/* ==========================================================================
   学习中心 · 样式
   设计基准：Notion 设计系统（DESIGN.md / awesome-design-md）
   - 画布纯白，侧栏暖灰，1px 发丝线做分隔，不用阴影堆叠
   - 单一强调色（紫 #5645d4）只出现在可点击、当前态与结论上
   - 圆角 4/6/8/12 四档；字重 400/500/600 三档，不用 700 以上
   - 正文 15.5px / 行高 1.85，中文长文优先可读性
   ========================================================================== */

:root {
  /* 面 */
  --c-bg: #ffffff;
  --c-bg-alt: #f7f7f5;
  --c-surface: #ffffff;
  --c-surface-2: #fafaf9;
  --c-surface-3: #f1f1ef;
  --c-border: #e9e7e4;
  --c-border-soft: #f0eeeb;
  --c-border-strong: #d9d6d1;

  /* 字 */
  --c-ink: #1a1a1a;
  --c-ink-2: #37352f;
  --c-ink-3: #5d5b54;
  --c-ink-4: #706d66;

  /* 强调 */
  --c-brand: #5645d4;
  --c-brand-ink: #3a2a99;
  --c-brand-soft: #f1effc;
  --c-brand-line: #d8d2f7;
  --c-brand-btn: #5645d4;
  --c-brand-btn-hover: #4534b3;

  /* 语义 */
  --c-teal: #0b6a5d;
  --c-teal-soft: #e4f2ef;
  --c-teal-line: #c6e3dc;
  --c-amber: #8f5209;
  --c-amber-soft: #fbf1e2;
  --c-amber-line: #efdfc6;
  --c-rose: #c0392b;
  --c-rose-soft: #fbeceb;
  --c-rose-line: #f1d7d3;
  --c-violet: #7b3ff2;
  --c-violet-soft: #f2ecfd;
  --c-sky: #1f6fb2;
  --c-sky-soft: #e9f2fa;

  --r-xs: 3px;
  --r-sm: 4px;
  --r-md: 6px;
  --r-lg: 8px;
  --r-xl: 12px;

  --sh-0: none;
  --sh-1: 0 1px 2px rgba(15, 15, 15, .03), 0 1px 1px rgba(15, 15, 15, .02);
  --sh-2: 0 6px 16px rgba(15, 15, 15, .07), 0 1px 3px rgba(15, 15, 15, .04);
  --sh-3: 0 12px 32px rgba(15, 15, 15, .10), 0 2px 6px rgba(15, 15, 15, .05);

  --font-sans: "Inter", "PingFang SC", "HarmonyOS Sans SC", "Microsoft YaHei", "Hiragino Sans GB", system-ui, sans-serif;
  --font-mono: "JetBrains Mono", ui-monospace, "Cascadia Mono", "SF Mono", Consolas, monospace;

  --sidebar-w: 276px;
  --top-h: 52px;
}

html[data-theme="dark"] {
  --c-bg: #191919;
  --c-bg-alt: #202020;
  --c-surface: #232323;
  --c-surface-2: #1f1f1f;
  --c-surface-3: #2a2a2a;
  --c-border: #2f2f2f;
  --c-border-soft: #282828;
  --c-border-strong: #3d3d3d;

  --c-ink: #e8e8e6;
  --c-ink-2: #d4d4d2;
  --c-ink-3: #a5a39d;
  --c-ink-4: #8a8882;

  --c-brand: #a99cf5;
  --c-brand-ink: #c9c0fa;
  --c-brand-soft: #262238;
  --c-brand-line: #3b3457;
  --c-brand-btn: #5645d4;
  --c-brand-btn-hover: #4534b3;

  --c-teal: #67c1ad;
  --c-teal-soft: #1c2b28;
  --c-teal-line: #2a443e;
  --c-amber: #d9a25f;
  --c-amber-soft: #2b2417;
  --c-amber-line: #463a24;
  --c-rose: #e0857a;
  --c-rose-soft: #2e211f;
  --c-rose-line: #4a332f;
  --c-violet: #b79bf7;
  --c-violet-soft: #251f36;
  --c-sky: #7fb4de;
  --c-sky-soft: #1b2630;

  --sh-1: 0 1px 2px rgba(0, 0, 0, .35);
  --sh-2: 0 6px 16px rgba(0, 0, 0, .45);
  --sh-3: 0 12px 32px rgba(0, 0, 0, .55);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: calc(var(--top-h) + 20px); }

body {
  margin: 0;
  background: var(--c-bg);
  color: var(--c-ink-2);
  font-family: var(--font-sans);
  font-size: 14.5px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

