:root {
  --bg: #f7f8fa;
  --surface: #ffffff;
  --surface-2: #f0f2f6;
  --text: #16191f;
  --muted: #5b6372;
  --line: #e2e5eb;
  --brand: #1d5fd1;
  --brand-ink: #ffffff;
  --brand-soft: #e7effc;
  --accent: #0e8a6a;
  --tip: #e9f7f1;
  --tip-line: #0e8a6a;
  --warn: #fff6e5;
  --warn-line: #d08a00;
  --note: #eef3fd;
  --note-line: #1d5fd1;
  --shadow: 0 1px 2px rgba(16, 24, 40, .06), 0 8px 24px rgba(16, 24, 40, .08);
  --radius: 12px;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0f1216; --surface: #161a20; --surface-2: #1d222a; --text: #e8ebf0; --muted: #9aa3b2; --line: #2a303a;
    --brand: #5b93f0; --brand-ink: #0b1220; --brand-soft: #1a2638; --accent: #3cc49c;
    --tip: #12241e; --tip-line: #3cc49c; --warn: #2a2210; --warn-line: #e0a530; --note: #16202f; --note-line: #5b93f0;
    --shadow: 0 1px 2px rgba(0,0,0,.4), 0 8px 24px rgba(0,0,0,.35);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #0f1216; --surface: #161a20; --surface-2: #1d222a; --text: #e8ebf0; --muted: #9aa3b2; --line: #2a303a;
  --brand: #5b93f0; --brand-ink: #0b1220; --brand-soft: #1a2638; --accent: #3cc49c;
  --tip: #12241e; --tip-line: #3cc49c; --warn: #2a2210; --warn-line: #e0a530; --note: #16202f; --note-line: #5b93f0;
  color-scheme: dark;
}

* { box-sizing: border-box; }
html { scroll-padding-top: 80px; -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--text); font: 16px/1.6 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; }
a { color: var(--brand); }
img { max-width: 100%; }
kbd { font: 12px var(--mono); border: 1px solid var(--line); border-bottom-width: 2px; border-radius: 4px; padding: 0 5px; color: var(--muted); background: var(--surface); }
.icon { width: 18px; height: 18px; flex: none; }
.skip { position: absolute; left: -999px; }
.skip:focus { left: 8px; top: 8px; z-index: 99; background: var(--surface); padding: 8px; }
.linkish { background: none; border: 0; color: var(--brand); font: inherit; padding: 0; cursor: pointer; text-decoration: underline; }

/* top bar */
.topbar { position: sticky; top: 0; z-index: 20; background: color-mix(in srgb, var(--surface) 92%, transparent); backdrop-filter: blur(8px); border-bottom: 1px solid var(--line); }
.topbar__inner { max-width: 1320px; margin: 0 auto; padding: 10px 16px; display: flex; align-items: center; gap: 16px; }
.brand { display: flex; align-items: center; gap: 10px; color: var(--text); text-decoration: none; font-size: 17px; white-space: nowrap; }
.brand b { color: var(--muted); font-weight: 500; }
.brand__mark { width: 30px; height: 30px; border-radius: 8px; background: var(--brand); color: var(--brand-ink); display: grid; place-items: center; font-weight: 800; }
.search-trigger { display: flex; align-items: center; gap: 8px; min-width: 220px; padding: 7px 10px; border: 1px solid var(--line); border-radius: 9px; background: var(--surface-2); color: var(--muted); font: inherit; font-size: 14px; cursor: pointer; }
.search-trigger kbd { margin-left: auto; }
.topnav { display: flex; gap: 4px; margin-left: auto; flex-wrap: wrap; }
.topnav a { color: var(--muted); text-decoration: none; padding: 6px 10px; border-radius: 8px; font-size: 14px; font-weight: 500; }
.topnav a:hover { background: var(--surface-2); color: var(--text); }
.topnav a[aria-current] { color: var(--brand); background: var(--brand-soft); }
.menu-btn { display: none; margin-left: auto; background: none; border: 0; padding: 8px; cursor: pointer; }
.menu-btn span { display: block; width: 20px; height: 2px; background: var(--text); margin: 4px 0; }

