/* All colours / fonts / radii come from theme tokens (data/themes/*.json → CSS custom properties).
   The values below are only fallbacks so the page is readable before the theme loads. */
:root {
  --bg: #f6f3ec; --surface: #fffdf8; --surface-2: #f0ebe0; --ink: #1c1a15; --ink-2: #49453b;
  --muted: #8b8577; --line: #e2dccd; --accent: #0b5d8f; --accent-ink: #fff; --accent-soft: #e3eef6;
  --pos: #c2410c; --neg: #1d4ed8; --warn: #b45309; --ok: #15803d;
  --c-photon: #d97706; --c-pd: #7c3aed; --c-tg: #0d9488; --c-fd: #2563eb; --c-rg: #db2777;
  --c-sf: #ea580c; --c-sel: #65a30d; --c-readout: #475569; --c-metric: #be123c;
  --accent-2: var(--c-pd); /* second accent for gradients; themes may override */
  --font-body: "Pretendard Variable", Pretendard, -apple-system, "Apple SD Gothic Neo", "Noto Sans KR", "Malgun Gothic", "맑은 고딕", "Segoe UI", sans-serif;
  --font-display: "Noto Serif KR", "Source Serif 4", Georgia, serif;
  --font-mono: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --radius: 10px; --radius-sm: 6px; --maxw: 820px; --sidebar-w: 290px;
  --shadow: 0 1px 2px rgba(0,0,0,.04), 0 6px 24px rgba(30,25,10,.06);
  --fs-body: 16.5px; --lh-body: 1.78;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg); color: var(--ink); font-family: var(--font-body);
  font-size: var(--fs-body); line-height: var(--lh-body); -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility; word-break: keep-all; overflow-wrap: anywhere;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }
code, kbd, .mono { font-family: var(--font-mono); font-size: .88em; }
code { background: var(--surface-2); padding: .08em .35em; border-radius: 4px; }
button { font: inherit; color: inherit; }
::selection { background: var(--accent-soft); }

/* ------------------------------------------------------------------ shell */
.topbar {
  position: sticky; top: 0; z-index: 40; height: 56px; display: flex; align-items: center; gap: 14px;
  padding: 0 18px; background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(1.4) blur(10px); border-bottom: 1px solid var(--line);
}
.read-progress { position: absolute; left: 0; bottom: -1px; height: 2px; width: 0; pointer-events: none;
  background: linear-gradient(90deg, var(--accent), var(--accent-2)); transition: width .08s linear; }
.brand { display: flex; align-items: baseline; gap: 10px; color: var(--ink); white-space: nowrap; }
.brand b { font-family: var(--font-display); font-size: 19px; letter-spacing: -.01em; }
.brand span { color: var(--muted); font-size: 12.5px; font-family: var(--font-mono); }
.topnav { display: flex; gap: 4px; margin-left: auto; align-items: center; }
.topnav a, .icon-btn {
  padding: 6px 11px; border-radius: 999px; color: var(--ink-2); font-size: 14px; border: 1px solid transparent;
  background: none; cursor: pointer; white-space: nowrap;
}
.topnav a:hover, .icon-btn:hover { background: var(--surface-2); text-decoration: none; }
.topnav a.active { background: var(--ink); color: var(--bg); }
.search { position: relative; }
.search input {
  width: 220px; padding: 7px 12px; border-radius: 999px; border: 1px solid var(--line); background: var(--surface);
  color: var(--ink); font: inherit; font-size: 14px;
}
.search-results {
  position: absolute; right: 0; top: 40px; width: 380px; max-height: 60vh; overflow: auto; background: var(--surface);
  border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow); padding: 6px; display: none;
}
.search-results.open { display: block; }
.search-results a { display: block; padding: 8px 10px; border-radius: var(--radius-sm); color: var(--ink); }
.search-results a:hover { background: var(--surface-2); text-decoration: none; }
.search-results small { display: block; color: var(--muted); font-size: 12.5px; }
.menu-btn { display: none; }

