/* ==========================================================
   《双螺旋情书》在线阅读站 · 主题
   —— 深夜机房 · 双链同旋 · 碳基与硅基 ——
   底色是凌晨三点的实验室；一条链是荧光薄荷（ZERO-0），
   一条链是暖琥珀（沈知微），它们缠绕、交叠、永不分离。
   ========================================================== */

:root {
  --bg: #0a0d11;
  --bg-glow: #111a22;
  --panel: #0f151b;
  --line: #1c262e;
  --ink: #d9d4c7;
  --ink-soft: #b3ad9f;
  --ink-dim: #878d91;
  --ai: #7ee2b8;      /* 硅基 · 荧光薄荷 */
  --human: #e0a184;   /* 碳基 · 暖琥珀 */
  --serif: "Noto Serif CJK SC", "Source Han Serif SC", "Songti SC", "STSong", "SimSun", serif;
  --mono: ui-monospace, "SF Mono", "JetBrains Mono", "Menlo", "Consolas", monospace;
}

* { box-sizing: border-box; }

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

body {
  margin: 0;
  background:
    radial-gradient(1100px 700px at 50% -8%, var(--bg-glow), transparent 72%),
    var(--bg);
  color: var(--ink);
  font-family: var(--serif);
  line-height: 2;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; text-decoration: none; }

::selection { background: var(--ai); color: #06210f; }

a:focus-visible { outline: 1px solid var(--ai); outline-offset: 4px; }

.mono { font-family: var(--mono); }

/* ---------- 双螺旋插画 ---------- */

.helix { display: block; height: auto; }
.helix line { stroke: rgba(217, 212, 199, 0.16); stroke-width: 1; }
.helix .strand { fill: none; stroke-width: 1.6; stroke-linecap: round; }
.helix .strand-ai { stroke: var(--ai); }
.helix .strand-human { stroke: var(--human); }

/* ---------- 首页 · 封面 ---------- */

.hero {
  text-align: center;
  padding: 10vh 1.5rem 3rem;
}

.kicker {
  margin: 0 0 1.8rem;
  font-size: 0.78rem;
  letter-spacing: 0.22em;
  color: var(--ink-dim);
}

.book-title {
  margin: 0;
  font-size: clamp(2.6rem, 9vw, 4.6rem);
  font-weight: 600;
  letter-spacing: 0.18em;
  text-indent: 0.18em;      /* 抵消字间距，保持视觉居中 */
  color: #f0e9da;
}

.hero .helix {
  width: min(340px, 80vw);
  margin: 2.6rem auto;
  opacity: 0.9;
}

.tagline {
  margin: 0;
  font-size: clamp(1rem, 3vw, 1.2rem);
  letter-spacing: 0.1em;
  color: var(--ink-soft);
}

/* ---------- 简介 ---------- */

.synopsis {
  max-width: 36em;
  margin: 0 auto;
  padding: 1.5rem 1.5rem 2rem;
  font-size: 1.06rem;
  color: var(--ink-soft);
}

.synopsis p { margin: 1.25em 0; }

/* ---------- 标签 ---------- */

.tags {
  max-width: 36em;
  margin: 0 auto 3.2rem;
  padding: 0 1.5rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
  justify-content: center;
}

.tag {
  font-size: 0.76rem;
  letter-spacing: 0.06em;
  color: var(--ink-dim);
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 0.3em 0.95em;
  transition: color 0.25s, border-color 0.25s;
}

.tag:hover { color: var(--ink); border-color: var(--ai); }

/* ---------- 目录 ---------- */

.toc {
  max-width: 40em;
  margin: 0 auto;
  padding: 0 1.5rem 4rem;
}

.toc-heading {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  margin: 0 0 0.5rem;
  padding-bottom: 0.9rem;
  border-bottom: 1px solid var(--line);
}

.toc-heading .mark {
  font-size: 0.95rem;
  letter-spacing: 0.4em;
  color: var(--ink);
}

.toc-count { font-size: 0.72rem; letter-spacing: 0.12em; color: var(--ink-dim); }

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

.toc-list li { border-bottom: 1px solid rgba(28, 38, 46, 0.55); }

.toc-list a {
  display: flex;
  align-items: baseline;
  gap: 1.1em;
  padding: 0.85rem 0.3rem;
  transition: background 0.25s, padding-left 0.25s;
}

