/* mathplum 样式系统（T6/T10）——复刻 doc/design/2026-11-05/v1/shots/ 三稿
   色板：plum #7C3AED / plumDeep #4C1D95 / plumLight #8B5CF6 / ink #1B1530 */
@font-face { font-family: 'Inter'; font-style: normal; font-weight: 400; font-display: swap; src: url('/assets/fonts/inter-latin-400-normal.woff2') format('woff2'); }
@font-face { font-family: 'Inter'; font-style: normal; font-weight: 500; font-display: swap; src: url('/assets/fonts/inter-latin-500-normal.woff2') format('woff2'); }
@font-face { font-family: 'Inter'; font-style: normal; font-weight: 600; font-display: swap; src: url('/assets/fonts/inter-latin-600-normal.woff2') format('woff2'); }
@font-face { font-family: 'Inter'; font-style: normal; font-weight: 700; font-display: swap; src: url('/assets/fonts/inter-latin-700-normal.woff2') format('woff2'); }
@font-face { font-family: 'Inter'; font-style: normal; font-weight: 800; font-display: swap; src: url('/assets/fonts/inter-latin-800-normal.woff2') format('woff2'); }

:root {
  --ink: #1B1530;
  --ink-soft: #5B5470;
  --plum: #7C3AED;
  --plum-deep: #4C1D95;
  --plum-light: #8B5CF6;
  --amber: #F59E0B;
  --green: #059669;
  --green-bg: #D1FAE5;
  --paper: #FBFAFE;
  --border: #E9E4F4;
  --tint: #F6F4FC;
  --white: #fff;
  --radius-card: 16px;
  --radius-lg: 20px;
  --shadow-card: 0 8px 24px rgba(27, 21, 48, .08);
  --shadow-hero: 0 12px 32px rgba(27, 21, 48, .10);
  --mx: clamp(20px, 8vw, 120px);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0; background: var(--paper); color: var(--ink);
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  font-size: 16px; line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}
h1, h2, h3 { line-height: 1.15; margin: 0 0 .5em; letter-spacing: -.02em; }
p { margin: 0 0 1em; }
a { color: var(--plum); text-decoration: none; }
a:hover { text-decoration: underline; }
img, svg { max-width: 100%; }
.skip { position: absolute; left: -999px; top: 0; background: var(--plum); color: #fff; padding: 8px 16px; border-radius: 0 0 8px 0; z-index: 99; }
.skip:focus { left: 0; }

.wrap { max-width: 1200px; margin: 0 auto; padding: 0 var(--mx); }
main { display: block; }

/* ---------- 顶栏 ---------- */
.site-header { background: var(--white); border-bottom: 1px solid var(--border); position: sticky; top: 0; z-index: 50; }
.nav { max-width: 1440px; margin: 0 auto; padding: 0 clamp(20px, 8vw, 120px); height: 76px; display: flex; align-items: center; gap: 40px; }
.logo { display: inline-flex; align-items: center; gap: 10px; font-size: 22px; font-weight: 800; color: var(--ink); letter-spacing: -.02em; }
.logo:hover { text-decoration: none; }
.nav-links { display: flex; gap: 34px; margin-left: 24px; }
.nav-links a { color: var(--ink-soft); font-weight: 500; font-size: 15px; }
.nav-links a:hover { color: var(--plum); text-decoration: none; }
.nav .btn-nav { margin-left: auto; }

/* ---------- 按钮 ---------- */
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; border: 0; cursor: pointer; font-family: inherit; font-weight: 600; border-radius: 999px; text-decoration: none; }
.btn:hover { text-decoration: none; }
.btn-primary { background: var(--plum); color: #fff; padding: 10px 22px; font-size: 15px; }
.btn-primary:hover { background: var(--plum-deep); }
.btn-gradient { background: linear-gradient(90deg, var(--plum-light), var(--plum-deep)); color: #fff; box-shadow: 0 8px 20px rgba(124, 58, 237, .35); }
.btn-gradient:hover { filter: brightness(1.06); }
.btn-white { background: #fff; color: var(--plum-deep); }
.btn-outline { background: #fff; color: var(--ink); border: 1px solid var(--border); }
.btn-lg { padding: 16px 36px; font-size: 16px; }
.btn-sm { padding: 8px 18px; font-size: 14px; }