::selection { background: var(--c-brand-soft); color: var(--c-brand-ink); }

a { color: var(--c-brand); text-decoration: none; transition: color .12s; }
a:hover { color: var(--c-brand-ink); text-decoration: underline; text-underline-offset: 3px; text-decoration-thickness: 1px; }

:focus-visible { outline: 2px solid var(--c-brand); outline-offset: 2px; border-radius: var(--r-sm); }

/* ==========================================================================
   顶栏
   ========================================================================== */
.topbar {
  position: fixed; top: 0; left: 0; right: 0; height: var(--top-h); z-index: 100;
  display: flex; align-items: center; gap: 14px;
  padding: 0 16px 0 18px;
  background: var(--c-bg);
  border-bottom: 1px solid var(--c-border);
}

.brand { display: flex; align-items: center; gap: 9px; flex: none; min-width: 0; }
.brand-mark {
  width: 22px; height: 22px; flex: none;
  border-radius: var(--r-sm);
  background: var(--c-ink);
  display: grid; place-items: center;
  color: var(--c-bg); font-size: 12px; font-weight: 600;
  letter-spacing: 0;
}
.brand-text { font-weight: 600; font-size: 13.5px; white-space: nowrap; letter-spacing: -.1px; color: var(--c-ink); }
.brand-text small {
  display: block; font-size: 10.5px; font-weight: 400; color: var(--c-ink-4);
  letter-spacing: 0; line-height: 1.35; margin-top: 1px;
}

.search-box { flex: 1; max-width: 400px; position: relative; }
.search-box input {
  width: 100%; height: 30px; padding: 0 30px 0 30px;
  border: 1px solid transparent; border-radius: var(--r-md);
  background: var(--c-surface-3); color: var(--c-ink);
  font-family: inherit; font-size: 13px; outline: none;
  transition: background .12s, border-color .12s;
}
.search-box input::placeholder { color: var(--c-ink-4); }
.search-box input:hover { background: var(--c-border-soft); }
.search-box input:focus { border-color: var(--c-brand); background: var(--c-surface); box-shadow: 0 0 0 3px var(--c-brand-soft); }
.search-box .ico {
  position: absolute; left: 9px; top: 50%; transform: translateY(-50%);
  color: var(--c-ink-4); pointer-events: none; display: flex;
}
.search-box kbd {
  position: absolute; right: 7px; top: 50%; transform: translateY(-50%);
  font-family: var(--font-mono); font-size: 10px; color: var(--c-ink-4);
  border: 1px solid var(--c-border); border-radius: var(--r-xs); padding: 0 4px;
  background: var(--c-surface); line-height: 16px;
}

.topbar-right { margin-left: auto; display: flex; align-items: center; gap: 2px; flex: none; }

.icon-btn {
  width: 30px; height: 30px; border-radius: var(--r-md); border: 1px solid transparent;
  background: transparent; color: var(--c-ink-3); cursor: pointer;
  display: grid; place-items: center; transition: background .12s, color .12s;
}
.icon-btn:hover { background: var(--c-surface-3); color: var(--c-ink); }

.progress-pill {
  display: flex; align-items: center; gap: 7px;
  padding: 3px 10px 3px 5px;
  border: 1px solid var(--c-border);
  border-radius: 999px;
  background: var(--c-surface);
  font-size: 11.5px; font-weight: 500; color: var(--c-ink-2);
  white-space: nowrap;
}
.progress-pill .ring { flex: none; }

/* ==========================================================================
   布局
   ========================================================================== */
.shell { display: flex; padding-top: var(--top-h); min-height: 100vh; }

.sidebar {
  width: var(--sidebar-w); flex: none;
  position: fixed; top: var(--top-h); bottom: 0; left: 0;
  overflow-y: auto; overscroll-behavior: contain;
  background: var(--c-bg-alt);
  border-right: 1px solid var(--c-border-soft);
  padding: 14px 8px 56px;
  scrollbar-width: thin;
  scrollbar-color: var(--c-border-strong) transparent;
}
.sidebar::-webkit-scrollbar { width: 9px; }
.sidebar::-webkit-scrollbar-thumb {
  background: var(--c-border-strong); border-radius: 999px;
  border: 3px solid var(--c-bg-alt);
}

