:root {
  --bg: #faf9f7;
  --bg-soft: #f4f2ee;
  --text: #2d2d2d;
  --text-soft: #5a5a5a;
  --text-mute: #999999;
  --border: #e8e5e0;
  --accent: #1e40af;
  --accent-soft: #eff6ff;
  --code-bg: #f0ede8;
}

[data-theme="dark"] {
  --bg: #0f0f0f;
  --bg-soft: #161616;
  --text: #e5e5e5;
  --text-soft: #aaaaaa;
  --text-mute: #777777;
  --border: #2a2a2a;
  --accent: #60a5fa;
  --accent-soft: #1a2233;
  --code-bg: #1a1a1a;
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, "Segoe UI", "Microsoft YaHei", "PingFang SC", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.9;
  font-size: 17px;
  transition: background 0.2s, color 0.2s;
}

/* Top bar */
.topbar {
  position: sticky; top: 0; z-index: 100;
  background: var(--bg);
  border-bottom: 1px solid var(--border);
}
.topbar-inner {
  max-width: 1200px; margin: 0 auto;
  padding: 0.7rem 1.5rem;
  display: flex; align-items: center; gap: 2rem;
}
.brand {
  font-size: 1.15rem; font-weight: 700;
  color: var(--text); text-decoration: none;
  letter-spacing: 2px;
}
.topnav { display: flex; gap: 1.5rem; flex: 1; flex-wrap: wrap; }
.topnav a {
  font-size: 0.9rem; color: var(--text-soft);
  text-decoration: none; padding: 0.3rem 0;
  border-bottom: 2px solid transparent;
  transition: color 0.15s, border-color 0.15s;
}
.topnav a:hover { color: var(--text); }
.topnav a.active { color: var(--text); border-bottom-color: var(--accent); }
.theme-toggle {
  background: none; border: 1px solid var(--border);
  color: var(--text-soft); border-radius: 6px;
  padding: 0.3rem 0.6rem; cursor: pointer; font-size: 1rem;
}
.theme-toggle:hover { color: var(--text); }

/* Layout: sidebar + content */
.layout {
  max-width: 1200px; margin: 0 auto;
  display: grid;
  grid-template-columns: 240px 1fr;
  gap: 3rem;
  padding: 2.5rem 1.5rem;
}

.sidebar {
  position: sticky; top: 80px;
  align-self: start;
  max-height: calc(100vh - 100px);
  overflow-y: auto;
  font-size: 0.9rem;
}
.sidebar-group { margin-bottom: 1.5rem; }
.sidebar-title {
  font-size: 0.72rem; letter-spacing: 2px;
  color: var(--text-mute);
  text-transform: uppercase;
  margin-bottom: 0.6rem;
  font-weight: 600;
}
.sidebar ul { list-style: none; }
.sidebar li { margin-bottom: 0.15rem; }
.sidebar a {
  display: block; padding: 0.3rem 0.7rem;
  color: var(--text-soft); text-decoration: none;
  border-left: 2px solid transparent;
  border-radius: 0 4px 4px 0;
  transition: all 0.15s;
}
.sidebar a:hover { color: var(--text); background: var(--bg-soft); }
.sidebar a.active {
  color: var(--accent);
  border-left-color: var(--accent);
  background: var(--accent-soft);
  font-weight: 500;
}

/* Article */
.content { min-width: 0; }
article h1 {
  font-size: 2rem; letter-spacing: 1px;
  margin-bottom: 0.8rem; font-weight: 600;
}
article .lead {
  font-size: 1.05rem; color: var(--text-soft);
  margin-bottom: 2rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--border);
}
article h2 {
  font-size: 1.35rem; margin: 2.5rem 0 1rem;
  font-weight: 600;
}
article h3 {
  font-size: 1.1rem; margin: 1.8rem 0 0.8rem;
  font-weight: 600;
}
article p { margin-bottom: 1rem; }
article ul, article ol { margin: 1rem 0 1rem 1.5rem; }
article li { margin-bottom: 0.4rem; }
article blockquote {
  border-left: 3px solid var(--accent);
  padding: 0.8rem 1.2rem;
  margin: 1.2rem 0;
  background: var(--accent-soft);
  border-radius: 0 6px 6px 0;
}
article table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
  font-size: 0.95rem;
}
article th, article td {
  padding: 0.6rem 0.9rem;
  text-align: left;
  border-bottom: 1px solid var(--border);
}
article th {
  font-weight: 600;
  background: var(--bg-soft);
  font-size: 0.88rem;
}
article hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 2.5rem 0;
}
article a { color: var(--accent); text-decoration: none; }
article a:hover { text-decoration: underline; }