.layout { display: grid; grid-template-columns: var(--sidebar-w) minmax(0, 1fr); min-height: calc(100vh - 56px); }
.sidebar {
  position: sticky; top: 56px; height: calc(100vh - 56px); overflow: auto; padding: 20px 14px 40px 18px;
  border-right: 1px solid var(--line); font-size: 14.5px;
}
.sidebar h4 { margin: 18px 8px 6px; font-size: 11.5px; letter-spacing: .12em; text-transform: uppercase; color: var(--muted); font-weight: 600; }
.toc-ch { display: flex; gap: 10px; align-items: baseline; padding: 6px 8px; border-radius: var(--radius-sm); color: var(--ink); line-height: 1.4; }
.toc-ch:hover { background: var(--surface-2); text-decoration: none; }
.toc-ch .num { font-family: var(--font-mono); font-size: 12px; color: var(--muted); min-width: 22px; }
.toc-ch.active { background: var(--surface); box-shadow: inset 3px 0 0 var(--chip, var(--accent)); font-weight: 600; }
.toc-sec { display: block; padding: 3px 8px 3px 40px; color: var(--ink-2); font-size: 13.5px; line-height: 1.45; border-radius: var(--radius-sm); }
.toc-sec:hover { background: var(--surface-2); text-decoration: none; }
.toc-sec.active { color: var(--accent); font-weight: 600; }
.dot { display: inline-block; width: 8px; height: 8px; border-radius: 50%; background: var(--chip, var(--accent)); flex: none; transform: translateY(-1px); }

main { min-width: 0; padding: 36px 40px 120px; }
.article { max-width: var(--maxw); margin: 0 auto; }
.wide { max-width: 1180px; margin: 0 auto; }

/* --------------------------------------------------------------- article */
.ch-head { margin: 8px 0 34px; padding-bottom: 26px; border-bottom: 1px solid var(--line); }
.ch-kicker, .eyebrow { font-family: var(--font-mono); font-size: 12.5px; color: var(--accent); font-weight: 600; letter-spacing: .12em; text-transform: uppercase; display: flex; gap: 10px; align-items: center; }
.ch-head h1 { font-family: var(--font-display); font-size: clamp(30px, 4vw, 42px); line-height: 1.22; margin: 12px 0 12px; letter-spacing: -.02em; font-weight: 700; }
.ch-head .lede { font-size: 18px; color: var(--ink-2); margin: 0; }
.objectives { margin-top: 22px; padding: 16px 20px; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); font-size: 15px; box-shadow: var(--shadow); }
.objectives b { font-size: 12px; letter-spacing: .1em; text-transform: uppercase; color: var(--muted); }
.objectives ul { list-style: none; margin: 8px 0 0; padding: 0; display: grid; gap: 4px; }
.objectives li { position: relative; padding-left: 24px; margin: 0; }
.objectives li::before { content: ""; position: absolute; left: 3px; top: .62em; width: 9px; height: 9px; border-radius: 3px; background: var(--accent); opacity: .85; }

.article h2 { font-family: var(--font-display); font-size: 27px; line-height: 1.3; margin: 64px 0 14px; letter-spacing: -.01em; scroll-margin-top: 80px; }
.article h2 .secnum { font-family: var(--font-mono); font-size: 15px; color: var(--accent); margin-right: 10px; font-weight: 400; }
.article h3 { font-size: 19px; margin: 34px 0 8px; scroll-margin-top: 80px; }
.article p { margin: 12px 0; }
.article ul, .article ol { padding-left: 22px; }
.article li { margin: 4px 0; }
.term { border-bottom: 1px dashed var(--accent); color: inherit; cursor: help; }
.cite { font-family: var(--font-mono); font-size: .74em; vertical-align: super; line-height: 0; margin-left: 1px; }
.cite a { padding: 0 1px; }

