:root {
  --bg: #f6f7f5;
  --panel: #ffffff;
  --panel-soft: #f0f3f1;
  --text: #202825;
  --muted: #66716c;
  --line: #dce2de;
  --accent: #176b70;
  --accent-soft: #e6f0ee;
  --danger: #a94c54;
  --success: #2f7857;
  --radius: 7px;
  --shadow: 0 7px 22px rgba(31, 45, 40, .045);
  --content: 1120px;
  font-family: Inter, "Noto Sans SC", "Microsoft YaHei", system-ui, sans-serif;
  color: var(--text);
  background: var(--bg);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 84px; }
body { min-width: 320px; min-height: 100vh; margin: 0; color: var(--text); background: var(--bg); line-height: 1.65; }
a { color: inherit; }
button, input, textarea, select { font: inherit; }
button { cursor: pointer; }
img { display: block; max-width: 100%; }

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  min-height: 58px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding: 0 max(22px, calc((100vw - var(--content)) / 2));
  border-bottom: 1px solid var(--line);
  background: #fff;
}
.site-logo { color: var(--text); font-size: 17px; font-weight: 900; letter-spacing: -.025em; text-decoration: none; }
.site-navigation { min-height: 58px; display: flex; align-items: center; gap: 28px; }
.site-navigation a { position: relative; color: var(--muted); font-size: 14px; text-decoration: none; white-space: nowrap; }
.site-navigation a:hover, .site-navigation a.is-active { color: var(--accent); }
.site-navigation a.is-active::after { content: ""; position: absolute; right: 0; bottom: -19px; left: 0; height: 2px; background: var(--accent); }
.site-navigation form { margin: 0; }
.site-navigation form button, .site-menu-button { padding: 6px 10px; border: 1px solid var(--line); border-radius: var(--radius); color: var(--muted); background: #fff; }
.site-navigation form button:hover, .site-menu-button:hover { color: var(--accent); border-color: var(--accent); }
.site-menu-button { display: none; }

.page-container { width: min(var(--content), calc(100% - 40px)); margin: 0 auto; }
.page-main { padding: 34px 0 72px; }
.breadcrumb { display: flex; align-items: center; flex-wrap: wrap; gap: 7px; margin: 0 0 24px; color: var(--muted); font-size: 13px; }
.breadcrumb a { color: var(--accent); text-decoration: none; }
.breadcrumb i { color: #9ca6a1; font-style: normal; }
.eyebrow { color: var(--accent); font-size: 11px; font-weight: 850; letter-spacing: .12em; text-transform: uppercase; }
.page-title { margin: 7px 0 9px; font-size: clamp(30px, 5vw, 48px); line-height: 1.15; letter-spacing: -.045em; }
.page-description { max-width: 720px; margin: 0; color: var(--muted); font-size: 16px; }
.page-heading { margin-bottom: 32px; }
.section-heading { display: flex; align-items: baseline; justify-content: space-between; gap: 18px; margin: 0 0 15px; }
.section-heading h2 { margin: 0; font-size: 21px; letter-spacing: -.025em; }
.section-heading p, .section-heading span { margin: 0; color: var(--muted); font-size: 12px; }
.content-section + .content-section { margin-top: 38px; }

.search-panel { padding: 28px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel); box-shadow: var(--shadow); }
.search-panel h1 { margin: 0 0 7px; font-size: clamp(26px, 4vw, 38px); letter-spacing: -.04em; }
.search-panel > p { margin: 0 0 20px; color: var(--muted); }
.global-search { height: 50px; display: flex; overflow: hidden; border: 1px solid #cbd5d0; border-radius: var(--radius); background: #fff; }
.global-search input { flex: 1; min-width: 0; padding: 0 15px; border: 0; outline: 0; color: var(--text); background: transparent; }
.global-search input:focus { box-shadow: inset 0 0 0 2px var(--accent-soft); }
.global-search button, .button-primary { padding: 0 20px; border: 0; color: #fff; background: var(--accent); font-weight: 800; }
.global-search button:hover, .button-primary:hover { background: #10595d; }

.category-grid, .subcategory-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }
.category-card, .subcategory-card {
  min-width: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr) 170px;
  gap: 22px;
  min-height: 190px;
  padding: 22px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  color: var(--text);
  background: var(--panel);
  box-shadow: var(--shadow);
  text-decoration: none;
  transition: border-color .16s ease, transform .16s ease;
}
.category-card:hover, .subcategory-card:hover { border-color: #9fbcb6; transform: translateY(-2px); }
.category-card h2, .subcategory-card h2 { margin: 2px 0 7px; font-size: 22px; }
.category-card p, .subcategory-card p { margin: 0; color: var(--muted); font-size: 13px; }
.category-card small, .subcategory-card small { display: block; margin-top: 17px; color: var(--accent); font-size: 12px; font-weight: 800; }
.category-illustration { width: 100%; aspect-ratio: 4 / 3; align-self: center; overflow: hidden; border: 1px solid var(--line); border-radius: 5px; background: var(--panel-soft); object-fit: cover; }
.subcategory-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.subcategory-card { grid-template-columns: 1fr; min-height: 0; padding: 17px; gap: 13px; }
.subcategory-card .category-illustration { aspect-ratio: 16 / 9; }
.subcategory-card h2 { font-size: 17px; }