.page-nav {
  display: flex;
  justify-content: space-between;
  margin-top: 3rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border);
  font-size: 0.9rem;
}
.page-nav a { color: var(--accent); text-decoration: none; }
.page-nav a:hover { text-decoration: underline; }

/* Simple content pages (no sidebar) */
.home { max-width: 760px; margin: 0 auto; padding: 3rem 1.5rem; }

/* Front page */
.front {
  min-height: 78vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 4rem 1.5rem;
  max-width: 780px;
  margin: 0 auto;
}
.front h1 {
  font-size: 2.2rem;
  font-weight: 600;
  letter-spacing: 6px;
  margin-bottom: 0.8rem;
}
.front .sub {
  font-size: 0.95rem;
  color: var(--text-soft);
  letter-spacing: 1px;
  margin-bottom: 4rem;
}
.front .triad {
  list-style: none;
  margin: 0 0 3rem;
  padding: 0;
  text-align: left;
  display: inline-block;
}
.front .triad li {
  font-size: 1.05rem;
  color: var(--text);
  line-height: 2.2;
  letter-spacing: 0.5px;
}
.front .triad .label {
  display: inline-block;
  min-width: 5.5rem;
  color: var(--accent);
  font-weight: 600;
  letter-spacing: 1px;
}
.front .closing {
  font-size: 0.95rem;
  color: var(--text-mute);
  margin-bottom: 4rem;
  letter-spacing: 1px;
}
.front-nav {
  display: flex;
  gap: 2.5rem;
  justify-content: center;
  flex-wrap: wrap;
}
.front-nav a {
  color: var(--accent);
  text-decoration: none;
  font-size: 0.95rem;
  letter-spacing: 1px;
  border-bottom: 1px solid transparent;
  padding-bottom: 2px;
  transition: border-color 0.15s;
}
.front-nav a:hover { border-bottom-color: var(--accent); }

/* Footer */
.footer {
  text-align: center;
  padding: 2rem 1.5rem;
  border-top: 1px solid var(--border);
  color: var(--text-mute);
  font-size: 0.85rem;
  line-height: 2;
  margin-top: 3rem;
}
.footer a { color: var(--text-mute); text-decoration: none; }
.footer a:hover { color: var(--text-soft); }

/* Resp
@media (max-width: 900px) {
  .topbar-inner { flex-wrap: wrap; gap: 0.8rem; }
  .topnav { gap: 0.8rem; font-size: 0.85rem; }
  .layout { grid-template-columns: 1fr; gap: 1.5rem; padding: 1.5rem 1rem; }
  .sidebar {
    position: static; max-height: none;
    border-bottom: 1px solid var(--border);
    padding-bottom: 1rem;
  }
  article h1 { font-size: 1.5rem; }
  article h2 { font-size: 1.15rem; }
  .home { padding: 2rem 1rem; }
}

@media (max-width: 700px) {
  .front h1 { font-size: 1.6rem; letter-spacing: 3px; }
  .front .sub { margin-bottom: 3rem; }
  .front .triad li { font-size: 0.95rem; line-height: 2; }
  .front .triad .label {
    display: block;
    min-width: 0;
    margin-bottom: 0.2rem;
  }
  .front .closing { margin-bottom: 3rem; }
  .front-nav { gap: 1.5rem; }
}