.nav-group { margin-bottom: 10px; }
.nav-group-title {
  display: flex; align-items: center; gap: 6px;
  padding: 5px 8px;
  font-size: 10.5px; font-weight: 600; letter-spacing: .7px;
  color: var(--c-ink-4); cursor: pointer; user-select: none;
  text-transform: uppercase;
  border-radius: var(--r-md);
}
.nav-group-title:hover { background: var(--c-border-soft); color: var(--c-ink-3); }
.nav-group-title .chev { margin-left: auto; color: var(--c-ink-4); transition: transform .15s; }
.nav-group.collapsed .chev { transform: rotate(-90deg); }
.nav-group.collapsed .nav-items { display: none; }

.nav-items { display: flex; flex-direction: column; gap: 1px; }
.nav-chapter {
  padding: 9px 8px 3px 10px;
  font-size: 10.5px; font-weight: 600; color: var(--c-ink-4);
  letter-spacing: .2px;
}
.nav-link {
  display: flex; align-items: center; gap: 7px;
  padding: 4px 8px 4px 10px;
  border-radius: var(--r-md);
  font-size: 12.5px; color: var(--c-ink-2); line-height: 1.55;
  cursor: pointer;
}
.nav-link:hover { background: var(--c-surface-3); color: var(--c-ink); text-decoration: none; }
.nav-link.active {
  background: var(--c-surface-3); color: var(--c-ink);
  font-weight: 600;
}
.nav-link.active::before { content: none; }
.nav-link .dot {
  width: 5px; height: 5px; flex: none; border-radius: 50%;
  background: var(--c-border-strong);
}
.nav-link.done .dot { background: var(--c-teal); }
.nav-link .lv {
  font-size: 9px; font-weight: 600; padding: 0 3px; flex: none;
  letter-spacing: .2px; border: 1px solid currentColor; border-radius: var(--r-xs);
  line-height: 1.5; opacity: .85;
}
.lv.core { color: var(--c-rose); }
.lv.important { color: var(--c-amber); }
.lv.extend { color: var(--c-ink-4); }

.nav-link.quick { padding-left: 8px; font-weight: 500; }
.nav-link.quick .lv { margin-left: auto; border: 0; color: var(--c-ink-4); font-weight: 500; }
.nav-link .nav-t { flex: 1; min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }

.main {
  flex: 1; margin-left: var(--sidebar-w);
  padding: 44px 56px 140px;
  min-width: 0;
}
.content { max-width: 856px; margin: 0 auto; }

@media (max-width: 1180px) {
  :root { --sidebar-w: 252px; }
  .main { padding: 36px 36px 120px; }
}
@media (max-width: 900px) {
  .sidebar {
    transform: translateX(-100%); transition: transform .2s ease; z-index: 90;
    box-shadow: var(--sh-3);
  }
  .sidebar.open { transform: none; background: var(--c-bg); }
  .main { margin-left: 0; padding: 24px 20px 110px; }
  .brand-text small { display: none; }
  .search-box { max-width: none; }
  .search-box kbd { display: none; }
  .progress-pill { display: none; }
}

/* ==========================================================================
   通用组件
   ========================================================================== */
.card {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--r-lg);
  padding: 24px 28px;
  margin-bottom: 14px;
}
.card.flush { padding: 0; overflow: hidden; }

.eyebrow {
  font-size: 10.5px; font-weight: 600; letter-spacing: 1.1px;
  color: var(--c-ink-4); margin-bottom: 7px; text-transform: uppercase;
}

h1.page-title {
  font-size: 27px; font-weight: 600; letter-spacing: -.5px; line-height: 1.35;
  margin: 0 0 10px; color: var(--c-ink);
}
.page-sub { color: var(--c-ink-3); font-size: 14.5px; margin: 0 0 26px; max-width: 660px; line-height: 1.8; }

h2.sec-title {
  font-size: 18px; font-weight: 600; letter-spacing: -.2px;
  margin: 34px 0 14px; padding-bottom: 9px;
  border-bottom: 1px solid var(--c-border-soft);
  display: flex; align-items: center; gap: 8px; color: var(--c-ink);
}
h2.sec-title:first-child { margin-top: 0; }
h2.sec-title::before { content: none; }
h3.sub-title { font-size: 14.5px; font-weight: 600; margin: 24px 0 9px; color: var(--c-ink); }

.pill {
  display: inline-flex; align-items: center; gap: 5px;
  padding: 1.5px 8px; border-radius: var(--r-sm); font-size: 11px; font-weight: 500;
  background: var(--c-surface-3); color: var(--c-ink-3); white-space: nowrap;
  line-height: 1.7;
}
.pill.core { background: var(--c-rose-soft); color: var(--c-rose); }
.pill.important { background: var(--c-amber-soft); color: var(--c-amber); }
.pill.extend { background: var(--c-surface-3); color: var(--c-ink-3); }
.pill.tag { background: var(--c-brand-soft); color: var(--c-brand-ink); border: 1px solid var(--c-brand-line); font-weight: 500; }
.pill.done { background: var(--c-teal-soft); color: var(--c-teal); }

