:root {
  --brand: #0b5fa5;
  --brand-hover: #094b85;
  --brand-soft: rgba(11, 95, 165, 0.06);
  --bg: #ffffff;
  --bg-panel: #f7f9fb;
  --surface: #ffffff;
  --ink: #0f1419;
  --text: #2b3138;
  --muted: #5c6670;
  --border: #dce1e7;
  --line: #eaedf1;
  --radius: 4px;
  --maxw: 1120px;
  --mono: "SF Mono", "Cascadia Code", "JetBrains Mono", Consolas, "Courier New", monospace;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  font-size: 15px;
  line-height: 1.8;
  -webkit-font-smoothing: antialiased;
}

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

.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 28px; }

/* ---------- header ---------- */
.site-header {
  background: rgba(255, 255, 255, 0.94);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 20;
  backdrop-filter: blur(8px);
}
.site-header .wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 66px;
  gap: 20px;
}
.logo { display: flex; flex-direction: column; line-height: 1.3; }
.logo-main {
  font-size: 17px;
  font-weight: 600;
  color: var(--ink);
  letter-spacing: 3px;
}
.logo-sub {
  font-family: var(--mono);
  font-size: 10px;
  color: var(--muted);
  letter-spacing: 2.5px;
}
.nav { display: flex; gap: 24px; }
.nav a {
  font-size: 14px;
  color: var(--muted);
  padding-bottom: 3px;
  border-bottom: 2px solid transparent;
}
.nav a:hover { color: var(--ink); }
.nav a.active { color: var(--brand); border-bottom-color: var(--brand); }

/* ---------- hero ---------- */
.hero {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 56px 0 48px;
}
.hero-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(0, 0.95fr);
  gap: 52px;
  align-items: center;
}
.hero .eyebrow {
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 3px;
  color: var(--brand);
  margin: 0 0 16px;
}
.hero h1 {
  margin: 0 0 16px;
  font-size: 34px;
  line-height: 1.35;
  font-weight: 600;
  color: var(--ink);
  letter-spacing: 1px;
}
.hero p.lead { margin: 0 0 20px; font-size: 15px; max-width: 640px; }
.hero .meta-line {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--muted);
  margin: -8px 0 24px;
}
.stats {
  display: flex;
  flex-wrap: wrap;
  gap: 34px;
  margin-bottom: 26px;
  padding: 14px 0 14px 18px;
  border-left: 2px solid var(--brand);
}
.stat b {
  display: block;
  font-family: var(--mono);
  font-size: 24px;
  font-weight: 600;
  color: var(--ink);
  line-height: 1.3;
}
.stat span { font-size: 12px; color: var(--muted); letter-spacing: 1px; }
.btn {
  display: inline-block;
  padding: 11px 28px;
  border-radius: 999px;
  font-size: 14px;
  font-weight: 500;
  background: var(--brand);
  color: #fff;
  letter-spacing: 1px;
}
.btn:hover { background: var(--brand-hover); color: #fff; }
.btn.ghost { background: transparent; color: var(--brand); border: 1px solid #c9d2dc; }
.btn.ghost:hover { border-color: var(--brand); background: var(--brand-soft); color: var(--brand); }
.btn-row { display: flex; gap: 14px; flex-wrap: wrap; }

/* ---------- hero features ---------- */
.hero-features {
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--surface);
  padding: 16px 20px 6px;
}
.hf-list { margin: 0; }
.hf {
  display: flex;
  align-items: baseline;
  gap: 12px;
  padding: 9px 0;
  border-bottom: 1px solid var(--line);
}
.hf:last-child { border-bottom: none; }
.hf-no { font-family: var(--mono); font-size: 12px; color: var(--brand); letter-spacing: 1px; }
.hf-name { font-size: 14px; font-weight: 500; color: var(--ink); }
.hf-desc { font-size: 12px; color: var(--muted); margin-top: 1px; line-height: 1.55; }

/* ---------- section headers ---------- */
.sec-eyebrow {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 3px;
  color: var(--brand);
  margin: 0 0 8px;
}
.sec-title {
  font-size: 24px;
  margin: 0 0 6px;
  font-weight: 600;
  color: var(--ink);
  letter-spacing: 0.5px;
}

/* ---------- notices ---------- */
.notices {
  background: var(--bg-panel);
  border-bottom: 1px solid var(--border);
  padding: 36px 0 30px;
}

