/* ==========================================================================
   RL, Decoded: design system
   Fonts: Inter (UI/body), Instrument Serif (display), JetBrains Mono (metrics)
   ========================================================================== */

:root {
  --font-sans: "Inter", ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --font-serif: "Instrument Serif", ui-serif, Georgia, "Times New Roman", serif;
  --font-mono: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

  --pro: #ff8a3d;
  --pro-soft: rgba(255, 138, 61, 0.14);
  --flash: #5aa2ff;
  --flash-soft: rgba(90, 162, 255, 0.14);
  --good: #3ecf8e;
  --good-soft: rgba(62, 207, 142, 0.13);
  --bad: #ff6b6b;
  --bad-soft: rgba(255, 107, 107, 0.13);
  --warn: #f5b942;
  --warn-soft: rgba(245, 185, 66, 0.13);
  --violet: #a58bff;
  --violet-soft: rgba(165, 139, 255, 0.14);

  --cat-code: #ff8a3d;
  --cat-general: #3ecf8e;
  --cat-visual: #5aa2ff;
  --cat-cyber: #ff6b6b;
  --cat-chat: #c7a6ff;

  --r-sm: 8px;
  --r-md: 12px;
  --r-lg: 18px;
  --r-xl: 26px;

  --rail-w: 19.5rem;
  --read-w: 44rem;
  --wide-w: 62rem;
  --gutter: clamp(1.1rem, 4vw, 3rem);

  --ease: cubic-bezier(0.22, 1, 0.36, 1);
  --t-fast: 160ms;
  --t-med: 320ms;
}

html[data-theme="dark"] {
  color-scheme: dark;
  --bg: #0a0b0e;
  --bg-2: #0e1015;
  --surface: #13151b;
  --surface-2: #191c24;
  --surface-3: #20242e;
  --line: rgba(255, 255, 255, 0.075);
  --line-2: rgba(255, 255, 255, 0.13);
  --text: #eceef2;
  --text-2: #b4b9c4;
  --muted: #8a909c;
  --faint: #5f6571;
  --accent: #ff7a2e;
  --accent-ink: #1a0c02;
  --grid: rgba(255, 255, 255, 0.06);
  --shadow: 0 1px 0 rgba(255,255,255,.03) inset, 0 20px 50px -20px rgba(0,0,0,.6);
  --glow: radial-gradient(60rem 30rem at 85% -10%, rgba(255,122,46,.10), transparent 60%),
          radial-gradient(50rem 30rem at -10% 10%, rgba(90,162,255,.08), transparent 60%);
}

html[data-theme="light"] {
  color-scheme: light;
  --bg: #f6f5f1;
  --bg-2: #efede7;
  --surface: #ffffff;
  --surface-2: #f7f6f2;
  --surface-3: #eeece6;
  --line: rgba(20, 20, 30, 0.08);
  --line-2: rgba(20, 20, 30, 0.15);
  --text: #15161a;
  --text-2: #3c404a;
  --muted: #6a6f7a;
  --faint: #9a9ea8;
  --accent: #e8590c;
  --accent-ink: #fff;
  --pro: #e8641c;
  --flash: #2f7ff0;
  --grid: rgba(20, 20, 30, 0.07);
  --shadow: 0 1px 2px rgba(20,20,30,.04), 0 18px 40px -24px rgba(20,20,30,.25);
  --glow: radial-gradient(60rem 30rem at 85% -10%, rgba(232,89,12,.07), transparent 60%),
          radial-gradient(50rem 30rem at -10% 10%, rgba(47,127,240,.06), transparent 60%);
}

/* ---------- Fluid scale: phone → 4K ---------- */
html { font-size: 15px; }
@media (min-width: 400px)  { html { font-size: 15.5px; } }
@media (min-width: 768px)  { html { font-size: 16px; } }
@media (min-width: 1440px) { html { font-size: 16.5px; } }
@media (min-width: 1920px) { html { font-size: 18px; } }
@media (min-width: 2400px) { html { font-size: 21px; } }
@media (min-width: 3000px) { html { font-size: 25px; } }
@media (min-width: 3600px) { html { font-size: 28px; } }

*, *::before, *::after { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  background-image: var(--glow);
  background-attachment: fixed;
  color: var(--text);
  font-family: var(--font-sans);
  font-feature-settings: "cv11", "ss01", "ss03";
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  min-height: 100vh;
}
img, svg { display: block; max-width: 100%; }
button { font: inherit; color: inherit; }
a { color: inherit; }
::selection { background: color-mix(in srgb, var(--accent) 35%, transparent); }

.skip { position: absolute; left: -999px; top: 0; z-index: 100; background: var(--accent); color: var(--accent-ink); padding: .6rem 1rem; border-radius: 0 0 var(--r-sm) 0; }
.skip:focus { left: 0; }

:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 6px; }

/* ---------- Shell ---------- */
.shell { display: grid; grid-template-columns: var(--rail-w) minmax(0, 1fr); min-height: 100vh; }
.stage { min-width: 0; display: flex; flex-direction: column; }

.rail {
  position: sticky; top: 0; height: 100vh; overflow: hidden;
  display: flex; flex-direction: column;
  border-right: 1px solid var(--line);
  background: color-mix(in srgb, var(--bg-2) 80%, transparent);
  backdrop-filter: blur(14px);
}
.rail__head { display: flex; align-items: center; justify-content: space-between; padding: 1.25rem 1.25rem .75rem; }
.brand { display: inline-flex; align-items: center; gap: .6rem; text-decoration: none; }
.brand__mark { width: 1.9rem; height: 1.9rem; color: var(--accent); }
.brand__text { font-family: var(--font-serif); font-size: 1.55rem; letter-spacing: -.01em; line-height: 1; }
.brand__text em { font-style: italic; color: var(--accent); }
.icon-btn.rail__close { display: none; }

.rail__progress { padding: .25rem 1.25rem 1rem; }
.progress-card { display: flex; align-items: center; gap: .85rem; padding: .8rem .9rem; border: 1px solid var(--line); border-radius: var(--r-md); background: var(--surface); }
.progress-card__txt { font-size: .8rem; color: var(--muted); line-height: 1.35; }
.progress-card__txt strong { display: block; color: var(--text); font-size: .92rem; font-weight: 600; }

.rail__nav { flex: 1; overflow-y: auto; padding: 0 .75rem 1rem; scrollbar-width: thin; }
.rail__module { margin-top: 1rem; }
.rail__module-title { font-size: .68rem; font-weight: 600; letter-spacing: .12em; text-transform: uppercase; color: var(--faint); padding: 0 .6rem .4rem; }
.rail__lesson {
  display: grid; grid-template-columns: 1.6rem 1fr auto; align-items: center; gap: .6rem;
  padding: .5rem .6rem; border-radius: var(--r-sm); text-decoration: none; color: var(--text-2);
  font-size: .88rem; line-height: 1.3; transition: background var(--t-fast), color var(--t-fast);
}
.rail__lesson:hover { background: var(--surface-2); color: var(--text); }
.rail__lesson[aria-current="page"] { background: var(--surface-2); color: var(--text); }
.rail__lesson.is-locked { color: var(--faint); }
.rail__num {
  width: 1.6rem; height: 1.6rem; border-radius: 50%; display: grid; place-items: center;
  font-size: .72rem; font-weight: 600; font-family: var(--font-mono);
  border: 1px solid var(--line-2); color: var(--muted);
}
.rail__lesson.is-passed .rail__num { background: var(--good-soft); border-color: transparent; color: var(--good); }
.rail__lesson.is-tried .rail__num { background: var(--warn-soft); border-color: transparent; color: var(--warn); }
.rail__lesson[aria-current="page"] .rail__num { border-color: var(--accent); color: var(--accent); }
.rail__meta { font-size: .7rem; font-family: var(--font-mono); color: var(--faint); }
.rail__lesson.is-passed .rail__meta { color: var(--good); }
.rail__lock { width: .85rem; height: .85rem; opacity: .6; }

.rail__foot { border-top: 1px solid var(--line); padding: .75rem; display: grid; gap: .15rem; }
.rail__link { display: flex; align-items: center; gap: .65rem; padding: .5rem .6rem; border-radius: var(--r-sm); text-decoration: none; color: var(--text-2); font-size: .88rem; }
.rail__link svg { width: 1.1rem; height: 1.1rem; opacity: .75; }
.rail__link:hover, .rail__link[aria-current="page"] { background: var(--surface-2); color: var(--text); }

