:root {
  --bg: #FBFAF6;
  --bg-soft: #F3F1E9;
  --ink: #1A1A1A;
  --ink-soft: #4a4a4a;
  --rule: #d9d4c3;
  --accent: #8a6a3b;
  --accent-soft: #c7a76a;
  --shadow: 0 2px 12px rgba(0,0,0,.06);
  --serif: "Noto Serif SC", "Source Han Serif SC", "Songti SC", "STSong", serif;
  --sans:  "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Helvetica Neue", system-ui, sans-serif;
}
[data-theme="dark"] {
  --bg: #161413;
  --bg-soft: #1f1c1a;
  --ink: #e8e3d6;
  --ink-soft: #a8a194;
  --rule: #3a3530;
  --accent: #d3b07a;
  --accent-soft: #8a6a3b;
  --shadow: 0 2px 12px rgba(0,0,0,.4);
}
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  color: var(--ink);
  font-family: var(--serif);
  font-size: var(--reader-size, 18px);
  line-height: 1.85;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* 顶部条 */
.topbar {
  position: sticky; top: 0; z-index: 50;
  display: flex; align-items: center; gap: 14px;
  padding: 10px 18px;
  background: rgba(251,250,246,.92);
  backdrop-filter: saturate(180%) blur(8px);
  border-bottom: 1px solid var(--rule);
  font-family: var(--sans);
}
[data-theme="dark"] .topbar { background: rgba(22,20,19,.92); }
.topbar .title {
  flex: 1; font-size: 14px; color: var(--ink-soft);
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}
.topbar .title a { color: inherit; text-decoration: none; }
.topbar button {
  background: transparent; border: 1px solid var(--rule);
  color: var(--ink); padding: 6px 10px; border-radius: 6px;
  cursor: pointer; font-family: var(--sans); font-size: 13px;
}
.topbar button:hover { border-color: var(--accent); color: var(--accent); }
.topbar .group { display: inline-flex; gap: 4px; }

.progress { height: 3px; background: var(--bg-soft); position: sticky; top: 49px; z-index: 49; }
.progress .bar { height: 100%; background: var(--accent); width: 0; transition: width .15s; }

/* 抽屉目录 */
.drawer-mask {
  position: fixed; inset: 0; background: rgba(0,0,0,.35);
  opacity: 0; pointer-events: none; transition: opacity .2s; z-index: 80;
}
.drawer-mask.open { opacity: 1; pointer-events: auto; }
.drawer {
  position: fixed; top: 0; bottom: 0; left: 0; width: min(340px, 86vw);
  background: var(--bg); border-right: 1px solid var(--rule);
  transform: translateX(-100%); transition: transform .25s;
  z-index: 90; overflow-y: auto; padding: 22px 22px 60px;
  font-family: var(--sans); box-shadow: var(--shadow);
}
.drawer.open { transform: translateX(0); }
.drawer h3 { margin: 0 0 6px; font-size: 13px; color: var(--ink-soft); font-weight: 500; letter-spacing: .08em; }
.drawer .book { font-family: var(--serif); font-size: 20px; margin: 0 0 18px; }
.drawer ol { list-style: none; padding: 0; margin: 0; }
.drawer ol li { margin: 2px 0; }
.drawer ol a {
  display: block; padding: 7px 10px; border-radius: 6px;
  color: var(--ink); text-decoration: none; font-size: 14px;
}
.drawer ol a:hover { background: var(--bg-soft); color: var(--accent); }
.drawer ol a.current { background: var(--bg-soft); color: var(--accent); font-weight: 600; }
.drawer .group-label { margin: 18px 0 6px; font-size: 12px; color: var(--ink-soft); letter-spacing: .1em; }