/* 首页排版重做 */
.front {
  min-height: calc(100vh - 60px);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 3rem 1.5rem;
  max-width: 720px;
  margin: 0 auto;
}
.front h1 {
  font-size: 2rem;
  font-weight: 600;
  letter-spacing: 8px;
  margin-bottom: 1rem;
}
.front .sub {
  font-size: 0.9rem;
  color: var(--text-mute);
  letter-spacing: 2px;
  margin-bottom: 5rem;
}
.front .triad {
  list-style: none;
  margin: 0 0 5rem;
  padding: 0;
  text-align: left;
  display: inline-block;
}
.front .triad li {
  font-size: 1rem;
  color: var(--text);
  line-height: 2.4;
  letter-spacing: 0.5px;
  white-space: nowrap;
}
.front .triad .label {
  display: inline-block;
  min-width: 6rem;
  color: var(--accent);
  font-weight: 600;
  letter-spacing: 2px;
}
.front .closing {
  display: none;
}
.front-nav {
  display: flex;
  gap: 3rem;
  justify-content: center;
  flex-wrap: wrap;
}
.front-nav a {
  color: var(--text-soft);
  text-decoration: none;
  font-size: 0.9rem;
  letter-spacing: 3px;
  transition: color 0.15s;
}
.front-nav a:hover {
  color: var(--accent);
}
@media (max-width: 700px) {
  .front h1 { font-size: 1.5rem; letter-spacing: 4px; }
  .front .sub { margin-bottom: 3rem; }
  .front .triad { margin-bottom: 3rem; }
  .front .triad li {
    font-size: 0.9rem;
    line-height: 2.2;
    white-space: normal;
  }
  .front .triad .label {
    display: block;
    min-width: 0;
    margin-bottom: 0.1rem;
  }
  .front-nav { gap: 1.5rem; }
  .front-nav a { font-size: 0.85rem; letter-spacing: 2px; }
}

/* 公理条目 */
.axiom {
  margin: 1.8rem 0;
  padding-left: 1.2rem;
  border-left: 3px solid var(--border);
  transition: border-color 0.15s;
}
.axiom:hover {
  border-left-color: var(--accent);
}
.axiom-label {
  font-size: 0.8rem;
  color: var(--text-mute);
  letter-spacing: 2px;
  margin-bottom: 0.3rem;
}
.axiom-body {
  font-size: 1.15rem;
  font-weight: 500;
  color: var(--text);
  line-height: 1.7;
}

/* 数字列表 */
.num-list {
  list-style: none;
  margin: 1.5rem 0;
  padding: 0;
}
.num-list li {
  padding: 0.7rem 0;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: baseline;
  gap: 1.5rem;
}
.num-list li:last-child {
  border-bottom: none;
}
.num-list .num {
  font-family: "SF Mono", Menlo, Consolas, monospace;
  font-size: 1.05rem;
  color: var(--accent);
  font-weight: 600;
  min-width: 9rem;
}
.num-list .desc {
  font-size: 0.95rem;
  color: var(--text-soft);
}
@media (max-width: 700px) {
  .num-list li {
    flex-direction: column;
    gap: 0.2rem;
  }
  .axiom-body { font-size: 1.05rem; }
}

/* 移动端强制单列修复 */
@media (max-width: 900px) {
  .layout { display: block !important; padding: 1rem !important; }
  .sidebar { position: static !important; max-height: none !important; margin-bottom: 2rem !important; border-right: none !important; }
  .content { width: 100% !important; max-width: 100% !important; min-width: 0 !important; }
  article { width: 100% !important; max-width: 100% !important; }
  .topbar-inner { flex-wrap: wrap !important; gap: 0.8rem !important; }
  .topnav { gap: 0.8rem !important; font-size: 0.85rem !important; }
}

/* 移动端适配 */
@media (max-width: 768px) {
  .layout {
    display: block !important;
  }
  .sidebar {
    width: 100% !important;
    margin-bottom: 2rem !important;
    border-right: none !important;
    border-bottom: 1px solid rgba(128,128,128,0.15) !important;
    padding-bottom: 1rem !important;
  }
  .content {
    width: 100% !important;
    max-width: 100% !important;
    padding-left: 0 !important;
  }
  .topnav {
    flex-wrap: wrap !important;
    gap: 0.8rem !important;
    font-size: 0.9rem !important;
  }
  .topbar-inner {
    flex-wrap: wrap !important;
    gap: 0.5rem !important;
  }
  article {
    max-width: 100% !important;
    padding: 0 !important;
  }
}