.topbar {
  position: sticky; top: 0; z-index: 20;
  display: flex; align-items: center; gap: .75rem;
  padding: .75rem var(--gutter);
  background: color-mix(in srgb, var(--bg) 78%, transparent);
  backdrop-filter: blur(14px) saturate(1.2);
  border-bottom: 1px solid var(--line);
}
.icon-btn.topbar__menu { display: none; }
.topbar__crumb { flex: 1; min-width: 0; font-size: .85rem; color: var(--muted); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.topbar__crumb strong { color: var(--text); font-weight: 500; }
.topbar__actions { display: flex; align-items: center; gap: .5rem; }
.topbar__read { position: absolute; left: 0; bottom: -1px; height: 2px; width: 0; background: linear-gradient(90deg, var(--accent), var(--flash)); transition: width 80ms linear; }

.icon-btn {
  width: 2.35rem; height: 2.35rem; display: inline-grid; place-items: center; flex: none;
  border: 1px solid var(--line); background: var(--surface); border-radius: 50%; cursor: pointer;
  transition: border-color var(--t-fast), background var(--t-fast);
}
.icon-btn:hover { border-color: var(--line-2); background: var(--surface-2); }
.icon-btn svg { width: 1.1rem; height: 1.1rem; }
html[data-theme="dark"] .i-moon, html[data-theme="light"] .i-sun { display: none; }

.pill-link {
  display: inline-flex; align-items: center; gap: .4rem; text-decoration: none;
  font-size: .8rem; font-weight: 500; padding: .45rem .8rem; border-radius: 999px;
  border: 1px solid var(--line); background: var(--surface); color: var(--text-2);
}
.pill-link svg { width: .9rem; height: .9rem; }
.pill-link:hover { color: var(--text); border-color: var(--line-2); }

.main { flex: 1; padding: clamp(1.5rem, 4vw, 3.5rem) var(--gutter) 6rem; outline: none; }
.main.is-entering > * { animation: rise var(--t-med) var(--ease) both; }
@keyframes rise { from { opacity: 0; transform: translateY(10px); } to { opacity: 1; transform: none; } }

.scrim { position: fixed; inset: 0; background: rgba(0,0,0,.5); z-index: 40; backdrop-filter: blur(2px); }

/* ---------- Layout widths ---------- */
.read { max-width: var(--read-w); margin-inline: auto; }
.wide { max-width: var(--wide-w); margin-inline: auto; }
.page { max-width: 76rem; margin-inline: auto; }

/* ---------- Typography ---------- */
.eyebrow { font-size: .75rem; font-weight: 600; letter-spacing: .14em; text-transform: uppercase; color: var(--accent); }
.display { font-family: var(--font-serif); font-weight: 400; letter-spacing: -.015em; line-height: 1.02; margin: .4rem 0 1rem; font-size: clamp(2.5rem, 6.5vw, 5.2rem); }
.display em { font-style: italic; color: var(--accent); }
h1.lesson-title { font-family: var(--font-serif); font-weight: 400; font-size: clamp(2.2rem, 5vw, 3.7rem); line-height: 1.05; letter-spacing: -.015em; margin: .5rem 0 .8rem; }
.lede { font-size: clamp(1.05rem, 1.6vw, 1.2rem); color: var(--text-2); line-height: 1.6; margin: 0 0 1.5rem; }
.prose h2 { font-family: var(--font-serif); font-weight: 400; font-size: clamp(1.7rem, 3vw, 2.25rem); line-height: 1.15; letter-spacing: -.01em; margin: 3.2rem 0 .9rem; scroll-margin-top: 5rem; }
.prose h3 { font-size: 1.1rem; font-weight: 650; letter-spacing: -.01em; margin: 2rem 0 .5rem; }
.prose p { margin: 0 0 1.1rem; color: var(--text-2); }
.prose p strong, .prose li strong { color: var(--text); font-weight: 600; }
.prose ul, .prose ol { padding-left: 1.3rem; margin: 0 0 1.2rem; color: var(--text-2); }
.prose li { margin: .35rem 0; }
.prose li::marker { color: var(--faint); }
.prose hr { border: 0; border-top: 1px solid var(--line); margin: 2.5rem 0; }
.prose blockquote { margin: 1.5rem 0; padding: 0 1.5rem; font-style: italic; font-family: var(--font-serif); font-size: 1.35rem; line-height: 1.4; color: var(--text); }
.prose a { color: var(--accent); text-underline-offset: 3px; }

code, .mono { font-family: var(--font-mono); font-size: .86em; }
.metric {
  font-family: var(--font-mono); font-size: .82em; font-weight: 500;
  padding: .1em .45em; border-radius: 6px; white-space: nowrap;
  background: var(--surface-3); color: var(--text); border: 1px solid var(--line);
}
.pro-c { color: var(--pro); font-weight: 600; }
.flash-c { color: var(--flash); font-weight: 600; }
.good-c { color: var(--good); font-weight: 600; }
.bad-c { color: var(--bad); font-weight: 600; }

/* Terms (glossary tooltips) */
.term {
  display: inline; padding: 0; margin: 0; border: 0; background: none; cursor: help;
  font: inherit; color: var(--text); font-weight: 500;
  text-decoration: underline dotted color-mix(in srgb, var(--accent) 70%, transparent);
  text-decoration-thickness: 1.5px; text-underline-offset: 4px;
}
.term:hover { color: var(--accent); }
.tip {
  position: fixed; z-index: 60; max-width: min(22rem, 90vw);
  padding: .8rem .95rem; border-radius: var(--r-md);
  background: var(--surface-3); border: 1px solid var(--line-2); box-shadow: var(--shadow);
  font-size: .86rem; line-height: 1.5; color: var(--text-2);
  animation: rise 160ms var(--ease);
}
.tip strong { display: block; color: var(--text); font-size: .9rem; margin-bottom: .2rem; }
.tip a { color: var(--accent); font-size: .78rem; }

/* ---------- Lesson header ---------- */
.lesson-head { margin-bottom: 2rem; }
.lesson-meta { display: flex; flex-wrap: wrap; gap: .5rem; margin-top: 1rem; }
.chip {
  display: inline-flex; align-items: center; gap: .4rem;
  font-size: .76rem; font-weight: 500; color: var(--muted);
  padding: .3rem .7rem; border-radius: 999px; border: 1px solid var(--line); background: var(--surface);
}
.chip svg { width: .85rem; height: .85rem; }
.chip--good { color: var(--good); background: var(--good-soft); border-color: transparent; }

.objectives {
  border: 1px solid var(--line); border-radius: var(--r-lg); background: var(--surface);
  padding: 1.2rem 1.4rem; margin: 1.8rem 0 2.2rem;
}
.objectives h4 { margin: 0 0 .6rem; font-size: .75rem; letter-spacing: .12em; text-transform: uppercase; color: var(--muted); font-weight: 600; }
.objectives ul { margin: 0; padding: 0; list-style: none; display: grid; gap: .45rem; }
.objectives li { display: grid; grid-template-columns: 1.2rem 1fr; gap: .5rem; color: var(--text-2); font-size: .95rem; }
.objectives li::before { content: "→"; color: var(--accent); font-weight: 600; }

/* ---------- Callouts ---------- */
.callout {
  position: relative; border-radius: var(--r-lg); padding: 1.1rem 1.3rem 1.15rem;
  margin: 1.6rem 0; border: 1px solid var(--line); background: var(--surface);
}
.callout > :last-child { margin-bottom: 0; }
.callout p { margin: 0 0 .7rem; }
.callout__label { display: inline-flex; align-items: center; gap: .45rem; font-size: .72rem; font-weight: 650; letter-spacing: .1em; text-transform: uppercase; margin-bottom: .5rem; }
.callout__label::before { content: ""; width: .5rem; height: .5rem; border-radius: 50%; background: currentColor; }
.callout--define { background: color-mix(in srgb, var(--flash) 5%, var(--surface)); }
.callout--define .callout__label { color: var(--flash); }
.callout--define dfn { font-style: normal; font-weight: 650; color: var(--text); }
.callout--wonder { background: linear-gradient(180deg, var(--violet-soft), transparent 70%), var(--surface); border-color: color-mix(in srgb, var(--violet) 30%, transparent); }
.callout--wonder .callout__label { color: var(--violet); }
.callout--wonder .q { font-family: var(--font-serif); font-size: 1.3rem; line-height: 1.35; color: var(--text); margin: 0 0 .7rem; }
.callout--warn { background: color-mix(in srgb, var(--warn) 5%, var(--surface)); }
.callout--warn .callout__label { color: var(--warn); }
.callout--correct { background: color-mix(in srgb, var(--good) 5%, var(--surface)); }
.callout--correct .callout__label { color: var(--good); }
.callout--analogy { background: var(--surface-2); border-style: dashed; }
.callout--analogy .callout__label { color: var(--muted); }
.callout--data { background: color-mix(in srgb, var(--accent) 5%, var(--surface)); }
.callout--data .callout__label { color: var(--accent); }