.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  height: 32px; padding: 0 12px; border-radius: var(--r-md);
  border: 1px solid var(--c-border-strong); background: var(--c-surface);
  color: var(--c-ink-2); font-family: inherit; font-size: 12.5px; font-weight: 500;
  cursor: pointer; white-space: nowrap;
  transition: background .12s, border-color .12s, color .12s;
}
.btn:hover { background: var(--c-surface-2); border-color: var(--c-ink-4); color: var(--c-ink); }
.btn.primary { background: var(--c-brand-btn); border-color: var(--c-brand-btn); color: #fff; }
.btn.primary:hover { background: var(--c-brand-btn-hover); border-color: var(--c-brand-btn-hover); color: #fff; }
.btn.ghost { background: transparent; border-color: transparent; color: var(--c-ink-3); }
.btn.ghost:hover { background: var(--c-surface-3); color: var(--c-ink); }
.btn.sm { height: 27px; padding: 0 9px; font-size: 11.5px; border-radius: var(--r-sm); }
.btn[disabled] { opacity: .4; cursor: not-allowed; }

.chip-row { display: flex; flex-wrap: wrap; gap: 6px; }

/* ==========================================================================
   正文排版
   ========================================================================== */
.prose { color: var(--c-ink-2); font-size: 15.5px; line-height: 1.88; }
.prose > *:first-child { margin-top: 0; }
.prose > *:last-child { margin-bottom: 0; }
.prose p { margin: 0 0 14px; }
.prose h4 {
  font-size: 15px; font-weight: 600; color: var(--c-ink);
  margin: 30px 0 10px; padding: 0;
  border: 0; line-height: 1.5; letter-spacing: -.1px;
}
.prose ul, .prose ol { margin: 0 0 14px; padding-left: 22px; }
.prose li { margin-bottom: 6px; }
.prose li::marker { color: var(--c-ink-4); }
.prose strong, .prose b { color: var(--c-ink); font-weight: 600; }
.prose em { font-style: normal; color: var(--c-brand-ink); font-weight: 500; background: var(--c-brand-soft); padding: 0 2px; border-radius: 2px; }

.prose table {
  width: 100%; border-collapse: separate; border-spacing: 0;
  margin: 18px 0 22px; font-size: 13.5px; background: var(--c-surface);
  border: 1px solid var(--c-border); border-radius: var(--r-lg);
  overflow: hidden;
}
.prose thead th {
  background: var(--c-bg-alt); color: var(--c-ink);
  font-weight: 600; text-align: left; font-size: 12.5px;
  border-bottom: 1px solid var(--c-border);
  padding: 9px 12px;
}
.prose th, .prose td {
  padding: 8px 12px; border-bottom: 1px solid var(--c-border-soft);
  vertical-align: top; text-align: left; line-height: 1.7;
}
.prose th + th, .prose td + td { border-left: 1px solid var(--c-border-soft); }
.prose tbody tr:last-child td, .prose tbody tr:last-child th { border-bottom: none; }
.prose tbody tr:hover td { background: var(--c-surface-2); }
.prose td strong { color: var(--c-ink); font-weight: 600; }

.prose .note {
  background: var(--c-bg-alt);
  border: 0;
  border-radius: var(--r-lg);
  padding: 14px 16px; margin: 18px 0; font-size: 14.5px;
  color: var(--c-ink-2); line-height: 1.8;
}
.prose .note strong { color: var(--c-ink); }

.prose code {
  font-family: var(--font-mono); font-size: .92em;
  background: var(--c-surface-3); padding: 1.5px 5px; border-radius: var(--r-xs);
  color: var(--c-ink); border: 1px solid var(--c-border-soft);
  white-space: nowrap;
}

/* 考点 / 易错 */
.box {
  padding: 15px 17px; margin: 18px 0; font-size: 14.5px;
  border-radius: var(--r-lg); border: 1px solid transparent;
  line-height: 1.82;
}
.box-title {
  display: flex; align-items: center; gap: 6px;
  font-size: 11.5px; font-weight: 600; letter-spacing: .5px;
  margin-bottom: 8px; text-transform: uppercase;
}
.box p:last-child, .box ul:last-child { margin-bottom: 0; }
.box.exam { background: var(--c-amber-soft); border-color: var(--c-amber-line); }
.box.exam .box-title { color: var(--c-amber); }
.box.trap { background: var(--c-rose-soft); border-color: var(--c-rose-line); }
.box.trap .box-title { color: var(--c-rose); }
.box.warn { background: var(--c-brand-soft); border-color: var(--c-brand-line); }
.box.warn .box-title { color: var(--c-brand-ink); }