.eq { margin: 18px 0; padding: 14px 18px; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); overflow-x: auto; position: relative; }
.eq .eq-label { position: absolute; right: 12px; top: 8px; font-family: var(--font-mono); font-size: 11.5px; color: var(--muted); }
.eq .eq-note { font-size: 13.5px; color: var(--ink-2); margin-top: 6px; border-top: 1px dashed var(--line); padding-top: 6px; }
.tex-fallback { font-family: var(--font-mono); font-size: 14px; white-space: pre-wrap; color: var(--ink-2); }

.callout { --cc: var(--accent); margin: 20px 0; padding: 14px 18px 14px 16px; border-radius: var(--radius-sm); border: 1px solid color-mix(in srgb, var(--cc) 22%, var(--line));
  border-left: 4px solid var(--cc); background: color-mix(in srgb, var(--cc) 7%, var(--surface)); }
.callout .c-title { font-weight: 700; font-size: 14px; letter-spacing: .02em; display: flex; gap: 8px; align-items: center; color: color-mix(in srgb, var(--cc) 70%, var(--ink)); }
.callout.key { --cc: var(--c-metric); }
.callout.warn { --cc: var(--warn); }
.callout.research { --cc: var(--c-tg); }
.callout.tip { --cc: var(--ok); }
.callout p { margin: 6px 0 0; }

.table-wrap { overflow-x: auto; margin: 18px 0; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
table { border-collapse: collapse; width: 100%; font-size: 14.5px; }
th, td { text-align: left; padding: 9px 12px; border-bottom: 1px solid var(--line); vertical-align: top; }
th { background: var(--surface-2); font-weight: 600; font-size: 13px; }
tr:last-child td { border-bottom: none; }

figure { margin: 24px 0; }
figcaption { font-size: 13.5px; color: var(--ink-2); margin-top: 8px; }
figcaption b { font-family: var(--font-mono); font-weight: 600; color: var(--ink); }
.figure-box { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 14px; }
.figure-box svg { width: 100%; height: auto; display: block; }

/* causal chain */
.chain { display: flex; flex-wrap: wrap; align-items: stretch; gap: 0; margin: 22px 0; }
.chain-step { flex: 1 1 140px; min-width: 130px; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 10px 12px; font-size: 14px; position: relative; border-top: 3px solid var(--chip, var(--accent)); }
.chain-step b { display: block; font-size: 14.5px; margin-bottom: 2px; }
.chain-step span { color: var(--ink-2); font-size: 13px; line-height: 1.5; display: block; }
.chain-arrow { display: flex; align-items: center; padding: 0 6px; color: var(--muted); font-size: 18px; }

/* quiz */
.quiz { margin: 24px 0; border: 1px solid var(--line); border-radius: var(--radius); padding: 16px 18px; background: var(--surface); }
.quiz .q { font-weight: 600; margin-bottom: 10px; }
.quiz button.opt { display: block; width: 100%; text-align: left; padding: 9px 12px; margin: 6px 0; border-radius: var(--radius-sm); border: 1px solid var(--line); background: var(--bg); cursor: pointer; font-size: 15px; }
.quiz button.opt:hover { border-color: var(--accent); }
.quiz button.opt.right { border-color: var(--ok); background: color-mix(in srgb, var(--ok) 10%, var(--bg)); }
.quiz button.opt.wrong { border-color: var(--pos); background: color-mix(in srgb, var(--pos) 8%, var(--bg)); }
.quiz .explain { margin-top: 10px; font-size: 14.5px; color: var(--ink-2); display: none; }
.quiz.done .explain { display: block; }