/* Up / down stories */
.story { display: grid; grid-template-columns: 1fr 1fr; gap: .9rem; margin: 1.4rem 0 1.8rem; }
.story__card { border: 1px solid var(--line); border-radius: var(--r-md); padding: 1rem 1.1rem; background: var(--surface); font-size: .93rem; color: var(--text-2); }
.story__card h5 { margin: 0 0 .4rem; font-size: .8rem; letter-spacing: .06em; text-transform: uppercase; display: flex; align-items: center; gap: .4rem; }
.story__card--up h5 { color: var(--good); }
.story__card--down h5 { color: var(--bad); }
.story__card--here { grid-column: 1 / -1; background: color-mix(in srgb, var(--accent) 5%, var(--surface)); }
.story__card--here h5 { color: var(--accent); }
.story__card p { margin: 0; }

/* Numbered flow */
.flow { counter-reset: flow; list-style: none; padding: 0 !important; display: grid; gap: .7rem; }
.flow li { counter-increment: flow; display: grid; grid-template-columns: 2.2rem 1fr; gap: .8rem; align-items: start; background: var(--surface); border: 1px solid var(--line); border-radius: var(--r-md); padding: .85rem 1rem; margin: 0 !important; }
.flow li::before { content: counter(flow); width: 2.2rem; height: 2.2rem; border-radius: 50%; display: grid; place-items: center; font-family: var(--font-mono); font-weight: 600; font-size: .85rem; background: var(--surface-3); color: var(--accent); }

.takeaways { border-radius: var(--r-lg); padding: 1.3rem 1.5rem; margin: 2.8rem 0 1rem; background: linear-gradient(135deg, color-mix(in srgb, var(--accent) 10%, transparent), transparent 55%), var(--surface); border: 1px solid var(--line); }
.takeaways h4 { margin: 0 0 .7rem; font-family: var(--font-serif); font-weight: 400; font-size: 1.5rem; }
.takeaways ul { margin: 0; }

/* Tables */
.table-wrap { overflow-x: auto; margin: 1.4rem 0; border: 1px solid var(--line); border-radius: var(--r-md); background: var(--surface); }
table.t { width: 100%; border-collapse: collapse; font-size: .88rem; }
table.t th, table.t td { padding: .65rem .9rem; text-align: left; border-bottom: 1px solid var(--line); vertical-align: top; }
table.t th { font-size: .72rem; letter-spacing: .08em; text-transform: uppercase; color: var(--muted); font-weight: 600; background: var(--surface-2); }
table.t tr:last-child td { border-bottom: 0; }
table.t td { color: var(--text-2); }
table.t td.num { font-family: var(--font-mono); text-align: right; white-space: nowrap; }

/* Stat tiles */
.stats { display: grid; grid-template-columns: repeat(auto-fit, minmax(10rem, 1fr)); gap: .75rem; margin: 1.5rem 0; }
.stat { border: 1px solid var(--line); border-radius: var(--r-md); background: var(--surface); padding: .9rem 1rem; }
.stat__label { font-size: .72rem; color: var(--muted); letter-spacing: .04em; }
.stat__value { font-family: var(--font-mono); font-size: 1.35rem; font-weight: 600; letter-spacing: -.02em; margin-top: .15rem; }
.stat__sub { font-size: .74rem; color: var(--faint); margin-top: .1rem; }

/* ---------- Figures / charts ---------- */
.fig { margin: 1.8rem 0 2rem; border: 1px solid var(--line); border-radius: var(--r-lg); background: var(--surface); padding: 1.1rem 1.1rem .9rem; box-shadow: var(--shadow); }
.fig--bleed { margin-inline: calc((var(--read-w) - min(var(--wide-w), 100vw - 2 * var(--gutter) - var(--rail-w))) / 2); }
.fig__head { display: flex; align-items: flex-start; justify-content: space-between; gap: 1rem; flex-wrap: wrap; margin-bottom: .6rem; }
.fig__title { font-family: var(--font-mono); font-size: .85rem; font-weight: 600; color: var(--text); }
.fig__sub { font-size: .8rem; color: var(--muted); margin-top: .15rem; line-height: 1.4; }
.fig__legend { display: flex; gap: .9rem; font-size: .76rem; color: var(--muted); flex-wrap: wrap; }
.fig__legend span { display: inline-flex; align-items: center; gap: .35rem; }
.fig__legend i { width: .8rem; height: 3px; border-radius: 2px; display: inline-block; }
.fig__legend i.dot { width: .55rem; height: .55rem; border-radius: 50%; }
.fig__legend i.dash { background: repeating-linear-gradient(90deg, var(--faint) 0 3px, transparent 3px 6px) !important; height: 2px; }
.fig__cap { font-size: .82rem; color: var(--muted); margin-top: .6rem; line-height: 1.5; }
.fig__cap b { color: var(--text-2); font-weight: 600; }

.chart { position: relative; width: 100%; }
.chart svg { width: 100%; height: auto; overflow: visible; }
.chart .grid line { stroke: var(--grid); }
.chart .axis text { fill: var(--faint); font-family: var(--font-mono); font-size: 10px; }
.chart .line { fill: none; stroke-width: 2; stroke-linejoin: round; stroke-linecap: round; }
.chart .line--pro { stroke: var(--pro); }
.chart .line--flash { stroke: var(--flash); }
.chart .area--pro { fill: url(#gPro); }
.chart .area--flash { fill: url(#gFlash); }
.chart .pt { stroke: var(--surface); stroke-width: 1.5; }
.chart .restart line { stroke-dasharray: 2 3; stroke-width: 1; }
.chart .restart--pro line { stroke: color-mix(in srgb, var(--pro) 55%, transparent); }
.chart .restart--flash line { stroke: color-mix(in srgb, var(--flash) 55%, transparent); }
.chart .note text { font-family: var(--font-sans); font-size: 10.5px; fill: var(--text-2); }
.chart .note line { stroke: var(--line-2); }
.chart .band { fill: color-mix(in srgb, var(--warn) 9%, transparent); }
.chart .xhair { stroke: var(--line-2); stroke-width: 1; }
.chart-tip {
  position: absolute; pointer-events: none; z-index: 5; min-width: 9rem;
  background: var(--surface-3); border: 1px solid var(--line-2); border-radius: var(--r-sm);
  padding: .5rem .65rem; font-size: .76rem; box-shadow: var(--shadow); transform: translate(-50%, -110%);
  font-family: var(--font-mono); white-space: nowrap;
}
.chart-tip .r { display: flex; justify-content: space-between; gap: 1rem; }
.chart-tip .h { color: var(--muted); margin-bottom: .2rem; font-family: var(--font-sans); font-weight: 600; font-size: .72rem; }

/* segmented control */
.seg { display: inline-flex; padding: 3px; border-radius: 999px; background: var(--surface-2); border: 1px solid var(--line); gap: 2px; flex-wrap: wrap; }
.seg button { border: 0; background: none; padding: .35rem .8rem; border-radius: 999px; font-size: .78rem; font-weight: 500; color: var(--muted); cursor: pointer; transition: all var(--t-fast); }
.seg button[aria-pressed="true"] { background: var(--surface); color: var(--text); box-shadow: 0 1px 3px rgba(0,0,0,.2); }
html[data-theme="light"] .seg button[aria-pressed="true"] { box-shadow: 0 1px 3px rgba(0,0,0,.08); }

/* ---------- Labs ---------- */
.lab { margin: 2rem 0 2.2rem; border-radius: var(--r-xl); border: 1px solid var(--line-2); background: linear-gradient(180deg, var(--surface-2), var(--surface)); box-shadow: var(--shadow); overflow: hidden; }
.lab__bar { display: flex; align-items: center; gap: .6rem; padding: .7rem 1.1rem; border-bottom: 1px solid var(--line); background: color-mix(in srgb, var(--surface-3) 50%, transparent); }
.lab__tag { font-size: .68rem; font-weight: 700; letter-spacing: .14em; text-transform: uppercase; color: var(--accent); padding: .2rem .55rem; border-radius: 999px; background: color-mix(in srgb, var(--accent) 13%, transparent); }
.lab__title { font-weight: 600; font-size: .92rem; }
.lab__body { padding: 1.2rem 1.2rem 1.3rem; }
.lab__hint { font-size: .85rem; color: var(--muted); margin: 0 0 1rem; }
.lab__row { display: flex; flex-wrap: wrap; gap: .75rem 1.25rem; align-items: center; margin-bottom: 1rem; }
.lab__out { margin-top: 1rem; padding: .85rem 1rem; border-radius: var(--r-md); background: var(--bg-2); border: 1px solid var(--line); font-size: .9rem; color: var(--text-2); }
.lab__out strong { color: var(--text); }