/* layout */
.layout { max-width: 1320px; margin: 0 auto; padding: 0 16px; display: grid; grid-template-columns: 250px minmax(0, 1fr) 200px; gap: 40px; }
.layout--wide { grid-template-columns: 250px minmax(0, 1fr); }
.sidebar { position: sticky; top: 64px; align-self: start; max-height: calc(100vh - 64px); overflow: auto; padding: 24px 0 40px; font-size: 14px; }
.sidebar__title a { font-weight: 700; color: var(--text); text-decoration: none; font-size: 15px; }
.sidebar__group { margin-top: 18px; }
.sidebar__section { text-transform: uppercase; letter-spacing: .06em; font-size: 11px; font-weight: 700; color: var(--muted); margin-bottom: 4px; }
.sidebar ul { list-style: none; margin: 0; padding: 0; }
.sidebar li a { display: block; padding: 4px 10px; margin-left: -10px; border-radius: 6px; color: var(--text); text-decoration: none; }
.sidebar li a:hover { background: var(--surface-2); }
.sidebar li a[aria-current] { background: var(--brand-soft); color: var(--brand); font-weight: 600; }
.sidebar__print { display: inline-flex; gap: 6px; align-items: center; margin-top: 24px; font-size: 13px; color: var(--muted); }
.pagetoc { position: sticky; top: 64px; align-self: start; padding: 32px 0; font-size: 13px; }
.pagetoc__title { font-weight: 700; color: var(--muted); margin-bottom: 6px; }
.pagetoc ul { list-style: none; padding: 0; margin: 0; border-left: 2px solid var(--line); }
.pagetoc a { display: block; padding: 3px 10px; color: var(--muted); text-decoration: none; }
.pagetoc a:hover { color: var(--text); }

/* article */
.article { min-width: 0; padding: 24px 0 80px; max-width: 780px; }
.crumbs { font-size: 13px; color: var(--muted); }
.crumbs a { color: var(--muted); }
.article h1 { font-size: 34px; line-height: 1.2; margin: 6px 0 8px; letter-spacing: -.01em; }
.lede { font-size: 18px; color: var(--muted); margin: 0 0 24px; }
.article h2 { font-size: 23px; margin: 40px 0 10px; padding-top: 8px; border-top: 1px solid var(--line); }
.article h3 { font-size: 18px; margin: 28px 0 8px; }
.anchor { float: left; margin-left: -22px; padding-right: 6px; color: var(--muted); text-decoration: none; opacity: 0; font-weight: 400; }
h2:hover .anchor, h3:hover .anchor { opacity: .6; }
.article ol, .article ul { padding-left: 24px; }
.article li { margin: 6px 0; }
.article ol > li::marker { font-weight: 700; color: var(--brand); }
.article code { font: 14px var(--mono); background: var(--surface-2); padding: 1px 5px; border-radius: 4px; }
.article table { border-collapse: collapse; width: 100%; margin: 16px 0; font-size: 15px; display: block; overflow-x: auto; }
.article th, .article td { border: 1px solid var(--line); padding: 8px 10px; text-align: left; vertical-align: top; }
.article th { background: var(--surface-2); }
.shot { display: block; margin: 18px 0 22px; }
.shot img { display: block; border: 1px solid var(--line); border-radius: 10px; box-shadow: var(--shadow); background: var(--surface); max-height: 640px; width: auto; }
.shot--narrow img { max-width: 300px; }
.shot__cap { display: block; font-size: 13px; color: var(--muted); margin-top: 8px; }
.callout { margin: 18px 0; padding: 12px 16px; border-left: 4px solid var(--note-line); background: var(--note); border-radius: 0 10px 10px 0; }
.callout p { margin: 4px 0; }
.callout--tip { background: var(--tip); border-color: var(--tip-line); }
.callout--warning, .callout--important { background: var(--warn); border-color: var(--warn-line); }
.article__ask { margin: 40px 0 16px; }
.article__ask button { display: inline-flex; gap: 8px; align-items: center; border: 1px dashed var(--brand); background: var(--brand-soft); color: var(--brand); padding: 10px 14px; border-radius: 10px; font: inherit; font-weight: 600; cursor: pointer; }
.pager { display: flex; justify-content: space-between; gap: 16px; margin-top: 24px; }
.pager a { flex: 1; border: 1px solid var(--line); border-radius: 10px; padding: 12px 14px; text-decoration: none; color: var(--text); background: var(--surface); font-weight: 600; }
.pager a span { display: block; font-size: 12px; color: var(--muted); font-weight: 500; }
.pager__next { text-align: right; }

/* cards */
.book-hero { display: flex; gap: 18px; align-items: flex-start; margin-top: 8px; }
.book-hero__icon { width: 44px; height: 44px; padding: 10px; border-radius: 12px; background: var(--brand-soft); color: var(--brand); flex: none; }
.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 12px; }
.card { display: block; padding: 14px 16px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); text-decoration: none; color: var(--text); }
.card:hover { border-color: var(--brand); }
.card span { display: block; font-size: 14px; color: var(--muted); margin-top: 4px; }

