/* Bilingual paper reader — no framework, no build step. */
:root {
  --bg: #f6f7f9;
  --panel: #ffffff;
  --ink: #1b1d21;
  --ink-soft: #5b6270;
  --line: #e6e8ec;
  --accent: #0b5fff;
  --en-ink: #4a5568;
  --en-bg: #f8f9fb;
  --zh-bg: #ffffff;
  --radius: 10px;
  --maxw: 1500px;
  --colw: 860px;
}
@media (prefers-color-scheme: dark) {
  html:not([data-theme="light"]) {
    --bg: #101216; --panel: #171a1f; --ink: #e6e8ec; --ink-soft: #9aa3b2;
    --line: #262b33; --accent: #6ea8ff; --en-ink: #a8b3c4; --en-bg: #1b1f25; --zh-bg: #171a1f;
  }
}
html[data-theme="dark"] {
  --bg: #101216; --panel: #171a1f; --ink: #e6e8ec; --ink-soft: #9aa3b2;
  --line: #262b33; --accent: #6ea8ff; --en-ink: #a8b3c4; --en-bg: #1b1f25; --zh-bg: #171a1f;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0; background: var(--bg); color: var(--ink);
  font-family: "Noto Serif CJK SC", "Source Han Serif SC", "Songti SC", Georgia, "Times New Roman", serif;
  font-size: 16.5px; line-height: 1.8;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ---------- top bar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 50;
  display: flex; align-items: center; gap: 18px;
  padding: 10px 22px; background: color-mix(in srgb, var(--panel) 92%, transparent);
  backdrop-filter: blur(8px); border-bottom: 1px solid var(--line);
}
.brand { font-weight: 700; color: var(--ink); letter-spacing: .02em; white-space: nowrap; }
.topnav { display: flex; gap: 14px; flex: 1; overflow-x: auto; }
.topnav a { color: var(--ink-soft); font-size: 14px; white-space: nowrap; }
.modes { display: flex; border: 1px solid var(--line); border-radius: 99px; overflow: hidden; }
.modes button {
  border: 0; background: transparent; color: var(--ink-soft);
  padding: 5px 12px; font-size: 13px; cursor: pointer; font-family: inherit;
}
.modes button.on { background: var(--accent); color: #fff; }
.theme {
  border: 1px solid var(--line); background: transparent; color: var(--ink-soft);
  width: 30px; height: 30px; border-radius: 50%; cursor: pointer; font-size: 15px;
}

/* ---------- shell ---------- */
.shell { display: grid; grid-template-columns: 268px minmax(0, 1fr); gap: 34px; max-width: var(--maxw); margin: 0 auto; padding: 26px 26px 80px; }
.sidebar { position: sticky; top: 62px; align-self: start; max-height: calc(100vh - 80px); overflow-y: auto; font-size: 14px; }
.toc-label { font-size: 12px; letter-spacing: .12em; color: var(--ink-soft); text-transform: uppercase; margin: 6px 0 10px; }
.sidebar a { display: block; color: var(--ink-soft); padding: 3px 0 3px 10px; border-left: 2px solid transparent; line-height: 1.5; }
.sidebar a.toc-l2 { font-weight: 600; color: var(--ink); margin-top: 8px; }
.sidebar a.toc-l3 { padding-left: 22px; font-size: 13.5px; }
.sidebar a:hover { border-left-color: var(--line); text-decoration: none; }
.sidebar a.active { border-left-color: var(--accent); color: var(--accent); }
.content { min-width: 0; }
.mobile-toc { display: none; }

/* ---------- paper head ---------- */
.paper-head { background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius); padding: 26px 30px; margin-bottom: 28px; }
.kicker { font-size: 12.5px; letter-spacing: .1em; color: var(--accent); text-transform: uppercase; margin-bottom: 10px; }
.paper-head h1 { font-size: 1.72em; line-height: 1.35; margin: 0 0 8px; }
.paper-head h1 .h-en { display: block; font-size: .58em; font-weight: 500; color: var(--en-ink); margin-top: 6px; line-height: 1.4; }
.paper-head .sub { color: var(--ink-soft); font-size: 15px; }
.paper-head .sub .h-en { display: block; color: var(--en-ink); font-size: .92em; }
.paper-head .meta { color: var(--ink-soft); font-size: 13.5px; margin-top: 6px; }
.actions { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 16px; }
.btn { display: inline-block; border: 1px solid var(--line); border-radius: 8px; padding: 6px 12px; font-size: 13.5px; color: var(--ink); background: var(--bg); }
.btn:hover { border-color: var(--accent); color: var(--accent); text-decoration: none; }
.notice { margin-top: 16px; padding: 12px 14px; border-left: 3px solid #e8a33d; background: color-mix(in srgb, #e8a33d 8%, transparent); font-size: 14px; color: var(--ink-soft); border-radius: 0 6px 6px 0; }
.notice p { margin: .3em 0; }