/* ==========================================================================
   首页
   ========================================================================== */
.hero {
  background: transparent;
  border: 0;
  border-bottom: 1px solid var(--c-border-soft);
  padding: 4px 0 26px;
  margin-bottom: 30px;
}
.hero::after { content: none; }
.hero h1 { margin: 0 0 12px; font-size: 31px; font-weight: 600; letter-spacing: -.7px; line-height: 1.3; color: var(--c-ink); }
.hero p { margin: 0; color: var(--c-ink-3); font-size: 14.5px; max-width: 640px; line-height: 1.85; }
.hero-stats {
  display: flex; gap: 30px; margin-top: 24px; flex-wrap: wrap;
  border-top: 0;
}
.hero-stat { padding: 0; margin-right: 0; border-right: 0; }
.hero-stat b {
  display: block; font-family: var(--font-sans);
  font-size: 22px; font-weight: 600; color: var(--c-ink);
  font-variant-numeric: tabular-nums; letter-spacing: -.4px; line-height: 1.3;
}
.hero-stat span { font-size: 11.5px; color: var(--c-ink-4); }

.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 10px; background: transparent; border: 0; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; background: transparent; border: 0; }
@media (max-width: 760px) { .grid-2, .grid-3 { grid-template-columns: 1fr; } }

.tile {
  display: block; background: var(--c-surface); padding: 15px 16px;
  cursor: pointer; color: inherit;
  border: 1px solid var(--c-border); border-radius: var(--r-lg);
  transition: background .12s, border-color .12s;
}
.tile:hover { background: var(--c-surface-2); border-color: var(--c-border-strong); text-decoration: none; }
.tile:hover h3 { color: var(--c-brand); }
.tile-ico {
  width: 26px; height: 26px; display: grid; place-items: center;
  background: var(--c-brand-soft); color: var(--c-brand);
  border-radius: var(--r-md);
  margin-bottom: 11px; font-family: var(--font-mono);
  font-size: 11px; font-weight: 600;
}
.tile h3 { margin: 0 0 4px; font-size: 14px; font-weight: 600; color: var(--c-ink); letter-spacing: -.1px; }
.tile p { margin: 0; font-size: 12.5px; color: var(--c-ink-3); line-height: 1.65; }
.tile-meta { margin-top: 11px; font-size: 11px; color: var(--c-ink-4); display: flex; gap: 12px; }

/* 进度 */
.bar { height: 4px; background: var(--c-surface-3); overflow: hidden; border-radius: 999px; }
.bar > i { display: block; height: 100%; background: var(--c-brand); border-radius: 999px; }

/* ==========================================================================
   交互引擎
   ========================================================================== */
.viz {
  background: var(--c-bg-alt); border: 1px solid var(--c-border);
  border-radius: var(--r-lg);
  padding: 18px; margin: 18px 0;
}
.viz-head { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; margin-bottom: 14px; }
.viz-head h4 {
  margin: 0; font-size: 13.5px; font-weight: 600; color: var(--c-ink);
  padding: 0; border: 0; letter-spacing: -.1px;
}
.viz-head .spacer { flex: 1; }
.viz canvas {
  display: block; width: 100%; background: var(--c-surface);
  border: 1px solid var(--c-border); border-radius: var(--r-md);
}
.viz.calc { padding: 22px 24px; }
.viz.calc .calc-fields { margin-bottom: 4px; }
.viz-hint { font-size: 11.5px; color: var(--c-ink-4); margin-top: 12px; line-height: 1.65; }

.ctrl { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.ctrl label { font-size: 12px; color: var(--c-ink-3); font-weight: 500; white-space: nowrap; }
.ctrl select, .ctrl input[type="number"], .ctrl input[type="text"] {
  height: 29px; padding: 0 8px; border-radius: var(--r-md);
  border: 1px solid var(--c-border-strong); background: var(--c-surface);
  color: var(--c-ink); font-family: inherit; font-size: 12.5px; outline: none;
  transition: border-color .12s, box-shadow .12s;
}
.ctrl select:focus, .ctrl input:focus { border-color: var(--c-brand); box-shadow: 0 0 0 3px var(--c-brand-soft); }
.ctrl input[type="number"] { width: 72px; font-family: var(--font-mono); font-variant-numeric: tabular-nums; }
.ctrl input[type="range"] { flex: 1; min-width: 120px; accent-color: var(--c-brand); height: 4px; }