/* ---------------------------------------------------------------- widgets */
.sim {
  margin: 28px -60px; background: var(--surface); border: 1px solid var(--line); border-radius: calc(var(--radius) + 4px);
  box-shadow: var(--shadow); overflow: hidden;
}
@media (max-width: 1280px) { .sim { margin: 28px 0; } }
.wide .sim { margin: 20px 0; }
.sim-head { display: flex; align-items: center; gap: 10px; padding: 12px 16px; border-bottom: 1px solid var(--line); background: linear-gradient(90deg, var(--accent-soft), var(--surface-2) 70%); }
.sim-head .badge { font-family: var(--font-mono); font-size: 11px; font-weight: 600; letter-spacing: .1em; text-transform: uppercase; padding: 1px 9px; border-radius: 999px; color: var(--accent); border: 1px solid var(--accent); background: var(--surface); }
.sim-head h4 { margin: 0; font-size: 15.5px; }
.sim-head .spacer { flex: 1; }
.sim-head button { border: 1px solid var(--line); background: var(--surface); border-radius: 999px; padding: 3px 10px; font-size: 12.5px; cursor: pointer; }
.sim-body { display: grid; grid-template-columns: 260px minmax(0, 1fr); }
.sim-controls { padding: 14px 16px; border-right: 1px solid var(--line); background: color-mix(in srgb, var(--surface-2) 40%, var(--surface)); }
.sim-view { padding: 14px 16px; min-width: 0; }
.sim-foot { padding: 10px 16px; border-top: 1px solid var(--line); font-size: 13.5px; color: var(--ink-2); background: var(--surface); }
.sim-desc { font-size: 13.5px; color: var(--ink-2); margin: 0 0 10px; }
@media (max-width: 860px) { .sim-body { grid-template-columns: 1fr; } .sim-controls { border-right: none; border-bottom: 1px solid var(--line); } }

.ctl { margin: 0 0 12px; }
.ctl-group { font-size: 11px; letter-spacing: .12em; text-transform: uppercase; color: var(--muted); margin: 16px 0 8px; font-weight: 600; border-top: 1px solid var(--line); padding-top: 10px; }
.ctl-group:first-child { margin-top: 0; border-top: none; padding-top: 0; }
.ctl label { display: flex; justify-content: space-between; align-items: baseline; gap: 8px; font-size: 13px; color: var(--ink-2); }
.ctl label .v { font-family: var(--font-mono); color: var(--ink); font-size: 12.5px; white-space: nowrap; }
.ctl input[type=range] { -webkit-appearance: none; appearance: none; width: 100%; height: 22px; margin: 2px 0 0; background: transparent; cursor: pointer; }
.ctl input[type=range]::-webkit-slider-runnable-track { height: 5px; border-radius: 3px; background: linear-gradient(90deg, var(--accent) var(--fill, 50%), var(--surface-2) var(--fill, 50%)); }
.ctl input[type=range]::-webkit-slider-thumb { -webkit-appearance: none; width: 16px; height: 16px; margin-top: -5.5px; border-radius: 50%; background: var(--surface); border: 2px solid var(--accent); box-shadow: 0 1px 4px rgba(0,0,0,.2); }
.ctl input[type=range]::-moz-range-track { height: 5px; border-radius: 3px; background: var(--surface-2); }
.ctl input[type=range]::-moz-range-progress { height: 5px; border-radius: 3px; background: var(--accent); }
.ctl input[type=range]::-moz-range-thumb { width: 12px; height: 12px; border-radius: 50%; background: var(--surface); border: 2px solid var(--accent); }
.ctl input[type=range]:focus-visible { outline: 2px solid var(--accent-soft); outline-offset: 2px; border-radius: 4px; }
.ctl select { width: 100%; padding: 5px 8px; border-radius: var(--radius-sm); border: 1px solid var(--line); background: var(--surface); color: var(--ink); font: inherit; font-size: 13.5px; margin-top: 3px; }
.ctl .hint { font-size: 11.5px; color: var(--muted); line-height: 1.4; }
.seg { display: flex; border: 1px solid var(--line); border-radius: var(--radius-sm); overflow: hidden; margin-top: 4px; }
.seg button { flex: 1; border: none; background: var(--surface); padding: 5px 4px; font-size: 12.5px; cursor: pointer; color: var(--ink-2); }
.seg button + button { border-left: 1px solid var(--line); }
.seg button.on { background: var(--ink); color: var(--bg); }
.toggle { display: flex; align-items: center; gap: 8px; font-size: 13px; cursor: pointer; color: var(--ink-2); }
.toggle input { accent-color: var(--accent); }