/* ---------- Hero（首页） ---------- */
.hero { background: linear-gradient(105deg, var(--plum-deep) 0%, var(--plum) 55%, var(--plum-light) 100%); color: #fff; padding: 84px 0 96px; position: relative; overflow: hidden; }
.hero-glyphs { position: absolute; inset: 0; pointer-events: none; user-select: none; }
.hero-glyphs span { position: absolute; font-weight: 800; color: rgba(255, 255, 255, .07); line-height: 1; }
.hero-badge { display: inline-block; background: rgba(255, 255, 255, .16); border: 1px solid rgba(255, 255, 255, .3); color: #fff; border-radius: 999px; padding: 6px 16px; font-size: 13px; font-weight: 700; letter-spacing: .1em; }
.hero h1 { font-size: clamp(40px, 5.5vw, 64px); font-weight: 800; color: #fff; margin: 22px 0 18px; }
.hero .hero-sub { font-size: 18px; color: rgba(255, 255, 255, .82); max-width: 640px; }
.hero-try { margin-top: 30px; background: rgba(255, 255, 255, .12); border: 1px solid rgba(255, 255, 255, .35); border-radius: 999px; padding: 16px 26px; max-width: 640px; color: rgba(255, 255, 255, .65); font-size: 16px; }
.hero-chips { margin-top: 26px; display: flex; flex-wrap: wrap; gap: 14px 34px; }
.hero-chips span { display: inline-flex; align-items: center; gap: 8px; color: rgba(255, 255, 255, .85); font-size: 14px; font-weight: 500; }
.hero-chips svg { flex: none; }

/* ---------- 区块 ---------- */
.section { padding: 72px 0 8px; }
.kicker { color: var(--plum); font-size: 13px; font-weight: 700; letter-spacing: .12em; text-transform: uppercase; }
.section h2 { font-size: clamp(26px, 3vw, 34px); font-weight: 800; margin: 10px 0 8px; }
.section .sub { color: var(--ink-soft); font-size: 15px; max-width: 720px; }

/* ---------- 卡片网格 ---------- */
.grid { display: grid; gap: 24px; margin-top: 30px; }
.grid-4 { grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); }
.grid-3 { grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); }
.grid-2 { grid-template-columns: repeat(auto-fit, minmax(340px, 1fr)); }
.card { background: var(--white); border-radius: var(--radius-card); box-shadow: var(--shadow-card); padding: 24px; position: relative; display: block; color: var(--ink); }
a.card:hover { text-decoration: none; transform: translateY(-2px); transition: transform .15s ease; }
.card-accent::before { content: ''; position: absolute; top: 0; left: 0; right: 0; height: 4px; border-radius: var(--radius-card) var(--radius-card) 0 0; background: linear-gradient(90deg, var(--plum-light), var(--plum-deep)); }
.card-flat { background: var(--tint); border: 1px solid var(--border); box-shadow: none; }
.card-dark { background: var(--ink); color: #fff; border-radius: var(--radius-lg); }
.card-dark h3 { color: #fff; }
.card-dark p { color: rgba(255, 255, 255, .7); }
.card h3 { font-size: 20px; font-weight: 700; margin: 14px 0 6px; }
.card .big { font-size: 28px; font-weight: 800; }
.card .ans { color: var(--plum); font-size: 24px; font-weight: 700; }
.card .meta { color: var(--ink-soft); font-size: 14px; }
.icon-chip { width: 44px; height: 44px; border-radius: 12px; background: rgba(124, 58, 237, .12); display: grid; place-items: center; }
.more-link { display: inline-block; margin-top: 20px; font-weight: 600; font-size: 14px; }

/* ---------- 面包屑 ---------- */
.breadcrumbs { font-size: 13px; color: var(--ink-soft); margin: 28px 0 18px; }
.breadcrumbs a { color: var(--ink-soft); font-weight: 500; }
.breadcrumbs a:hover { color: var(--plum); }
.crumb-sep { color: var(--border); margin: 0 6px; }

/* ---------- 内容页骨架 ---------- */
.page-head h1 { font-size: clamp(34px, 4.5vw, 52px); font-weight: 800; letter-spacing: -.02em; }
.page-head .lede { font-size: 17px; color: var(--ink-soft); max-width: 780px; }
.article-body { font-size: 16px; }
.article-body h2 { font-size: clamp(24px, 3vw, 30px); font-weight: 800; margin: 54px 0 18px; }
.article-body h3 { font-size: 20px; font-weight: 700; margin: 28px 0 10px; }