.readout {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: 8px; background: transparent; border: 0;
  margin-top: 14px;
}
.readout > div {
  background: var(--c-surface); padding: 9px 12px;
  border: 1px solid var(--c-border); border-radius: var(--r-md);
}
.readout dt { font-size: 10.5px; color: var(--c-ink-4); margin-bottom: 2px; letter-spacing: .2px; }
.readout dd {
  margin: 0; font-family: var(--font-mono); font-size: 14px; font-weight: 600;
  color: var(--c-ink); font-variant-numeric: tabular-nums; line-height: 1.45;
}
.readout dd.accent { color: var(--c-brand); }
.readout dd small { font-size: 10px; color: var(--c-ink-4); font-weight: 400; margin-left: 2px; }

.verdict {
  margin-top: 14px; padding: 12px 14px;
  background: var(--c-brand-soft);
  border: 1px solid var(--c-brand-line);
  border-radius: var(--r-md);
  font-size: 13.5px; color: var(--c-ink-2); line-height: 1.78;
}
.verdict b { color: var(--c-brand-ink); font-weight: 600; }

/* ==========================================================================
   计算器
   ========================================================================== */
.calc-fields {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 14px 20px;
}
.cf { display: flex; flex-direction: column; gap: 5px; }
.cf label { font-size: 11.5px; font-weight: 500; color: var(--c-ink-3); }
.cf input, .cf select {
  height: 33px; padding: 0 9px; border-radius: var(--r-md);
  border: 1px solid var(--c-border-strong); background: var(--c-surface);
  color: var(--c-ink); font-family: var(--font-mono); font-size: 13px;
  font-variant-numeric: tabular-nums; outline: none;
  transition: border-color .12s, box-shadow .12s;
}
.cf select { font-family: inherit; }
.cf input:focus, .cf select:focus { border-color: var(--c-brand); box-shadow: 0 0 0 3px var(--c-brand-soft); }
.cf .unit { font-size: 10.5px; color: var(--c-ink-4); }

.calc-result { margin-top: 20px; padding-top: 18px; border-top: 1px solid var(--c-border); }
.calc-headline {
  font-family: var(--font-mono); font-size: 30px; font-weight: 600;
  color: var(--c-brand); letter-spacing: -.8px; line-height: 1.2;
  padding: 0 0 14px; font-variant-numeric: tabular-nums; word-break: break-all;
}
.calc-headline .calc-sub {
  font-family: var(--font-sans); font-size: 12px; font-weight: 500;
  color: var(--c-ink-4); margin-left: 9px; letter-spacing: 0; vertical-align: middle;
}

.calc-steps {
  width: 100%; border-collapse: separate; border-spacing: 0; font-size: 13px;
  border: 1px solid var(--c-border); border-radius: var(--r-lg); overflow: hidden;
}
.calc-steps thead th {
  background: var(--c-bg-alt); color: var(--c-ink-3);
  font-size: 11px; font-weight: 600; text-align: left;
  padding: 8px 11px; letter-spacing: .3px;
  border-bottom: 1px solid var(--c-border);
}
.calc-steps td {
  padding: 9px 11px; border-top: 1px solid var(--c-border-soft);
  color: var(--c-ink-2); vertical-align: top; line-height: 1.7;
}
.calc-steps thead th + th, .calc-steps td + td { border-left: 1px solid var(--c-border-soft); }
.calc-steps td.mono {
  font-family: var(--font-mono); font-size: 12.5px; color: var(--c-ink-3); line-height: 1.65;
}
.calc-steps td.v {
  font-family: var(--font-mono); font-weight: 600; color: var(--c-ink);
  font-variant-numeric: tabular-nums; white-space: nowrap;
}
@media (max-width: 760px) {
  .calc-headline { font-size: 23px; }
  .calc-steps { font-size: 12px; }
  .calc-steps td.mono { font-size: 11px; }
}

/* ==========================================================================
   检索
   ========================================================================== */
.search-results { display: flex; flex-direction: column; gap: 2px; border-top: 0; }
.sr-item {
  padding: 12px 13px; border: 1px solid transparent; border-radius: var(--r-lg);
  background: var(--c-surface); cursor: pointer;
}
.sr-item:hover { background: var(--c-surface-2); border-color: var(--c-border); }
.sr-item h4 { margin: 0 0 2px; font-size: 13.5px; font-weight: 600; color: var(--c-ink); }
.sr-item .path { font-size: 11px; color: var(--c-ink-4); margin-bottom: 4px; }
.sr-item .snip { font-size: 13px; color: var(--c-ink-3); line-height: 1.7; }
.sr-item mark { background: #fbf3c4; color: var(--c-ink); padding: 0 2px; border-radius: 2px; }
html[data-theme="dark"] .sr-item mark { background: #4a4218; color: #f3e6a8; }

