/* ============ 设计令牌 Design Tokens ============ */
:root, [data-theme="light"] {
  --font: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Inter", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  --font-serif: "Songti SC", "Noto Serif SC", "Source Han Serif SC", Georgia, "Times New Roman", serif;
  --mono: "SF Mono", "JetBrains Mono", Menlo, Consolas, monospace;

  --bg: #f5f6f8;
  --bg-2: #eceef2;
  --card: #ffffff;
  --card-2: #f9fafb;
  --fg: #0b1220;
  --fg-2: #3f4a5c;
  --fg-3: #6b7486;
  --muted: #9aa3b2;
  --border: #e4e7ec;
  --border-2: #d3d8e0;
  --hover: rgba(15, 23, 42, .045);
  --overlay: rgba(10, 14, 22, .45);

  --success: #16a34a;
  --warning: #f59e0b;
  --danger: #ef4444;
  --info: #0ea5e9;

  /* 图表分类色（按固定顺序使用） */
  --s1: #2a78d6; --s2: #eb6834; --s3: #1baf7a; --s4: #eda100;
  --s5: #e87ba4; --s6: #008300; --s7: #6250d6; --s8: #e34948;
  --grid: #e9ecf1;

  --radius-sm: 8px;
  --radius: 12px;
  --r-ctl: 8px;
  --r-tag: 6px;
  --r-card: 12px;
  --radius-lg: 18px;
  --radius-xl: 24px;
  --shadow-sm: 0 1px 2px rgba(16, 24, 40, .06);
  --shadow: 0 1px 2px rgba(16, 24, 40, .04), 0 4px 12px rgba(16, 24, 40, .06);
  --shadow-lg: 0 12px 32px -8px rgba(16, 24, 40, .18), 0 4px 8px rgba(16, 24, 40, .05);
  --shadow-xl: 0 24px 60px -12px rgba(16, 24, 40, .28);

  --ease-out: cubic-bezier(.22, 1, .36, 1);
  --ease-in-out: cubic-bezier(.65, 0, .35, 1);
  --ease-spring: cubic-bezier(.34, 1.56, .64, 1);

  --anno: #f43f5e;
}

[data-theme="dark"] {
  color-scheme: dark;
  --bg: #0a0c10;
  --bg-2: #141820;
  --card: #12161d;
  --card-2: #171c25;
  --fg: #eef1f6;
  --fg-2: #b8c1cf;
  --fg-3: #8a94a6;
  --muted: #5d6676;
  --border: #232935;
  --border-2: #2f3744;
  --hover: rgba(255, 255, 255, .05);
  --overlay: rgba(0, 0, 0, .6);
  --s1: #3987e5; --s2: #d95926; --s3: #199e70; --s4: #c98500;
  --s5: #d55181; --s6: #008300; --s7: #9085e9; --s8: #e66767;
  --grid: #222833;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, .4);
  --shadow: 0 1px 2px rgba(0, 0, 0, .3), 0 4px 14px rgba(0, 0, 0, .35);
  --shadow-lg: 0 14px 36px -8px rgba(0, 0, 0, .6);
  --shadow-xl: 0 28px 64px -12px rgba(0, 0, 0, .75);
}

/* 主题色单独声明，避免局部 data-theme="light" 覆盖用户选择的主题色 */
:root { --primary: #4f46e5; --primary-fg: #ffffff; }

/* 派生令牌：在任何覆盖了 --primary 的容器上加 .tok 重新计算 */
:root, .tok {
  --primary-soft: color-mix(in srgb, var(--primary) 12%, transparent);
  --primary-soft-2: color-mix(in srgb, var(--primary) 22%, transparent);
  --primary-border: color-mix(in srgb, var(--primary) 40%, transparent);
  --primary-strong: color-mix(in srgb, var(--primary) 82%, #000);
}