.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: .5rem;
  padding: .7rem 1.2rem; border-radius: 999px; border: 1px solid var(--line-2);
  background: var(--surface); color: var(--text); font-weight: 550; font-size: .9rem;
  cursor: pointer; text-decoration: none; transition: transform var(--t-fast), background var(--t-fast), border-color var(--t-fast), opacity var(--t-fast);
  -webkit-tap-highlight-color: transparent;
}
.btn:hover { border-color: var(--faint); background: var(--surface-2); }
.btn:active { transform: scale(.98); }
.btn[disabled] { opacity: .4; cursor: not-allowed; transform: none; }
.btn--primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.btn--primary:hover { background: color-mix(in srgb, var(--accent) 88%, white); border-color: transparent; }
.btn--ghost { background: transparent; border-color: transparent; color: var(--muted); }
.btn--ghost:hover { background: var(--surface-2); color: var(--text); border-color: transparent; }
.btn--sm { padding: .45rem .85rem; font-size: .8rem; }
.btn svg { width: 1rem; height: 1rem; }

.range { display: grid; gap: .35rem; min-width: min(16rem, 100%); flex: 1; }
.range label { display: flex; justify-content: space-between; font-size: .8rem; color: var(--muted); }
.range output { font-family: var(--font-mono); color: var(--text); font-weight: 600; }
input[type="range"] { -webkit-appearance: none; appearance: none; width: 100%; height: 1.4rem; background: transparent; cursor: pointer; }
input[type="range"]::-webkit-slider-runnable-track { height: 4px; border-radius: 4px; background: linear-gradient(90deg, var(--accent) var(--p, 50%), var(--surface-3) var(--p, 50%)); }
input[type="range"]::-moz-range-track { height: 4px; border-radius: 4px; background: var(--surface-3); }
input[type="range"]::-moz-range-progress { height: 4px; border-radius: 4px; background: var(--accent); }
input[type="range"]::-webkit-slider-thumb { -webkit-appearance: none; width: 1.15rem; height: 1.15rem; margin-top: -.45rem; border-radius: 50%; background: var(--text); border: 3px solid var(--accent); box-shadow: 0 2px 8px rgba(0,0,0,.3); }
input[type="range"]::-moz-range-thumb { width: .9rem; height: .9rem; border-radius: 50%; background: var(--text); border: 3px solid var(--accent); }

/* rollout tiles */
.tiles { display: grid; grid-template-columns: repeat(8, minmax(0, 1fr)); gap: .45rem; }
.tile {
  aspect-ratio: 1; border-radius: var(--r-sm); display: grid; place-items: center; position: relative;
  font-family: var(--font-mono); font-size: .72rem; font-weight: 600;
  background: var(--surface-3); color: var(--faint); border: 1px solid var(--line);
  transition: background var(--t-med), color var(--t-med), transform var(--t-med) var(--ease);
}
.tile.is-pass { background: var(--good-soft); color: var(--good); border-color: color-mix(in srgb, var(--good) 35%, transparent); }
.tile.is-fail { background: var(--bad-soft); color: var(--bad); border-color: color-mix(in srgb, var(--bad) 30%, transparent); }
.tile.pop { animation: pop 380ms var(--ease) both; }
@keyframes pop { 0% { transform: scale(.6); opacity: 0; } 100% { transform: none; opacity: 1; } }
.tile small { position: absolute; bottom: 3px; font-size: .58rem; opacity: .8; }

.verdict { display: inline-flex; align-items: center; gap: .4rem; font-size: .78rem; font-weight: 600; padding: .25rem .65rem; border-radius: 999px; }
.verdict--good { background: var(--good-soft); color: var(--good); }
.verdict--bad { background: var(--bad-soft); color: var(--bad); }
.verdict--warn { background: var(--warn-soft); color: var(--warn); }
.verdict--info { background: var(--flash-soft); color: var(--flash); }

.minibar { display: flex; height: 2.2rem; border-radius: var(--r-sm); overflow: hidden; border: 1px solid var(--line); }
.minibar > div { display: grid; place-items: center; font-size: .72rem; font-weight: 600; font-family: var(--font-mono); color: rgba(0,0,0,.72); transition: flex-basis var(--t-med) var(--ease); min-width: 0; overflow: hidden; white-space: nowrap; }

/* code blocks */
pre.code { margin: .5rem 0; padding: .8rem .95rem; border-radius: var(--r-sm); background: var(--bg-2); border: 1px solid var(--line); font-family: var(--font-mono); font-size: .8rem; line-height: 1.55; overflow-x: auto; color: var(--text-2); }
pre.code .k { color: var(--violet); } pre.code .c { color: var(--faint); } pre.code .s { color: var(--good); }

/* grader lab */
.sol-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: .8rem; }
.sol { border: 1px solid var(--line); border-radius: var(--r-md); background: var(--surface); padding: .8rem .9rem; display: flex; flex-direction: column; }
.sol__head { display: flex; justify-content: space-between; align-items: center; gap: .5rem; font-size: .82rem; font-weight: 600; }
.sol__score { font-family: var(--font-mono); font-size: 1.05rem; font-weight: 700; }
.sol__why { font-size: .78rem; color: var(--muted); margin-top: .35rem; line-height: 1.45; }

/* advantage lab */
.adv { display: grid; grid-template-columns: repeat(16, minmax(0, 1fr)); gap: 3px; align-items: center; height: 11rem; position: relative; }
.adv__col { position: relative; height: 100%; }
.adv__bar { position: absolute; left: 12%; right: 12%; border-radius: 3px; transition: all var(--t-med) var(--ease); }
.adv__zero { position: absolute; left: 0; right: 0; top: 50%; border-top: 1px dashed var(--line-2); }
.adv__dot { position: absolute; left: 50%; top: 50%; width: .6rem; height: .6rem; border-radius: 50%; transform: translate(-50%, -50%); }

/* entropy lab */
.probs { display: grid; gap: .5rem; }
.prob { display: grid; grid-template-columns: minmax(7rem, 11rem) 1fr 3.4rem; align-items: center; gap: .7rem; font-size: .84rem; }
.prob__track { height: .8rem; background: var(--surface-3); border-radius: 999px; overflow: hidden; }
.prob__fill { height: 100%; border-radius: 999px; background: linear-gradient(90deg, var(--accent), color-mix(in srgb, var(--accent) 60%, var(--flash))); transition: width var(--t-med) var(--ease); }
.prob__v { font-family: var(--font-mono); text-align: right; color: var(--text); font-size: .8rem; }
.gauge { height: .55rem; border-radius: 999px; background: linear-gradient(90deg, var(--bad), var(--warn) 30%, var(--good) 55%, var(--flash)); position: relative; margin: .6rem 0 .3rem; }
.gauge__pin { position: absolute; top: 50%; width: 1rem; height: 1rem; border-radius: 50%; background: var(--text); border: 3px solid var(--bg); transform: translate(-50%, -50%); transition: left var(--t-med) var(--ease); box-shadow: 0 2px 6px rgba(0,0,0,.4); }
.gauge-labels { display: flex; justify-content: space-between; font-size: .7rem; color: var(--faint); }

/* timeline lab */
.gantt { position: relative; }
.gantt svg text { font-family: var(--font-mono); font-size: 10px; fill: var(--muted); }
.gantt .lbl { font-family: var(--font-sans); font-size: 11px; fill: var(--text-2); font-weight: 600; }

/* log decoder */
.logline { font-family: var(--font-mono); font-size: clamp(.72rem, 1.6vw, .9rem); line-height: 2.1; padding: 1rem; border-radius: var(--r-md); background: var(--bg-2); border: 1px solid var(--line); overflow-x: auto; }
.logline button { font: inherit; border: 0; padding: .15rem .35rem; border-radius: 5px; background: var(--surface-3); color: var(--text); cursor: pointer; transition: background var(--t-fast), color var(--t-fast); margin: 0 .05rem; }
.logline button:hover, .logline button[aria-pressed="true"] { background: var(--accent); color: var(--accent-ink); }
.logline .sep { color: var(--faint); }
.decode { margin-top: 1rem; min-height: 7.5rem; }
.decode h5 { margin: 0 0 .3rem; font-family: var(--font-mono); font-size: .9rem; color: var(--accent); }
.decode p { margin: 0 0 .5rem; font-size: .9rem; color: var(--text-2); }
.decode .inf { font-size: .76rem; color: var(--warn); }

