:root {
  --primary: #4f46e5;
  --primary-soft: #e0e7ff;
  --primary-dark: #3730a3;
  --accent: #ea580c;
  --bg: #f5f6fb;
  --surface: #ffffff;
  --surface-2: #f8fafc;
  --ink: #1e1b4b;
  --ink-2: #4b5563;
  --line: #e5e7eb;
  --ok: #059669;
  --radius: 14px;
  --shadow: 0 1px 2px rgba(16, 24, 40, .06), 0 8px 24px -12px rgba(16, 24, 40, .18);
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB",
          "Microsoft YaHei", "Noto Sans SC", Roboto, Helvetica, Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --primary: #818cf8;
    --primary-soft: #26264a;
    --primary-dark: #c7d2fe;
    --accent: #fb923c;
    --bg: #0e1020;
    --surface: #171a2e;
    --surface-2: #1e2138;
    --ink: #e8eaf6;
    --ink-2: #a5acc4;
    --line: #2b2f4a;
    --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 10px 30px -14px rgba(0, 0, 0, .7);
  }
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.55;
  color: var(--ink);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

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

:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
  border-radius: 6px;
}

/* ---------- Header ---------- */
.topbar {
  position: sticky; top: 0; z-index: 40;
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  backdrop-filter: saturate(1.4) blur(12px);
  border-bottom: 1px solid var(--line);
}
.topbar-inner {
  max-width: 1180px; margin: 0 auto;
  padding: 12px 20px;
  display: flex; align-items: center; gap: 16px;
}
.brand { display: flex; align-items: center; gap: 10px; min-width: 0; }
.brand .logo {
  width: 36px; height: 36px; border-radius: 10px;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  display: grid; place-items: center; color: #fff; flex: none;
}
.brand .logo svg { width: 20px; height: 20px; }
.brand h1 { font-size: 17px; margin: 0; letter-spacing: .2px; white-space: nowrap; }
.brand .sub { font-size: 12px; color: var(--ink-2); white-space: nowrap; }

.search { margin-left: auto; position: relative; flex: 1; max-width: 380px; }
.search input {
  width: 100%; height: 42px; padding: 0 38px 0 38px;
  border: 1px solid var(--line); border-radius: 999px;
  background: var(--surface-2); color: var(--ink); font-size: 14.5px;
}
.search input::placeholder { color: var(--ink-2); }
.search .icon-l, .search .icon-r {
  position: absolute; top: 50%; transform: translateY(-50%);
  color: var(--ink-2); display: grid; place-items: center;
}
.search .icon-l { left: 12px; }
.search .icon-r { right: 8px; background: none; border: 0; cursor: pointer; width: 28px; height: 28px; border-radius: 50%; }
.search .icon-r:hover { background: var(--line); }
.search svg { width: 18px; height: 18px; }

.menu-btn { display: none; }

/* ---------- Tabs ---------- */
.tabs { display: flex; gap: 6px; margin-left: 6px; }
.tab {
  min-height: 38px; padding: 0 14px; border-radius: 999px; cursor: pointer;
  border: 1px solid var(--line); background: var(--surface-2); color: var(--ink-2);
  font: inherit; font-size: 13.5px; font-weight: 600; white-space: nowrap;
}
.tab:hover { color: var(--ink); }
.tab.active { background: var(--primary); border-color: var(--primary); color: #fff; }

/* ---------- 知识架构首页 ---------- */
.kmap-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); gap: 14px; }
.kmap-card {
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 16px 18px; box-shadow: var(--shadow); display: flex; flex-direction: column; gap: 8px;
  transition: transform .18s ease, border-color .18s ease;
}
.kmap-card:hover { transform: translateY(-2px); border-color: color-mix(in srgb, var(--primary) 45%, var(--line)); }
.kmap-card .kc-sub { font-size: 12.5px; color: var(--primary); font-weight: 700; letter-spacing: .02em; }
.kmap-card h3 { margin: 0; font-size: 17px; line-height: 1.35; }
.kmap-card p { margin: 0; font-size: 13.5px; color: var(--ink-2); }
.kmap-card .kc-meta { display: flex; gap: 12px; font-size: 12.5px; color: var(--ink-2); margin-top: 2px; }
.kmap-card .btn { margin-top: 6px; }