/* ---------- 答案主卡 ---------- */
.answer-card { background: var(--white); border-radius: var(--radius-lg); box-shadow: var(--shadow-hero); padding: 40px 48px; position: relative; overflow: hidden; margin: 30px 0 10px; }
.answer-card::before { content: ''; position: absolute; top: 0; left: 0; right: 0; height: 6px; background: linear-gradient(90deg, var(--plum-light), var(--plum-deep)); }
.answer-eq { display: flex; align-items: baseline; gap: 22px; flex-wrap: wrap; }
.answer-eq .frac-src { font-size: clamp(36px, 4vw, 56px); font-weight: 800; }
.answer-eq .eq { font-size: clamp(30px, 3.4vw, 44px); font-weight: 700; color: var(--ink-soft); }
.answer-eq .dec { font-size: clamp(48px, 6vw, 76px); font-weight: 800; color: var(--plum); letter-spacing: -.03em; }
.badge { display: inline-block; border-radius: 999px; padding: 6px 14px; font-size: 12px; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; }
.badge-green { background: var(--green-bg); color: var(--green); }
.answer-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 40px; align-items: center; margin-top: 10px; }
.triple { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; margin-top: 30px; }
.triple .tile { background: var(--tint); border-radius: 12px; padding: 16px 20px; }
.triple .tile .k { font-size: 12px; font-weight: 700; color: var(--ink-soft); text-transform: uppercase; letter-spacing: .06em; }
.triple .tile .v { font-size: 17px; font-weight: 700; margin-top: 2px; }

/* ---------- 步骤卡 ---------- */
.steps { display: grid; gap: 16px; margin-top: 24px; }
.step { background: var(--white); border: 1px solid var(--border); border-radius: 14px; padding: 22px 26px 22px 96px; position: relative; }
.step .num { position: absolute; left: 22px; top: 20px; width: 52px; height: 52px; border-radius: 50%; background: var(--plum); color: #fff; font-size: 22px; font-weight: 700; display: grid; place-items: center; }
.step h3 { font-size: 19px; margin: 0 0 4px; }
.step p { margin: 0; color: var(--ink-soft); font-size: 15px; }
.step .math-line { font-size: 18px; font-weight: 600; color: var(--ink); margin-top: 8px; font-variant-numeric: tabular-nums; }

/* ---------- 双栏：场景 + 因子树 ---------- */
.duo { display: grid; grid-template-columns: 1.9fr 1fr; gap: 24px; margin-top: 24px; }
.panel-card { background: var(--white); border: 1px solid var(--border); border-radius: var(--radius-card); padding: 26px 28px; }
.panel-card h3 { font-size: 18px; }
.panel-card p { color: var(--ink-soft); font-size: 15px; }
.panel-tint { background: var(--tint); }
.panel-card .worked { color: var(--plum); font-weight: 600; font-size: 15px; }
.factor-tree { display: flex; align-items: center; gap: 18px; flex-wrap: wrap; font-size: 15px; }
.factor-tree .node { background: #fff; border: 1px solid var(--border); border-radius: 10px; padding: 8px 14px; font-weight: 700; }
.factor-tree .arrow { color: var(--ink-soft); font-weight: 700; }
.factor-tree .prime { color: var(--green); font-weight: 600; }

/* ---------- FAQ ---------- */
.faq-list { display: grid; gap: 14px; margin-top: 24px; }
.faq { background: var(--white); border: 1px solid var(--border); border-radius: 14px; padding: 18px 24px; }
.faq h3 { font-size: 16px; margin: 0 0 6px; }
.faq p { margin: 0; color: var(--ink-soft); font-size: 14.5px; }

/* ---------- CTA 横幅 ---------- */
.cta-band { background: linear-gradient(120deg, var(--plum-deep), var(--plum)); border-radius: var(--radius-lg); color: #fff; padding: 38px 40px; display: flex; align-items: center; justify-content: space-between; gap: 24px; flex-wrap: wrap; margin: 56px 0 20px; }
.cta-band h2 { color: #fff; font-size: 24px; margin: 0 0 6px; }
.cta-band p { color: rgba(255, 255, 255, .8); margin: 0; font-size: 15px; }

/* ---------- 再练几道 ---------- */
.practice-mini { margin-top: 48px; }
.practice-mini ol { font-size: 17px; line-height: 2.1; }
.practice-mini details { margin-top: 12px; background: var(--tint); border-radius: 12px; padding: 12px 18px; font-size: 15px; }
.practice-mini summary { cursor: pointer; font-weight: 600; color: var(--plum); }

/* ---------- 页脚 ---------- */
.site-footer { background: var(--ink); color: #fff; margin-top: 80px; }
.footer-inner { max-width: 1440px; margin: 0 auto; padding: 30px clamp(20px, 8vw, 120px); display: flex; align-items: center; gap: 40px; flex-wrap: wrap; }
.logo-footer { color: #fff; font-size: 18px; }
.footer-links { display: flex; gap: 14px; align-items: center; color: rgba(255, 255, 255, .7); font-size: 14px; }
.footer-links a { color: rgba(255, 255, 255, .7); }
.footer-links a:hover { color: #fff; }
.footer-mail { margin-left: auto; color: rgba(255, 255, 255, .7); font-weight: 500; font-size: 14px; }
.footer-bottom { border-top: 1px solid rgba(255, 255, 255, .12); padding: 14px clamp(20px, 8vw, 120px); font-size: 12.5px; color: rgba(255, 255, 255, .5); }