/* ---------- two column layout ---------- */
.layout {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 44px 28px 20px;
  display: grid;
  grid-template-columns: 216px minmax(0, 1fr);
  gap: 56px;
  align-items: start;
}
.sidebar {
  position: sticky;
  top: 92px;
  max-height: calc(100vh - 130px);
  overflow-y: auto;
}
.sidebar-title {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 2px;
  color: var(--muted);
  margin: 0 0 12px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border);
}
.side-nav { display: flex; flex-direction: column; }
.side-nav a {
  font-size: 13px;
  color: var(--text);
  padding: 5px 0 5px 13px;
  border-left: 2px solid transparent;
  line-height: 1.6;
}
.side-nav a:hover { color: var(--brand); }
.side-nav a.active {
  color: var(--brand);
  font-weight: 500;
  border-left-color: var(--brand);
}
.content { min-width: 0; }

/* ---------- content blocks ---------- */
.block { border-top: 1px solid var(--line); padding: 26px 0; }
.block:first-child { border-top: none; padding-top: 0; }
.block h2, .block .sec-title {
  font-size: 22px;
  margin: 0 0 6px;
  font-weight: 600;
  color: var(--ink);
}
.block .sub { color: var(--muted); font-size: 14px; margin: 0 0 18px; }
.block p { margin: 0 0 10px; }
.block ul { margin: 0 0 10px; padding-left: 20px; }
.block li { margin-bottom: 6px; }

/* ---------- search ---------- */
.search-bar { margin: 20px 0 8px; }
.hero .search-bar.hero-search { margin: 4px 0 18px; max-width: 540px; }
.hero .search-bar.hero-search input {
  padding: 14px 18px;
  font-size: 15px;
  border-radius: 12px;
  box-shadow: 0 1px 3px rgba(15, 20, 25, 0.06);
}
.search-bar input {
  width: 100%;
  padding: 13px 18px;
  font-size: 15px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: #f5f7f9;
  color: var(--ink);
  font-family: inherit;
}
.search-bar input::placeholder { color: var(--muted); }
.search-bar input:focus {
  outline: none;
  background: var(--surface);
  border-color: var(--brand);
}
.search-hint { font-size: 13px; color: var(--muted); margin-bottom: 18px; }

/* ---------- chapters ---------- */
.chapter { padding: 22px 0; border-top: 1px solid var(--line); scroll-margin-top: 90px; }
.chapter:first-of-type { border-top: none; padding-top: 6px; }
.chapter-head { display: flex; align-items: baseline; justify-content: space-between; gap: 16px; }
.ch-num { font-family: var(--mono); font-size: 12px; color: var(--brand); font-weight: 600; letter-spacing: 1px; margin-right: 4px; }
.ch-title { font-size: 17px; font-weight: 600; color: var(--ink); }
.ch-meta { font-family: var(--mono); font-size: 12px; color: var(--muted); }
.lesson-list { list-style: none; margin: 12px 0 0; padding: 0; }
.lesson-list li { border-bottom: 1px solid var(--line); }
.lesson-list li:last-child { border-bottom: none; }
.lesson {
  display: flex;
  align-items: baseline;
  gap: 14px;
  padding: 9px 12px;
  color: var(--text);
  font-size: 14px;
  border-radius: var(--radius);
}
.lesson:hover { background: var(--brand-soft); }
.lesson .no { flex: 0 0 46px; font-family: var(--mono); font-size: 12px; color: var(--brand); font-variant-numeric: tabular-nums; }
.lesson .body { flex: 1; min-width: 0; }
.lesson .name { display: block; color: var(--ink); }
.lesson .desc {
  display: block;
  font-size: 12px;
  color: var(--muted);
  line-height: 1.55;
  margin-top: 1px;
}
.lesson .dur { font-family: var(--mono); font-size: 12px; color: var(--muted); font-variant-numeric: tabular-nums; }
.empty { padding: 24px 10px; color: var(--muted); font-size: 14px; }

/* ---------- items ---------- */
.block { counter-reset: itemno; }
.item {
  display: flex;
  align-items: baseline;
  gap: 16px;
  padding: 15px 0;
  border-bottom: 1px solid var(--line);
  counter-increment: itemno;
}
.item::before {
  content: counter(itemno, decimal-leading-zero);
  font-family: var(--mono);
  font-size: 12px;
  font-weight: 600;
  color: var(--brand);
  flex: 0 0 28px;
  align-self: baseline;
}
.item > div { flex: 1; min-width: 0; }
.item.highlight {
  background: var(--brand-soft);
  border-radius: 4px;
  margin-left: -14px;
  padding-left: 14px;
  padding-right: 14px;
}
.item.highlight::before { color: var(--ink); }
.item:last-child { border-bottom: none; }
.item-name { font-size: 15px; font-weight: 500; color: var(--ink); }
.item-desc { font-size: 13px; color: var(--muted); margin-top: 2px; }
.item-kind { font-family: var(--mono); font-size: 12px; color: var(--muted); letter-spacing: 1px; white-space: nowrap; }
.tag {
  display: inline-block;
  border: 1px solid var(--brand);
  color: var(--brand);
  font-size: 11px;
  padding: 1px 8px;
  border-radius: 2px;
  margin-left: 8px;
  letter-spacing: 1px;
}
.contact-list { list-style: none; margin: 0; padding: 0; }
.contact-list li {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
  padding: 10px 0;
  border-bottom: 1px solid var(--line);
}
.contact-list li:last-child { border-bottom: none; }
.contact-list .k { color: var(--muted); font-size: 14px; }
.contact-list .v {
  font-family: var(--mono);
  font-weight: 500;
  font-size: 13px;
  color: var(--brand);
  background: var(--brand-soft);
  padding: 2px 12px;
  border-radius: 4px;
}
.note {
  background: var(--brand-soft);
  border-left: 2px solid var(--brand);
  padding: 14px 18px;
  font-size: 14px;
  color: var(--text);
  margin: 18px 0;
}