.readouts { display: grid; grid-template-columns: repeat(auto-fill, minmax(132px, 1fr)); gap: 8px; margin: 0 0 12px; }
.ro { background: var(--bg); border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 7px 10px; }
.ro .k { font-size: 11.5px; color: var(--muted); line-height: 1.3; }
.ro .val { font-family: var(--font-mono); font-size: 16px; font-weight: 600; line-height: 1.35; }
.ro .val small { font-size: 11px; color: var(--muted); font-weight: 400; margin-left: 2px; }
.ro.flash { animation: flash .6s ease; }
.ro .delta { font-family: var(--font-mono); font-size: 11px; }
.up { color: var(--pos); } .down { color: var(--neg); }
@keyframes flash { 0% { background: var(--accent-soft); } 100% { background: var(--bg); } }

.plots { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 10px; }
.plot { position: relative; background: var(--bg); border: 1px solid var(--line); border-radius: var(--radius-sm); }
.plot svg { display: block; width: 100%; height: auto; font-family: var(--font-body); }
.plot-wide { grid-column: 1 / -1; }
.plot-wide svg { max-height: 460px; }
.plot .tip { position: absolute; pointer-events: none; background: var(--ink); color: var(--bg); font-family: var(--font-mono); font-size: 11px; padding: 4px 7px; border-radius: 5px; white-space: nowrap; display: none; z-index: 2; }
.plot-title { font-size: 12.5px; font-weight: 600; fill: var(--ink); }
.anim-bar { display: flex; gap: 8px; align-items: center; margin: 6px 0 10px; font-size: 13px; }
.anim-bar input[type=range] { flex: 1; accent-color: var(--accent); }
.btn { border: 1px solid var(--line); background: var(--surface); border-radius: 999px; padding: 4px 12px; cursor: pointer; font-size: 13px; }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.btn:hover { filter: brightness(.97); }

/* -------------------------------------------------------- causal widgets */
.causal-mini .prop { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; margin: 8px 0; }
.causal-mini .lvl { display: flex; flex-direction: column; gap: 6px; }
.prop-wrap { display: flex; gap: 10px; align-items: stretch; overflow-x: auto; padding-bottom: 6px; }
.prop-col { display: flex; flex-direction: column; gap: 6px; min-width: 150px; }
.prop-col h5 { margin: 0 0 2px; font-size: 10.5px; letter-spacing: .12em; text-transform: uppercase; color: var(--muted); }
.prop-arrow { align-self: center; color: var(--muted); }
.node-chip { border: 1px solid var(--line); border-left: 3px solid var(--chip, var(--accent)); border-radius: var(--radius-sm); padding: 5px 8px; background: var(--bg); font-size: 12.5px; transition: background .3s, transform .3s; cursor: pointer; }
.node-chip .nm { display: block; color: var(--ink-2); }
.node-chip .nv { font-family: var(--font-mono); font-weight: 600; font-size: 13px; }
.node-chip.changed { background: color-mix(in srgb, var(--accent) 9%, var(--bg)); }
.node-chip.pulse { animation: pulse .7s ease; }
@keyframes pulse { 0% { transform: scale(1); } 40% { transform: scale(1.04); background: var(--accent-soft); } 100% { transform: scale(1); } }