/* ---------- 广告位容器（F12：不加载网络） ---------- */
.ad-slot { border: 1px dashed var(--border); border-radius: 12px; background: var(--tint); color: var(--ink-soft); font-size: 12px; letter-spacing: .1em; text-transform: uppercase; display: grid; place-items: center; min-height: 110px; margin: 48px 0; }

/* ---------- 生成器页 ---------- */
.ws-layout { display: grid; grid-template-columns: 400px 1fr; gap: 40px; margin-top: 34px; align-items: start; }
.ws-panel { background: var(--white); border-radius: var(--radius-lg); box-shadow: var(--shadow-hero); padding: 28px; }
.ws-panel .field-label { font-size: 12px; font-weight: 700; letter-spacing: .1em; color: var(--ink-soft); margin: 22px 0 10px; }
.ws-panel .field-label:first-child { margin-top: 0; }
.pill-row { display: flex; gap: 10px; flex-wrap: wrap; }
.pill { min-width: 52px; height: 44px; padding: 0 18px; border-radius: 10px; border: 1px solid var(--border); background: var(--tint); font-family: inherit; font-size: 15px; font-weight: 600; color: var(--ink); cursor: pointer; }
.pill[aria-pressed="true"] { background: var(--plum); border-color: var(--plum); color: #fff; }
.topic-row { display: flex; align-items: center; gap: 12px; padding: 6px 0; cursor: pointer; font-size: 15px; }
.topic-row input { width: 20px; height: 20px; accent-color: var(--plum); }
.ws-actions { display: grid; gap: 12px; margin-top: 26px; }
.ws-actions .btn { width: 100%; padding: 14px; font-size: 15px; }
.print-row { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }

.ws-paper { background: var(--white); border-radius: var(--radius-lg); box-shadow: 0 20px 50px rgba(27, 21, 48, .12); padding: 44px 48px; }
.ws-paper .ws-title { text-align: center; font-size: 13px; font-weight: 600; color: var(--ink-soft); }
.ws-blank { display: flex; gap: 40px; margin: 14px 0 8px; font-size: 13px; color: var(--ink-soft); }
.ws-blank .line { flex: 1; border-bottom: 1px solid var(--ink-soft); max-width: 220px; height: 1.2em; }
.ws-grid { display: grid; grid-template-columns: 1fr 1fr; column-gap: 48px; margin-top: 14px; font-size: 15.5px; }
.ws-grid .prob { padding: 12px 0; border-bottom: 1px solid var(--tint); font-variant-numeric: tabular-nums; }
.ws-answers { display: none; margin-top: 24px; border-top: 3px solid var(--plum); padding-top: 16px; page-break-before: always; }
.ws-answers h2 { font-size: 20px; margin: 0 0 10px; }
.ws-answers .ans-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 6px 24px; font-size: 14px; }
.ws-foot { margin-top: 22px; font-size: 13px; color: var(--ink-soft); }

/* ---------- 法律页 ---------- */
.legal { max-width: 780px; }
.legal h1 { font-size: clamp(30px, 4vw, 42px); font-weight: 800; }
.legal h2 { font-size: 22px; margin-top: 36px; }
.legal p, .legal li { color: var(--ink-soft); }

/* ---------- 打印（T10：两套 @media print） ---------- */
/* 第一套：试卷卷——题+留白，隐藏导航/广告/页脚/答案 */
@media print {
  .no-print, .site-header, .site-footer, .ad-slot, .breadcrumbs, .ws-panel, .ws-answers, .cta-band { display: none !important; }
  body { background: #fff; font-size: 12pt; }
  .ws-layout { display: block; margin: 0; }
  .ws-paper { box-shadow: none; border-radius: 0; padding: 0; }
  .wrap { padding: 0; }
  a { color: inherit; text-decoration: none; }
}
/* 第二套：答案页——自动分页，页眉标 Answer Key */
@media print {
  body[data-print="answers"] .ws-paper .ws-blank,
  body[data-print="answers"] .ws-paper .ws-grid { display: none; }
  body[data-print="answers"] .ws-answers { display: block; }
  body[data-print="answers"] .ws-answers h2::before { content: 'Answer Key · '; }
}

/* ---------- 响应式 ---------- */
@media (max-width: 960px) {
  .nav { height: 64px; gap: 18px; }
  .nav-links { display: none; }
  .answer-grid, .duo, .ws-layout { grid-template-columns: 1fr; }
  .triple { grid-template-columns: 1fr; }
  .ws-grid { grid-template-columns: 1fr; }
  .answer-card { padding: 28px 24px; }
}