/* ============ 基础 ============ */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 76px; }
body {
  margin: 0;
  font-family: var(--font);
  font-size: 14px;
  line-height: 1.6;
  color: var(--fg);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  transition: background-color .3s, color .3s;
}
img, svg { display: block; }
svg { flex-shrink: 0; }
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; }
h1, h2, h3, h4, h5, p { margin: 0; }
code, kbd, pre { font-family: var(--mono); }
::selection { background: var(--primary-soft-2); }
:focus-visible { outline: 2px solid var(--primary); outline-offset: 2px; }

.wrap { max-width: 1320px; margin: 0 auto; padding: 0 32px; }
.muted { color: var(--fg-3); }
.mono { font-family: var(--mono); }
.num { font-variant-numeric: tabular-nums; }
.row { display: flex; align-items: center; gap: 8px; }
.row-wrap { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; }
.col { display: flex; flex-direction: column; gap: 8px; }
.spacer { flex: 1; }
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); }

/* ============ 顶栏 ============ */
.topbar {
  position: fixed; inset: 0 0 auto 0; z-index: 900;
  height: 60px; display: flex; align-items: center; gap: 20px;
  padding: 0 24px;
  background: color-mix(in srgb, var(--bg) 78%, transparent);
  backdrop-filter: saturate(180%) blur(16px);
  -webkit-backdrop-filter: saturate(180%) blur(16px);
  border-bottom: 1px solid color-mix(in srgb, var(--border) 70%, transparent);
}
.brand { display: flex; align-items: center; gap: 10px; flex-shrink: 0; }
.brand-mark {
  width: 26px; height: 26px; border-radius: 8px;
  background: conic-gradient(from 210deg, var(--primary), #ec4899, #f59e0b, #10b981, var(--primary));
  box-shadow: inset 0 0 0 5px color-mix(in srgb, var(--bg) 85%, transparent);
}
.brand-name { font-weight: 700; font-size: 15px; display: flex; align-items: baseline; gap: 6px; }
.brand-name small { font-weight: 500; font-size: 11px; color: var(--fg-3); letter-spacing: .04em; }
.topnav { display: flex; gap: 2px; overflow-x: auto; scrollbar-width: none; flex: 1; justify-content: center; }
.topnav::-webkit-scrollbar { display: none; }
.topnav a {
  padding: 6px 11px; border-radius: 999px; font-size: 13px; color: var(--fg-2);
  white-space: nowrap; transition: background .2s, color .2s;
}
.topnav a:hover { background: var(--hover); color: var(--fg); }
.topnav a.on { background: var(--fg); color: var(--bg); }
.top-tools { display: flex; align-items: center; gap: 12px; flex-shrink: 0; }
.tool-switch { display: flex; align-items: center; gap: 6px; font-size: 12px; color: var(--fg-2); cursor: pointer; user-select: none; }
.tool-switch input { display: none; }
.tool-switch-ui {
  width: 28px; height: 16px; border-radius: 99px; background: var(--border-2); position: relative; transition: background .2s;
}
.tool-switch-ui::after {
  content: ""; position: absolute; top: 2px; left: 2px; width: 12px; height: 12px; border-radius: 50%;
  background: #fff; box-shadow: 0 1px 2px rgba(0,0,0,.25); transition: transform .25s var(--ease-spring);
}
.tool-switch input:checked + .tool-switch-ui { background: var(--primary); }
.tool-switch input:checked + .tool-switch-ui::after { transform: translateX(12px); }
.accent-dots { display: flex; gap: 5px; }
.accent-dot {
  width: 16px; height: 16px; border-radius: 50%; border: 0; cursor: pointer; padding: 0;
  background: var(--c); box-shadow: 0 0 0 2px var(--bg), 0 0 0 3px transparent; transition: box-shadow .2s, transform .2s;
}
.accent-dot:hover { transform: scale(1.15); }
.accent-dot.on { box-shadow: 0 0 0 2px var(--bg), 0 0 0 3.5px var(--c); }
.icon-btn {
  width: 34px; height: 34px; border-radius: 10px; border: 1px solid var(--border); background: var(--card);
  display: grid; place-items: center; cursor: pointer; color: var(--fg-2); transition: all .2s;
}
.icon-btn:hover { color: var(--fg); border-color: var(--border-2); }
.scroll-progress {
  position: fixed; top: 60px; left: 0; height: 2px; width: 100%; z-index: 901;
  background: linear-gradient(90deg, var(--primary), #ec4899);
  transform-origin: 0 50%; transform: scaleX(0);
}

