:root {
  --ink: #071b2c;
  --muted: #5d6e7c;
  --accent: #277f80;
  --paper: rgba(251, 252, 253, 0.93);
  --rule: rgba(7, 27, 44, 0.14);
  font-family: Inter, "Noto Sans SC", "PingFang SC", system-ui, sans-serif;
  color: var(--ink);
  background:
    linear-gradient(180deg, rgba(7, 27, 44, 0.30), rgba(7, 27, 44, 0.58)),
    #dfe8ed url("../images/charles-scroll-background.jpg") center / cover fixed;
}
* { box-sizing: border-box; }
body { margin: 0; min-height: 100vh; line-height: 1.8; }
.reader-head {
  position: sticky;
  top: 0;
  z-index: 5;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 17px max(22px, calc((100vw - 920px) / 2));
  border-bottom: 1px solid var(--rule);
  background: rgba(251, 252, 253, 0.88);
  backdrop-filter: blur(16px) saturate(140%);
}
.reader-head a {
  display: inline-flex;
  align-items: center;
  padding: 7px 12px;
  border-radius: 999px;
  color: var(--ink);
  text-decoration: none;
  transition: color 180ms ease, background-color 180ms ease;
}
.reader-head a:hover {
  color: var(--accent);
  background: rgba(7, 27, 44, 0.06);
  text-decoration: none;
}
.brand { font-size: 20px; font-weight: 700; }
.back { color: var(--accent) !important; font-size: 14px; }
.reader-shell {
  display: grid;
  grid-template-columns: 220px minmax(0, 1fr);
  align-items: start;
  gap: 24px;
  width: min(1164px, calc(100% - 32px));
  margin: 42px auto 80px;
}
.toc-panel {
  position: sticky;
  top: 88px;
  max-height: calc(100vh - 112px);
  overflow: auto;
  border: 1px solid rgba(255, 255, 255, 0.7);
  border-radius: 14px;
  background: rgba(251, 252, 253, 0.9);
  box-shadow: 0 16px 42px rgba(7, 27, 44, 0.14);
  backdrop-filter: blur(14px) saturate(130%);
}
.toc-panel summary {
  position: sticky;
  top: 0;
  padding: 15px 17px;
  border-bottom: 1px solid var(--rule);
  background: rgba(251, 252, 253, 0.96);
  cursor: pointer;
  font-size: 14px;
  font-weight: 700;
}
.toc { display: grid; padding: 10px; }
.toc-link {
  padding: 7px 8px;
  border-radius: 7px;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.45;
  text-decoration: none;
}
.toc-link:hover { color: var(--accent); background: rgba(39, 127, 128, 0.08); }
.toc-link--sub { padding-left: 22px; font-size: 12px; }
/* 当前正在读的小节：左侧竖标尺 + 文字加深，和首页导轨同一套语言（不用下划线） */
.toc-link[aria-current="true"] {
  color: var(--ink);
  font-weight: 600;
  background: rgba(39, 127, 128, 0.12);
  box-shadow: inset 3px 0 0 var(--accent);
}
.toc-link[aria-current="true"]:hover { color: var(--ink); }
.toc-empty { padding: 8px; color: var(--muted); font-size: 13px; }
.markdown-body {
  min-width: 0;
  min-height: 65vh;
  padding: clamp(28px, 6vw, 72px);
  border: 1px solid rgba(255, 255, 255, 0.7);
  border-radius: 18px;
  background: var(--paper);
  box-shadow: 0 24px 70px rgba(7, 27, 44, 0.2);
}
.markdown-body h1, .markdown-body h2, .markdown-body h3 { line-height: 1.3; letter-spacing: -0.025em; }
.markdown-body h1 { margin: 0 0 32px; font-size: clamp(34px, 6vw, 58px); }
.article-upload-date {
  margin: -18px 0 34px;
  color: var(--muted);
  font-size: 14px;
  font-variant-numeric: tabular-nums;
}
.markdown-body h2 { margin: 48px 0 18px; padding-bottom: 10px; border-bottom: 1px solid var(--rule); font-size: 28px; }
