/* 把话说尽 · 一个语文老师的编程课
   样式说明：全部使用系统字体，不加载任何外部资源，断网也能正常显示。 */

:root {
  --paper: #fbf8f1;
  --paper-2: #f4efe3;
  --ink: #221f1a;
  --ink-2: #5a5348;
  --ink-3: #8c8477;
  --rule: #e0d8c6;
  --accent: #9c3b2c;
  --mark: rgba(156, 59, 44, 0.14);
  --strong: #14110b;
  --code-bg: #f2ecdd;
  --measure: 33em;
  --serif: "Songti SC", "Noto Serif CJK SC", "Source Han Serif SC",
           "Times New Roman", "STSong", "SimSun", serif;
  --mono: "SF Mono", "SFMono-Regular", Menlo, Consolas, "Courier New", monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --paper: #191714;
    --paper-2: #221f1a;
    --ink: #e8e2d6;
    --ink-2: #b0a799;
    --ink-3: #867d6f;
    --rule: #332e27;
    --accent: #d4816e;
    --mark: rgba(212, 129, 110, 0.18);
    --strong: #fffaf0;
    --code-bg: #241f19;
  }
}

* { 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(--serif);
  font-size: 19px;
  line-height: 1.95;
  letter-spacing: 0.012em;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }

/* ── 顶栏 ───────────────────────────────── */

.progress {
  position: fixed;
  top: 0; left: 0;
  height: 2px;
  width: 0;
  background: var(--accent);
  z-index: 30;
  transition: width 80ms linear;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.72rem 1.2rem;
  background: var(--paper);
  border-bottom: 1px solid var(--rule);
  font-size: 0.76rem;
  letter-spacing: 0.18em;
}

.topbar .brand {
  color: var(--ink-2);
  letter-spacing: 0.26em;
}
.topbar .brand:hover { color: var(--accent); text-decoration: none; }

.topbar nav { display: flex; gap: 1.1rem; }
.topbar nav a { color: var(--ink-3); }
.topbar nav a:hover { color: var(--accent); text-decoration: none; }
.topbar nav a.on { color: var(--accent); }

/* ── 版心 ───────────────────────────────── */

.wrap {
  max-width: var(--measure);
  margin: 0 auto;
  padding: 0 1.4rem;
}

main { padding-bottom: 4rem; }

/* ── 封面 ───────────────────────────────── */

.cover {
  padding: clamp(3rem, 12vh, 7rem) 0 3rem;
  text-align: center;
}

.cover .kicker {
  margin: 0;
  font-size: 0.78rem;
  letter-spacing: 0.34em;
  color: var(--accent);
  text-indent: 0.34em;
}

.book-title {
  margin: 0.7em 0 0;
  font-size: clamp(3rem, 11vw, 5.2rem);
  line-height: 1.12;
  font-weight: 600;
  letter-spacing: 0.09em;
  text-indent: 0.09em;
}

.book-sub {
  margin: 1.1em 0 0;
  font-size: 0.95rem;
  letter-spacing: 0.2em;
  color: var(--ink-2);
  text-indent: 0.2em;
}

.rule-mark {
  width: 2.2rem;
  height: 1px;
  margin: 2.2rem auto;
  background: var(--accent);
  opacity: 0.55;
}

.tagline {
  margin: 0;
  font-size: 0.98rem;
  line-height: 2.15;
  color: var(--ink-2);
}

.lead {
  margin: 1.6em auto 0;
  max-width: min(26rem, 100%);
  font-size: 0.95rem;
  line-height: 2;
  color: var(--ink-2);
}

.cta {
  display: inline-block;
  margin-top: 2.4rem;
  padding: 0.72em 2.2em;
  border: 1px solid var(--accent);
  color: var(--accent);
  font-size: 0.86rem;
  letter-spacing: 0.2em;
  border-radius: 2px;
  transition: background 160ms ease, color 160ms ease;
}
.cta:hover {
  background: var(--accent);
  color: var(--paper);
  text-decoration: none;
}

/* ── 目录 ───────────────────────────────── */

.toc { padding-top: 2rem; }

.toc > h2 {
  margin: 0 0 2rem;
  font-size: 0.8rem;
  font-weight: 400;
  letter-spacing: 0.34em;
  color: var(--ink-3);
  text-align: center;
}

.part { margin: 0 0 2.8rem; }

.part > h3 {
  margin: 0 0 0.9rem;
  padding-bottom: 0.65rem;
  border-bottom: 1px solid var(--rule);
  font-size: 0.8rem;
  font-weight: 400;
  letter-spacing: 0.16em;
  color: var(--accent);
}

.part ol { margin: 0; padding: 0; list-style: none; }

.part li { border-bottom: 1px dotted var(--rule); }
.part li:last-child { border-bottom: 0; }

.row {
  display: flex;
  align-items: baseline;
  gap: 1rem;
  padding: 0.66rem 0;
  color: var(--ink);
  font-size: 0.98rem;
}
a.row:hover { text-decoration: none; }
a.row:hover .t { color: var(--accent); }

.row .n {
  min-width: 2.1em;
  font-size: 0.74rem;
  letter-spacing: 0.08em;
  color: var(--ink-3);
  font-variant-numeric: tabular-nums;
}
.row .t { flex: 1; }
.row .badge {
  font-size: 0.68rem;
  letter-spacing: 0.14em;
  color: var(--ink-3);
}

.pending { opacity: 0.46; }
.pending .t { color: var(--ink-2); }

.project {
  margin: 0.9rem 0 0;
  padding-left: 3.1rem;
  font-size: 0.78rem;
  letter-spacing: 0.06em;
  color: var(--ink-3);
  font-style: italic;
}