/* ============ 首屏 ============ */
.hero { position: relative; padding: 140px 0 60px; overflow: hidden; }
.hero-bg { position: absolute; inset: 0; pointer-events: none; overflow: hidden; }
.hero-bg i {
  position: absolute; border-radius: 50%; filter: blur(80px); opacity: .45;
  animation: heroFloat 18s ease-in-out infinite alternate;
}
.hero-bg i:nth-child(1) { width: 520px; height: 520px; left: -120px; top: -80px; background: var(--primary); }
.hero-bg i:nth-child(2) { width: 420px; height: 420px; right: -60px; top: 40px; background: #ec4899; animation-delay: -6s; opacity: .3; }
.hero-bg i:nth-child(3) { width: 380px; height: 380px; left: 40%; top: 260px; background: #06b6d4; animation-delay: -12s; opacity: .25; }
[data-theme="dark"] .hero-bg i { opacity: .28; }
.hero-grid {
  position: absolute; inset: 0;
  background-image: linear-gradient(var(--border) 1px, transparent 1px), linear-gradient(90deg, var(--border) 1px, transparent 1px);
  background-size: 56px 56px;
  mask-image: radial-gradient(ellipse 70% 60% at 50% 30%, #000 30%, transparent 75%);
  -webkit-mask-image: radial-gradient(ellipse 70% 60% at 50% 30%, #000 30%, transparent 75%);
  opacity: .6;
}
@keyframes heroFloat { to { transform: translate(60px, 40px) scale(1.12); } }
.hero .wrap { position: relative; }
.hero-eyebrow {
  display: inline-flex; align-items: center; gap: 8px; padding: 5px 12px 5px 6px; border-radius: 999px;
  background: color-mix(in srgb, var(--card) 70%, transparent); border: 1px solid var(--border);
  font-size: 12px; color: var(--fg-2); backdrop-filter: blur(8px);
}
.hero-eyebrow b { background: var(--primary); color: var(--primary-fg); padding: 1px 8px; border-radius: 99px; font-size: 11px; font-weight: 600; }
.hero h1 {
  margin-top: 22px; font-size: clamp(44px, 7vw, 92px); line-height: 1.02; letter-spacing: -.04em; font-weight: 800;
}
.hero h1 .grad {
  background: linear-gradient(100deg, var(--primary) 10%, #ec4899 50%, #f59e0b 90%);
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero-lead { margin-top: 22px; max-width: 760px; font-size: 18px; color: var(--fg-2); line-height: 1.75; }
.hero-cta { margin-top: 30px; display: flex; gap: 12px; flex-wrap: wrap; }
.formula {
  margin-top: 56px; display: grid; grid-template-columns: repeat(5, 1fr); gap: 0;
  border: 1px solid var(--border); border-radius: var(--radius-xl); overflow: hidden;
  background: color-mix(in srgb, var(--card) 85%, transparent); backdrop-filter: blur(10px);
}
.formula-item { padding: 22px 22px 20px; position: relative; border-right: 1px solid var(--border); transition: background .25s; }
.formula-item:last-child { border-right: 0; }
.formula-item:hover { background: var(--hover); }
.formula-item:not(:last-child)::after {
  content: "×"; position: absolute; right: -11px; top: 50%; transform: translateY(-50%); z-index: 2;
  width: 22px; height: 22px; display: grid; place-items: center; border-radius: 50%; font-size: 13px;
  background: var(--card); border: 1px solid var(--border); color: var(--fg-3);
}
.formula-no { font-family: var(--mono); font-size: 11px; color: var(--fg-3); }
.formula-item h3 { font-size: 18px; margin-top: 8px; display: flex; align-items: center; gap: 8px; }
.formula-item h3 svg { color: var(--primary); }
.formula-item p { font-size: 12.5px; color: var(--fg-3); margin-top: 6px; line-height: 1.6; }
.formula-item .formula-count { margin-top: 12px; font-size: 28px; font-weight: 700; letter-spacing: -.02em; font-variant-numeric: tabular-nums; }
.formula-item .formula-count small { font-size: 12px; color: var(--fg-3); font-weight: 500; margin-left: 4px; }
.hero-sentence {
  margin-top: 22px; padding: 18px 22px; border-radius: var(--radius-lg); border: 1px dashed var(--border-2);
  font-size: 15px; line-height: 2; color: var(--fg-2); background: color-mix(in srgb, var(--card) 60%, transparent);
}
.hero-sentence mark {
  background: var(--primary-soft); color: var(--primary); padding: 2px 8px; border-radius: 6px; font-weight: 600;
}
.hero-sentence mark[data-k]::before { content: attr(data-k) " · "; font-weight: 500; opacity: .7; font-size: 12px; }
.hero-tips { margin-top: 16px; display: flex; flex-wrap: wrap; gap: 18px; font-size: 13px; color: var(--fg-3); }
.hero-tips span { display: flex; align-items: center; gap: 6px; }
.hero-tips svg { color: var(--primary); }