/* ==========================================================================
   知识点页
   ========================================================================== */
.kp-header { margin-bottom: 20px; }
.kp-breadcrumb {
  font-size: 11.5px; color: var(--c-ink-4); margin-bottom: 10px;
  display: flex; gap: 7px; align-items: center; flex-wrap: wrap;
}
.kp-breadcrumb a { color: var(--c-ink-4); }
.kp-breadcrumb a:hover { color: var(--c-brand); }
.kp-title { font-size: 26px; font-weight: 600; letter-spacing: -.5px; margin: 4px 0 10px; line-height: 1.35; color: var(--c-ink); }
.kp-actions { display: flex; gap: 7px; flex-wrap: wrap; margin-top: 16px; }

.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; background: transparent; border: 0; margin-top: 28px; }
.pager a {
  padding: 13px 15px; background: var(--c-surface);
  border: 1px solid var(--c-border); border-radius: var(--r-lg);
  text-decoration: none; color: inherit;
  transition: background .12s, border-color .12s;
}
.pager a:hover { background: var(--c-surface-2); border-color: var(--c-border-strong); text-decoration: none; }
.pager .dir { font-size: 10px; color: var(--c-ink-4); letter-spacing: .4px; }
.pager .ttl { font-size: 13px; font-weight: 600; color: var(--c-ink); margin-top: 3px; line-height: 1.5; }
.pager a.next { text-align: right; }
.pager .empty { background: transparent; border-color: var(--c-border-soft); }

/* ==========================================================================
   视频
   ========================================================================== */
.video-list { display: flex; flex-direction: column; gap: 2px; border-top: 0; }
.vd {
  display: flex; align-items: flex-start; gap: 11px;
  padding: 10px 12px; border: 1px solid transparent; border-radius: var(--r-lg);
  transition: background .12s, border-color .12s;
}
.vd:hover { background: var(--c-surface-2); border-color: var(--c-border); }
.vd-no {
  flex: none; width: 21px; height: 21px; display: grid; place-items: center;
  border: 0; border-radius: var(--r-sm);
  background: var(--c-surface-3); color: var(--c-ink-3);
  font-family: var(--font-mono); font-size: 10.5px; font-weight: 600; margin-top: 1px;
}
.vd-main { flex: 1; min-width: 0; }
.vd-t { font-size: 13.5px; font-weight: 500; color: var(--c-ink); line-height: 1.55; }
.vd-t:hover { color: var(--c-brand); text-decoration: none; }
.vd-meta { font-size: 11px; color: var(--c-ink-4); margin-top: 3px; display: flex; gap: 10px; flex-wrap: wrap; }
.vd-dur { font-family: var(--font-mono); font-variant-numeric: tabular-nums; }
.vd-act { flex: none; display: flex; gap: 6px; align-items: center; }

.vd-frame { margin: 14px 0 0; border: 1px solid var(--c-border); border-radius: var(--r-lg); overflow: hidden; background: #0b0b0b; }
.vd-frame iframe { display: block; width: 100%; aspect-ratio: 16 / 9; border: 0; }
.vd-fallback { font-size: 11.5px; color: #9a9a9a; padding: 8px 11px; background: #16171a; }
.vd-empty {
  padding: 12px 13px; border: 1px dashed var(--c-border-strong); border-radius: var(--r-lg);
  font-size: 12.5px; color: var(--c-ink-4);
}

@media (max-width: 760px) {
  .vd-dur { display: none; }
}

/* ==========================================================================
   工具页 / 题库
   ========================================================================== */
.tool-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 10px; background: transparent; border: 0; }