/* home */
.home { max-width: 1100px; margin: 0 auto; padding: 0 16px 60px; }
.hero { text-align: center; padding: 56px 0 32px; }
.hero h1 { font-size: 42px; margin: 0 0 8px; letter-spacing: -.02em; }
.hero p { color: var(--muted); font-size: 18px; margin: 0 auto; max-width: 640px; }
.hero-ask { margin: 28px auto 10px; max-width: 680px; display: flex; align-items: center; gap: 10px; padding: 8px 8px 8px 16px; background: var(--surface); border: 1px solid var(--line); border-radius: 14px; box-shadow: var(--shadow); }
.hero-ask .icon { color: var(--brand); }
.hero-ask input { flex: 1; min-width: 0; border: 0; outline: 0; background: transparent; color: var(--text); font: inherit; font-size: 17px; padding: 8px 0; }
.hero-ask button, .ask-form button { border: 0; background: var(--brand); color: var(--brand-ink); padding: 10px 18px; border-radius: 10px; font: inherit; font-weight: 700; cursor: pointer; }
.hero-hint { font-size: 14px !important; }
.hero-cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(230px, 1fr)); gap: 16px; }
.hero-card { display: flex; flex-direction: column; gap: 6px; padding: 20px; background: var(--surface); border: 1px solid var(--line); border-radius: 14px; text-decoration: none; color: var(--text); }
.hero-card:hover { border-color: var(--brand); box-shadow: var(--shadow); }
.hero-card__icon { width: 40px; height: 40px; padding: 9px; border-radius: 10px; background: var(--brand-soft); color: var(--brand); }
.hero-card strong { font-size: 18px; margin-top: 6px; }
.hero-card span { color: var(--muted); font-size: 14px; flex: 1; }
.hero-card em { font-style: normal; font-size: 13px; color: var(--brand); font-weight: 600; }
.popular h2 { margin-top: 40px; }
.foot { text-align: center; color: var(--muted); margin-top: 48px; font-size: 14px; }

/* search */
.search-modal { position: fixed; inset: 0; z-index: 50; background: rgba(10, 14, 20, .45); display: flex; justify-content: center; align-items: flex-start; padding: 10vh 16px 16px; }
.search-modal[hidden] { display: none; }
.search-modal__box { width: 100%; max-width: 640px; background: var(--surface); border-radius: 14px; box-shadow: var(--shadow); overflow: hidden; max-height: 78vh; display: flex; flex-direction: column; }
.search-modal__input { display: flex; align-items: center; gap: 10px; padding: 12px 14px; border-bottom: 1px solid var(--line); color: var(--muted); }
.search-modal__input input { flex: 1; border: 0; outline: 0; font: inherit; font-size: 17px; background: transparent; color: var(--text); }
.search-modal__input button { border: 1px solid var(--line); background: var(--surface-2); color: var(--muted); border-radius: 6px; font-size: 12px; padding: 3px 6px; cursor: pointer; }
.search-results { overflow: auto; }
.search-results a { display: block; padding: 10px 16px; text-decoration: none; color: var(--text); border-bottom: 1px solid var(--line); }
.search-results a:hover, .search-results a.active { background: var(--brand-soft); }
.search-results small { color: var(--muted); display: block; font-size: 12px; }
.search-results p { margin: 2px 0 0; font-size: 14px; color: var(--muted); }
.search-results mark { background: color-mix(in srgb, var(--brand) 25%, transparent); color: inherit; border-radius: 2px; }
.search-empty { padding: 16px; color: var(--muted); }
.search-ask button { width: 100%; text-align: left; display: flex; gap: 8px; align-items: center; padding: 12px 16px; border: 0; background: var(--surface-2); color: var(--brand); font: inherit; font-weight: 600; cursor: pointer; }

