
  font-weight: 600;
  margin-bottom: 8px;
  padding-left: 2px;
}

.book-toc .toc-chapter {
  display: block;
  padding: 6px 10px;
  color: var(--ink-soft);
  border-left: 2px solid transparent;
  line-height: 1.45;
  border-bottom: none;
}
.book-toc .toc-chapter:hover {
  color: var(--ink);
  background: var(--paper-soft);
}
.book-toc .toc-chapter.active {
  color: var(--navy);
  border-left-color: var(--navy);
  background: var(--navy-pale);
  font-weight: 500;
}
.book-toc .toc-chapter .num {
  color: var(--ink-muted);
  margin-right: 6px;
  font-variant-numeric: tabular-nums;
  font-family: var(--font-num);
  font-size: 11px;
}
.book-toc .toc-chapter.active .num { color: var(--navy); }

/* =========================================================
   右侧章内锚点
   ========================================================= */

.chapter-anchors {
  position: sticky;
  top: 64px;
  align-self: start;
  padding: 32px 0;
  font-size: 12px;
}
.chapter-anchors .label {
  font-size: 10px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--ink-muted);
  font-weight: 600;
  margin-bottom: 12px;
}
.chapter-anchors a {
  display: block;
  padding: 5px 0 5px 12px;
  color: var(--ink-muted);
  border-left: 2px solid transparent;
  line-height: 1.5;
  border-bottom: none;
}
.chapter-anchors a:hover { color: var(--ink); }
.chapter-anchors a.active {
  color: var(--navy);
  border-left-color: var(--navy);
}

/* =========================================================
   主内容区
   ========================================================= */

.chapter-main {
  padding: 56px 0 96px;
  max-width: 720px;
  color: var(--ink-soft);
}

.eyebrow {
  display: inline-block;
  font-size: 10.5px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--orange);
  font-weight: 700;
  margin-bottom: 14px;
}

h1.chapter-title {
  font-family: var(--font-sans);
  font-size: 36px;
  line-height: 1.2;
  font-weight: 700;
  letter-spacing: -0.015em;
  color: var(--ink);
  margin: 0 0 10px;
}

.chapter-subtitle {
  font-size: 17px;
  font-weight: 400;
  color: var(--ink-muted);
  margin: 0 0 32px;
  line-height: 1.5;
}

p.lede {
  font-size: 16.5px;
  line-height: 1.65;
  color: var(--ink-soft);
  margin: 0 0 40px;
  padding: 18px 22px 18px 22px;
  background: var(--paper-soft);
  border-left: 3px solid var(--navy);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

.chapter-main h2 {
  font-family: var(--font-sans);
  font-size: 22px;
  font-weight: 700;
  color: var(--ink);
  margin: 56px 0 14px;
  letter-spacing: -0.005em;
  scroll-margin-top: 80px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--rule);
}
.chapter-main h2 .num {
  color: var(--orange);
  margin-right: 10px;
  font-variant-numeric: tabular-nums;
  font-family: var(--font-num);
  font-weight: 600;
  font-size: 16px;
}

.chapter-main h3 {
  font-family: var(--font-sans);
  font-size: 15px;
  font-weight: 600;
  letter-spacing: 0;
  color: var(--ink);
  margin: 28px 0 10px;
  scroll-margin-top: 80px;
}

.chapter-main h4 {
  font-family: var(--font-sans);
  font-size: 11.5px;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-muted);
  margin: 24px 0 6px;
}

.chapter-main p { margin: 12px 0; }

.chapter-main ul, .chapter-main ol {
  padding-left: 22px;
  margin: 12px 0;
}
.chapter-main li {
  margin-bottom: 6px;
}
.chapter-main li::marker {
  color: var(--orange);
}

.chapter-main strong { color: var(--ink); }

/* =========================================================
   术语 (term)
   ========================================================= */

.term {
  border-bottom: 1px dotted var(--navy);
  color: var(--navy);
  cursor: help;
  transition: color 0.12s;
}
.term:hover {
  color: var(--orange);
  border-bottom-color: var(--orange);
}

#term-tooltip {
  position: fixed;
  z-index: 1000;
  max-width: 320px;
  background: var(--paper);
  border: 1px solid var(--rule-strong);
  border-radius: var(--radius-md);
  padding: 14px 16px;
  box-shadow: var(--shadow-md);
  font-family: var(--font-sans);
  font-size: 13px;
  line-height: 1.5;
  color: var(--ink-soft);
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.12s;
}
#term-tooltip.visible { opacity: 1; }
#term-tooltip .tooltip-title {
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--navy);
  font-weight: 700;
  margin-bottom: 4px;
}
#term-tooltip .tooltip-en {
  color: var(--ink-muted);
  font-style: italic;
  font-weight: 400;
  font-size: 11px;
  margin-left: 6px;
  letter-spacing: 0;
  text-transform: none;
}
#term-tooltip .tooltip-body {
  color: var(--ink-soft);
  margin-top: 6px;
}

/* =========================================================
   代码 / 公式
   ========================================================= */

code {
  font-family: var(--font-mono);
  font-size: 13px;
  background: var(--paper-pale);
  color: var(--navy);
  padding: 1px 6px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--rule);
}

pre {
  background: var(--paper-soft);
  color: var(--ink-soft);
  font-family: var(--font-mono);
  font-size: 12.5px;
  line-height: 1.6;
  padding: 18px 22px;
  border: 1px solid var(--rule);
  border-left: 3px solid var(--navy);
  border-radius: var(--radius-md);
  overflow-x: auto;
  margin: 18px 0 22px;
}
pre code {
  background: none;
  border: none;
  padding: 0;
  color: inherit;
}