.colophon {
  margin-top: 4rem;
  padding-top: 1.6rem;
  border-top: 1px solid var(--rule);
  font-size: 0.76rem;
  letter-spacing: 0.1em;
  color: var(--ink-3);
  text-align: center;
  line-height: 2.2;
}

/* ── 章节页 ─────────────────────────────── */

.chapter-head {
  padding: clamp(2.6rem, 8vh, 4.5rem) 0 0;
}

.chapter-head .part {
  margin: 0 0 1.1rem;
  font-size: 0.72rem;
  letter-spacing: 0.2em;
  color: var(--ink-3);
}

.chapter-head h1 {
  margin: 0;
  font-size: clamp(1.62rem, 5.2vw, 2.1rem);
  line-height: 1.55;
  font-weight: 600;
  letter-spacing: 0.03em;
}

.chapter-head h1 .num {
  display: block;
  margin-bottom: 0.5rem;
  font-size: 0.72rem;
  font-weight: 400;
  letter-spacing: 0.3em;
  color: var(--accent);
}

.chapter-head .meta {
  margin: 1.4rem 0 0;
  padding-bottom: 1.6rem;
  border-bottom: 1px solid var(--rule);
  font-size: 0.74rem;
  letter-spacing: 0.12em;
  color: var(--ink-3);
}

/* ── 正文 ───────────────────────────────── */

article { padding-top: 1.2rem; }

article p {
  margin: 0 0 0.72em;
  text-indent: 2em;
}

article > h2:first-child { margin-top: 1.1em; }

article h2 {
  margin: 2.5em 0 1em;
  font-size: 1.28em;
  font-weight: 600;
  line-height: 1.6;
  letter-spacing: 0.02em;
  page-break-after: avoid;
}

article h2::before {
  content: "";
  display: inline-block;
  width: 0.4em;
  height: 0.4em;
  margin-right: 0.62em;
  vertical-align: 0.14em;
  background: var(--accent);
  border-radius: 1px;
}

article h3 {
  margin: 2em 0 0.7em;
  font-size: 1.06em;
  font-weight: 600;
  color: var(--ink-2);
}

article strong {
  font-weight: 700;
  color: var(--strong);
}

article em { font-style: normal; color: var(--ink-2); }

article blockquote {
  margin: 1.7em 0;
  padding: 0.1em 0 0.1em 1.15em;
  border-left: 2px solid var(--accent);
  color: var(--ink-2);
  font-size: 0.96em;
}
article blockquote p { text-indent: 0; margin: 0.45em 0; }

article p.li {
  position: relative;
  padding-left: 1.25em;
  text-indent: 0;
}
article p.li::before {
  content: "";
  position: absolute;
  left: 0.3em;
  top: 0.92em;
  width: 0.3em;
  height: 0.3em;
  background: var(--accent);
  border-radius: 50%;
  opacity: 0.7;
}

article hr {
  margin: 2.6em 0;
  border: 0;
  height: 1px;
  background: var(--rule);
}

article code {
  padding: 0.12em 0.36em;
  border: 1px solid var(--rule);
  border-radius: 3px;
  background: var(--code-bg);
  font-family: var(--mono);
  font-size: 0.86em;
  letter-spacing: 0;
}

article pre {
  margin: 1.5em 0;
  padding: 1em 1.15em;
  overflow-x: auto;
  border: 1px solid var(--rule);
  border-radius: 5px;
  background: var(--code-bg);
  line-height: 1.75;
  -webkit-overflow-scrolling: touch;
}

article pre code {
  padding: 0;
  border: 0;
  background: none;
  font-size: 0.83em;
}

article table {
  width: 100%;
  margin: 1.6em 0;
  border-collapse: collapse;
  font-size: 0.9em;
}
article th, article td {
  padding: 0.55em 0.7em;
  border-bottom: 1px solid var(--rule);
  text-align: left;
  vertical-align: top;
}
article th { font-weight: 600; color: var(--ink-2); }

/* ── 翻页 ───────────────────────────────── */

.pager {
  display: flex;
  justify-content: space-between;
  gap: 1.2rem;
  margin-top: 3.6rem;
  padding-top: 1.6rem;
  border-top: 1px solid var(--rule);
  font-size: 0.8rem;
}

.pager a {
  display: block;
  max-width: 46%;
  color: var(--ink-2);
  letter-spacing: 0.04em;
}
.pager a:hover { color: var(--accent); text-decoration: none; }
.pager .dir {
  display: block;
  font-size: 0.68rem;
  letter-spacing: 0.18em;
  color: var(--ink-3);
  margin-bottom: 0.3em;
}
.pager .next { text-align: right; margin-left: auto; }

/* ── 手机 ───────────────────────────────── */

@media (max-width: 640px) {
  body { font-size: 17.5px; line-height: 1.9; }
  .wrap { padding: 0 1.15rem; }
  .topbar { font-size: 0.72rem; padding: 0.68rem 1.15rem; }
  .topbar nav { gap: 0.85rem; }
  .book-title { font-size: clamp(2.6rem, 15vw, 3.4rem); }
  article h2 { margin-top: 2.1em; }
  .pager { flex-direction: column; gap: 1rem; }
  .pager a { max-width: 100%; }
  .pager .next { text-align: left; margin-left: 0; }
}

/* ── 打印 ───────────────────────────────── */

@media print {
  .topbar, .progress, .pager, .cta, .colophon { display: none; }
  body { background: #fff; color: #000; font-size: 11pt; line-height: 1.85; }
  article h2 { page-break-after: avoid; }
  article pre, article blockquote, article table { page-break-inside: avoid; }
  a { color: #000; }
}