.cmap { display: grid; grid-template-columns: minmax(0, 1fr) 340px; gap: 16px; }
@media (max-width: 1100px) { .cmap { grid-template-columns: 1fr; } }
.cmap-canvas { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); overflow: auto; position: relative; max-height: calc(100vh - 110px); cursor: grab; overscroll-behavior: contain; }
.cmap-canvas.dragging { cursor: grabbing; user-select: none; }
.cmap-canvas svg { display: block; }
.cmap-tools { position: sticky; top: 0; left: 0; z-index: 2; display: flex; flex-wrap: wrap; align-items: center; gap: 4px; padding: 6px 8px; cursor: default;
  background: color-mix(in srgb, var(--surface) 92%, transparent); backdrop-filter: blur(6px); border-bottom: 1px solid var(--line); }
.cmap-tools button { border: 1px solid var(--line); background: var(--bg); color: var(--ink); border-radius: 999px; padding: 2px 10px; font-size: 12.5px; cursor: pointer; line-height: 1.5; }
.cmap-tools button:hover { border-color: var(--accent); color: var(--accent); }
.cmap-zl { font-family: var(--font-mono); font-size: 12px; min-width: 42px; text-align: center; color: var(--ink-2); }
.cmap-hint { margin-left: auto; font-size: 11.5px; color: var(--muted); }
.cmap:fullscreen { background: var(--bg); padding: 12px; grid-template-columns: minmax(0, 1fr) 340px; }
.cmap:fullscreen .cmap-canvas { max-height: calc(100vh - 24px); }
.cmap:fullscreen .cmap-side { max-height: calc(100vh - 24px); top: 0; }
.cmap-side { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 16px; position: sticky; top: 72px; align-self: start; max-height: calc(100vh - 90px); overflow: auto; }
.cnode rect { fill: var(--bg); stroke: var(--line); stroke-width: 1; rx: 7; transition: fill .25s; }
.cnode.param rect { fill: var(--surface); stroke-dasharray: 0; }
.cnode .bar { rx: 2; }
.cnode text { font-size: 11.5px; fill: var(--ink); pointer-events: none; }
.cnode text.v { font-family: var(--font-mono); font-size: 11px; fill: var(--ink-2); }
.cnode { cursor: pointer; }
.cnode.dim { opacity: .22; }
.cnode.sel rect { stroke: var(--ink); stroke-width: 2; }
.cnode.up rect { fill: color-mix(in srgb, var(--pos) 12%, var(--bg)); }
.cnode.down rect { fill: color-mix(in srgb, var(--neg) 12%, var(--bg)); }
.cedge { fill: none; stroke: var(--line); stroke-width: 1.3; }
.cedge.hot { stroke: var(--accent); stroke-width: 2; stroke-dasharray: 6 5; animation: dash 0.9s linear infinite; }
.cedge.dim { opacity: .15; }
.cedge.hl { stroke: var(--ink-2); stroke-width: 1.8; }
@keyframes dash { to { stroke-dashoffset: -22; } }
.col-label { font-size: 11px; letter-spacing: .14em; text-transform: uppercase; fill: var(--muted); font-weight: 600; }

/* --------------------------------------------------------------- pages */
.hero { display: grid; grid-template-columns: minmax(0, 1.05fr) minmax(0, 1fr); gap: 40px; align-items: center; padding: 28px 0 44px; margin-bottom: 36px; border-bottom: 1px solid var(--line); }
.hero h1 { font-family: var(--font-display); font-size: clamp(32px, 3.8vw, 50px); line-height: 1.16; letter-spacing: -.025em; margin: 14px 0 18px; }
.hero h1 .grad { background: linear-gradient(90deg, var(--accent), var(--accent-2)); -webkit-background-clip: text; background-clip: text; color: transparent; }
.hero p { font-size: 17.5px; color: var(--ink-2); max-width: 620px; margin: 0; }
.hero .cta { display: flex; gap: 10px; flex-wrap: wrap; margin-top: 26px; }
.hero .cta a { padding: 11px 18px; border-radius: 12px; font-weight: 700; font-size: 15px; border: 1px solid var(--line); background: var(--surface); color: var(--ink); transition: border-color .15s, filter .15s; }
.hero .cta a.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.hero .cta a:hover { text-decoration: none; border-color: var(--accent); filter: brightness(1.05); }
.hero-visual { margin: 0; padding: 22px 20px 14px; border: 1px solid var(--line); border-radius: 18px; box-shadow: var(--shadow);
  background: radial-gradient(ellipse at 50% 45%, var(--accent-soft), transparent 70%), var(--surface); }
.hero-visual svg { display: block; width: 100%; height: auto; }
.hero-visual figcaption { font-size: 12.5px; color: var(--muted); margin-top: 10px; text-align: center; }
@media (max-width: 1180px) { .hero { grid-template-columns: 1fr; } .hero-visual { max-width: 640px; } }