/* ---------- brand figure ---------- */
.brand-figure { margin: 20px 0 0; }
.brand-figure img {
  display: block;
  width: 100%;
  max-width: 260px;
  border-radius: 4px;
  border: 1px solid var(--border);
}
.brand-figure figcaption {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 2px;
  color: var(--muted);
  margin-top: 8px;
}

/* ---------- letter ---------- */
.letter-body {
  max-width: 720px;
  margin: 0 auto;
  font-size: 15.5px;
  line-height: 1.95;
}
.letter-body p { margin: 0 0 18px; }
.letter-body strong {
  font-family: var(--mono);
  font-size: 13px;
  color: var(--brand);
  letter-spacing: 1px;
}
.letter-hello { font-size: 17px; color: var(--ink); font-weight: 500; }
.letter-quote {
  font-size: 17px;
  color: var(--ink);
  font-weight: 600;
  border-left: 2px solid var(--brand);
  padding-left: 16px;
  margin: 26px 0;
}
.letter-wish { color: var(--ink); font-weight: 500; }
.letter-sign {
  text-align: right;
  font-family: var(--mono);
  font-size: 14px;
  color: var(--ink);
  margin-top: 34px;
}
.letter-sign span { font-size: 12px; color: var(--muted); }
.letter-back { display: flex; gap: 12px; flex-wrap: wrap; justify-content: flex-end; margin-top: 30px; }

/* ---------- qr code ---------- */
.qr-grid { display: flex; gap: 36px; flex-wrap: wrap; }
.qr { margin: 0; }
.qr img {
  display: block;
  width: 176px;
  height: 176px;
  object-fit: contain;
  background: #ffffff;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 8px;
}
.qr figcaption { font-size: 13px; color: var(--ink); margin-top: 10px; }
.qr figcaption span { display: block; font-family: var(--mono); font-size: 12px; color: var(--muted); margin-top: 2px; }

/* ---------- announcements ---------- */
.ann-box { padding-top: 4px; }
.ann-row {
  display: flex;
  align-items: baseline;
  gap: 16px;
  padding: 10px 0;
  border-bottom: 1px solid var(--border);
  font-size: 14px;
}
.ann-row:last-child { border-bottom: none; }
.ann-date { font-family: var(--mono); font-size: 12px; color: var(--brand); white-space: nowrap; font-variant-numeric: tabular-nums; }
.ann-text { flex: 1; }
.ann-link { margin-left: auto; font-size: 13px; white-space: nowrap; }

/* ---------- footer ---------- */
.site-footer {
  border-top: 1px solid var(--border);
  background: var(--bg-panel);
  padding: 32px 0;
  color: var(--muted);
  font-size: 13px;
}
.site-footer .wrap { display: flex; flex-direction: column; gap: 6px; }
.site-footer .foot-brand { font-size: 14px; color: var(--ink); font-weight: 500; letter-spacing: 2px; }
.site-footer a { color: var(--muted); margin-right: 16px; }
.site-footer a:hover { color: var(--brand); }

@media (max-width: 960px) {
  .hero-grid { grid-template-columns: minmax(0, 1fr); gap: 30px; }
}
@media (max-width: 900px) {
  .layout { grid-template-columns: minmax(0, 1fr); gap: 0; padding: 28px 18px 10px; }
  .sidebar { display: none; }
  .wrap { padding: 0 18px; }
  .hero { padding: 36px 0 30px; }
  .hero h1 { font-size: 26px; }
  .stats { gap: 22px; }
  .nav { gap: 14px; }
  .nav a { font-size: 13px; }
  .logo-sub { display: none; }
  .lesson { padding: 8px 8px; gap: 10px; }
  .lesson .dur { display: none; }
}