:root {
  --bg: #f5f8fb;
  --ink: #122235;
  --muted: #62758a;
  --line: rgba(32, 64, 96, .16);
  --paper: rgba(255, 255, 255, .86);
  --navy: #193a5a;
  --blue: #2d74d8;
  --green: #1d9f77;
  --amber: #d99529;
  --red: #e35d4f;
  --shadow: 0 18px 52px rgba(37, 74, 108, .12);
  font-family: Inter, "SF Pro Display", "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  color: var(--ink);
  background: var(--bg);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  min-width: 320px;
  background:
    linear-gradient(120deg, rgba(231, 240, 248, .82), rgba(255, 255, 255, .78) 42%, rgba(238, 246, 241, .76)),
    radial-gradient(circle at 8% 12%, rgba(45, 116, 216, .12), transparent 34%);
  letter-spacing: 0;
}
a { color: inherit; text-decoration: none; }
a:hover { color: var(--blue); }
img { max-width: 100%; display: block; }
.skip-link { position: absolute; left: -999px; top: 8px; z-index: 20; padding: 10px 14px; background: #fff; border: 1px solid var(--line); }
.skip-link:focus { left: 12px; }
.learning-top {
  position: sticky;
  top: 0;
  z-index: 10;
  width: min(1180px, calc(100% - 32px));
  margin: 14px auto 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  padding: 12px 14px;
  border: 1px solid var(--line);
  background: rgba(255,255,255,.82);
  backdrop-filter: blur(18px);
  box-shadow: 0 10px 26px rgba(29, 62, 92, .08);
  border-radius: 10px;
}
.learning-brand { display: inline-flex; align-items: center; gap: 10px; min-width: max-content; }
.learning-mark {
  width: 32px;
  height: 32px;
  border-radius: 9px;
  background:
    linear-gradient(135deg, var(--navy), var(--blue)),
    linear-gradient(45deg, transparent 42%, rgba(255,255,255,.7) 42% 58%, transparent 58%);
  box-shadow: inset 0 0 0 1px rgba(255,255,255,.5);
}
.learning-brand strong { font-size: 18px; }
.learning-brand em { font-style: normal; color: var(--muted); font-size: 13px; }
.chapter-nav { display: flex; flex-wrap: wrap; justify-content: flex-end; gap: 4px; }
.chapter-nav a { padding: 9px 11px; border-radius: 8px; color: #2b4a63; font-size: 14px; }
.chapter-nav a:hover { background: rgba(45,116,216,.08); }
.chapter-toggle { display: none; border: 0; border-radius: 8px; padding: 9px 12px; color: #fff; background: var(--navy); }
main { width: min(1180px, calc(100% - 32px)); margin: 0 auto; }
section { scroll-margin-top: 96px; }
.handbook-hero {
  position: relative;
  display: grid;
  grid-template-columns: minmax(0, .84fr) minmax(440px, 1.16fr);
  gap: 28px;
  align-items: center;
  min-height: 640px;
  padding: 54px 0 40px;
}
.hero-index h1, .page-cover h1 {
  margin: 16px 0;
  font-size: clamp(39px, 5vw, 74px);
  line-height: 1.04;
}
.hero-index p, .page-cover p, .section-head p, .lesson-card p, .chapter-deck p, .network-board p, .plain-copy p, .contact-desk p, .support-strip p {
  color: var(--muted);
  line-height: 1.86;
}
.overline, .section-head span, .page-cover span {
  display: inline-flex;
  color: var(--blue);
  font-weight: 900;
  font-size: 13px;
  letter-spacing: .06em;
  text-transform: uppercase;
}
.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; margin: 26px 0 0; }
.solid-action, .line-action, .text-link, .support-strip a {
  display: inline-flex;
  min-height: 44px;
  align-items: center;
  justify-content: center;
  padding: 11px 18px;
  border-radius: 10px;
  font-weight: 850;
}
.solid-action { color: #fff; background: linear-gradient(135deg, var(--navy), var(--blue)); box-shadow: 0 14px 30px rgba(45,116,216,.2); }
.line-action, .text-link, .support-strip a { border: 1px solid var(--line); background: rgba(255,255,255,.72); color: #264762; }
.learning-visual {
  margin: 0;
  border: 1px solid rgba(255,255,255,.86);
  padding: 8px;
  border-radius: 16px;
  background: rgba(255,255,255,.52);
  box-shadow: var(--shadow);