/* pipeline lab */
.pipe { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: .6rem; margin-bottom: 1rem; }
.pipe button {
  text-align: left; border: 1px solid var(--line); background: var(--surface); border-radius: var(--r-md);
  padding: .8rem .9rem; cursor: pointer; position: relative; transition: all var(--t-fast);
}
.pipe button .n { font-family: var(--font-mono); font-size: .7rem; color: var(--faint); }
.pipe button .t { display: block; font-weight: 600; font-size: .95rem; margin-top: .15rem; }
.pipe button .s { display: block; font-size: .76rem; color: var(--muted); margin-top: .15rem; }
.pipe button[aria-pressed="true"] { border-color: var(--accent); background: color-mix(in srgb, var(--accent) 8%, var(--surface)); }
.pipe button[aria-pressed="true"] .n { color: var(--accent); }
.pipe-panel { display: grid; grid-template-columns: minmax(0, 1.1fr) minmax(0, 1fr); gap: 1rem; }
.pipe-panel > * { min-width: 0; }
.pipe-panel dl { margin: 0; display: grid; gap: .6rem; }
.pipe-panel dt { font-size: .7rem; text-transform: uppercase; letter-spacing: .1em; color: var(--faint); font-weight: 600; }
.pipe-panel dd { margin: 0; font-size: .9rem; color: var(--text-2); }
.pipe-art { margin: 0; white-space: pre-wrap; overflow-wrap: anywhere; border-radius: var(--r-md); background: var(--bg-2); border: 1px solid var(--line); padding: 1rem; font-family: var(--font-mono); font-size: .78rem; color: var(--text-2); line-height: 1.7; }
.pipe-art .hl { color: var(--accent); }
.pipe-art .ok { color: var(--good); }
.pipe-art .no { color: var(--bad); }

/* incident timeline */
.tl { position: relative; }
.tl svg text { font-family: var(--font-mono); font-size: 10px; fill: var(--muted); }
.tl-list { list-style: none; padding: 0; margin: 1rem 0 0; display: grid; gap: .5rem; }
.tl-list li { display: grid; grid-template-columns: 4.2rem 1fr; gap: .8rem; font-size: .86rem; color: var(--text-2); padding: .6rem .8rem; border-radius: var(--r-sm); background: var(--bg-2); border: 1px solid var(--line); }
.tl-list li b { font-family: var(--font-mono); font-size: .75rem; color: var(--accent); font-weight: 600; }

/* ---------- Quiz ---------- */
.quiz { margin: 3.5rem 0 1rem; }
.quiz-cta {
  position: relative; overflow: hidden; border-radius: var(--r-xl); padding: clamp(1.4rem, 3vw, 2.2rem);
  border: 1px solid color-mix(in srgb, var(--accent) 35%, var(--line));
  background:
    radial-gradient(30rem 14rem at 100% 0%, color-mix(in srgb, var(--accent) 18%, transparent), transparent 70%),
    radial-gradient(24rem 14rem at 0% 100%, color-mix(in srgb, var(--flash) 12%, transparent), transparent 70%),
    var(--surface);
  display: grid; grid-template-columns: 1fr auto; gap: 1.2rem; align-items: center;
}
.quiz-cta h3 { font-family: var(--font-serif); font-weight: 400; font-size: clamp(1.7rem, 3vw, 2.3rem); margin: .25rem 0 .35rem; line-height: 1.1; }
.quiz-cta p { margin: 0; color: var(--text-2); font-size: .95rem; }
.quiz-cta__best { margin-top: .7rem !important; font-size: .82rem !important; }

.quiz-card {
  border-radius: var(--r-xl); border: 1px solid var(--line-2); background: var(--surface);
  box-shadow: var(--shadow); overflow: hidden;
}
.quiz-card__top { padding: 1.1rem clamp(1.1rem, 3vw, 1.8rem) 0; }
.quiz-card__meta { display: flex; justify-content: space-between; align-items: center; font-size: .8rem; color: var(--muted); margin-bottom: .7rem; gap: 1rem; }
.quiz-card__meta b { color: var(--text); font-family: var(--font-mono); }
.quiz-steps { display: grid; grid-template-columns: repeat(10, 1fr); gap: 4px; }
.quiz-steps span { height: 4px; border-radius: 4px; background: var(--surface-3); transition: background var(--t-med); }
.quiz-steps span.is-done { background: color-mix(in srgb, var(--accent) 55%, transparent); }
.quiz-steps span.is-now { background: var(--accent); }

.quiz-stage { position: relative; padding: 1.4rem clamp(1.1rem, 3vw, 1.8rem) .6rem; min-height: 22rem; }
.quiz-q { transition: opacity 260ms var(--ease), transform 260ms var(--ease); }
.quiz-q.out-left { opacity: 0; transform: translateX(-22px); }
.quiz-q.out-right { opacity: 0; transform: translateX(22px); }
.quiz-q.in-right { opacity: 0; transform: translateX(22px); transition: none; }
.quiz-q.in-left { opacity: 0; transform: translateX(-22px); transition: none; }
.quiz-q h4 { font-size: clamp(1.1rem, 2vw, 1.3rem); font-weight: 600; line-height: 1.4; margin: 0 0 1.1rem; letter-spacing: -.01em; }
.quiz-q .ctx { font-size: .85rem; color: var(--muted); margin: -.6rem 0 1rem; }
.opts { display: grid; gap: .6rem; }
.opt {
  display: grid; grid-template-columns: 1.9rem 1fr; gap: .8rem; align-items: center; text-align: left;
  padding: .85rem 1rem; border-radius: var(--r-md); border: 1px solid var(--line); background: var(--surface-2);
  cursor: pointer; font-size: .95rem; line-height: 1.45; color: var(--text-2);
  transition: border-color var(--t-fast), background var(--t-fast), color var(--t-fast), transform var(--t-fast);
}
.opt:hover { border-color: var(--line-2); color: var(--text); }
.opt:active { transform: scale(.995); }
.opt__k { width: 1.9rem; height: 1.9rem; border-radius: 50%; display: grid; place-items: center; font-family: var(--font-mono); font-size: .78rem; font-weight: 600; border: 1px solid var(--line-2); color: var(--muted); transition: all var(--t-fast); }
.opt[aria-checked="true"] { border-color: var(--accent); background: color-mix(in srgb, var(--accent) 9%, var(--surface-2)); color: var(--text); }
.opt[aria-checked="true"] .opt__k { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }

.quiz-nav { display: flex; justify-content: space-between; align-items: center; gap: .75rem; padding: 1rem clamp(1.1rem, 3vw, 1.8rem) 1.3rem; border-top: 1px solid var(--line); background: var(--surface-2); }
.quiz-nav__hint { font-size: .75rem; color: var(--faint); text-align: center; flex: 1; }

.score { padding: clamp(1.5rem, 4vw, 2.5rem) clamp(1.1rem, 3vw, 1.8rem); text-align: center; }
.ring { width: 9.5rem; height: 9.5rem; margin: 0 auto 1rem; position: relative; }
.ring svg { width: 100%; height: 100%; transform: rotate(-90deg); }
.ring circle { fill: none; stroke-width: 9; }
.ring .bg { stroke: var(--surface-3); }
.ring .fg { stroke-linecap: round; transition: stroke-dashoffset 1.1s var(--ease); }
.ring__txt { position: absolute; inset: 0; display: grid; place-items: center; align-content: center; }
.ring__txt b { font-family: var(--font-serif); font-weight: 400; font-size: 3.2rem; line-height: 1; }
.ring__txt span { font-size: .75rem; color: var(--muted); font-family: var(--font-mono); }
.score h3 { font-family: var(--font-serif); font-weight: 400; font-size: clamp(1.8rem, 3.5vw, 2.5rem); margin: .2rem 0 .4rem; }
.score > p { color: var(--text-2); max-width: 32rem; margin: 0 auto 1.4rem; }
.score__actions { display: flex; gap: .6rem; justify-content: center; flex-wrap: wrap; }
.review { text-align: left; margin-top: 2rem; display: grid; gap: .6rem; }
.review__item { border: 1px solid var(--line); border-radius: var(--r-md); padding: .85rem 1rem; background: var(--surface-2); }
.review__item summary { cursor: pointer; list-style: none; display: grid; grid-template-columns: 1.5rem 1fr; gap: .6rem; font-size: .92rem; font-weight: 500; color: var(--text); }
.review__item summary::-webkit-details-marker { display: none; }
.review__mark { width: 1.5rem; height: 1.5rem; border-radius: 50%; display: grid; place-items: center; font-size: .75rem; font-weight: 700; }
.review__mark.ok { background: var(--good-soft); color: var(--good); }
.review__mark.no { background: var(--bad-soft); color: var(--bad); }
.review__body { padding: .7rem 0 0 2.1rem; font-size: .87rem; color: var(--text-2); }
.review__body p { margin: .3rem 0; }
.review__body .you { color: var(--bad); }
.review__body .ans { color: var(--good); }