/* ============ 章节 ============ */
.section { padding: 110px 0 30px; position: relative; }
.sec-head { display: grid; grid-template-columns: 1fr auto; gap: 24px; align-items: end; margin-bottom: 40px; }
.sec-no { font-family: var(--mono); font-size: 12px; color: var(--primary); letter-spacing: .1em; display: flex; align-items: center; gap: 10px; }
.sec-no::after { content: ""; width: 40px; height: 1px; background: var(--primary); opacity: .5; }
.sec-head h2 { font-size: clamp(32px, 4vw, 48px); letter-spacing: -.03em; line-height: 1.1; margin-top: 12px; font-weight: 800; }
.sec-head h2 small { font-size: .42em; font-weight: 500; color: var(--fg-3); letter-spacing: 0; margin-left: 12px; }
.sec-head p { margin-top: 14px; max-width: 780px; font-size: 15.5px; color: var(--fg-2); line-height: 1.8; }
.sec-chips { display: flex; flex-wrap: wrap; gap: 6px; justify-content: flex-end; max-width: 420px; }
.sec-chips span {
  font-size: 12px; padding: 4px 10px; border-radius: 999px; border: 1px solid var(--border); color: var(--fg-2); background: var(--card);
}
.sub-head { display: flex; align-items: flex-end; justify-content: space-between; gap: 20px; margin: 64px 0 22px; flex-wrap: wrap; }
.sub-head:first-child { margin-top: 0; }
.sub-head h3 { font-size: 24px; letter-spacing: -.02em; font-weight: 700; display: flex; align-items: baseline; gap: 10px; }
.sub-head h3 em { font-style: normal; font-size: 13px; font-weight: 500; color: var(--fg-3); font-family: var(--mono); }
.sub-head p { font-size: 14px; color: var(--fg-3); margin-top: 6px; max-width: 760px; line-height: 1.7; }

.panel { background: var(--card); border: 1px solid var(--border); border-radius: var(--radius-lg); }
.panel-pad { padding: 22px; }