/* KaTeX 调整以适应白底 */
.katex { font-size: 1.05em !important; color: var(--ink); }
.katex-display {
  margin: 22px 0 !important;
  padding: 18px 0;
  border-top: 1px solid var(--rule);
  border-bottom: 1px solid var(--rule);
  background: var(--paper-soft);
}
.katex-display > .katex {
  font-size: 1.15em !important;
}

/* =========================================================
   callout
   ========================================================= */

.callout {
  margin: 22px 0;
  padding: 14px 20px;
  background: var(--paper-soft);
  border-left: 3px solid var(--navy);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  font-size: 14px;
  line-height: 1.6;
  color: var(--ink-soft);
}
.callout strong { color: var(--ink); }
.callout p { margin: 8px 0; }
.callout p:first-child { margin-top: 0; }
.callout p:last-child { margin-bottom: 0; }

.callout::before {
  content: "Note";
  display: block;
  font-size: 9.5px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--navy);
  font-weight: 700;
  margin-bottom: 8px;
}

.callout.note {
  border-left-color: var(--gray);
  background: var(--paper-pale);
}
.callout.note::before { content: "Aside"; color: var(--gray); }

.callout.warn {
  border-left-color: var(--orange);
  background: var(--orange-pale);
}
.callout.warn::before { content: "Caution"; color: var(--orange); }

.callout.inference {
  border-left-color: var(--gold);
  background: #faf5e8;
}
.callout.inference::before { content: "Editorial Inference"; color: var(--gold); }

.callout.formula {
  border-left-color: var(--navy);
  background: var(--navy-pale);
}
.callout.formula::before { content: "Formula"; color: var(--navy); }

/* =========================================================
   可折叠推导
   ========================================================= */

details.derivation {
  margin: 22px 0;
  border: 1px solid var(--rule);
  border-radius: var(--radius-md);
  background: var(--paper-soft);
  font-size: 14px;
}
details.derivation summary {
  padding: 12px 18px;
  cursor: pointer;
  color: var(--navy);
  font-size: 12.5px;
  font-weight: 600;
  letter-spacing: 0.02em;
  list-style: none;
  position: relative;
}
details.derivation summary::-webkit-details-marker { display: none; }
details.derivation summary::before {
  content: "▸";
  margin-right: 10px;
  display: inline-block;
  color: var(--orange);
  transition: transform 0.15s;
}
details.derivation[open] summary::before { transform: rotate(90deg); }
details.derivation > *:not(summary) {
  padding: 0 20px;
}
details.derivation > *:last-child {
  padding-bottom: 16px;
}

/* =========================================================
   图 figure
   ========================================================= */

figure.case-figure,
figure.concept-figure {
  margin: 32px 0;
  padding: 0;
}

figure.case-figure img,
figure.concept-figure img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  border-radius: var(--radius-sm);
  border: 1px solid var(--rule);
  background: var(--paper);
}

figure.concept-figure svg {
  display: block;
  width: 100%;
  height: auto;
  background: var(--paper);
  border: 1px solid var(--rule);
  border-radius: var(--radius-sm);
}

figcaption {
  margin-top: 10px;
  font-family: var(--font-sans);
  font-size: 12.5px;
  color: var(--ink-muted);
  line-height: 1.55;
  border-top: 1px solid var(--rule);
  padding-top: 8px;
}
figcaption .fig-num {
  color: var(--navy);
  font-weight: 700;
  margin-right: 6px;
  font-variant-numeric: tabular-nums;
}
figcaption .fig-title {
  color: var(--ink);
  font-weight: 600;
}

/* =========================================================
   交互滑块
   ========================================================= */

.slider-demo {
  margin: 32px 0;
  padding: 22px;
  background: var(--paper-soft);
  border: 1px solid var(--rule);
  border-radius: var(--radius-md);
}
.slider-demo label {
  display: block;
  font-size: 12.5px;
  color: var(--ink-muted);
  margin-bottom: 6px;
  font-weight: 500;
}
.slider-demo input[type="range"] {
  width: 100%;
  accent-color: var(--navy);
}
.slider-demo .value {
  font-family: var(--font-num);
  color: var(--navy);
  font-size: 13.5px;
  font-weight: 600;
  margin-left: 8px;
  display: inline-block;
  min-width: 3.5em;
  text-align: right;
}
/* label 至少 2 行高, 防止数值变长导致下方内容上下跳 */
.slider-demo label {
  min-height: 38px;
}

/* ---------------------------------------------------------
   .slider-demo 内部三种标准 grid · auto-fit 自然响应
   写新章节交互件时一律用这三个 class · 不要在 HTML 里写内联 grid
   --------------------------------------------------------- */

/* 滑块输入行 · 自动从 N 列折到单列 (每格最小 180px) */
.slider-demo .slider-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 16px;
  margin-bottom: 18px;
}

/* 实时读数卡片行 · 自动从 N 列折到 2 列再到 1 列 (每格最小 110px) */
.slider-demo .readout-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(110px, 1fr));
  gap: 12px;
  padding: 12px;
  background: var(--paper);
  border: 1px solid var(--rule);
  border-radius: 4px;
  margin-bottom: 16px;
}

/* SVG 小多图面板 · 自动从 2 列折到 1 列 (每格最小 260px) */
.slider-demo .panel-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 14px;
}