/* ---------- article ---------- */
.article-body { max-width: var(--colw); }
.article-body h2 {
  font-size: 1.34em; margin: 2.1em 0 .7em; padding-bottom: .3em; border-bottom: 1px solid var(--line);
}
.article-body h3 { font-size: 1.12em; margin: 1.7em 0 .6em; }
.article-body h4 { font-size: 1em; margin: 1.4em 0 .5em; color: var(--ink-soft); }
.h-en { font-weight: 500; color: var(--en-ink); }
.article-body h2 .h-en, .article-body h3 .h-en, .article-body h4 .h-en {
  display: block; font-size: .62em; font-weight: 400; margin-top: 2px; letter-spacing: .01em;
}

/* paragraph pairs */
.pair {
  display: grid; grid-template-columns: 1fr; gap: 0;
  margin: 0 0 1.15em; border-left: 2px solid var(--line); padding-left: 14px;
}
.pair .en {
  font-family: ui-serif, Georgia, "Times New Roman", serif;
  font-size: .95em; line-height: 1.62; color: var(--en-ink);
  background: var(--en-bg); border-radius: 6px; padding: 8px 12px; margin-bottom: 7px;
}
.pair .zh p { margin: .2em 0; }
.pair .zh p:first-child { margin-top: 0; }
.pair .zh p:last-child { margin-bottom: 0; }
.pair.solo { border-left-color: transparent; padding-left: 0; }

/* two-column layout for wide screens */
@media (min-width: 1180px) {
  body.wide-pairs .pair { grid-template-columns: 1fr 1fr; gap: 20px; align-items: start; }
  body.wide-pairs .pair .en { margin-bottom: 0; }
}

.unit { margin: 1em 0; }
.unit.fig { text-align: center; }
.unit.fig img { max-width: 100%; height: auto; background: #fff; padding: 6px; border: 1px solid var(--line); border-radius: 6px; }
pre.code {
  background: color-mix(in srgb, var(--ink) 4%, var(--panel)); border: 1px solid var(--line);
  border-radius: 8px; padding: 12px 14px; overflow-x: auto; font-size: 13px; line-height: 1.5;
}
pre.code code { font-family: "Cascadia Mono", Consolas, Menlo, monospace; }
.article-body table { border-collapse: collapse; width: 100%; font-size: .9em; display: block; overflow-x: auto; }
.article-body th, .article-body td { border: 1px solid var(--line); padding: 6px 9px; vertical-align: top; }
.article-body blockquote { margin: 1em 0; padding: .3em 1em; border-left: 3px solid var(--line); color: var(--ink-soft); }

/* mode switching */
body[data-mode="zh"] .pair .en, body[data-mode="zh"] .h-en { display: none !important; }
body[data-mode="en"] .pair .zh, body[data-mode="en"] .h-zh { display: none !important; }
body[data-mode="en"] .pair .en { margin-bottom: 0; }
body[data-mode="en"] .unit, body[data-mode="en"] .notice { opacity: .55; }

/* ---------- home ---------- */
.home-main { max-width: 1080px; margin: 0 auto; padding: 46px 26px 90px; }
.hero h1 { font-size: 2.05em; line-height: 1.3; margin: 0 0 14px; }
.lead { color: var(--ink-soft); font-size: 1.06em; max-width: 46em; }
.cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(290px, 1fr)); gap: 18px; margin: 34px 0 44px; }
.card {
  display: block; background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 20px 22px; color: var(--ink); transition: border-color .15s, transform .15s;
}
.card:hover { border-color: var(--accent); transform: translateY(-2px); text-decoration: none; }
.card-venue { font-size: 12px; letter-spacing: .1em; color: var(--accent); text-transform: uppercase; }
.card h2 { font-size: 1.12em; margin: 8px 0 6px; line-height: 1.4; }
.card-en { font-size: .82em; color: var(--en-ink); line-height: 1.45; }
.card-sub { color: var(--ink-soft); font-size: .92em; margin: 10px 0 6px; }
.card-authors { font-size: .8em; color: var(--ink-soft); }
.prose { max-width: 44em; }
.prose h2 { font-size: 1.2em; margin-top: 2em; }

/* ---------- footer ---------- */
.foot { border-top: 1px solid var(--line); padding: 22px 26px 40px; color: var(--ink-soft); font-size: 12.5px; text-align: center; }
.foot p { margin: .4em 0; }

/* ---------- responsive ---------- */
@media (max-width: 1020px) {
  .shell { grid-template-columns: 1fr; padding: 18px 16px 60px; }
  .sidebar { display: none; }
  .mobile-toc { display: block; margin-bottom: 20px; font-size: 14px; }
  .mobile-toc details { background: var(--panel); border: 1px solid var(--line); border-radius: 8px; padding: 10px 14px; }
  .mobile-toc summary { cursor: pointer; color: var(--ink-soft); }
  .mobile-toc a { display: block; padding: 2px 0; }
  .topnav { display: none; }
  .paper-head { padding: 20px 18px; }
  body { font-size: 16px; }
}

/* ---------- print ---------- */
@media print {
  .topbar, .sidebar, .mobile-toc, .foot, .actions, .modes { display: none !important; }
  .shell { display: block; padding: 0; max-width: none; }
  .paper-head { border: 0; padding: 0; }
  .pair { break-inside: avoid; }
  .pair .en { background: none; border-left: 2px solid #ccc; }
  body { background: #fff; font-size: 11pt; }
}