/* ---------- Layout ---------- */
.wrap { max-width: 1180px; margin: 0 auto; padding: 22px 20px 60px; }
.layout { display: grid; grid-template-columns: 268px 1fr; gap: 22px; align-items: start; }
.layout.kmap-mode { grid-template-columns: 1fr; }

.sidebar {
  position: sticky; top: 76px;
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 12px; max-height: calc(100vh - 100px); overflow: auto;
}
.side-title {
  font-size: 12px; font-weight: 700; letter-spacing: .08em;
  color: var(--ink-2); text-transform: uppercase; padding: 6px 8px;
}
.subject {
  border-radius: 10px; margin-bottom: 2px;
}
.subject > button {
  width: 100%; display: flex; align-items: center; gap: 10px;
  background: none; border: 0; cursor: pointer; color: var(--ink);
  font: inherit; font-size: 14.5px; font-weight: 600;
  padding: 10px 10px; border-radius: 10px; text-align: left; min-height: 44px;
}
.subject > button:hover { background: var(--surface-2); }
.subject.active > button { background: var(--primary-soft); color: var(--primary-dark); }
.subject .dot {
  width: 26px; height: 26px; border-radius: 8px; flex: none;
  display: grid; place-items: center; color: #fff; font-size: 13px; font-weight: 700;
}
.subject .cnt {
  margin-left: auto; font-size: 12px; color: var(--ink-2);
  background: var(--surface-2); border: 1px solid var(--line);
  border-radius: 999px; padding: 1px 8px; font-weight: 600;
}
.chapters { display: none; padding: 2px 4px 8px 46px; }
.subject.open .chapters { display: block; }
.chapters button {
  display: flex; width: 100%; align-items: center; gap: 6px;
  background: none; border: 0; cursor: pointer; color: var(--ink-2);
  font: inherit; font-size: 13.5px; padding: 7px 8px; border-radius: 8px; text-align: left;
}
.chapters button:hover { background: var(--surface-2); color: var(--ink); }
.chapters button.on { color: var(--primary); font-weight: 700; }
.chapters .c-cnt { margin-left: auto; font-size: 11.5px; opacity: .7; }

/* ---------- Main ---------- */
.page-head { display: flex; align-items: baseline; gap: 12px; flex-wrap: wrap; margin: 2px 0 14px; }
.page-head h2 { margin: 0; font-size: 21px; }
.page-head .crumb { color: var(--ink-2); font-size: 13.5px; }
.stats { display: flex; gap: 18px; flex-wrap: wrap; margin-bottom: 16px; color: var(--ink-2); font-size: 13.5px; }
.stats b { color: var(--ink); font-size: 15px; }

.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(258px, 1fr)); gap: 14px; }

.card {
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 14px 15px 13px;
  box-shadow: var(--shadow); display: flex; flex-direction: column; gap: 8px;
  transition: transform .18s ease, box-shadow .18s ease, border-color .18s ease;
}
.card:hover { transform: translateY(-2px); border-color: color-mix(in srgb, var(--primary) 40%, var(--line)); }
.card-top { display: flex; align-items: center; gap: 8px; }
.badge {
  font-size: 11.5px; font-weight: 700; padding: 2px 9px; border-radius: 999px;
  border: 1px solid transparent; letter-spacing: .02em;
}
.badge.md { background: var(--primary-soft); color: var(--primary-dark); }
.badge.pdf { background: #ffe4e6; color: #9f1239; }
.badge.img { background: #dcfce7; color: #166534; }
.badge.tag { background: var(--surface-2); color: var(--ink-2); border-color: var(--line); font-weight: 600; }
.card .date { margin-left: auto; font-size: 12px; color: var(--ink-2); white-space: nowrap; }
.card h3 { margin: 0; font-size: 15.5px; line-height: 1.4; }
.card .meta { font-size: 12.5px; color: var(--ink-2); }
.tags { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 2px; }
.card-actions { display: flex; gap: 8px; margin-top: auto; padding-top: 8px; }
.btn {
  flex: 1; min-height: 38px; display: inline-flex; align-items: center; justify-content: center;
  gap: 6px; border-radius: 10px; font-size: 13.5px; font-weight: 600;
  background: var(--primary); color: #fff; border: 1px solid var(--primary); cursor: pointer;
}
.btn:hover { text-decoration: none; filter: brightness(1.06); }
.btn.ghost { background: var(--surface-2); color: var(--ink); border-color: var(--line); }
.btn svg { width: 15px; height: 15px; }