.next-lesson { display: flex; justify-content: space-between; gap: 1rem; margin-top: 3rem; padding-top: 1.5rem; border-top: 1px solid var(--line); }
.next-lesson a, .next-lesson button { flex: 1; max-width: 48%; text-decoration: none; border: 1px solid var(--line); border-radius: var(--r-md); padding: .9rem 1.1rem; background: var(--surface); cursor: pointer; text-align: left; transition: border-color var(--t-fast); }
.next-lesson a:hover, .next-lesson button:hover { border-color: var(--line-2); }
.next-lesson small { display: block; font-size: .72rem; color: var(--faint); text-transform: uppercase; letter-spacing: .1em; font-weight: 600; }
.next-lesson span { font-weight: 550; font-size: .95rem; }
.next-lesson .is-next { margin-left: auto; text-align: right; }
.next-lesson .is-locked { opacity: .6; }

/* ---------- Home ---------- */
.hero { display: grid; grid-template-columns: minmax(0, 1.3fr) minmax(0, 1fr); gap: clamp(1.5rem, 4vw, 4rem); align-items: center; padding: clamp(.5rem, 3vw, 2.5rem) 0 clamp(2rem, 5vw, 4rem); }
.hero .lede { max-width: 36rem; }
.hero__cta { display: flex; gap: .7rem; flex-wrap: wrap; margin-top: 1.6rem; }
.hero__art { border: 1px solid var(--line); border-radius: var(--r-xl); background: var(--surface); padding: 1.1rem; box-shadow: var(--shadow); }
.hero__art .fig__title { margin-bottom: .3rem; }
.live-dot { display: inline-block; width: .5rem; height: .5rem; border-radius: 50%; background: var(--faint); margin-right: .4rem; vertical-align: middle; }

.section-title { font-family: var(--font-serif); font-weight: 400; font-size: clamp(1.8rem, 3.4vw, 2.6rem); margin: 3.5rem 0 .4rem; letter-spacing: -.01em; }
.section-sub { color: var(--muted); margin: 0 0 1.5rem; max-width: 40rem; }

.modules { display: grid; grid-template-columns: repeat(auto-fill, minmax(min(100%, 19rem), 1fr)); gap: 1rem; }
.mod { border: 1px solid var(--line); border-radius: var(--r-lg); background: var(--surface); padding: 1.2rem 1.25rem 1rem; display: flex; flex-direction: column; }
.mod__n { font-family: var(--font-mono); font-size: .72rem; color: var(--accent); font-weight: 600; letter-spacing: .08em; }
.mod h3 { margin: .25rem 0 .3rem; font-size: 1.15rem; font-weight: 650; letter-spacing: -.01em; }
.mod p { margin: 0 0 .8rem; font-size: .88rem; color: var(--muted); }
.mod ol { list-style: none; padding: 0; margin: auto 0 0; display: grid; gap: .1rem; border-top: 1px solid var(--line); padding-top: .6rem; }
.mod li a { display: flex; justify-content: space-between; gap: .5rem; padding: .35rem .3rem; border-radius: 6px; text-decoration: none; font-size: .88rem; color: var(--text-2); }
.mod li a:hover { background: var(--surface-2); color: var(--text); }
.mod li a em { font-style: normal; font-family: var(--font-mono); font-size: .72rem; color: var(--faint); }
.mod li a em.ok { color: var(--good); }

.how { display: grid; grid-template-columns: repeat(auto-fit, minmax(min(100%, 14rem), 1fr)); gap: 1rem; }
.how > div { border-top: 1px solid var(--line-2); padding-top: 1rem; }
.how b { display: block; font-size: 1rem; margin-bottom: .25rem; }
.how span { font-size: .88rem; color: var(--muted); }

/* ---------- Explorer ---------- */
.ex-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(min(100%, 24rem), 1fr)); gap: 1rem; }
.ex-grid .fig { margin: 0; display: flex; flex-direction: column; }
.ex-grid .fig__cap { margin-top: auto; padding-top: .5rem; }
.ex-controls { display: flex; flex-wrap: wrap; gap: .75rem; align-items: center; margin: 0 0 1.4rem; }
.ex-group { font-size: .75rem; letter-spacing: .12em; text-transform: uppercase; color: var(--muted); font-weight: 600; margin: 2rem 0 .8rem; grid-column: 1 / -1; }

/* ---------- Glossary ---------- */
.search { width: 100%; padding: .85rem 1.1rem .85rem 2.8rem; border-radius: 999px; border: 1px solid var(--line-2); background: var(--surface) url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%238a909c' stroke-width='2'%3E%3Ccircle cx='11' cy='11' r='7'/%3E%3Cpath d='M20 20l-3.5-3.5'/%3E%3C/svg%3E") no-repeat 1rem center / 1.1rem; color: var(--text); font: inherit; font-size: .95rem; }
.search:focus { outline: none; border-color: var(--accent); }
.gloss { display: grid; gap: .6rem; margin-top: 1.5rem; }
.gloss__item { border: 1px solid var(--line); border-radius: var(--r-md); background: var(--surface); padding: .95rem 1.1rem; scroll-margin-top: 5rem; }
.gloss__item:target { border-color: var(--accent); }
.gloss__item h3 { margin: 0 0 .25rem; font-size: 1rem; font-weight: 650; display: flex; flex-wrap: wrap; align-items: baseline; gap: .5rem; }
.gloss__item h3 small { font-weight: 400; font-size: .75rem; color: var(--faint); font-family: var(--font-mono); }
.gloss__item p { margin: 0; font-size: .92rem; color: var(--text-2); }
.gloss__item a { font-size: .8rem; color: var(--accent); }

/* ---------- Settings ---------- */
.set-row { display: flex; justify-content: space-between; align-items: center; gap: 1rem; padding: 1rem 0; border-bottom: 1px solid var(--line); }
.set-row p { margin: .15rem 0 0; font-size: .85rem; color: var(--muted); }
.switch { position: relative; width: 2.9rem; height: 1.65rem; flex: none; }
.switch input { opacity: 0; width: 100%; height: 100%; margin: 0; cursor: pointer; position: absolute; z-index: 1; }
.switch span { position: absolute; inset: 0; border-radius: 999px; background: var(--surface-3); border: 1px solid var(--line-2); transition: background var(--t-fast); }
.switch span::after { content: ""; position: absolute; top: 2px; left: 2px; width: calc(1.65rem - 6px); height: calc(1.65rem - 6px); border-radius: 50%; background: var(--text); transition: transform var(--t-fast) var(--ease); }
.switch input:checked + span { background: var(--accent); border-color: var(--accent); }
.switch input:checked + span::after { transform: translateX(1.25rem); background: #fff; }

/* toast */
.toast { position: fixed; left: 50%; bottom: 1.5rem; transform: translate(-50%, 150%); z-index: 80; background: var(--surface-3); border: 1px solid var(--line-2); color: var(--text); padding: .75rem 1.1rem; border-radius: 999px; font-size: .88rem; box-shadow: var(--shadow); transition: transform var(--t-med) var(--ease); max-width: calc(100vw - 2rem); text-align: center; }
.toast.is-on { transform: translate(-50%, 0); }

/* ---------- Responsive ---------- */
@media (max-width: 1100px) {
  :root { --rail-w: 18rem; }
}
@media (max-width: 1023px) {
  .shell { grid-template-columns: minmax(0, 1fr); }
  .rail { position: fixed; left: 0; top: 0; bottom: 0; width: min(21rem, 86vw); z-index: 50; transform: translateX(-102%); transition: transform var(--t-med) var(--ease); background: var(--bg-2); box-shadow: 20px 0 60px rgba(0,0,0,.4); }
  .rail.is-open { transform: none; }
  .icon-btn.rail__close { display: inline-grid; }
  .icon-btn.topbar__menu { display: inline-grid; }
  .fig--bleed { margin-inline: 0; }
}
@media (max-width: 820px) {
  .hero { grid-template-columns: 1fr; }
  .pipe-panel { grid-template-columns: minmax(0, 1fr); }
  .quiz-cta { grid-template-columns: 1fr; }
  .quiz-cta .btn { justify-self: start; }
}
@media (max-width: 640px) {
  .story { grid-template-columns: 1fr; }
  .sol-grid { grid-template-columns: 1fr; }
  .pipe { grid-template-columns: 1fr; }
  .pipe button { display: grid; grid-template-columns: auto 1fr; column-gap: .6rem; align-items: baseline; }
  .pipe button .s { grid-column: 1 / -1; }
  .tiles { gap: .3rem; }
  .pill-link { display: none; }
  .next-lesson { flex-direction: column; }
  .next-lesson a, .next-lesson button { max-width: none; }
  .quiz-nav__hint { display: none; }
  .quiz-stage { min-height: 24rem; }
  .fig { padding: .85rem .75rem .75rem; border-radius: var(--r-md); }
  .lab__body { padding: 1rem .85rem 1.1rem; }
  .prob { grid-template-columns: 6.5rem 1fr 3rem; font-size: .78rem; }
  .adv { height: 9rem; }
  .tl-list li { grid-template-columns: 1fr; gap: .1rem; }
}
@media (min-width: 1600px) {
  :root { --read-w: 46rem; --wide-w: 66rem; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: 1ms !important; transition-duration: 1ms !important; }
}