/* 主分类切换（大号胶囊标签） */
.big-tabs { display: inline-flex; gap: 4px; padding: 5px; border-radius: 16px; background: var(--card); border: 1px solid var(--border); flex-wrap: wrap; }
.big-tabs button {
  border: 0; background: none; cursor: pointer; padding: 10px 18px; border-radius: 11px; font-size: 14px; font-weight: 600;
  color: var(--fg-2); display: flex; align-items: center; gap: 8px; transition: background .25s, color .25s;
}
.big-tabs button small { font-weight: 500; font-size: 11px; color: var(--fg-3); }
.big-tabs button:hover { color: var(--fg); }
.big-tabs button.on { background: var(--fg); color: var(--bg); }
.big-tabs button.on small { color: color-mix(in srgb, var(--bg) 70%, transparent); }
.tab-panel { display: none; }
.tab-panel.on { display: block; animation: panelIn .45s var(--ease-out); }
@keyframes panelIn { from { opacity: 0; transform: translateY(10px); } }

/* 滚动显现 */
.rv { opacity: 0; transform: translateY(18px); transition: opacity .7s var(--ease-out), transform .7s var(--ease-out); }
.rv.in { opacity: 1; transform: none; }

/* ============ 检查器 / 标注 ============ */
.inspector-tip {
  position: fixed; z-index: 1200; pointer-events: none; opacity: 0; transform: translateY(4px);
  transition: opacity .12s, transform .12s;
  background: var(--anno); color: #fff; font-size: 11.5px; font-weight: 600; line-height: 1;
  padding: 5px 8px; border-radius: 6px; white-space: nowrap; box-shadow: 0 6px 16px -4px rgba(244, 63, 94, .5);
}
.inspector-tip.show { opacity: 1; transform: none; }
.inspector-tip small { font-weight: 500; opacity: .85; margin-left: 4px; }
body.inspect-on [data-ui].ui-hover { outline: 1.5px solid var(--anno) !important; outline-offset: -1px; }
.anno-host { position: relative; }
.anno-tag {
  position: absolute; top: 2px; left: 2px; z-index: 60; pointer-events: none;
  background: var(--anno); color: #fff; font: 600 10px/1 var(--font); padding: 3px 5px; border-radius: 4px;
  white-space: nowrap; box-shadow: 0 2px 6px rgba(0,0,0,.2); letter-spacing: 0; text-transform: none; font-style: normal;
}
body.anno-all [data-ui] { outline: 1px dashed color-mix(in srgb, var(--anno) 70%, transparent); outline-offset: -1px; }

/* 图表悬浮提示 */
.chart-tip {
  position: fixed; z-index: 1200; pointer-events: none; opacity: 0;
  background: var(--card); color: var(--fg); border: 1px solid var(--border); box-shadow: var(--shadow-lg);
  border-radius: 8px; padding: 6px 10px; font-size: 12px; white-space: nowrap; transition: opacity .12s;
}
.chart-tip.show { opacity: 1; }

/* 页脚 */
.site-footer { margin-top: 80px; border-top: 1px solid var(--border); padding: 40px 0 60px; color: var(--fg-3); font-size: 13px; }
.site-footer .wrap { display: flex; justify-content: space-between; gap: 20px; flex-wrap: wrap; }

/* 代码片段 */
.code-chip {
  display: inline-block; font-family: var(--mono); font-size: 11px; padding: 2px 6px; border-radius: 5px;
  background: var(--bg-2); color: var(--fg-2); border: 1px solid var(--border); white-space: nowrap;
}

/* 响应式 */
@media (max-width: 1100px) {
  .topnav { justify-content: flex-start; }
  .formula { grid-template-columns: repeat(2, 1fr); }
  .formula-item { border-bottom: 1px solid var(--border); }
  .formula-item::after { display: none; }
}
@media (max-width: 760px) {
  .wrap { padding: 0 18px; }
  .topnav, .accent-dots { display: none; }
  .sec-head { grid-template-columns: 1fr; }
  .sec-chips { justify-content: flex-start; }
  .formula { grid-template-columns: 1fr; }
}
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: .01ms !important; animation-iteration-count: 1 !important; transition-duration: .01ms !important; }
  html { scroll-behavior: auto; }
}