/* 手机版 · 收紧 padding / 字号 */
@media (max-width: 600px) {
  .slider-demo { padding: 14px; margin: 24px 0; }
  .slider-demo h4 { font-size: 14.5px; }
  .slider-demo label { font-size: 11.5px; }
  .slider-demo .value { font-size: 12.5px; margin-left: 4px; }
  .slider-demo .slider-row { gap: 12px; }
  .slider-demo .readout-row { gap: 10px; padding: 10px; }
}

/* =========================================================
   章末导航
   ========================================================= */

.chapter-nav {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin-top: 72px;
  padding-top: 24px;
  border-top: 1px solid var(--rule);
}
.chapter-nav a {
  flex: 1;
  display: block;
  padding: 16px 20px;
  background: var(--paper);
  border: 1px solid var(--rule);
  border-radius: var(--radius-md);
  transition: border-color 0.12s, background 0.12s;
  color: var(--ink-soft);
  border-bottom-width: 1px;
}
.chapter-nav a:hover {
  border-color: var(--navy);
  background: var(--paper-soft);
}
.chapter-nav a.next { text-align: right; }
.chapter-nav .nav-direction {
  font-size: 10.5px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--ink-muted);
  font-weight: 600;
  margin-bottom: 4px;
}
.chapter-nav .nav-title {
  font-size: 14px;
  color: var(--ink);
  font-weight: 500;
}

/* =========================================================
   表格 (Bloomberg / 研报风格)
   ========================================================= */

.chapter-main table {
  width: 100%;
  border-collapse: collapse;
  margin: 18px 0 26px;
  font-size: 13.5px;
  font-feature-settings: "tnum" 1;
}
.chapter-main th, .chapter-main td {
  text-align: left;
  padding: 10px 12px;
  border-bottom: 1px solid var(--rule);
  vertical-align: top;
}
.chapter-main th {
  font-size: 10.5px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--ink-muted);
  font-weight: 700;
  border-bottom: 2px solid var(--ink);
  background: var(--paper-soft);
}
.chapter-main tr:hover td { background: var(--paper-soft); }

.chapter-main td.num,
.chapter-main td.numeric {
  font-family: var(--font-num);
  text-align: right;
}

/* =========================================================
   首页 (index.html) 专用
   ========================================================= */

.book-cover {
  max-width: 920px;
  margin: 0 auto;
  padding: 80px 32px 56px;
}

.book-cover .cover-meta {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 12px;
  flex-wrap: wrap;
  font-size: 11px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--ink-muted);
  margin-bottom: 36px;
  padding-bottom: 16px;
  border-bottom: 2px solid var(--ink);
}
.book-cover .cover-meta strong {
  color: var(--ink);
  font-weight: 700;
}

.book-cover h1 {
  font-family: var(--font-sans);
  font-size: 56px;
  line-height: 1.05;
  font-weight: 700;
  letter-spacing: -0.025em;
  color: var(--ink);
  margin: 0 0 14px;
}
.book-cover h1 .subtitle {
  display: block;
  color: var(--ink-muted);
  font-weight: 400;
  font-size: 32px;
  margin-top: 6px;
  letter-spacing: -0.015em;
}

.book-cover .tagline {
  font-size: 17px;
  color: var(--ink-soft);
  max-width: 620px;
  margin: 0 0 36px;
  line-height: 1.6;
}

.book-cover .progress-bar {
  margin: 24px 0 0;
  padding: 16px 22px;
  background: var(--paper-soft);
  border: 1px solid var(--rule);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  gap: 18px;
}
.book-cover .progress-bar .progress-label {
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-muted);
  font-weight: 600;
  white-space: nowrap;
}
.book-cover .progress-bar .progress-track {
  flex: 1;
  height: 4px;
  background: var(--rule);
  border-radius: 2px;
  overflow: hidden;
}
.book-cover .progress-bar .progress-fill {
  height: 100%;
  background: var(--orange);
}
.book-cover .progress-bar .progress-numbers {
  font-family: var(--font-num);
  font-size: 13px;
  color: var(--ink);
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}

/* TOC list */

.cover-toc {
  max-width: 920px;
  margin: 0 auto 96px;
  padding: 0 32px;
}

.cover-toc .part-section {
  margin-bottom: 32px;
}

.cover-toc .part-header {
  display: flex;
  align-items: baseline;
  gap: 16px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--rule);
  margin-bottom: 12px;
}
.cover-toc .part-label {
  font-size: 10.5px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--orange);
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}
.cover-toc .part-name {
  font-family: var(--font-sans);
  font-size: 18px;
  font-weight: 700;
  color: var(--ink);
  letter-spacing: -0.005em;
}
.cover-toc .part-count {
  margin-left: auto;
  font-size: 11px;
  color: var(--ink-muted);
  font-family: var(--font-num);
}

.cover-toc .chapter-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0 24px;
}

.cover-toc .chapter-list li {
  border-bottom: 1px dotted var(--rule);
}

.cover-toc .chapter-list a {
  display: flex;
  padding: 10px 0;
  align-items: baseline;
  gap: 10px;
  font-size: 14px;
  color: var(--ink-soft);
  border-bottom: none;
  min-width: 0;
}
.cover-toc .chapter-list a:hover {
  color: var(--navy);
}

.cover-toc .chapter-list .ch-num {
  color: var(--ink-muted);
  font-family: var(--font-num);
  font-variant-numeric: tabular-nums;
  font-size: 12px;
  font-weight: 500;
  min-width: 28px;
  flex: 0 0 auto;
}