@media print {
  .rail, .topbar, .quiz, .lab__bar { display: none !important; }
  .shell { display: block; }
}

/* ---------- Standalone home (no sidebar) ---------- */
.topbar__brand, .topbar__start { display: none; }
body.is-home .shell { grid-template-columns: minmax(0, 1fr); }
body.is-home .rail, body.is-home .scrim { display: none; }
body.is-home .icon-btn.topbar__menu, body.is-home .topbar__crumb { display: none; }
body.is-home .topbar__brand { display: inline-flex; margin-right: auto; }
body.is-home .topbar__start { display: inline-flex; }
body.is-home .topbar { border-bottom-color: transparent; }
body.is-home .brand__text { font-size: 1.4rem; }

.home { max-width: 78rem; margin-inline: auto; }
.home .hero { padding-top: clamp(1rem, 5vw, 4.5rem); }
.home .display { font-size: clamp(2.8rem, 7vw, 6rem); }
.hero__note { margin-top: 1.2rem; font-size: .82rem; color: var(--faint); }

.big-numbers { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); margin: clamp(2rem, 5vw, 4rem) 0; }
.big-numbers > div { padding: 1.6rem 1.2rem; }
.big-numbers > div + div { box-shadow: -1px 0 0 var(--line); }
.big-numbers b { display: block; font-family: var(--font-serif); font-weight: 400; font-size: clamp(2.4rem, 4.5vw, 3.8rem); line-height: 1; letter-spacing: -.02em; }
.big-numbers span { display: block; margin-top: .5rem; font-size: .85rem; color: var(--muted); line-height: 1.4; }

.home-h2 { font-family: var(--font-serif); font-weight: 400; font-size: clamp(2rem, 4vw, 3.2rem); line-height: 1.08; letter-spacing: -.015em; margin: 0 0 .6rem; max-width: 40rem; }
.home-sub { color: var(--muted); margin: 0 0 2rem; max-width: 38rem; font-size: 1.02rem; }
.home-sec { margin: clamp(3.5rem, 8vw, 7rem) 0; }

.qs { display: grid; grid-template-columns: repeat(auto-fill, minmax(min(100%, 22rem), 1fr)); gap: 1px; background: var(--line); border: 1px solid var(--line); border-radius: var(--r-lg); overflow: hidden; }
.qs > div { background: var(--bg); padding: 1.5rem 1.4rem; }
.qs i { display: block; font-style: normal; font-family: var(--font-mono); font-size: .72rem; color: var(--faint); margin-bottom: .6rem; }
.qs p { margin: 0; font-family: var(--font-serif); font-size: 1.45rem; line-height: 1.25; }

.facts { display: grid; grid-template-columns: repeat(6, minmax(0, 1fr)); gap: 1rem; }
.fact { grid-column: span 2; border: 1px solid var(--line); border-radius: var(--r-lg); background: var(--surface); padding: 1.4rem 1.4rem 1.3rem; display: flex; flex-direction: column; gap: .6rem; }
.fact--wide { grid-column: span 3; }
.fact__n { font-family: var(--font-serif); font-size: clamp(2.2rem, 3.6vw, 3rem); line-height: 1; letter-spacing: -.02em; }
.fact p { margin: 0; color: var(--text-2); font-size: .95rem; }
.fact small { margin-top: auto; font-size: .75rem; color: var(--faint); }

.invite { text-align: center; padding: clamp(3rem, 7vw, 6rem) 1rem; border-top: 1px solid var(--line); }
.invite .home-h2 { margin-inline: auto; }
.invite .home-sub { margin-inline: auto; }
.invite__meta { display: flex; justify-content: center; gap: 1.5rem; flex-wrap: wrap; font-size: .85rem; color: var(--muted); margin-bottom: 1.8rem; }

@media (max-width: 900px) {
  .big-numbers { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .big-numbers > div:nth-child(3) { box-shadow: none; }
  .big-numbers > div:nth-child(n+3) { border-top: 1px solid var(--line); }
  .facts { grid-template-columns: minmax(0, 1fr); }
  .fact, .fact--wide { grid-column: auto; }
}
@media (max-width: 640px) {
  body.is-home .topbar__start { display: none; }
}

/* ==========================================================================
   Animated illustrations (anim.js). Paused until scrolled into view.
   ========================================================================== */
.anim-fig { margin: 2rem 0 2.2rem; border: 1px solid var(--line); border-radius: var(--r-xl); background: radial-gradient(40rem 20rem at 50% 0%, color-mix(in srgb, var(--accent) 6%, transparent), transparent 70%), var(--surface); padding: clamp(.8rem, 2.5vw, 1.6rem); overflow: hidden; }
.anim-fig figcaption { font-size: .84rem; color: var(--muted); margin-top: .8rem; line-height: 1.5; text-align: center; max-width: 40rem; margin-inline: auto; }
.anim-fig figcaption b { color: var(--text-2); }
.anim svg { width: 100%; height: auto; overflow: visible; }
.anim:not(.in-view) *, .anim:not(.in-view) { animation-play-state: paused !important; }
.a-t1 { font: 600 13px var(--font-sans); fill: var(--text); }
.a-t2 { font: 500 11px var(--font-mono); fill: var(--muted); }
.a-big { font: 400 38px var(--font-serif); fill: var(--text); }

/* loop */
.a-loop__trail { stroke-dasharray: 100; stroke-dashoffset: 100; animation: a-draw 6s linear infinite; }
.a-loop__halo { opacity: 0; animation: a-halo 6s ease-in-out infinite; animation-delay: calc(var(--i) * 1.5s - .25s); }
.a-loop__grow { stroke-dasharray: 100; stroke-dashoffset: 100; animation: a-draw 6s ease-in-out infinite; }
@keyframes a-draw { to { stroke-dashoffset: 0; } }
@keyframes a-halo { 0%, 100% { opacity: 0; } 4% { opacity: 1; } 20% { opacity: 0; } }

/* tree */
.a-tree__p { fill: none; stroke: var(--line-2); stroke-width: 1.6; stroke-dasharray: 100; stroke-dashoffset: 100; animation: a-tree 9s ease-in-out infinite; animation-delay: calc(var(--i) * .06s); }
@keyframes a-tree { 0% { stroke-dashoffset: 100; } 25% { stroke-dashoffset: 0; stroke: var(--line-2); stroke-width: 1.6; opacity: 1; } 45%, 85% { stroke-dashoffset: 0; } 92%, 100% { stroke-dashoffset: 0; opacity: 0; } }
.a-tree__p.is-ok { animation-name: a-tree-ok; }
.a-tree__p.is-no { animation-name: a-tree-no; }
@keyframes a-tree-ok { 0% { stroke-dashoffset: 100; } 25% { stroke-dashoffset: 0; stroke: var(--line-2); stroke-width: 1.6; } 45%, 85% { stroke-dashoffset: 0; stroke: var(--good); stroke-width: 4; opacity: 1; } 95%, 100% { stroke-dashoffset: 0; opacity: 0; stroke: var(--good); } }
@keyframes a-tree-no { 0% { stroke-dashoffset: 100; } 25% { stroke-dashoffset: 0; stroke: var(--line-2); stroke-width: 1.6; opacity: 1; } 45%, 85% { stroke-dashoffset: 0; stroke: var(--bad); stroke-width: 1; opacity: .3; } 95%, 100% { stroke-dashoffset: 0; opacity: 0; } }
.a-tree__end { opacity: 0; animation: a-end 9s ease infinite; animation-delay: calc(var(--i) * .06s); }
.a-tree__end circle { fill: var(--surface-3); }
.a-tree__end text { font: 700 10px var(--font-sans); }
.a-tree__end.is-ok circle { fill: var(--good-soft); stroke: var(--good); } .a-tree__end.is-ok text { fill: var(--good); }
.a-tree__end.is-no circle { fill: var(--bad-soft); stroke: var(--bad); } .a-tree__end.is-no text { fill: var(--bad); }
@keyframes a-end { 0%, 24% { opacity: 0; } 30%, 88% { opacity: 1; } 96%, 100% { opacity: 0; } }
.a-tree__verdict { opacity: 0; animation: a-verdict 9s ease infinite; }
@keyframes a-verdict { 0%, 34% { opacity: 0; } 40%, 86% { opacity: 1; } 94%, 100% { opacity: 0; } }