  overflow: hidden;
}
.learning-visual img { width: 100%; border-radius: 10px; aspect-ratio: 16/9; object-fit: cover; }
.course-check {
  position: absolute;
  right: 48px;
  bottom: 38px;
  width: min(350px, 42%);
  padding: 18px;
  border: 1px solid rgba(255,255,255,.9);
  background: rgba(255,255,255,.74);
  backdrop-filter: blur(18px);
  box-shadow: var(--shadow);
  border-radius: 14px;
}
.course-check b { display: block; margin-bottom: 10px; }
.course-check ol { margin: 0; padding-left: 22px; color: #34556d; line-height: 1.9; }
.chapter-deck, .download-desk, .network-board, .case-ledger, .guide-shelf, .question-bank, .platform-matrix, .three-steps, .network-notes, .device-manual, .help-desk, .plain-copy, .contact-desk, .legacy-note, .support-strip {
  margin: 26px 0;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: var(--paper);
  backdrop-filter: blur(18px);
  box-shadow: 0 16px 44px rgba(37, 74, 108, .08);
  padding: 26px;
}
.chapter-deck {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 14px;
}
.chapter-deck article, .device-table a, .network-rows article, .case-grid article, .lesson-card, .platform-grid a, .device-manual article, .help-desk article, .three-steps li {
  border: 1px solid var(--line);
  background: rgba(255,255,255,.68);
  border-radius: 10px;
  padding: 18px;
}
.section-head { display: grid; gap: 8px; margin-bottom: 18px; }
.section-head h2, .platform-matrix h2, .three-steps h2, .network-notes h2, .plain-copy h2, .contact-desk h2, .legacy-note h2 {
  margin: 0;
  font-size: clamp(25px, 3vw, 42px);
  line-height: 1.16;
}
.device-table, .network-rows, .case-grid, .guide-list, .platform-grid {
  display: grid;
  gap: 14px;
}
.device-table { grid-template-columns: repeat(4, 1fr); }
.device-table b, .platform-grid strong, .network-rows strong, .help-desk strong { display: block; margin-bottom: 8px; font-size: 18px; }
.device-table span, .help-desk span { color: var(--muted); line-height: 1.75; }
.network-rows, .case-grid { grid-template-columns: repeat(4, 1fr); }
.guide-list { grid-template-columns: repeat(4, 1fr); }
.all-guides .guide-list { grid-template-columns: repeat(2, 1fr); }
.lesson-card time { color: var(--muted); margin-right: 8px; }
.lesson-card span { color: var(--amber); font-weight: 900; }
.lesson-card h3 { line-height: 1.28; margin: 12px 0 8px; }
.question-list { display: grid; gap: 10px; }
.question-list details {
  border: 1px solid var(--line);
  background: rgba(255,255,255,.7);
  border-radius: 10px;
  padding: 14px 16px;
}
.question-list summary { cursor: pointer; font-weight: 850; line-height: 1.5; }
.question-list p { color: var(--muted); line-height: 1.8; }
.page-cover {
  margin: 46px 0 24px;
  padding: 42px;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: linear-gradient(135deg, rgba(255,255,255,.92), rgba(237,246,255,.72));
  box-shadow: 0 18px 44px rgba(37,74,108,.08);
}
.platform-grid { grid-template-columns: repeat(4, 1fr); }
.source-note {
  margin-top: 16px;
  border: 1px solid rgba(217,149,41,.28);
  background: rgba(255,249,236,.78);
  border-radius: 10px;
  padding: 16px;
}
.source-note p { margin-bottom: 0; color: #6a4b17; line-height: 1.8; }
.three-steps ol { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(3, 1fr); gap: 14px; }
.three-steps span { display: block; color: var(--muted); line-height: 1.75; margin-top: 8px; }
.network-notes > div { display: grid; grid-template-columns: repeat(3, 1fr); gap: 14px; }
.network-notes p { color: var(--muted); line-height: 1.82; }
.device-manual { display: grid; grid-template-columns: repeat(2, 1fr); gap: 14px; }
.device-manual h2 { margin-top: 0; }
.device-manual li { color: #36556b; margin: 8px 0; }
.help-desk { display: grid; grid-template-columns: repeat(5, 1fr); gap: 12px; }
