/* 道德经 · 逐章讲解 —— 全站样式 */
:root {
  --paper: #f7f3ea;        /* 宣纸 */
  --paper-deep: #efe9db;
  --ink: #2b2a26;          /* 墨色 */
  --ink-soft: #5a564c;
  --cinnabar: #a03a2a;     /* 朱砂 */
  --seal: #b5442f;
  --line: #d8d0bf;
  --serif: "Noto Serif SC", "Source Han Serif SC", "Songti SC", STSong, SimSun, "TW-Kai", serif;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  font-family: var(--serif);
  background: var(--paper);
  color: var(--ink);
  line-height: 1.9;
  font-size: 17px;
}

a { color: var(--cinnabar); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ===== 页头 ===== */
header.site {
  border-bottom: 1px solid var(--line);
  background: linear-gradient(180deg, #faf7ef, var(--paper));
}
.site-inner {
  max-width: 860px; margin: 0 auto; padding: 22px 20px 16px;
  display: flex; align-items: baseline; justify-content: space-between; flex-wrap: wrap; gap: 8px;
}
.site-title { font-size: 26px; letter-spacing: .35em; font-weight: 700; color: var(--ink); }
.site-title:hover { text-decoration: none; }
.site-title .yin { color: var(--seal); border: 1.5px solid var(--seal); border-radius: 4px;
  display: inline-block; padding: 0 6px; margin-right: 4px; font-size: 20px; letter-spacing: 0;
  transform: translateY(-2px); }
.site-sub { font-size: 13px; color: var(--ink-soft); letter-spacing: .2em; }
nav.site-nav { font-size: 14.5px; display: flex; gap: 18px; }
nav.site-nav a { color: var(--ink-soft); letter-spacing: .1em; }
nav.site-nav a:hover { color: var(--cinnabar); text-decoration: none; border-bottom: 2px solid var(--cinnabar); }

/* ===== 首页题辞 ===== */
.hero { text-align: center; padding: 64px 20px 56px;
  background: radial-gradient(ellipse at 50% 30%, #fbf8f0 0%, var(--paper) 70%); }
.hero .motto {
  font-size: clamp(24px, 5vw, 38px); letter-spacing: .12em; line-height: 2;
  writing-mode: vertical-rl; margin: 0 auto; max-height: 340px;
  border-left: 1px solid var(--line); border-right: 1px solid var(--line);
  padding: 18px 26px;
}
.hero .attr { margin-top: 18px; color: var(--ink-soft); font-size: 14px; letter-spacing: .3em; }
.hero .actions { margin-top: 26px; display: flex; gap: 14px; justify-content: center; flex-wrap: wrap; }
.btn {
  display: inline-block; padding: 9px 26px; border: 1.5px solid var(--cinnabar);
  color: var(--cinnabar); border-radius: 3px; font-size: 15px; letter-spacing: .25em;
  background: transparent; cursor: pointer; font-family: inherit;
}
.btn:hover { background: var(--cinnabar); color: #fff; text-decoration: none; }
.btn.ghost { border-color: var(--ink-soft); color: var(--ink-soft); }
.btn.ghost:hover { background: var(--ink-soft); color: #fff; }

/* ===== 区块 ===== */
main { max-width: 860px; margin: 0 auto; padding: 30px 20px 70px; }
section.block { margin-top: 42px; }
h2.block-title {
  font-size: 21px; letter-spacing: .4em; text-align: center; color: var(--ink);
  margin-bottom: 6px;
}
h2.block-title::after {
  content: ""; display: block; width: 46px; height: 3px; margin: 10px auto 0;
  background: var(--seal); border-radius: 2px;
}
.block-lead { text-align: center; color: var(--ink-soft); font-size: 14px; margin-bottom: 24px; letter-spacing: .1em; }

