:root {
  --bg: #f4f1e8;
  --panel: rgba(255, 253, 247, 0.82);
  --panel-strong: rgba(255, 251, 240, 0.95);
  --text: #1f1d18;
  --muted: #6a6458;
  --line: rgba(50, 43, 31, 0.14);
  --accent: #10684d;
  --accent-soft: rgba(16, 104, 77, 0.12);
  --shadow: 0 18px 48px rgba(45, 37, 23, 0.12);
  --code: #fbf7ef;
  --font-serif: "京華老宋體", "京华老宋体", "JingHua Old Song", "Songti SC", "Songti TC", "STSong", "Iowan Old Style", "Palatino Linotype", "Noto Serif SC", serif;
}

* {
  box-sizing: border-box;
}

html {
  font-size: 16px;
  overflow-x: hidden;
}

body {
  margin: 0;
  overflow-x: hidden;
  -webkit-text-size-adjust: 100%;
  color: var(--text);
  background:
    radial-gradient(circle at top left, rgba(233, 213, 173, 0.35), transparent 32%),
    radial-gradient(circle at bottom right, rgba(111, 156, 133, 0.2), transparent 28%),
    var(--bg);
  font-family: var(--font-serif);
}

a {
  color: var(--accent);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

.layout {
  min-height: 100vh;
  display: grid;
  grid-template-columns: 320px minmax(0, 1fr);
}

.sidebar {
  position: sticky;
  top: 0;
  height: 100vh;
  overflow: auto;
  border-right: 1px solid var(--line);
  background: var(--panel);
  backdrop-filter: blur(12px);
}

.sidebar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 24px 24px 12px;
}

.brand {
  font-size: 1.1rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--text);
}

.sidebar-close,
.menu-button {
  border: 0;
  background: transparent;
  color: var(--text);
  font-size: 1.5rem;
  cursor: pointer;
}

.sidebar-search {
  padding: 0 24px 20px;
}

.sidebar-search input {
  width: 100%;
  padding: 12px 14px;
  border-radius: 12px;
  border: 1px solid var(--line);
  background: white;
  font: inherit;
}

.sidebar-nav {
  padding: 0 14px 40px;
}

.sidebar-group {
  margin-bottom: 8px;
  border: none;
}

.sidebar-group summary {
  margin: 0 10px 4px;
  padding: 6px 0;
  font-size: 0.82rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  color: var(--muted);
  cursor: pointer;
  user-select: none;
  list-style: none;
}

.sidebar-group summary::-webkit-details-marker {
  display: none;
}

.sidebar-group summary::before {
  content: "▸ ";
  display: inline;
  font-size: 0.7rem;
  transition: transform 0.15s;
}

.sidebar-group[open] > summary::before {
  content: "▾ ";
}

.sidebar-group h3 {
  margin: 0 10px 8px;
  font-size: 0.82rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  color: var(--muted);
}

.sidebar-group ul {
  list-style: none;
  margin: 0;
  padding: 0;
}

.sidebar-group li {
  margin: 0;
}

.sidebar-group a {
  display: block;
  padding: 9px 10px;
  border-radius: 10px;
  color: var(--text);
  line-height: 1.35;
}

.sidebar-note-title,
.sidebar-note-meta {
  display: block;
}

.sidebar-note-meta {
  margin-top: 3px;
  font-size: 0.78rem;
  color: var(--muted);
}

.sidebar-group a:hover,
.sidebar-group a.is-active {
  background: var(--accent-soft);
  color: var(--accent);
  text-decoration: none;
}

.main {
  min-width: 0;
  padding: 32px;
}

.topbar {
  max-width: 980px;
  margin: 0 auto 26px;
  display: flex;
  align-items: flex-start;
  gap: 12px;
}

.topbar-meta {
  min-width: 0;
  word-break: break-word;
}

.topbar-meta h1 {
  margin: 4px 0 10px;
  font-size: clamp(1.4rem, 3.5vw, 2.6rem);
  line-height: 1.25;
}

.topbar-meta p,
.eyebrow {
  margin: 0;
  color: var(--muted);
}

.topbar-subline {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 14px;
}

.eyebrow {
  text-transform: uppercase;
  letter-spacing: 0.12em;
  font-size: 0.78rem;
}

.note-content {
  max-width: 980px;
  margin: 0 auto;
  padding: 34px;
  background: var(--panel-strong);
  border: 1px solid var(--line);
  border-radius: 24px;
  box-shadow: var(--shadow);
}