.plain-copy, .contact-desk, .legacy-note { max-width: 880px; margin-left: auto; margin-right: auto; }
.plain-copy p, .contact-desk p, .legacy-note p { font-size: 17px; }
.contact-desk a, .legacy-note a { color: var(--blue); font-weight: 900; }
.legacy-note div { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 14px; }
.legacy-note div a { border: 1px solid var(--line); border-radius: 999px; padding: 9px 12px; background: #fff; }
.support-strip { display: flex; justify-content: space-between; align-items: center; gap: 16px; }
.support-strip div { display: flex; flex-wrap: wrap; gap: 10px; }
.article-page { max-width: 920px; margin: 46px auto; }
.article-head {
  border: 1px solid var(--line);
  background: rgba(255,255,255,.9);
  border-radius: 16px;
  padding: 34px;
  box-shadow: 0 18px 44px rgba(37,74,108,.08);
}
.article-head span { color: var(--amber); font-weight: 900; }
.article-head time { color: var(--muted); margin-left: 10px; }
.article-head h1 { font-size: clamp(32px, 4vw, 56px); line-height: 1.14; margin: 14px 0; }
.article-head p, .article-body p { color: var(--muted); line-height: 1.9; font-size: 17px; }
.article-body { max-width: 840px; margin: 0 auto; padding: 16px 4px; }
.article-body h2 { margin-top: 34px; font-size: 28px; }
.article-next { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 26px; }
.article-next a { border: 1px solid var(--line); border-radius: 999px; background: rgba(255,255,255,.72); padding: 10px 14px; }
.not-found {
  min-height: 58vh;
  display: grid;
  place-content: center;
  text-align: center;
}
.not-found h1 { font-size: clamp(40px, 5vw, 70px); margin: 0 0 12px; }
.learning-footer {
  width: min(1180px, calc(100% - 32px));
  margin: 36px auto 28px;
  display: grid;
  grid-template-columns: 1.1fr 1.6fr;
  gap: 18px;
  padding: 24px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: #102235;
  color: #eaf3fb;
}
.footer-note span { display: block; font-weight: 900; margin-bottom: 6px; }
.footer-note p { margin: 0; color: #b9c8d7; line-height: 1.7; }
.footer-links { display: flex; flex-wrap: wrap; gap: 10px; justify-content: flex-end; align-items: center; }
.footer-links a { color: #dbe9f7; border: 1px solid rgba(255,255,255,.14); border-radius: 999px; padding: 8px 11px; }
@media (max-width: 900px) {
  .chapter-toggle { display: inline-flex; }
  .chapter-nav {
    position: absolute;
    left: 12px;
    right: 12px;
    top: calc(100% + 8px);
    display: none;
    flex-direction: column;
    align-items: stretch;
    padding: 10px;
    border: 1px solid var(--line);
    border-radius: 10px;
    background: rgba(255,255,255,.96);
  }
  .chapter-nav.is-open { display: flex; }
  .handbook-hero { grid-template-columns: 1fr; min-height: auto; }
  .course-check { position: relative; right: auto; bottom: auto; width: 100%; }
  .chapter-deck, .device-table, .network-rows, .case-grid, .guide-list, .all-guides .guide-list, .platform-grid, .device-manual, .help-desk, .network-notes > div, .learning-footer { grid-template-columns: 1fr; }
  .three-steps ol { grid-template-columns: 1fr; }
  .support-strip { align-items: stretch; flex-direction: column; }
  .footer-links { justify-content: flex-start; }
}
@media (max-width: 520px) {
  main, .learning-top, .learning-footer { width: min(100% - 20px, 1180px); }
  .learning-brand em { display: none; }
  .handbook-hero { padding-top: 34px; }
  .page-cover, .chapter-deck, .download-desk, .network-board, .case-ledger, .guide-shelf, .question-bank, .platform-matrix, .three-steps, .network-notes, .device-manual, .help-desk, .plain-copy, .contact-desk, .legacy-note, .support-strip, .article-head { padding: 20px; }
  .hero-index h1, .page-cover h1 { font-size: 34px; }
  .hero-actions { flex-direction: column; }
  .solid-action, .line-action { width: 100%; }
}