.numbers { display: grid; grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); gap: 1px; background: var(--line); border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; margin: 0 0 8px; }
.numbers div { background: var(--surface); padding: 16px 18px; display: flex; flex-direction: column; gap: 2px; }
.numbers b { font-family: var(--font-mono); font-size: 28px; font-weight: 600; letter-spacing: -.02em; line-height: 1.2; font-variant-numeric: tabular-nums; }
.numbers .k { font-weight: 600; font-size: 14px; color: var(--ink); }
.numbers span { font-size: 13px; color: var(--muted); line-height: 1.45; }
.home-h { font-family: var(--font-display); font-size: 27px; letter-spacing: -.01em; margin: 56px 0 6px; }
.home-sub { color: var(--ink-2); margin: 0 0 22px; font-size: 15.5px; }
.home .cards { margin-top: 0; }
.paths { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 14px; }
.path { padding: 16px 18px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
.path h3 { margin: 0 0 4px; font-size: 16.5px; }
.path p { margin: 0 0 12px; font-size: 14px; color: var(--ink-2); line-height: 1.6; }
.path .steps { display: flex; flex-wrap: wrap; gap: 6px; }
.path .steps a { font-family: var(--font-mono); font-size: 12px; font-weight: 600; padding: 2px 10px; border-radius: 999px; color: var(--chip, var(--accent));
  background: color-mix(in srgb, var(--chip, var(--accent)) 12%, var(--surface)); border: 1px solid color-mix(in srgb, var(--chip, var(--accent)) 30%, transparent); }
.path .steps a:hover { text-decoration: none; background: color-mix(in srgb, var(--chip, var(--accent)) 22%, var(--surface)); }
.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(250px, 1fr)); gap: 14px; margin: 30px 0; }
.card { display: block; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 16px 18px; color: var(--ink); border-top: 4px solid var(--chip, var(--accent)); transition: transform .15s, box-shadow .15s; }
.card:hover { transform: translateY(-2px); box-shadow: var(--shadow); text-decoration: none; border-color: color-mix(in srgb, var(--chip, var(--accent)) 50%, var(--line)); }
.card .num { font-family: var(--font-mono); font-size: 12px; font-weight: 600; letter-spacing: .08em; color: var(--chip, var(--accent)); }
.card h3 { font-family: var(--font-display); margin: 4px 0 6px; font-size: 19px; }
.card p { margin: 0; font-size: 14px; color: var(--ink-2); line-height: 1.6; }
.card .tags { margin-top: 10px; display: flex; flex-wrap: wrap; gap: 4px; }
.tag { font-size: 11px; padding: 1px 7px; border-radius: 999px; background: var(--surface-2); color: var(--ink-2); }

.ref-list { list-style: none; padding: 0; counter-reset: none; }
.ref-list li { padding: 12px 0; border-bottom: 1px solid var(--line); scroll-margin-top: 80px; }
.ref-list li:target { background: var(--accent-soft); }
.ref-list .rid { font-family: var(--font-mono); font-size: 12px; color: var(--muted); }
.ref-list .rnote { font-size: 13.5px; color: var(--ink-2); margin-top: 4px; }
.gloss dt { font-weight: 700; margin-top: 16px; scroll-margin-top: 80px; }
.gloss dt small { font-weight: 400; color: var(--muted); margin-left: 8px; }
.gloss dd { margin: 4px 0 0; color: var(--ink-2); }
.gloss dt:target { color: var(--accent); }