/* 二级目录（章节 -> 小节） */
.drawer details { margin: 2px 0; }
.drawer details > summary {
  list-style: none; cursor: pointer;
  display: flex; align-items: center; gap: 6px;
  padding: 7px 10px; border-radius: 6px;
  font-size: 14px; color: var(--ink);
  user-select: none;
}
.drawer details > summary::-webkit-details-marker { display: none; }
.drawer details > summary::before {
  content: "›"; display: inline-block; width: 12px;
  color: var(--ink-soft); transition: transform .15s; font-size: 14px;
  transform: translateY(-1px);
}
.drawer details[open] > summary::before { transform: rotate(90deg); }
.drawer details > summary:hover { background: var(--bg-soft); color: var(--accent); }
.drawer details > summary .label-text { flex: 1; }
.drawer details.current > summary { background: var(--bg-soft); color: var(--accent); font-weight: 600; }
.drawer ol.sub { padding: 2px 0 6px 22px; border-left: 1px dashed var(--rule); margin-left: 14px; }
.drawer ol.sub a {
  padding: 5px 10px; font-size: 13px; color: var(--ink-soft);
  display: flex; gap: 8px; align-items: baseline;
}
.drawer ol.sub a .sub-num {
  color: var(--accent); font-family: var(--sans); font-size: 11px;
  min-width: 2.4em; letter-spacing: .03em;
}
.drawer ol.sub a:hover { color: var(--accent); background: var(--bg-soft); }

/* 阅读主体 */
.reader {
  max-width: 36em; margin: 0 auto; padding: 48px 24px 120px;
}
.reader .eyebrow {
  font-family: var(--sans); font-size: 12px; letter-spacing: .25em;
  color: var(--accent); text-transform: uppercase; margin-bottom: 12px;
}
.reader h1 {
  font-size: 1.9em; line-height: 1.35; margin: 0 0 8px;
  font-weight: 700; letter-spacing: .02em;
}
.reader .lead {
  color: var(--ink-soft); font-style: italic; margin: 0 0 36px;
  border-left: 3px solid var(--accent-soft); padding-left: 14px;
}
.reader h3 {
  margin: 2.4em 0 .8em; font-size: 1.15em; line-height: 1.5;
  font-family: var(--sans); font-weight: 600;
  border-bottom: 1px solid var(--rule); padding-bottom: .35em;
}
.reader h3 .sec-num {
  display: inline-block; color: var(--accent); margin-right: .5em;
  font-feature-settings: "tnum";
}
.reader p {
  margin: 0 0 1.1em; text-indent: 2em;
  text-align: justify; hyphens: auto;
}
.reader p:has(img), .reader p:has(> img:only-child) { text-indent: 0; text-align: center; }
.reader img {
  max-width: 100%; height: auto; border: 1px solid var(--rule);
  border-radius: 4px; box-shadow: var(--shadow);
  background: var(--bg-soft);
}
.reader blockquote {
  margin: 1.4em 0; padding: .2em 1em; border-left: 3px solid var(--accent);
  color: var(--ink-soft); font-style: italic;
}
.reader hr { border: 0; border-top: 1px solid var(--rule); margin: 2.4em 0; }
.reader a { color: var(--accent); }

/* 编按（编者注） */
.reader aside.editor-note {
  margin: 1.4em 0;
  padding: 12px 16px;
  background: var(--bg-soft);
  border-left: 3px solid var(--accent-soft);
  font-family: var(--sans);
  font-size: .88em;
  line-height: 1.75;
  color: var(--ink-soft);
  border-radius: 0 6px 6px 0;
  text-indent: 0;
}
.reader aside.editor-note .en-label {
  font-weight: 600; color: var(--accent); letter-spacing: .05em;
}
.reader aside.editor-note .en-sep { color: var(--accent); margin: 0 6px 0 2px; }

/* 图例说明 */
.reader p.figure-caption {
  text-indent: 0; text-align: center;
  font-family: var(--sans); font-size: .85em;
  color: var(--ink-soft);
  margin: -6px auto 1.8em;
  max-width: 92%;
  line-height: 1.7;
  letter-spacing: .02em;
}

/* 章末导航 */
.nav-foot {
  max-width: 36em; margin: 60px auto 80px; padding: 0 24px;
  display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 10px;
  font-family: var(--sans);
}
.nav-foot a, .nav-foot span {
  display: block; padding: 14px; border: 1px solid var(--rule);
  border-radius: 8px; text-decoration: none; color: var(--ink);
  font-size: 13px; line-height: 1.4; background: var(--bg-soft);
}
.nav-foot a:hover { border-color: var(--accent); color: var(--accent); }
.nav-foot .label { display: block; font-size: 11px; color: var(--ink-soft); letter-spacing: .1em; margin-bottom: 4px; }
.nav-foot .center { text-align: center; }
.nav-foot .right { text-align: right; }
.nav-foot .disabled { opacity: .4; }