.article-list { overflow: hidden; border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel); box-shadow: var(--shadow); }
.article-list-item { min-height: 72px; display: flex; align-items: center; justify-content: space-between; gap: 20px; padding: 14px 17px; border-bottom: 1px solid var(--line); text-decoration: none; }
.article-list-item:last-child { border-bottom: 0; }
.article-list-item:hover { background: #fafcfb; }
.article-list-item strong, .article-list-item small { display: block; }
.article-list-item small { margin-top: 3px; color: var(--muted); font-size: 12px; }
.article-list-item i { color: var(--accent); font-size: 12px; font-style: normal; white-space: nowrap; }
.status-label { display: inline-flex; padding: 3px 7px; border-radius: 999px; color: var(--muted); background: var(--panel-soft); font-size: 10px; }

.category-intro { display: grid; grid-template-columns: minmax(0, 1fr) 300px; gap: 36px; align-items: center; margin-bottom: 36px; }
.category-intro .category-illustration { aspect-ratio: 16 / 9; }
.category-content-layout { display: grid; grid-template-columns: 240px minmax(0, 1fr); gap: 26px; align-items: start; }
.category-content-main { min-width: 0; }
.category-sidebar { position: sticky; top: 82px; min-width: 0; }
.category-sidebar h2 { margin: 0 0 10px; font-size: 15px; }
.knowledge-tree-compact { max-height: calc(100vh - 126px); overflow: auto; padding: 15px; font-size: 12px; }
.knowledge-tree-compact ul { padding-left: 16px; }
.placeholder-panel { padding: 38px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel); box-shadow: var(--shadow); }
.placeholder-panel h1 { margin: 0 0 8px; font-size: 34px; letter-spacing: -.04em; }
.placeholder-panel p { color: var(--muted); }
.placeholder-panel ul { margin: 20px 0; color: var(--muted); }
.text-link { color: var(--accent); font-weight: 800; text-decoration: none; }

.article-heading { display: grid; grid-template-columns: minmax(0, 1fr) minmax(300px, 420px); gap: 42px; align-items: center; margin-bottom: 28px; }
.article-heading h1 { margin: 7px 0 10px; font-size: clamp(34px, 5vw, 54px); line-height: 1.13; letter-spacing: -.052em; }
.article-heading .article-meta { display: flex; gap: 14px; flex-wrap: wrap; margin-top: 16px; color: var(--muted); font-size: 12px; }
.article-cover { overflow: hidden; border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel-soft); box-shadow: var(--shadow); }
.article-cover img { width: 100%; aspect-ratio: 16 / 9; object-fit: cover; }
.article-cover figcaption { padding: 8px 11px; color: var(--muted); font-size: 11px; }
.article-section-nav { position: sticky; top: 58px; z-index: 50; padding: 10px 0; border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); background: var(--bg); }
.article-section-nav .page-tabs { display: flex; gap: 7px; overflow: auto; }
.article-section-nav button { flex: 0 0 auto; padding: 7px 10px; border: 1px solid var(--line); border-radius: var(--radius); color: var(--muted); background: var(--panel); font-size: 12px; }
.article-section-nav button:hover, .article-section-nav button.is-active { color: #fff; border-color: var(--accent); background: var(--accent); }
.article-section-nav button span { margin-right: 5px; opacity: .7; }
.page-status-row { display: flex; align-items: center; gap: 16px; padding-top: 8px; color: var(--muted); font-size: 11px; }
.page-status-copy { display: flex; gap: 8px; min-width: 0; }
.page-progress { flex: 1; height: 3px; overflow: hidden; background: var(--line); }
.page-progress span { display: block; width: 12.5%; height: 100%; background: var(--accent); }
.article-body { padding-top: 28px; }
.article-body .lesson-page > .wrap, .article-body > .wrap { width: 100%; max-width: none; }
.article-body .lesson-page { padding: 0; }
.article-body h2 { letter-spacing: -.03em; }
.article-body pre { overflow: auto; border-radius: var(--radius); }
.related-links { margin-top: 46px; padding-top: 28px; border-top: 1px solid var(--line); }

.knowledge-tree { padding: 24px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel); box-shadow: var(--shadow); }
.knowledge-tree ul { margin: 8px 0; padding-left: 24px; }
.knowledge-tree li { margin: 7px 0; color: var(--muted); }
.knowledge-tree a { color: var(--text); text-decoration: none; }
.knowledge-tree a:hover { color: var(--accent); }
.knowledge-tree strong { color: var(--text); }

