/* ===== 基础变量 ===== */
:root {
  --bg: #f6f7fb;
  --panel: #ffffff;
  --text: #1c2030;
  --text-soft: #4b5266;
  --muted: #79809a;
  --border: #e6e8f0;
  --accent: #4f6bed;
  --accent-soft: #eef1ff;
  --code-bg: #1a1f33;
  --code-text: #dfe4f5;
  --radius: 14px;
  --sidebar-w: 286px;
  --mono: "SFMono-Regular", "JetBrains Mono", Consolas, "Courier New", monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1219;
    --panel: #161a24;
    --text: #e6e9f2;
    --text-soft: #b3bacd;
    --muted: #828ba3;
    --border: #262c3a;
    --accent: #7c93ff;
    --accent-soft: #1d2440;
    --code-bg: #0c0f16;
    --code-text: #cdd4e8;
  }
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  font-size: 15.5px;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}

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

/* ===== 布局 ===== */
.layout { display: flex; min-height: 100vh; }

/* ===== 侧边栏 ===== */
.sidebar {
  position: sticky;
  top: 0;
  flex: 0 0 var(--sidebar-w);
  width: var(--sidebar-w);
  height: 100vh;
  overflow-y: auto;
  padding: 26px 20px 20px;
  background: var(--panel);
  border-right: 1px solid var(--border);
}

.sidebar::-webkit-scrollbar { width: 6px; }
.sidebar::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }

.brand { margin-bottom: 18px; }

.brand-title {
  display: block;
  font-size: 17px;
  font-weight: 700;
  letter-spacing: .2px;
}

.brand-sub {
  margin: 6px 0 0;
  font-size: 12.5px;
  color: var(--muted);
  line-height: 1.6;
}

.search {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 0 10px;
  height: 36px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--bg);
  margin-bottom: 18px;
}

.search svg { width: 15px; height: 15px; fill: var(--muted); flex: none; }

.search input {
  flex: 1;
  border: 0;
  outline: 0;
  background: transparent;
  color: var(--text);
  font-size: 13px;
}

.nav-group { margin-bottom: 16px; }

.nav-group-head {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 0 8px;
  margin-bottom: 6px;
  font-size: 11.5px;
  font-weight: 600;
  letter-spacing: .6px;
  text-transform: uppercase;
  color: var(--muted);
}

.nav-count {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 17px;
  height: 17px;
  padding: 0 4px;
  border-radius: 5px;
  background: var(--accent-soft);
  color: var(--accent);
  font-size: 10.5px;
  letter-spacing: 0;
}

.nav-item {
  display: block;
  padding: 9px 10px;
  margin-bottom: 2px;
  border-radius: 9px;
  transition: background .16s, color .16s;
}

.nav-item:hover { background: var(--bg); }

.nav-item.is-active {
  background: var(--accent-soft);
  box-shadow: inset 2px 0 0 var(--accent);
}

.nav-item.is-active .nav-item-title { color: var(--accent); font-weight: 600; }

.nav-item-title {
  display: block;
  font-size: 13.5px;
  line-height: 1.5;
  color: var(--text-soft);
}

.nav-item-meta {
  display: block;
  margin-top: 3px;
  font-size: 11.5px;
  color: var(--muted);
}

.is-hidden { display: none !important; }

.side-foot {
  margin-top: 22px;
  padding-top: 14px;
  border-top: 1px solid var(--border);
  font-size: 12px;
  color: var(--muted);
  display: flex;
  align-items: center;
  gap: 8px;
}

.side-foot a:hover { color: var(--accent); }

.dot {
  width: 3px;
  height: 3px;
  border-radius: 50%;
  background: currentColor;
  display: inline-block;
  opacity: .55;
  flex: none;
}

/* ===== 主区 ===== */
.main { flex: 1; min-width: 0; }

.container {
  max-width: 820px;
  margin: 0 auto;
  padding: 56px 32px 40px;
}

/* ===== 首页 Hero ===== */
.hero { padding-bottom: 12px; }

.hero-kicker {
  margin: 0 0 10px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 1.4px;
  text-transform: uppercase;
  color: var(--accent);
}

.hero-title {
  margin: 0 0 14px;
  font-size: 34px;
  line-height: 1.3;
  letter-spacing: -.4px;
}

.hero-desc {
  margin: 0 0 26px;
  font-size: 15.5px;
  color: var(--text-soft);
}

.hero-stats { display: flex; gap: 34px; }

.stat { display: flex; flex-direction: column; }

.stat strong { font-size: 22px; line-height: 1.2; }

.stat span { font-size: 12px; color: var(--muted); margin-top: 2px; }

.section-title {
  margin: 46px 0 18px;
  font-size: 14px;
  font-weight: 600;
  letter-spacing: .6px;
  color: var(--muted);
  text-transform: uppercase;
}

/* ===== 文章卡片 ===== */
.card-list { display: grid; gap: 14px; }

.card {
  display: block;
  padding: 20px 22px;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: transform .18s, box-shadow .18s, border-color .18s;
}

.card:hover {
  transform: translateY(-2px);
  border-color: transparent;
  box-shadow: 0 10px 28px rgba(20, 28, 60, .10);
}