.cover-toc .chapter-list .ch-title {
  flex: 1 1 auto;
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.cover-toc .chapter-list .ch-status {
  flex: 0 0 auto;
}

.cover-toc .chapter-list .ch-status {
  font-size: 9.5px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  font-weight: 700;
  padding: 2px 7px;
  border-radius: 2px;
  white-space: nowrap;
  font-family: var(--font-sans);
}
.cover-toc .chapter-list .ch-status.ready {
  color: var(--navy);
  background: var(--navy-pale);
}
.cover-toc .chapter-list .ch-status.pilot {
  color: var(--paper);
  background: var(--orange);
}
.cover-toc .chapter-list .ch-status.wip {
  color: var(--ink-faint);
  background: transparent;
  border: 1px dashed var(--rule-strong);
}

.cover-toc .chapter-list a.unbuilt {
  color: var(--ink-faint);
  cursor: not-allowed;
}
.cover-toc .chapter-list a.unbuilt:hover {
  color: var(--ink-faint);
}
.cover-toc .chapter-list a.unbuilt .ch-num {
  color: var(--ink-faint);
}

@media (max-width: 720px) {
  .book-cover h1 { font-size: 38px; }
  .book-cover h1 .subtitle { font-size: 24px; }
  .cover-toc .chapter-list { grid-template-columns: 1fr; }
}

@media (max-width: 600px) {
  .book-cover { padding: 56px 20px 40px; }
  .book-cover h1 { font-size: 34px; letter-spacing: -0.02em; }
  .book-cover h1 .subtitle { font-size: 20px; }
  .book-cover .cover-meta {
    font-size: 10px;
    letter-spacing: 0.12em;
    margin-bottom: 28px;
    padding-bottom: 12px;
  }
  .book-cover .tagline { font-size: 15px; }
  .book-cover .progress-bar {
    flex-wrap: wrap;
    gap: 10px 14px;
    padding: 14px 16px;
  }
  .book-cover .progress-bar .progress-label { font-size: 10px; }
  .book-cover .progress-bar .progress-track { flex: 1 1 100%; order: 3; }
  .cover-toc { padding: 0 20px; }
  .cover-toc .part-header { gap: 10px; }
  .cover-toc .part-name { font-size: 16px; }
  .cover-toc .chapter-list { gap: 0; }
  .cover-toc .chapter-list .ch-status { font-size: 8.5px; padding: 2px 6px; letter-spacing: 0.1em; }
}

@media (max-width: 380px) {
  .book-cover h1 { font-size: 30px; }
  .book-cover h1 .subtitle { font-size: 18px; }
}

/* =========================================================
   登录 / 鉴权 (login.html · auth.js · 付费内容)
   ========================================================= */

.auth-body { background: var(--paper); }
.auth-body .book-header { border-bottom-color: var(--rule); }

.auth-page {
  max-width: 540px;
  margin: 0 auto;
  padding: 88px 32px 96px;
  animation: auth-fade-in 0.5s ease-out;
}

@keyframes auth-fade-in {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}

.auth-meta {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 10px 16px;
  flex-wrap: wrap;
  font-size: 10.5px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--ink-muted);
  margin-bottom: 36px;
  padding-bottom: 14px;
  border-bottom: 2px solid var(--ink);
  font-family: var(--font-num);
  font-variant-numeric: tabular-nums;
}
.auth-meta strong {
  color: var(--orange);
  font-weight: 700;
  letter-spacing: 0.18em;
}
.auth-meta .auth-meta-version {
  color: var(--ink-faint);
}

h1.auth-title {
  font-family: var(--font-sans);
  font-size: 44px;
  line-height: 1.05;
  font-weight: 700;
  letter-spacing: -0.022em;
  color: var(--ink);
  margin: 0 0 16px;
}
h1.auth-title .subtitle {
  display: block;
  color: var(--ink-muted);
  font-weight: 400;
  font-size: 16px;
  margin-top: 10px;
  letter-spacing: -0.005em;
  font-style: italic;
  font-family: var(--font-sans);
}

.auth-lede {
  font-size: 14.5px;
  color: var(--ink-soft);
  line-height: 1.65;
  margin: 0 0 44px;
  padding: 14px 18px;
  background: var(--paper-soft);
  border-left: 3px solid var(--navy);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
}
.auth-lede a {
  color: var(--navy);
  font-weight: 500;
  border-bottom: 1px solid var(--rule-strong);
}
.auth-lede a:hover {
  color: var(--orange);
  border-bottom-color: var(--orange);
}

.auth-form { margin: 0; }

.auth-field {
  margin-bottom: 24px;
}
.auth-field label {
  display: flex;
  align-items: baseline;
  gap: 10px;
  margin-bottom: 8px;
}
.auth-field label .key {
  font-size: 10.5px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--ink);
  font-weight: 700;
}
.auth-field label .key-en {
  font-family: var(--font-num);
  font-size: 10px;
  letter-spacing: 0.04em;
  color: var(--ink-faint);
  font-style: italic;
  font-weight: 400;
  text-transform: none;
}
.auth-field input {
  width: 100%;
  padding: 13px 14px;
  border: 1px solid var(--rule-strong);
  border-radius: var(--radius-sm);
  background: var(--paper);
  font-family: var(--font-mono);
  font-size: 16px;  /* iOS Safari 16+ = 不触发 auto-zoom */
  color: var(--ink);
  letter-spacing: 0.02em;
  box-sizing: border-box;
  font-feature-settings: "tnum" 1;
  -webkit-appearance: none;
  appearance: none;
  transition: border-color 0.14s, box-shadow 0.14s, background 0.14s;
}
.auth-field input::placeholder { color: var(--ink-faint); }
.auth-field input:hover {
  border-color: var(--ink-muted);
}
.auth-field input:focus {
  outline: none;
  border-color: var(--navy);
  background: var(--paper);
  box-shadow: inset 0 -2px 0 0 var(--orange);
}
.auth-field input:-webkit-autofill {
  -webkit-text-fill-color: var(--ink);
  -webkit-box-shadow: 0 0 0 1000px var(--paper) inset;
  box-shadow: 0 0 0 1000px var(--paper) inset;
  caret-color: var(--ink);
}