.markdown-body h3 { margin: 32px 0 12px; font-size: 21px; }
.markdown-body p, .markdown-body ul, .markdown-body ol { margin: 0 0 20px; }
.markdown-body a { color: var(--accent); text-underline-offset: 3px; }
.markdown-body img { display: block; max-width: 100%; height: auto; margin: 30px auto; border-radius: 12px; }
.markdown-body blockquote { margin: 28px 0; padding: 12px 20px; border-left: 4px solid var(--accent); color: var(--muted); background: rgba(39, 127, 128, 0.07); }
.markdown-body blockquote p { margin: 0; }
.markdown-body code { padding: 2px 6px; border-radius: 5px; background: rgba(7, 27, 44, 0.08); font-family: "SFMono-Regular", Consolas, monospace; font-size: 0.9em; }
.markdown-body pre {
  overflow-x: auto;
  margin: 26px 0;
  padding: 20px;
  border: 1px solid #d5e0e7;
  border-radius: 10px;
  background: #f4f7f9;
  color: #243746;
  box-shadow: 0 8px 22px rgba(7, 27, 44, 0.06);
  line-height: 1.65;
  scrollbar-color: #a8bac6 transparent;
}
.markdown-body pre code,
.markdown-body pre code.hljs {
  display: block;
  overflow: visible;
  padding: 0;
  background: transparent;
  color: inherit;
}
.markdown-body hr { height: 1px; margin: 40px 0; border: 0; background: var(--rule); }
.table-wrap { overflow-x: auto; margin: 26px 0; }
table { width: 100%; border-collapse: collapse; font-size: 14px; }
th, td { padding: 10px 12px; border: 1px solid var(--rule); text-align: left; }
th { background: rgba(7, 27, 44, 0.06); }
.loading, .reader-error { color: var(--muted); }
.reader-error h1 { color: var(--ink); }
.reader-foot {
  padding: 34px 20px 38px;
  border-top: 1px solid rgba(7, 27, 44, 0.08);
  background: rgba(251, 252, 253, 0.94);
  color: rgba(7, 27, 44, 0.58);
  text-align: center;
  backdrop-filter: blur(14px) saturate(130%);
}
.reader-foot p {
  margin: 0;
  font-size: 15px;
  letter-spacing: 0.01em;
}
.back-top {
  position: fixed;
  right: 22px;
  bottom: 22px;
  z-index: 6;
  display: grid;
  place-items: center;
  width: 46px;
  height: 46px;
  border: 1px solid rgba(255, 255, 255, 0.62);
  border-radius: 50%;
  background: #071b2c;
  color: #fff;
  box-shadow: 0 12px 30px rgba(7, 27, 44, 0.28);
  cursor: pointer;
  opacity: 0;
  pointer-events: none;
  transform: translateY(10px);
  transition: opacity 180ms ease, transform 180ms ease;
}
.back-top.is-visible { opacity: 1; pointer-events: auto; transform: none; }
/* 正文可用宽度不足时，把目录改为文章前的折叠区，避免侧栏挤压正文。 */
@media (max-width: 1180px) {
  .reader-shell {
    grid-template-columns: minmax(0, 1fr);
    width: min(920px, calc(100% - 32px));
  }
  .toc-panel {
    position: static;
    width: 100%;
    max-height: none;
    margin: 0 0 32px;
    border-color: var(--rule);
    background: rgba(223, 232, 237, 0.56);
    box-shadow: none;
    backdrop-filter: none;
  }
  .toc-panel summary {
    position: static;
    background: transparent;
  }
  .toc-panel[open] { max-height: min(60vh, 520px); }
}
@media (max-width: 620px) {
  .reader-shell { width: calc(100% - 20px); margin-top: 18px; }
  .markdown-body { padding: 24px 20px; border-radius: 12px; }
  .reader-head { padding-inline: 16px; }
  .reader-foot { padding-block: 28px 32px; }
  .back-top { right: 14px; bottom: 14px; width: 42px; height: 42px; }
}