/* 首页 */
.home {
  max-width: 42em; margin: 0 auto; padding: 80px 24px 120px;
}
.home .cover {
  text-align: center; margin-bottom: 56px;
  padding: 48px 24px; background: var(--bg-soft);
  border: 1px solid var(--rule); border-radius: 10px;
}
.home .cover .sub { font-family: var(--sans); letter-spacing: .25em; color: var(--accent); font-size: 12px; }
.home .cover h1 { font-size: 2.6em; margin: 18px 0 8px; line-height: 1.25; }
.home .cover .en { color: var(--ink-soft); font-style: italic; }
.home .cover .author { margin-top: 18px; font-family: var(--sans); font-size: 14px; color: var(--ink-soft); }
.home .cta {
  display: inline-block; margin-top: 28px;
  padding: 12px 28px; background: var(--accent); color: #fff;
  border-radius: 999px; text-decoration: none; font-family: var(--sans); font-size: 14px;
  letter-spacing: .1em;
}
.home .cta:hover { background: var(--ink); }
.home h2 {
  font-family: var(--sans); font-size: 13px; letter-spacing: .2em;
  color: var(--ink-soft); margin: 48px 0 14px; font-weight: 500;
}
.home .toc { list-style: none; padding: 0; margin: 0; }
.home .toc li {
  border-bottom: 1px dashed var(--rule);
}
.home .toc a {
  display: flex; gap: 16px; align-items: baseline;
  padding: 16px 6px; text-decoration: none; color: var(--ink);
}
.home .toc a:hover { color: var(--accent); background: var(--bg-soft); }
.home .toc .num {
  font-family: var(--sans); color: var(--accent); font-size: 13px;
  min-width: 3.2em; letter-spacing: .05em;
}
.home .toc .t { flex: 1; font-size: 1.05em; }
.home .toc .meta { font-family: var(--sans); font-size: 12px; color: var(--ink-soft); }

/* 响应式 */
@media (max-width: 720px) {
  body { font-size: var(--reader-size, 17px); }
  .topbar { padding: 8px 12px; gap: 8px; }
  .topbar button { padding: 5px 8px; font-size: 12px; }
  .topbar .title { font-size: 12px; }
  .progress { top: 41px; }

  .reader { padding: 28px 18px 60px; }
  .reader h1 { font-size: 1.5em; line-height: 1.3; }
  .reader h3 { font-size: 1.05em; margin: 1.8em 0 .6em; }
  .reader p { text-indent: 2em; }

  .reader aside.editor-note { padding: 10px 12px; font-size: .9em; }
  .reader p.figure-caption { font-size: .82em; max-width: 100%; }

  .home { padding: 40px 16px 60px; }
  .home .cover { padding: 32px 16px; margin-bottom: 36px; }
  .home .cover h1 { font-size: 1.8em; }
  .home .cover .en { font-size: .9em; }
  .home .toc a { padding: 14px 4px; gap: 10px; }
  .home .toc .num { min-width: 2.8em; font-size: 12px; }
  .home .toc .t { font-size: 1em; }

  /* 章末导航：手机上改成纵向 */
  .nav-foot {
    grid-template-columns: 1fr;
    gap: 8px; margin: 40px auto 60px;
  }
  .nav-foot a, .nav-foot span { padding: 12px 14px; }
  .nav-foot .right { text-align: left; }

  .drawer { width: min(320px, 88vw); padding: 18px 16px 60px; }
}

@media (max-width: 380px) {
  /* 极窄屏：隐藏顶部书名，只保留章节名 */
  .topbar .title .book-title { display: none; }
  .topbar button { padding: 4px 6px; font-size: 11px; }
}

/* 触屏：取消 hover 残留态 */
@media (hover: none) {
  .topbar button:hover, .drawer ol a:hover, .nav-foot a:hover { color: inherit; border-color: var(--rule); background: inherit; }
}