/* 目录 */
.toc-part { margin-top: 30px; }
.toc-part > h3 {
  font-size: 17px; color: var(--seal); letter-spacing: .5em; text-align: center;
  margin-bottom: 16px;
}
.toc-part > h3 small { font-size: 12px; color: var(--ink-soft); letter-spacing: .15em; display: block; margin-top: 2px; }
ul.toc {
  list-style: none; display: grid; grid-template-columns: repeat(auto-fill, minmax(168px, 1fr));
  gap: 8px 14px;
}
ul.toc li a {
  display: block; border: 1px solid var(--line); background: #fbf8f1;
  padding: 8px 14px; border-radius: 3px; font-size: 15px; color: var(--ink);
  transition: border-color .15s, background .15s;
}
ul.toc li a:hover { border-color: var(--seal); background: #fff; text-decoration: none; }
ul.toc li a .num { color: var(--cinnabar); margin-right: 8px; font-size: 13px; }
ul.toc li a .theme { color: var(--ink-soft); font-size: 13px; margin-left: 6px; }

/* 简介正文 */
.prose p { margin: 0 0 16px; text-indent: 2em; text-align: justify; }
.prose p.no-indent { text-indent: 0; }
.prose h3 { margin: 26px 0 10px; font-size: 17px; color: var(--seal); letter-spacing: .2em; }

/* ===== 章节页 ===== */
article.chapter { margin-top: 8px; }
.ch-head { text-align: center; padding: 34px 0 26px; border-bottom: 1px solid var(--line); }
.ch-head .part { font-size: 13px; color: var(--ink-soft); letter-spacing: .4em; margin-bottom: 10px; }
.ch-head h1 { font-size: 30px; letter-spacing: .25em; font-weight: 700; }
.ch-head .theme { margin-top: 10px; font-size: 15px; color: var(--cinnabar); letter-spacing: .3em; }

h3.sec {
  margin: 40px 0 16px; font-size: 16px; letter-spacing: .5em; color: var(--ink);
  display: flex; align-items: center; gap: 14px;
}
h3.sec::before, h3.sec::after { content: ""; flex: 1; height: 1px; background: var(--line); }

.orig {
  background: #fbf8f1; border: 1px solid var(--line); border-radius: 4px;
  padding: 26px 30px; font-size: 19.5px; line-height: 2.25; letter-spacing: .06em;
  text-align: center;
}
.orig p { margin: 0 0 14px; }
.orig p:last-child { margin-bottom: 0; }
.orig .k { color: var(--seal); }

.yiwen p { margin-bottom: 12px; text-align: justify; }
.yiwen p:last-child { margin-bottom: 0; }

.notes { list-style: none; }
.notes li {
  padding: 9px 0 9px 0; border-bottom: 1px dashed var(--line);
  font-size: 15.5px; text-align: justify;
}
.notes li:last-child { border-bottom: none; }
.notes .term { color: var(--cinnabar); margin-right: 10px; white-space: nowrap; font-weight: 700; }

.jiexi p { margin-bottom: 14px; text-align: justify; }
.jiexi p:last-child { margin-bottom: 0; }

/* 章末导航 */
.ch-nav {
  margin-top: 54px; border-top: 1px solid var(--line); padding-top: 22px;
  display: flex; justify-content: space-between; gap: 12px; font-size: 15px;
}
.ch-nav a { flex: 1; border: 1px solid var(--line); background: #fbf8f1;
  padding: 10px 16px; border-radius: 3px; color: var(--ink); }
.ch-nav a:hover { border-color: var(--seal); text-decoration: none; background: #fff; }
.ch-nav a.next { text-align: right; }
.ch-nav .lab { display: block; font-size: 12px; color: var(--ink-soft); letter-spacing: .2em; }
.ch-nav .idx { display: block; margin-top: 24px; text-align: center; }
.ch-nav .idx a { display: inline-block; border: none; background: none; color: var(--cinnabar);
  letter-spacing: .2em; padding: 6px 10px; }

/* ===== 页脚 ===== */
footer.site {
  border-top: 1px solid var(--line); background: var(--paper-deep);
  color: var(--ink-soft); font-size: 13px; text-align: center;
  padding: 26px 20px; letter-spacing: .12em; line-height: 2.2;
}
footer.site a { color: var(--ink-soft); border-bottom: 1px dotted var(--ink-soft); }
footer.site a:hover { color: var(--cinnabar); }

/* ===== 响应式 ===== */
@media (max-width: 640px) {
  body { font-size: 16px; }
  .site-title { font-size: 22px; }
  .orig { font-size: 18px; padding: 20px 18px; }
  .ch-head h1 { font-size: 25px; }
  ul.toc { grid-template-columns: repeat(auto-fill, minmax(140px, 1fr)); }
}