.card-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 10px;
}

.card-tag {
  padding: 3px 9px;
  border-radius: 6px;
  background: var(--accent-soft);
  color: var(--accent);
  font-size: 11.5px;
  font-weight: 600;
}

.card-date { font-size: 12px; color: var(--muted); }

.card-title {
  margin: 0 0 8px;
  font-size: 18.5px;
  line-height: 1.45;
  letter-spacing: -.2px;
}

.card-summary {
  margin: 0 0 14px;
  font-size: 14px;
  color: var(--text-soft);
}

.card-foot {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 12.5px;
  color: var(--muted);
}

.card-arrow { color: var(--accent); font-weight: 600; }

/* ===== 文章页 ===== */
.post { padding-bottom: 10px; }

.post-header { margin-bottom: 34px; }

.post-tag {
  display: inline-block;
  padding: 4px 10px;
  border-radius: 6px;
  background: var(--accent-soft);
  color: var(--accent);
  font-size: 12px;
  font-weight: 600;
  margin-bottom: 14px;
}

.post h1 {
  margin: 0 0 14px;
  font-size: 31px;
  line-height: 1.35;
  letter-spacing: -.5px;
}

.post-summary {
  margin: 0 0 18px;
  padding-left: 14px;
  border-left: 3px solid var(--accent);
  color: var(--text-soft);
  font-size: 15px;
}

.post-meta-line {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 12.5px;
  color: var(--muted);
}

.post-content h2 {
  margin: 40px 0 14px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border);
  font-size: 21px;
  line-height: 1.4;
  letter-spacing: -.2px;
  scroll-margin-top: 24px;
}

.post-content h3 { margin: 26px 0 10px; font-size: 17px; }

.post-content p { margin: 0 0 16px; color: var(--text-soft); }

.post-content ul,
.post-content ol { margin: 0 0 18px; padding-left: 22px; color: var(--text-soft); }

.post-content li { margin-bottom: 7px; }

.post-content strong { color: var(--text); font-weight: 600; }

.post-content code {
  padding: 2px 6px;
  border-radius: 5px;
  background: var(--accent-soft);
  color: var(--accent);
  font-family: var(--mono);
  font-size: 12.8px;
}

.formula {
  margin: 20px 0;
  padding: 16px 18px;
  border-radius: 10px;
  background: var(--accent-soft);
  color: var(--text);
  font-family: var(--mono);
  font-size: 13.5px;
  text-align: center;
  overflow-x: auto;
}

pre {
  margin: 0 0 20px;
  padding: 16px 18px;
  border-radius: 10px;
  background: var(--code-bg);
  overflow-x: auto;
}

pre code {
  padding: 0;
  background: transparent;
  color: var(--code-text);
  font-family: var(--mono);
  font-size: 13px;
  line-height: 1.7;
}

blockquote {
  margin: 20px 0;
  padding: 12px 18px;
  border-left: 3px solid var(--accent);
  border-radius: 0 10px 10px 0;
  background: var(--accent-soft);
}

blockquote p { margin: 0; }

/* ===== 上下篇 ===== */
.post-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin: 46px 0 0;
}

.post-nav-item {
  padding: 14px 16px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--panel);
  transition: border-color .16s, transform .16s;
}

.post-nav-item:hover { border-color: var(--accent); transform: translateY(-1px); }

.post-nav-item.is-next { text-align: right; }

.post-nav-label {
  display: block;
  font-size: 11.5px;
  color: var(--muted);
  margin-bottom: 4px;
}

.post-nav-title {
  display: block;
  font-size: 13.5px;
  line-height: 1.5;
  color: var(--text-soft);
}

/* ===== 底部 ===== */
.site-footer {
  margin-top: 56px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 12.5px;
}

.footer-line {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
}

.icp { transition: color .16s; }
.icp:hover { color: var(--accent); }

.footer-note { margin: 8px 0 0; font-size: 12px; opacity: .8; }

/* ===== 移动端 ===== */
.menu-toggle {
  display: none;
  position: fixed;
  top: 14px;
  right: 14px;
  z-index: 60;
  width: 40px;
  height: 40px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--panel);
  cursor: pointer;
  padding: 11px 10px;
  flex-direction: column;
  justify-content: space-between;
}

.menu-toggle span {
  display: block;
  height: 2px;
  border-radius: 2px;
  background: var(--text);
}

.overlay {
  display: none;
  position: fixed;
  inset: 0;
  z-index: 40;
  background: rgba(10, 14, 30, .42);
}

.overlay.is-open { display: block; }

@media (max-width: 900px) {
  .menu-toggle { display: flex; }

  .sidebar {
    position: fixed;
    inset: 0 auto 0 0;
    z-index: 50;
    transform: translateX(-100%);
    transition: transform .24s ease;
    box-shadow: 0 0 40px rgba(10, 14, 30, .18);
  }

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

  .container { padding: 64px 20px 32px; }
  .hero-title { font-size: 27px; }
  .post h1 { font-size: 25px; }
  .post-nav { grid-template-columns: 1fr; }
  .post-nav-item.is-next { text-align: left; }
  .hero-stats { gap: 24px; }
}