.auth-submit {
  width: 100%;
  margin-top: 10px;
  padding: 15px 20px;
  background: var(--ink);
  color: var(--paper);
  border: none;
  border-radius: var(--radius-sm);
  font-family: var(--font-sans);
  font-size: 11.5px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  font-weight: 700;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  -webkit-appearance: none;
  appearance: none;
  transition: background 0.16s, transform 0.06s, box-shadow 0.16s;
  box-shadow: inset 0 -2px 0 0 rgba(217, 119, 6, 0);
}
.auth-submit:hover {
  background: var(--navy);
  box-shadow: inset 0 -2px 0 0 var(--orange);
}
.auth-submit:active { transform: translateY(1px); }
.auth-submit:focus-visible {
  outline: 2px solid var(--orange);
  outline-offset: 3px;
}
.auth-submit:disabled,
.auth-submit.is-loading {
  background: var(--ink-muted);
  cursor: not-allowed;
  box-shadow: none;
}
.auth-submit-arrow {
  font-family: var(--font-num);
  font-size: 15px;
  letter-spacing: 0;
  display: inline-block;
  transition: transform 0.16s;
}
.auth-submit:hover .auth-submit-arrow { transform: translateX(4px); }
.auth-submit.is-loading .auth-submit-arrow {
  animation: auth-pulse 0.9s ease-in-out infinite;
}
@keyframes auth-pulse {
  0%, 100% { opacity: 0.35; transform: translateX(0); }
  50%      { opacity: 1;    transform: translateX(3px); }
}

.auth-status {
  margin-top: 22px;
  min-height: 1.4em;
  font-size: 12.5px;
  font-family: var(--font-mono);
  letter-spacing: 0.02em;
  color: var(--ink-muted);
  padding: 8px 0 8px 14px;
  border-left: 2px solid var(--rule);
  transition: border-color 0.14s, color 0.14s, background 0.14s;
  line-height: 1.45;
}
.auth-status:empty {
  border-left-color: transparent;
  padding: 0;
  min-height: 0;
  margin-top: 12px;
}
.auth-status.pending {
  color: var(--navy);
  border-left-color: var(--navy);
}
.auth-status.success {
  color: var(--green);
  border-left-color: var(--green);
}
.auth-status.error {
  color: var(--red);
  border-left-color: var(--red);
  background: linear-gradient(to right, rgba(157, 44, 44, 0.04), transparent 60%);
}

.auth-foot {
  margin-top: 64px;
  padding-top: 20px;
  border-top: 1px dotted var(--rule-strong);
  font-size: 11.5px;
  color: var(--ink-muted);
  text-align: center;
  letter-spacing: 0.04em;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  flex-wrap: wrap;
}
.auth-foot-sep { color: var(--ink-faint); }
.auth-foot a {
  color: var(--navy);
  border-bottom: 1px solid transparent;
  font-weight: 500;
}
.auth-foot a:hover {
  border-bottom-color: var(--navy);
  color: var(--orange);
}

@media (max-width: 600px) {
  .auth-page { padding: 48px 20px 56px; }
  h1.auth-title { font-size: 32px; letter-spacing: -0.02em; }
  h1.auth-title .subtitle { font-size: 14px; margin-top: 6px; }
  .auth-meta {
    font-size: 9.5px;
    letter-spacing: 0.14em;
    margin-bottom: 28px;
    padding-bottom: 12px;
  }
  .auth-lede {
    font-size: 13.5px;
    padding: 12px 14px;
    margin: 0 0 32px;
  }
  .auth-field { margin-bottom: 18px; }
  .auth-field label { gap: 8px; }
  .auth-field label .key-en { font-size: 9.5px; }
  .auth-field input { padding: 12px 13px; }
  .auth-submit {
    padding: 14px 16px;
    font-size: 11px;
    letter-spacing: 0.14em;
  }
  .auth-status { font-size: 12px; }
  .auth-foot {
    margin-top: 44px;
    font-size: 11px;
    gap: 6px;
  }
}

@media (max-width: 380px) {
  h1.auth-title { font-size: 28px; }
  .auth-submit {
    font-size: 10.5px;
    letter-spacing: 0.1em;
    padding: 13px 14px;
  }
}

/* ─── 付费内容保护：锁定提示 ─────────────────────────────── */

.locked-placeholder {
  margin: 72px auto;
  max-width: 560px;
  padding: 28px 28px 26px;
  text-align: left;
  border: 1px solid var(--rule);
  border-left: 3px solid var(--orange);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  background: var(--orange-pale);
  color: var(--ink-soft);
  position: relative;
  box-shadow: var(--shadow-xs);
}
.locked-placeholder::before {
  content: "ACCESS REQUIRED · 需要凭证";
  display: block;
  font-size: 10px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--orange);
  font-weight: 700;
  margin-bottom: 14px;
}
.locked-placeholder .locked-title {
  font-size: 17px;
  font-weight: 700;
  margin: 0 0 8px 0;
  color: var(--ink);
  letter-spacing: -0.005em;
  line-height: 1.35;
}
.locked-placeholder .locked-hint {
  font-size: 13.5px;
  margin: 6px 0 0;
  color: var(--ink-soft);
  line-height: 1.6;
}
.locked-placeholder a {
  color: var(--navy);
  font-weight: 500;
  border-bottom: 1px solid var(--rule-strong);
  text-decoration: none;
}
.locked-placeholder a:hover {
  border-bottom-color: var(--orange);
  color: var(--orange);
}