.toc-list a:hover { background: var(--panel); padding-left: 0.75rem; }

.toc-no {
  flex: none;
  width: 4.2em;
  font-size: 0.78rem;
  letter-spacing: 0.1em;
  color: var(--ink-dim);
  transition: color 0.25s;
}

.toc-list a:hover .toc-no { color: var(--ai); }

.toc-title {
  font-size: 1.02rem;
  color: var(--ink-soft);
  transition: color 0.25s;
}

.toc-list a:hover .toc-title { color: var(--ink); }

/* ---------- 阅读页 · 顶栏 ---------- */

.reader-head {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.75rem 1.2rem;
  font-size: 0.85rem;
  background: rgba(10, 13, 17, 0.82);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}

.reader-book { letter-spacing: 0.1em; color: var(--ink-soft); transition: color 0.2s; }
.reader-book:hover { color: var(--ai); }
.reader-pos { font-size: 0.72rem; letter-spacing: 0.14em; color: var(--ink-dim); }

/* ---------- 阅读页 · 正文 ---------- */

.chapter {
  max-width: 36em;
  margin: 0 auto;
  padding: 3.5rem 1.5rem 2rem;
}

.chapter-no {
  margin: 0 0 1.2rem;
  text-align: center;
  font-size: 0.8rem;
  letter-spacing: 0.32em;
  color: var(--ai);
}

.chapter-title {
  margin: 0;
  text-align: center;
  font-size: clamp(1.5rem, 4.5vw, 2rem);
  font-weight: 600;
  letter-spacing: 0.06em;
}

.chapter-body {
  margin-top: 2.8rem;
  font-size: 1.07rem;
  line-height: 2.1;
  color: #d6d1c4;
}

.chapter-body p { margin: 1.35em 0; }
.chapter-body strong { color: var(--ink); font-weight: 600; }
.chapter-body em { color: var(--ink-soft); }
.chapter-body code {
  font-family: var(--mono);
  font-size: 0.9em;
  color: var(--ai);
  background: var(--panel);
  padding: 0.1em 0.4em;
  border-radius: 3px;
}
.chapter-body blockquote {
  margin: 1.8em 0;
  padding: 0.2em 1.1em;
  border-left: 2px solid var(--human);
  color: var(--ink-soft);
}

/* ---------- 阅读页 · 翻页 ---------- */

.pager {
  max-width: 36em;
  margin: 0 auto;
  padding: 2.5rem 1.5rem 4rem;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 1rem;
  align-items: stretch;
}

.pager-link {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
  min-width: 0;
  padding: 0.9rem 1.1rem;
  border: 1px solid var(--line);
  border-radius: 8px;
  transition: border-color 0.25s, background 0.25s;
}

.pager-link:hover { border-color: var(--ai); background: var(--panel); }

.pager-link .dir { font-size: 0.72rem; letter-spacing: 0.2em; color: var(--ink-dim); transition: color 0.25s; }
.pager-link:hover .dir { color: var(--ai); }

.pager-link .t {
  font-size: 0.95rem;
  color: var(--ink-soft);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.pager-link.next { text-align: right; align-items: flex-end; }
.pager-link.toc-link { align-items: center; justify-content: center; color: var(--ink-dim); }
.pager-link.toc-link:hover { color: var(--ink); }
.pager-link.is-empty { visibility: hidden; }

/* ---------- 页脚 ---------- */

.footer {
  text-align: center;
  padding: 1rem 1.5rem 3.5rem;
}

.footer .helix { width: 140px; margin: 0 auto 1.2rem; opacity: 0.55; }

.foot-line {
  margin: 0 0 0.7rem;
  font-size: 0.95rem;
  letter-spacing: 0.32em;
  text-indent: 0.32em;
  color: var(--ink-soft);
}

.foot-sub {
  margin: 0;
  font-size: 0.7rem;
  letter-spacing: 0.12em;
  color: var(--ink-dim);
}

/* ---------- 小屏 ---------- */

@media (max-width: 640px) {
  .pager { grid-template-columns: 1fr; }
  .pager-link.is-empty { display: none; }
  .pager-link.next { text-align: left; align-items: flex-start; }
  .chapter { padding-top: 2.6rem; }
  .hero { padding-top: 8vh; }
}

@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; }
}