/* ask */
.ask-fab { position: fixed; right: 20px; bottom: 20px; z-index: 30; display: flex; align-items: center; gap: 8px; border: 0; border-radius: 999px; padding: 12px 18px; background: var(--brand); color: var(--brand-ink); font: inherit; font-weight: 700; box-shadow: var(--shadow); cursor: pointer; }
.ask-panel { position: fixed; right: 20px; bottom: 20px; z-index: 40; width: min(440px, calc(100vw - 32px)); height: min(640px, calc(100vh - 100px)); display: flex; flex-direction: column; background: var(--surface); border: 1px solid var(--line); border-radius: 16px; box-shadow: var(--shadow); overflow: hidden; }
.ask-panel[hidden] { display: none; }
.ask-panel__head { display: flex; align-items: center; gap: 8px; padding: 10px 12px; border-bottom: 1px solid var(--line); }
.ask-panel__head > div { display: flex; align-items: center; gap: 6px; color: var(--brand); }
.ask-panel__head strong { color: var(--text); }
.ask-scope { margin-left: auto; font: inherit; font-size: 13px; padding: 4px 6px; border: 1px solid var(--line); border-radius: 6px; background: var(--surface-2); color: var(--text); max-width: 170px; }
.ask-close { border: 0; background: none; font-size: 24px; line-height: 1; color: var(--muted); cursor: pointer; padding: 0 4px; }
.ask-log { flex: 1; overflow: auto; padding: 14px; display: flex; flex-direction: column; gap: 10px; }
.ask-msg { max-width: 92%; padding: 10px 12px; border-radius: 12px; font-size: 15px; line-height: 1.5; overflow-wrap: anywhere; }
.ask-msg p { margin: 0 0 8px; } .ask-msg p:last-child { margin: 0; }
.ask-msg ol, .ask-msg ul { margin: 4px 0 8px; padding-left: 20px; }
.ask-msg img { border-radius: 8px; border: 1px solid var(--line); margin: 6px 0; max-height: 280px; }
.ask-msg--bot { background: var(--surface-2); align-self: flex-start; }
.ask-msg--me { background: var(--brand); color: var(--brand-ink); align-self: flex-end; }
.ask-msg--err { background: var(--warn); }
.ask-msg .typing { display: inline-block; width: 40px; height: 10px; background: radial-gradient(circle, var(--muted) 3px, transparent 4px) 0 50% / 13px 10px repeat-x; animation: blink 1s infinite; }
@keyframes blink { 50% { opacity: .3; } }
.ask-form { display: flex; gap: 8px; padding: 10px; border-top: 1px solid var(--line); }
.ask-form textarea { flex: 1; resize: none; border: 1px solid var(--line); border-radius: 10px; padding: 9px 10px; font: inherit; font-size: 15px; background: var(--surface-2); color: var(--text); max-height: 120px; }
.ask-foot { margin: 0; padding: 0 12px 10px; font-size: 11px; color: var(--muted); }

/* print book */
.print-book { max-width: 820px; margin: 0 auto; padding: 24px 16px 80px; }
.print-cover { padding: 40px 0; border-bottom: 1px solid var(--line); }
.print-cover h1 { font-size: 40px; }
.print-cover button { display: inline-flex; gap: 8px; align-items: center; border: 0; background: var(--brand); color: var(--brand-ink); padding: 10px 16px; border-radius: 10px; font: inherit; font-weight: 700; cursor: pointer; }
.print-chapter { padding-top: 32px; }
.print-chapter h2 { font-size: 22px; }
.print-book .anchor { display: none; }

@media (max-width: 1100px) { .layout { grid-template-columns: 230px minmax(0, 1fr); } .pagetoc { display: none; } }
@media (max-width: 820px) {
  .layout, .layout--wide { grid-template-columns: minmax(0, 1fr); gap: 0; }
  .sidebar { position: static; max-height: none; padding: 16px 0 0; border-bottom: 1px solid var(--line); }
  .sidebar__group, .sidebar__print { display: none; }
  .search-trigger { min-width: 0; flex: 1; }
  .search-trigger kbd { display: none; }
  .menu-btn { display: block; margin-left: 0; }
  .topnav { display: none; position: absolute; left: 0; right: 0; top: 100%; background: var(--surface); border-bottom: 1px solid var(--line); flex-direction: column; padding: 8px 16px; }
  .topnav.open { display: flex; }
  .brand span:last-child b { display: none; }
  .hero h1 { font-size: 32px; }
  .article h1 { font-size: 28px; }
  .ask-fab span { display: none; }
  .ask-panel { right: 8px; left: 8px; bottom: 8px; width: auto; height: calc(100vh - 80px); }
  .pager { flex-direction: column; }
}
@media print {
  .topbar, .sidebar, .pagetoc, .ask-fab, .ask-panel, .search-modal, .article__ask, .pager, .noprint { display: none !important; }
  body { background: #fff; color: #000; font-size: 11pt; }
  .print-chapter { break-before: page; }
  .shot img { box-shadow: none; max-height: 420px; }
  a { color: #000; text-decoration: none; }
}