/* ─── 章节顶栏内的"已登录用户 + 登出" ───────────────────── */

.omb-watermark-layer {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 1;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: repeat(8, 1fr);
  opacity: 0.045;
  font-size: 12.5px;
  color: var(--ink);
  transform: rotate(-22deg) scale(1.4);
  transform-origin: center;
  user-select: none;
  font-family: var(--font-mono);
  letter-spacing: 0.02em;
}
.omb-watermark-layer span {
  display: flex;
  align-items: center;
  justify-content: center;
  white-space: nowrap;
}

.omb-auth-control {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  margin-left: 18px;
  font-size: 12px;
  line-height: 1;
}
.omb-auth-control .omb-user {
  color: var(--ink-soft);
  font-family: var(--font-num);
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.02em;
  font-size: 12px;
  display: inline-flex;
  align-items: baseline;
  gap: 6px;
}
.omb-auth-control .omb-user::before {
  content: "USER";
  color: var(--ink-faint);
  letter-spacing: 0.16em;
  font-size: 9.5px;
  font-weight: 700;
  font-family: var(--font-sans);
}
.omb-auth-control .omb-logout {
  background: transparent;
  border: 1px solid var(--rule-strong);
  border-radius: var(--radius-sm);
  padding: 5px 12px;
  font-size: 9.5px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  font-weight: 700;
  cursor: pointer;
  color: var(--ink-muted);
  font-family: var(--font-sans);
  transition: border-color 0.14s, color 0.14s, background 0.14s;
}
.omb-auth-control .omb-logout:hover {
  background: var(--ink);
  color: var(--paper);
  border-color: var(--ink);
}
.omb-auth-control .omb-logout:active { transform: translateY(1px); }

@media (max-width: 720px) {
  .omb-auth-control { gap: 8px; margin-left: 12px; }
  .omb-auth-control .omb-user::before { display: none; }
}

/* =========================================================
   Cover page (index.html) · Frontispiece
   桌面上的书 · 白底编辑式
   ========================================================= */

.cover-body {
  background: var(--paper);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  /* 极淡的 navy 微光从底部，呼应封面图深色调 */
  background-image:
    radial-gradient(ellipse at 50% 110%, rgba(26, 58, 82, 0.05) 0%, transparent 55%);
}

.cover-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--rule);
}

.cover-header-inner {
  max-width: 1280px;
  margin: 0 auto;
  padding: 14px 32px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 24px;
  min-width: 0;
}

.cover-brand-mark {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.18em;
  color: var(--ink-muted);
  font-weight: 700;
  text-transform: uppercase;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.cover-header-nav {
  display: flex;
  gap: 22px;
  align-items: center;
  flex-shrink: 0;
}

.cover-header-link {
  font-size: 12.5px;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--ink-muted);
  border-bottom: none;
  position: relative;
  padding-bottom: 2px;
}
.cover-header-link::after {
  content: "";
  position: absolute;
  inset: auto 0 0 0;
  height: 1px;
  background: var(--navy);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.2s cubic-bezier(0.2, 0.8, 0.2, 1);
}
.cover-header-link:hover {
  color: var(--navy);
  border-bottom: none;
}
.cover-header-link:hover::after { transform: scaleX(1); }

.cover-page {
  flex: 1;
  max-width: 1280px;
  width: 100%;
  margin: 0 auto;
  padding: 0 48px;
  display: grid;
  grid-template-columns: 1.05fr 1.25fr;
  gap: 96px;
  align-items: center;
  min-height: calc(100vh - 60px);
}

/* —— Cover stage · 书的物理摆放 —— */

.cover-page-stage {
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 56px 0;
  position: relative;
}

/* 衬底纸面阴影 (under the book, like a desk surface) */
.cover-page-stage::after {
  content: "";
  position: absolute;
  left: 50%;
  bottom: 56px;
  width: 70%;
  height: 16px;
  transform: translateX(-50%) translateY(8px);
  background: radial-gradient(ellipse at center, rgba(15, 23, 42, 0.12) 0%, transparent 65%);
  pointer-events: none;
  filter: blur(8px);
}

.cover-book {
  position: relative;
  width: 100%;
  max-width: 420px;
  margin: 0;
  transform: rotate(-1.4deg);
  transition: transform 0.5s cubic-bezier(0.2, 0.8, 0.2, 1);
  animation: cover-book-enter 0.9s cubic-bezier(0.2, 0.8, 0.2, 1) 0.05s both;
}
.cover-book:hover { transform: rotate(-0.4deg) translateY(-2px); }

.cover-book-img {
  display: block;
  width: 100%;
  height: auto;
  border-radius: 2px;
  /* 3 层阴影叠加 — 实体书的物理深度 */
  box-shadow:
    0 1px 2px rgba(15, 23, 42, 0.14),
    0 12px 28px -10px rgba(15, 23, 42, 0.22),
    0 36px 72px -20px rgba(15, 23, 42, 0.28);
}