.section-title { font-size: 15px; font-weight: 700; margin: 26px 0 12px; display: flex; align-items: center; gap: 8px; }
.section-title svg { width: 17px; height: 17px; color: var(--primary); }

.gallery { display: grid; grid-template-columns: repeat(auto-fill, minmax(180px, 1fr)); gap: 12px; }
.shot {
  border: 1px solid var(--line); border-radius: 12px; overflow: hidden;
  background: var(--surface); box-shadow: var(--shadow); cursor: zoom-in; padding: 0;
  display: block; width: 100%;
}
.shot img { display: block; width: 100%; aspect-ratio: 4 / 3; object-fit: cover; background: #fff; }
.shot figcaption { font-size: 12px; color: var(--ink-2); padding: 7px 9px; text-align: left; }

.empty {
  border: 1px dashed var(--line); border-radius: var(--radius);
  padding: 40px 20px; text-align: center; color: var(--ink-2); background: var(--surface);
}
.empty svg { width: 34px; height: 34px; color: var(--primary); opacity: .7; }
.empty p { margin: 10px 0 0; }

.howto {
  margin-top: 34px; background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 18px 20px; box-shadow: var(--shadow);
}
.howto h2 { margin: 0 0 8px; font-size: 16.5px; }
.howto ol { margin: 8px 0 0; padding-left: 20px; color: var(--ink-2); font-size: 14px; }
.howto li { margin: 4px 0; }
.howto code { font-family: var(--mono); font-size: 12.5px; background: var(--surface-2); padding: 1px 6px; border-radius: 6px; border: 1px solid var(--line); }

.foot { text-align: center; color: var(--ink-2); font-size: 12.5px; margin-top: 28px; }

/* ---------- Lightbox ---------- */
.lightbox {
  position: fixed; inset: 0; z-index: 90; display: none;
  background: rgba(10, 12, 24, .86); backdrop-filter: blur(4px);
  padding: 24px; cursor: zoom-out;
}
.lightbox.on { display: grid; place-items: center; }
.lightbox img { max-width: 96vw; max-height: 90vh; border-radius: 10px; box-shadow: 0 20px 60px rgba(0,0,0,.5); }
.lightbox .lb-cap { position: absolute; bottom: 18px; left: 0; right: 0; text-align: center; color: #e5e7eb; font-size: 13px; }

/* ---------- Responsive ---------- */
@media (max-width: 900px) {
  .layout { grid-template-columns: 1fr; }
  .sidebar { position: static; max-height: none; display: none; }
  .sidebar.open { display: block; }
  .menu-btn {
    display: inline-grid; place-items: center; width: 42px; height: 42px;
    background: var(--surface-2); border: 1px solid var(--line); border-radius: 10px;
    color: var(--ink); cursor: pointer; flex: none;
  }
  .menu-btn svg { width: 20px; height: 20px; }
  .brand .sub { display: none; }
  .brand h1 { font-size: 15.5px; }
  .topbar-inner { flex-wrap: wrap; }
  .tabs { order: 3; width: 100%; margin-left: 0; }
  .search { max-width: none; }
}
@media (min-width: 901px) { .menu-btn { display: none; } }

@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; transition: none !important; scroll-behavior: auto !important; }
}