/* boat */
.a-boat__coin { animation: a-coin 2.6s linear infinite; animation-delay: calc(var(--i) * .65s); }
@keyframes a-coin { 0%, 8% { opacity: 0; } 30%, 100% { opacity: 1; } }

.a-boat__bar { transform-box: fill-box; transform-origin: left center; animation: a-bar 7s ease-in infinite; }
@keyframes a-bar { from { transform: scaleX(0); } to { transform: scaleX(1); } }

/* collapse */
.a-collapse__bar { fill: var(--accent); transform-box: fill-box; transform-origin: 50% 100%; animation: 9s ease-in-out infinite; }
.a-collapse__bar.b0 { animation-name: c0; } .a-collapse__bar.b1 { animation-name: c1; } .a-collapse__bar.b2 { animation-name: c2; } .a-collapse__bar.b3 { animation-name: c3; } .a-collapse__bar.b4 { animation-name: c4; }
@keyframes c0 { 0%, 28% { transform: scaleY(.34); } 36%, 61% { transform: scaleY(.62); } 69%, 94% { transform: scaleY(.98); fill: var(--bad); } 100% { transform: scaleY(.34); } }
@keyframes c1 { 0%, 28% { transform: scaleY(.28); } 36%, 61% { transform: scaleY(.22); } 69%, 94% { transform: scaleY(.02); } 100% { transform: scaleY(.28); } }
@keyframes c2 { 0%, 28% { transform: scaleY(.22); } 36%, 61% { transform: scaleY(.11); } 69%, 94% { transform: scaleY(.01); } 100% { transform: scaleY(.22); } }
@keyframes c3 { 0%, 28% { transform: scaleY(.12); } 36%, 61% { transform: scaleY(.04); } 69%, 94% { transform: scaleY(.005); } 100% { transform: scaleY(.12); } }
@keyframes c4 { 0%, 28% { transform: scaleY(.05); } 36%, 61% { transform: scaleY(.01); } 69%, 94% { transform: scaleY(0); } 100% { transform: scaleY(.05); } }
.a-collapse__labels text { opacity: 0; animation: 9s ease infinite; }
.a-collapse__labels .l0 { animation-name: l0; } .a-collapse__labels .l1 { animation-name: l1; } .a-collapse__labels .l2 { animation-name: l2; }
@keyframes l0 { 0%, 28% { opacity: 1; } 33%, 97% { opacity: 0; } 100% { opacity: 1; } }
@keyframes l1 { 0%, 31% { opacity: 0; } 36%, 61% { opacity: 1; } 66%, 100% { opacity: 0; } }
@keyframes l2 { 0%, 64% { opacity: 0; } 69%, 94% { opacity: 1; } 99%, 100% { opacity: 0; } }

/* eras */
.a-eras__line { stroke-dasharray: 100; stroke-dashoffset: 100; animation: a-draw 3.2s cubic-bezier(.5,0,.2,1) forwards; }
.a-eras__pt { opacity: 0; animation: a-pop .5s var(--ease) forwards; animation-delay: calc(var(--i) * .38s + .2s); transform-box: fill-box; transform-origin: center; }
@keyframes a-pop { from { opacity: 0; transform: translateY(6px); } to { opacity: 1; transform: none; } }

/* finale */
.a-fin__star { fill: var(--text); opacity: .15; animation: a-twinkle 3.4s ease-in-out infinite; animation-delay: calc(var(--i) * .31s); }
@keyframes a-twinkle { 50% { opacity: .8; } }
.a-fin__poly { stroke-dasharray: 100; stroke-dashoffset: 100; animation: a-draw 4s var(--ease) forwards .4s; }
.a-fin__node { fill: var(--surface-3); stroke: var(--line-2); animation: a-node 5s ease-in-out infinite; animation-delay: calc(var(--i) * .3125s); }
.a-fin__node.is-ok { fill: var(--good); stroke: none; }
@keyframes a-node { 0%, 100% { r: 4; } 8% { r: 7; } 20% { r: 4; } }
.a-fin__txt { font: italic 400 46px var(--font-serif); fill: var(--text); }

/* history list */
.hist { list-style: none; padding: 0 !important; margin: 1.6rem 0 2rem; position: relative; }
.hist::before { content: ""; position: absolute; left: 4.6rem; top: .4rem; bottom: .4rem; width: 1px; background: linear-gradient(var(--violet), var(--flash), var(--accent)); }
.hist li { display: grid; grid-template-columns: 4rem 1fr; gap: 1.4rem; margin: 0 0 1.4rem !important; position: relative; }
.hist li::after { content: ""; position: absolute; left: calc(4.6rem - 5px); top: .45rem; width: 11px; height: 11px; border-radius: 50%; background: var(--bg); border: 2px solid var(--flash); }
.hist b { font-family: var(--font-mono); font-size: .85rem; color: var(--accent); text-align: right; padding-top: .1rem; }
.hist h4 { margin: 0 0 .2rem; font-size: 1rem; font-weight: 650; color: var(--text); }
.hist p { margin: 0 !important; font-size: .93rem; }

/* stories & insider notes */
.callout--tale { background: var(--surface-2); }
.callout--tale .callout__label { color: var(--warn); }
.callout--tale h4 { font-family: var(--font-serif); font-weight: 400; font-size: 1.55rem; line-height: 1.2; margin: 0 0 .6rem; color: var(--text); }
.callout--secret { background: linear-gradient(135deg, color-mix(in srgb, var(--violet) 10%, transparent), transparent 60%), var(--surface); }
.callout--secret .callout__label { color: var(--violet); }

/* resources */
.path { display: grid; gap: 1rem; margin: 1.5rem 0 2rem; }
.path__lvl { border: 1px solid var(--line); border-radius: var(--r-lg); background: var(--surface); padding: 1.1rem 1.3rem; }
.path__lvl h4 { margin: 0 0 .1rem; font-size: 1.05rem; }
.path__lvl > span { font-size: .8rem; color: var(--faint); font-family: var(--font-mono); }
.path__lvl ul { margin: .7rem 0 0 !important; }
.finale { text-align: center; margin: 3rem 0 1rem; }
.finale h2 { font-family: var(--font-serif) !important; font-size: clamp(2.4rem, 6vw, 4.2rem) !important; line-height: 1.05 !important; margin: 1.5rem 0 .8rem !important; }
.finale h2 em { color: var(--accent); }
.finale p { max-width: 34rem; margin-inline: auto !important; }

@media (max-width: 640px) {
  .hist::before { left: 3.6rem; }
  .hist li { grid-template-columns: 3rem 1fr; gap: 1.2rem; }
  .hist li::after { left: calc(3.6rem - 5px); }
  .a-t2 { font-size: 13px; } .a-t1 { font-size: 15px; }
}
@media (prefers-reduced-motion: reduce) {
  .anim * { animation: none !important; }
  .a-eras__pt, .a-tree__end, .a-tree__verdict { opacity: 1 !important; }
  .a-eras__line, .a-tree__p, .a-fin__poly, .a-loop__trail, .a-loop__grow { stroke-dashoffset: 0 !important; }
}
.loop-sec { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: clamp(1.5rem, 5vw, 5rem); align-items: center; }
.loop-sec .anim { max-width: 34rem; justify-self: center; width: 100%; }
@media (max-width: 900px) { .loop-sec { grid-template-columns: minmax(0, 1fr); } }
.prose a.btn { color: var(--text); text-decoration: none; }
.prose a.btn--primary { color: var(--accent-ink); }

/* footer */
.site-foot { display: flex; flex-wrap: wrap; justify-content: center; align-items: center; gap: .4rem .7rem; padding: 1.6rem var(--gutter) 2rem; border-top: 1px solid var(--line); font-size: .8rem; color: var(--faint); text-align: center; }
.site-foot strong { color: var(--text-2); font-weight: 600; }
.site-foot a { color: var(--muted); text-underline-offset: 3px; }
.site-foot a:hover { color: var(--text); }
.main { padding-bottom: 4rem; }
@media (max-width: 480px) { .site-foot__sep { display: none; } .site-foot { flex-direction: column; } }