.markdown-body {
  line-height: 1.8;
  font-size: 1.05rem;
}

.markdown-body h1,
.markdown-body h2,
.markdown-body h3,
.markdown-body h4 {
  line-height: 1.15;
  margin: 1.8em 0 0.8em;
  scroll-margin-top: 32px;
}

.markdown-body p,
.markdown-body ul,
.markdown-body ol,
.markdown-body blockquote,
.markdown-body pre,
.markdown-body table {
  margin: 0 0 1.1em;
}

.markdown-body img {
  max-width: 100%;
  height: auto;
  display: block;
  margin: 18px auto;
  border-radius: 18px;
  box-shadow: 0 14px 34px rgba(24, 20, 12, 0.12);
}

.markdown-body code {
  font-family: "SFMono-Regular", "JetBrains Mono", "Cascadia Code", monospace;
  background: var(--code);
  padding: 0.18em 0.42em;
  border-radius: 6px;
  font-size: 0.92em;
}

.markdown-body pre {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  padding: 18px;
  background: #211d17;
  color: #f6eee3;
  border-radius: 18px;
  max-width: 100%;
}

.markdown-body pre code {
  background: transparent;
  color: inherit;
  padding: 0;
}

.markdown-body blockquote {
  margin-left: 0;
  padding: 4px 0 4px 20px;
  border-left: 4px solid rgba(16, 104, 77, 0.35);
  color: #423c32;
}

.markdown-body table {
  width: 100%;
  border-collapse: collapse;
  display: block;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.markdown-body th,
.markdown-body td {
  padding: 10px 12px;
  border: 1px solid var(--line);
  text-align: left;
  white-space: nowrap;
}

.markdown-body td:first-child,
.markdown-body th:first-child {
  white-space: normal;
  min-width: 80px;
}

.redirect-page {
  min-height: 100vh;
  display: grid;
  place-items: center;
}

.redirect-card {
  padding: 28px 30px;
  border-radius: 18px;
  background: var(--panel-strong);
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
}

@media (min-width: 961px) {
  .menu-button,
  .sidebar-close {
    display: none;
  }
}

@media (max-width: 960px) {
  .layout {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: fixed;
    inset: 0 auto 0 0;
    width: min(86vw, 340px);
    max-width: 340px;
    transform: translateX(-100%);
    transition: transform 180ms ease;
    z-index: 10;
    box-shadow: 22px 0 40px rgba(21, 17, 11, 0.14);
  }

  body.sidebar-open .sidebar {
    transform: translateX(0);
  }

  .main {
    padding: 12px;
    max-width: 100vw;
  }

  .topbar {
    margin-bottom: 14px;
    flex-direction: row;
    align-items: center;
    gap: 10px;
  }

  .menu-button {
    flex-shrink: 0;
  }

  .topbar-meta h1 {
    font-size: 1.25rem;
    line-height: 1.3;
    margin: 2px 0 6px;
  }

  .topbar-subline {
    flex-direction: column;
    gap: 2px;
    font-size: 0.75rem;
  }

  .eyebrow {
    font-size: 0.7rem;
  }

  .note-content {
    padding: 16px;
    border-radius: 14px;
    overflow-x: hidden;
  }

  .markdown-body {
    font-size: 0.95rem;
    line-height: 1.75;
  }

  .markdown-body h1 { font-size: 1.4rem; }
  .markdown-body h2 { font-size: 1.2rem; }
  .markdown-body h3 { font-size: 1.05rem; }

  .markdown-body th,
  .markdown-body td {
    padding: 8px 10px;
    font-size: 0.85rem;
  }

  .markdown-body pre {
    padding: 14px;
    font-size: 0.82rem;
    border-radius: 12px;
  }

  .markdown-body blockquote {
    padding-left: 14px;
    font-size: 0.93rem;
  }
}

/* ── Extra small screens (≤480px) ───────────────────────── */
@media (max-width: 480px) {
  .main {
    padding: 8px;
  }

  .note-content {
    padding: 14px;
    border-radius: 12px;
  }

  .topbar-meta h1 {
    font-size: 1.1rem;
  }
}

/* ── Top navigation bar (multi-section) ───────────────────────── */
.top-nav {
  display: flex;
  gap: 4px;
  padding: 8px 16px;
  background: #1a1d27;
  border-bottom: 1px solid #2a2d3a;
}
.top-nav .nav-link {
  padding: 5px 14px;
  border-radius: 6px;
  font-size: 0.88rem;
  color: #888;
  text-decoration: none;
  transition: color 0.15s, background 0.15s;
}
.top-nav .nav-link:hover { color: #e6e6e6; background: #2a2d3a; }
.top-nav .nav-link.active {
  color: #fff;
  background: #2a3f6a;
}