/* 左侧书脊条 — 物理书的暗示 */
.cover-book-spine {
  position: absolute;
  top: 4px;
  bottom: 4px;
  left: 0;
  width: 4px;
  background: linear-gradient(
    180deg,
    #050d18 0%,
    #1a3a52 18%,
    #1a3a52 82%,
    #050d18 100%
  );
  border-radius: 1px 0 0 1px;
  box-shadow: inset -1px 0 0 rgba(0, 0, 0, 0.4);
  z-index: 1;
}

@keyframes cover-book-enter {
  from {
    opacity: 0;
    transform: rotate(-3.5deg) translateY(24px);
  }
  to {
    opacity: 1;
    transform: rotate(-1.4deg) translateY(0);
  }
}

/* —— Cover info · 编辑式文字栏 —— */

.cover-page-info {
  max-width: 520px;
}

.cover-page-info > * {
  opacity: 0;
  animation: cover-info-enter 0.7s cubic-bezier(0.2, 0.8, 0.2, 1) both;
}
.cover-page-eyebrow  { animation-delay: 0.25s; }
.cover-page-title    { animation-delay: 0.35s; }
.cover-page-tagline  { animation-delay: 0.45s; }
.cover-page-progress { animation-delay: 0.55s; }
.cover-page-actions  { animation-delay: 0.65s; }
.cover-page-bullets  { animation-delay: 0.75s; }

@keyframes cover-info-enter {
  from { opacity: 0; transform: translateY(10px); }
  to   { opacity: 1; transform: translateY(0); }
}

.cover-page-eyebrow {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.18em;
  color: var(--ink-muted);
  text-transform: uppercase;
  font-weight: 700;
  margin: 0 0 28px;
}
.cover-page-eyebrow-rule {
  display: inline-block;
  width: 36px;
  height: 1px;
  background: var(--navy);
}
.cover-page-eyebrow-dot {
  color: var(--rule-strong);
  letter-spacing: 0;
}

.cover-page-title {
  margin: 0 0 32px;
  display: flex;
  flex-direction: column;
  gap: 6px;
  line-height: 1;
  font-weight: 400;  /* per-span overrides */
}

.cover-page-title-en {
  font-family: var(--font-sans);
  font-size: 14px;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--navy);
  font-weight: 700;
}

.cover-page-title-zh {
  font-family: var(--font-sans);
  font-size: clamp(40px, 5.4vw, 64px);
  line-height: 1.04;
  color: var(--ink);
  font-weight: 800;
  letter-spacing: -0.025em;
  margin-top: 6px;
}

.cover-page-title-sub {
  font-family: var(--font-sans);
  font-size: 17px;
  font-weight: 400;
  letter-spacing: 0.02em;
  color: var(--ink-muted);
  font-style: italic;
  margin-top: 10px;
}

.cover-page-tagline {
  font-size: 16px;
  line-height: 1.7;
  color: var(--ink-soft);
  max-width: 38ch;
  margin: 0 0 36px;
}

.cover-page-progress {
  display: flex;
  align-items: center;
  gap: 14px;
  margin: 0 0 36px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  font-weight: 700;
}
.cover-page-progress-label { color: var(--ink-muted); }
.cover-page-progress-track {
  flex: 0 1 200px;
  height: 2px;
  background: var(--rule);
  position: relative;
}
.cover-page-progress-fill {
  position: absolute;
  inset: 0 auto 0 0;
  background: var(--navy);
}
.cover-page-progress-numbers { color: var(--ink); }

.cover-page-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin: 0 0 40px;
}

.cover-page-cta {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 14px 24px;
  font-size: 14px;
  font-weight: 600;
  letter-spacing: 0.02em;
  text-decoration: none;
  border: 1px solid;
  transition: background 0.16s, border-color 0.16s, color 0.16s, transform 0.16s;
  border-radius: 2px;
  font-family: var(--font-sans);
}
.cover-page-cta:hover { border-bottom: 1px solid; }

.cover-page-cta-primary {
  background: var(--navy);
  border-color: var(--navy);
  color: var(--paper);
}
.cover-page-cta-primary:hover {
  background: #0e2538;
  border-color: #0e2538;
  color: var(--paper);
  transform: translateY(-1px);
}

.cover-page-cta-secondary {
  background: transparent;
  border-color: var(--rule-strong);
  color: var(--ink-soft);
}
.cover-page-cta-secondary:hover {
  border-color: var(--navy);
  color: var(--navy);
  background: var(--navy-pale);
}

.cover-page-cta-arrow {
  display: inline-block;
  transition: transform 0.2s cubic-bezier(0.2, 0.8, 0.2, 1);
  font-family: var(--font-mono);
}
.cover-page-cta:hover .cover-page-cta-arrow {
  transform: translateX(3px);
}
.cover-page-cta-secondary:hover .cover-page-cta-arrow {
  transform: translate(2px, -2px);
}

.cover-page-bullets {
  list-style: none;
  margin: 0;
  padding: 24px 0 0;
  border-top: 1px solid var(--rule);
  display: flex;
  flex-wrap: wrap;
  gap: 28px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--ink-muted);
}
.cover-page-bullets li {
  display: flex;
  flex-direction: column;
  gap: 3px;
}
.cover-page-bullets-key {
  font-size: 18px;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--ink);
  text-transform: none;
}

/* —— Footer tag —— */

.cover-page-footer {
  max-width: 1280px;
  margin: 0 auto;
  padding: 24px 48px 40px;
  display: flex;
  align-items: center;
  gap: 16px;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--ink-faint);
  border-top: 1px solid var(--rule);
}
.cover-page-footer-tag {
  display: inline-block;
  padding: 3px 8px;
  background: var(--navy);
  color: var(--paper);
  border-radius: 1px;
  letter-spacing: 0.22em;
  font-weight: 700;
}