.pager { display: flex; justify-content: space-between; gap: 12px; margin-top: 70px; padding-top: 20px; border-top: 1px solid var(--line); }
.pager a { flex: 1; padding: 12px 16px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); color: var(--ink); }
.pager a small { display: block; color: var(--muted); font-size: 12px; }
.pager a.next { text-align: right; }
.pager a:hover { text-decoration: none; border-color: var(--accent); transform: translateY(-1px); box-shadow: var(--shadow); }
.pager a { transition: transform .15s, box-shadow .15s, border-color .15s; }

/* right-rail "On this page" — only when there is room beside the article (+ wide sims) */
.otp { display: none; }
@media (min-width: 1500px) {
  .ch-shell { display: grid; grid-template-columns: minmax(0, var(--maxw)) 210px; gap: 72px; justify-content: center; }
  .ch-shell .article { margin: 0; }
  .otp { display: block; position: sticky; top: 84px; align-self: start; max-height: calc(100vh - 110px); overflow: auto; padding-top: 8px; font-size: 13px; }
  .otp h4 { margin: 0 0 10px; font-size: 11px; letter-spacing: .14em; text-transform: uppercase; color: var(--muted); font-weight: 600; }
  .otp a { display: block; padding: 4px 0 4px 12px; border-left: 2px solid var(--line); color: var(--ink-2); line-height: 1.45; }
  .otp a:hover { color: var(--ink); text-decoration: none; }
  .otp a.active { border-left-color: var(--accent); color: var(--accent); font-weight: 600; }
  .toc-secs { display: none !important; } /* the rail replaces the sidebar's section list */
}

.popover { position: fixed; z-index: 60; max-width: 340px; background: var(--ink); color: var(--bg); padding: 10px 12px; border-radius: var(--radius-sm); font-size: 13.5px; line-height: 1.55; box-shadow: var(--shadow); pointer-events: none; }
.popover b { display: block; margin-bottom: 2px; }

.err { padding: 14px; border: 1px solid var(--pos); border-radius: var(--radius); color: var(--pos); background: var(--surface); }
.muted { color: var(--muted); }

@media (max-width: 960px) {
  .layout { grid-template-columns: 1fr; }
  .sidebar { position: fixed; z-index: 50; left: 0; top: 56px; width: 300px; background: var(--bg); transform: translateX(-102%); transition: transform .2s; box-shadow: var(--shadow); }
  body.nav-open .sidebar { transform: none; }
  .menu-btn { display: inline-block; }
  main { padding: 24px 18px 100px; }
  .search input { width: 140px; }
  .brand span { display: none; }
}
@media print {
  .topbar, .sidebar, .sim-controls, .pager, .otp { display: none !important; }
  .layout { display: block; }
  .sim { margin: 12px 0; box-shadow: none; break-inside: avoid; }
}
@media (max-width: 640px) {
  .topbar { gap: 8px; padding: 0 10px; }
  .brand b { font-size: 16px; }
  .search, .topnav a[href="#/lab"] { display: none; }
  .ch-head h1 { font-size: 28px; }
  .article h2 { font-size: 22px; }
}

.code-fig { margin: 20px 0; border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; background: var(--surface); }
.code-head { display: flex; gap: 10px; align-items: center; padding: 6px 12px; background: var(--surface-2); border-bottom: 1px solid var(--line); font-size: 13px; }
.code-head .mono { font-size: 11px; text-transform: uppercase; letter-spacing: .08em; color: var(--muted); }
.codeblock { margin: 0; padding: 12px 14px; overflow-x: auto; font-family: var(--font-mono); font-size: 12.5px; line-height: 1.55; color: var(--ink); }
.codeblock code { background: none; padding: 0; font-size: inherit; }