.q-block {
  background: var(--c-surface); border: 1px solid var(--c-border); border-radius: var(--r-lg);
  padding: 22px 26px; margin-bottom: 12px;
}
.q-stem { font-size: 14.5px; line-height: 1.85; color: var(--c-ink); margin-bottom: 16px; }
.q-stem .qn {
  display: inline-block; min-width: 20px; font-weight: 600; color: var(--c-brand);
  font-family: var(--font-mono); margin-right: 5px;
}
.opts { display: flex; flex-direction: column; gap: 6px; }
.opt {
  display: flex; gap: 10px; align-items: flex-start;
  padding: 9px 12px; border: 1px solid var(--c-border); border-radius: var(--r-md);
  cursor: pointer; font-size: 14px; line-height: 1.7; background: var(--c-surface);
  color: var(--c-ink-2);
  transition: background .12s, border-color .12s;
}
.opt:hover { background: var(--c-surface-2); border-color: var(--c-border-strong); }
.opt .k {
  flex: none; width: 19px; height: 19px; border: 1px solid var(--c-border-strong);
  border-radius: var(--r-xs);
  color: var(--c-ink-3); display: grid; place-items: center;
  font-size: 10.5px; font-weight: 600; font-family: var(--font-mono); margin-top: 2px;
}
.opt.correct { background: var(--c-teal-soft); border-color: var(--c-teal-line); }
.opt.correct .k { border-color: var(--c-teal); background: var(--c-teal); color: #fff; }
.opt.wrong { background: var(--c-rose-soft); border-color: var(--c-rose-line); }
.opt.wrong .k { border-color: var(--c-rose); background: var(--c-rose); color: #fff; }
.opt.picked { border-color: var(--c-brand); box-shadow: 0 0 0 3px var(--c-brand-soft); }
.opt.locked { cursor: default; }
.q-block.answered .opt { cursor: default; }
.q-block.answered .opt:hover { background: var(--c-surface); border-color: var(--c-border); }
.q-block.answered .opt.correct:hover { background: var(--c-teal-soft); border-color: var(--c-teal-line); }
.q-block.answered .opt.wrong:hover { background: var(--c-rose-soft); border-color: var(--c-rose-line); }

.explain {
  margin-top: 16px; padding: 15px 17px;
  background: var(--c-bg-alt); border: 1px solid var(--c-border); border-radius: var(--r-lg);
  font-size: 13.5px; line-height: 1.82; color: var(--c-ink-2);
  display: none;
}
.explain.show { display: block; }
.explain h5 {
  margin: 0 0 7px; font-size: 10.5px; font-weight: 600; letter-spacing: .6px;
  color: var(--c-brand); text-transform: uppercase;
}
.explain p { margin: 0 0 9px; }
.explain p:last-child { margin: 0; }
.explain .note {
  background: var(--c-surface); border: 1px solid var(--c-border-soft);
  border-radius: var(--r-md);
  padding: 9px 12px; margin: 10px 0 0; font-size: 13px;
}

.score-bar {
  display: flex; align-items: center; gap: 22px; flex-wrap: wrap;
  padding: 13px 18px; background: var(--c-surface);
  border: 1px solid var(--c-border); border-radius: var(--r-lg);
  margin-bottom: 16px; font-size: 13px;
}
.score-bar .stat { display: flex; align-items: baseline; gap: 5px; }
.score-bar .stat b {
  font-family: var(--font-mono); font-size: 16px; font-weight: 600; color: var(--c-ink);
  font-variant-numeric: tabular-nums;
}
.score-bar .stat span { font-size: 11px; color: var(--c-ink-4); }

/* ==========================================================================
   杂项
   ========================================================================== */
.empty-state {
  padding: 56px 24px; color: var(--c-ink-4); text-align: center;
  border: 1px dashed var(--c-border-strong); border-radius: var(--r-lg);
  font-size: 13.5px; line-height: 1.8;
}
.empty-state .big { font-size: 20px; opacity: .45; margin-bottom: 10px; font-family: var(--font-mono); }

.toast {
  position: fixed; bottom: 26px; left: 50%; transform: translate(-50%, 14px);
  background: var(--c-ink); color: var(--c-bg);
  padding: 10px 18px; font-size: 12.5px; font-weight: 500;
  border-radius: var(--r-md); box-shadow: var(--sh-2);
  opacity: 0; pointer-events: none; transition: .18s ease; z-index: 300;
}
.toast.show { opacity: 1; transform: translate(-50%, 0); }

.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; border: 0;
}

.loading { padding: 60px 0; color: var(--c-ink-4); font-size: 12.5px; display: flex; align-items: center; gap: 10px; }
.spinner {
  width: 14px; height: 14px; border: 1.5px solid var(--c-border-strong);
  border-top-color: var(--c-brand); border-radius: 50%;
  animation: spin .7s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

@media print {
  .topbar, .sidebar, .kp-actions, .pager, .search-box, .vd-frame, .vd-act { display: none !important; }
  .main { margin-left: 0; padding: 0; }
  body { background: #fff; color: #222; font-size: 12pt; }
  .card, .q-block, .prose table { break-inside: avoid; border-color: #ccc; box-shadow: none; }
  .hero { border: 0; }
}