/* —— 响应式 —— */

@media (max-width: 1000px) {
  .cover-page {
    grid-template-columns: 1fr;
    gap: 56px;
    padding: 40px 32px;
    min-height: 0;
  }
  .cover-page-stage { padding: 40px 0 24px; }
  .cover-book { max-width: 340px; }
  .cover-page-info { max-width: none; }
}

@media (max-width: 600px) {
  .cover-header-inner { padding: 12px 18px; }
  .cover-brand-mark { font-size: 10px; letter-spacing: 0.14em; }
  .cover-header-nav { gap: 14px; }
  .cover-header-link { font-size: 11.5px; }

  .cover-page { padding: 24px 18px; gap: 36px; }
  .cover-page-stage { padding: 16px 0; }
  .cover-book { max-width: 260px; transform: rotate(-1.2deg); }

  .cover-page-title-en { font-size: 12px; letter-spacing: 0.18em; }
  .cover-page-title-sub { font-size: 14px; }
  .cover-page-tagline { font-size: 14.5px; }
  .cover-page-eyebrow { font-size: 9.5px; gap: 8px; flex-wrap: wrap; }
  .cover-page-eyebrow-rule { width: 24px; }

  .cover-page-actions { flex-direction: column; gap: 10px; }
  .cover-page-cta { width: 100%; justify-content: center; padding: 13px 18px; }

  .cover-page-bullets { gap: 18px 24px; }
  .cover-page-bullets-key { font-size: 16px; }

  .cover-page-footer { padding: 20px 18px 32px; flex-wrap: wrap; gap: 10px; }
}

/* =========================================================
   Login page · auth-split
   ========================================================= */

.auth-split-body {
  background: var(--paper);
}

/* 当 auth-split-body 存在时, 覆盖默认 .auth-page 的样式不会冲突 — 我们用全新 selectors */

.auth-split {
  display: grid;
  grid-template-columns: 1fr 1fr;
  min-height: calc(100vh - 52px);
  max-width: 1320px;
  margin: 0 auto;
}

.auth-split-cover {
  background: var(--navy-pale);
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  padding: 60px 48px;
  position: relative;
  overflow: hidden;
  border-right: 1px solid var(--rule);
}
/* 微点阵纹理 · 呼应封面图底部的星点 */
.auth-split-cover::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: radial-gradient(
    circle at 1px 1px,
    rgba(26, 58, 82, 0.08) 1px,
    transparent 0
  );
  background-size: 22px 22px;
  pointer-events: none;
  opacity: 0.6;
}

.auth-split-cover-frame {
  position: relative;
  max-width: 360px;
  width: 100%;
  z-index: 1;
  animation: cover-book-enter 0.9s cubic-bezier(0.2, 0.8, 0.2, 1) 0.1s both;
}

.auth-split-cover-img {
  display: block;
  width: 100%;
  height: auto;
  border-radius: 2px;
  transform: rotate(-1.6deg);
  transform-origin: center;
  box-shadow:
    0 1px 2px rgba(15, 23, 42, 0.16),
    0 14px 28px -10px rgba(15, 23, 42, 0.24),
    0 40px 72px -20px rgba(15, 23, 42, 0.30);
}

.auth-split-cover-spine {
  position: absolute;
  top: 4px;
  bottom: 4px;
  left: 0;
  width: 4px;
  background: linear-gradient(
    180deg,
    #050d18 0%,
    #1a3a52 18%,
    #1a3a52 82%,
    #050d18 100%
  );
  border-radius: 1px 0 0 1px;
  box-shadow: inset -1px 0 0 rgba(0, 0, 0, 0.4);
  z-index: 2;
  transform: rotate(-1.6deg);
  transform-origin: center;
}

.auth-split-cover-caption {
  margin-top: 36px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  text-align: center;
  z-index: 1;
  max-width: 320px;
}
.auth-split-cover-eyebrow {
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.22em;
  font-weight: 700;
  color: var(--navy);
  text-transform: uppercase;
}
.auth-split-cover-line {
  font-size: 13px;
  color: var(--ink-muted);
  line-height: 1.55;
}

.auth-split-form {
  background: var(--paper);
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 60px 64px;
  max-width: 560px;
  width: 100%;
}

/* 重设 auth 内部组件的边距 · 在 split 上下文里更紧凑 */
.auth-split-form .auth-meta { margin-bottom: 18px; }
.auth-split-form .auth-title { margin-bottom: 14px; }
.auth-split-form .auth-lede  { margin-bottom: 28px; }
.auth-split-form .auth-form  { margin-bottom: 20px; }

@media (max-width: 900px) {
  .auth-split {
    grid-template-columns: 1fr;
    min-height: 0;
  }
  .auth-split-cover {
    padding: 36px 24px 32px;
    border-right: none;
    border-bottom: 1px solid var(--rule);
  }
  .auth-split-cover-frame { max-width: 220px; }
  .auth-split-cover-caption { margin-top: 24px; }
  .auth-split-form { padding: 36px 24px 48px; max-width: none; }
}

@media (max-width: 600px) {
  .auth-split-cover { padding: 28px 18px; }
  .auth-split-cover-frame { max-width: 180px; }
  .auth-split-cover-caption { display: none; }
  .auth-split-form { padding: 28px 18px 40px; }
}