.glossary-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; }
.glossary-entry { padding: 17px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel); }
.glossary-entry h2 { margin: 0 0 5px; color: var(--accent); font-size: 17px; }
.glossary-entry p { margin: 0; color: var(--muted); font-size: 13px; }

.ai-layout { display: grid; grid-template-columns: 280px minmax(0, 1fr); gap: 18px; }
.ai-info, .chat-panel { padding: 20px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel); box-shadow: var(--shadow); }
.ai-info h2, .chat-panel h2 { margin: 0 0 6px; font-size: 20px; }
.ai-info p, .status { color: var(--muted); font-size: 13px; }
.status.ready { color: var(--success); }
.status.error { color: var(--danger); }
.messages { min-height: 180px; max-height: 430px; margin: 14px 0; overflow: auto; }
.message { max-width: 88%; margin: 8px 0; padding: 10px 12px; border-radius: var(--radius); color: var(--text); background: var(--panel-soft); white-space: pre-wrap; overflow-wrap: anywhere; }
.message.user { margin-left: auto; color: var(--accent); background: var(--accent-soft); }
.message.pending { color: var(--muted); }
.empty-state { padding: 24px; color: var(--muted); text-align: center; }
.chat-form textarea { width: 100%; min-height: 90px; resize: vertical; padding: 11px; border: 1px solid var(--line); border-radius: var(--radius); color: var(--text); background: #fff; outline: 0; }
.chat-form textarea:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.form-footer { display: flex; justify-content: space-between; gap: 10px; margin-top: 9px; }
.form-footer button { padding: 8px 13px; border: 1px solid var(--line); border-radius: var(--radius); color: var(--muted); background: #fff; }
.form-footer .button-primary { color: #fff; border-color: var(--accent); }

.login-page { display: flex; min-height: calc(100vh - 59px); align-items: center; justify-content: center; padding: 40px 20px; }
.login-card { width: min(420px, 100%); padding: 30px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel); box-shadow: var(--shadow); }
.login-card h1 { margin: 0 0 7px; font-size: 28px; letter-spacing: -.04em; }
.login-card > p { color: var(--muted); }
.login-card form { margin-top: 22px; }
.login-card label { display: block; margin-bottom: 7px; font-size: 13px; font-weight: 800; }
.login-card input { width: 100%; height: 46px; padding: 0 11px; border: 1px solid var(--line); border-radius: var(--radius); outline: 0; }
.login-card input:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.login-card form button { width: 100%; height: 44px; margin-top: 12px; border: 0; border-radius: var(--radius); color: #fff; background: var(--accent); font-weight: 800; }
.login-card .error { padding: 9px 11px; color: var(--danger); background: #f8ebec; }
.login-card .note { margin-top: 15px; font-size: 11px; text-align: center; }

.site-footer { margin-top: 54px; padding: 24px 20px; border-top: 1px solid var(--line); color: var(--muted); background: #fff; font-size: 12px; text-align: center; }

@media (max-width: 900px) {
  .category-content-layout { grid-template-columns: 1fr; }
  .category-sidebar { position: static; }
  .site-header { padding-inline: 20px; }
  .site-menu-button { display: block; }
  .site-navigation { position: absolute; top: 58px; right: 14px; left: 14px; min-height: 0; display: none; align-items: stretch; flex-direction: column; gap: 0; padding: 8px; border: 1px solid var(--line); border-radius: var(--radius); background: #fff; box-shadow: var(--shadow); }
  .site-navigation.is-open { display: flex; }
  .site-navigation a, .site-navigation form button { width: 100%; padding: 9px; text-align: left; }
  .site-navigation a.is-active::after { display: none; }
  .category-grid, .subcategory-grid { grid-template-columns: 1fr 1fr; }
  .category-intro, .article-heading, .ai-layout { grid-template-columns: 1fr; }
  .article-heading .article-cover { max-width: 620px; }
}

@media (max-width: 620px) {
  .page-container { width: min(var(--content), calc(100% - 24px)); }
  .page-main { padding-top: 24px; }
  .search-panel, .placeholder-panel { padding: 20px; }
  .category-grid, .subcategory-grid, .glossary-grid { grid-template-columns: 1fr; }
  .category-card { grid-template-columns: 1fr 118px; min-height: 158px; padding: 17px; gap: 14px; }
  .category-card h2 { font-size: 19px; }
  .article-heading { gap: 22px; }
  .article-section-nav { top: 58px; }
  .page-status-copy span { display: none; }
  .form-footer { align-items: stretch; flex-direction: column; }
}

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

/* Legacy article shell isolation */
.site-header .site-navigation,.breadcrumb{position:static;top:auto;z-index:auto;padding:0;border:0;background:transparent;box-shadow:none;backdrop-filter:none}
.article-section-nav{position:sticky;top:58px}
.preview-tags .is-selected,.preview-cards .is-selected{border-color:var(--accent)}