/* SortLab interface */
*, *::before, *::after { box-sizing: border-box; }

:root {
    color-scheme: light;
    --page: #f4f6f2;
    --page-soft: #eef2ec;
    --surface: #ffffff;
    --surface-raised: #ffffff;
    --ink: #16212a;
    --ink-soft: #34434d;
    --muted: #66747c;
    --faint: #64737a;
    --line: #d9dfda;
    --line-strong: #c4cec7;
    --primary: #5148c8;
    --primary-dark: #3931a4;
    --primary-soft: #eceafe;
    --primary-contrast: #ffffff;
    --focus: #332ba5;
    --teal: #167e75;
    --teal-soft: #dff3ee;
    --coral: #df6d53;
    --coral-soft: #fae7e1;
    --coral-text: #993c29;
    --gold: #bd7a21;
    --good: #1b7b56;
    --good-soft: #e0f2e9;
    --danger: #b74444;
    --danger-soft: #f9e4e4;
    --lab: #111a23;
    --lab-raised: #182530;
    --lab-soft: #22313d;
    --lab-line: #344653;
    --lab-text: #f3f7f7;
    --lab-muted: #aebcc4;
    --shadow-sm: 0 1px 2px rgba(19, 32, 40, .05), 0 4px 12px rgba(19, 32, 40, .04);
    --shadow-md: 0 16px 44px rgba(19, 32, 40, .09);
    --shadow-lg: 0 28px 80px rgba(19, 32, 40, .16);
    --radius-sm: 9px;
    --radius: 16px;
    --radius-lg: 24px;
    --shell: min(1240px, calc(100% - 48px));
    --font-sans: ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI Variable", "Segoe UI", sans-serif;
    --font-mono: "JetBrains Mono", "SFMono-Regular", Consolas, monospace;
}

:root[data-theme="dark"] {
    color-scheme: dark;
    --page: #0d141b;
    --page-soft: #101a22;
    --surface: #151f28;
    --surface-raised: #1a2630;
    --ink: #eff5f3;
    --ink-soft: #c6d2d1;
    --muted: #96a6a8;
    --faint: #a7b4b6;
    --line: #2c3b43;
    --line-strong: #3d5059;
    --primary: #8b83f4;
    --primary-dark: #aaa5ff;
    --primary-soft: #29284e;
    --primary-contrast: #101525;
    --focus: #9af5e8;
    --teal: #55c7b9;
    --teal-soft: #193e3b;
    --coral: #f19379;
    --coral-soft: #492b27;
    --coral-text: #ffb29e;
    --gold: #e1aa59;
    --good: #6ed5aa;
    --good-soft: #173c2f;
    --danger: #ff9898;
    --danger-soft: #4a2629;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, .25), 0 4px 12px rgba(0, 0, 0, .12);
    --shadow-md: 0 16px 44px rgba(0, 0, 0, .26);
    --shadow-lg: 0 28px 80px rgba(0, 0, 0, .35);
}

html { scroll-behavior: smooth; scroll-padding-top: 88px; }
html.sortlab-loading body { opacity: 0; }
body { margin: 0; min-width: 320px; min-height: 100vh; background: var(--page); color: var(--ink); font-family: var(--font-sans); font-size: 16px; line-height: 1.6; text-rendering: optimizeLegibility; transition: opacity .12s ease; }
button, input, select { font: inherit; }
button, a { -webkit-tap-highlight-color: transparent; }
button { color: inherit; }
a { color: inherit; }
img { max-width: 100%; }
h1, h2, h3, h4, p { margin-top: 0; }
h1, h2, h3 { letter-spacing: -.035em; line-height: 1.08; }
p { color: var(--muted); }
code, kbd { font-family: var(--font-mono); }
button:focus-visible, a:focus-visible, input:focus-visible, select:focus-visible, [tabindex]:focus-visible { outline: 3px solid var(--focus); outline-offset: 3px; }
[hidden] { display: none !important; }

.sr-only { position: absolute !important; width: 1px !important; height: 1px !important; padding: 0 !important; margin: -1px !important; overflow: hidden !important; clip: rect(0, 0, 0, 0) !important; white-space: nowrap !important; border: 0 !important; }
.skip-link { position: fixed; z-index: 9999; top: 8px; left: 8px; transform: translateY(-150%); padding: 10px 16px; border-radius: 8px; background: var(--ink); color: var(--surface); text-decoration: none; font-weight: 700; }
.skip-link:focus { transform: none; }
.section-shell { width: var(--shell); margin-inline: auto; }

/* Navigation */
.site-header { position: sticky; z-index: 1000; top: 0; border-bottom: 1px solid color-mix(in srgb, var(--line) 82%, transparent); background: color-mix(in srgb, var(--page) 90%, transparent); backdrop-filter: blur(18px); }
.nav-shell { width: var(--shell); height: 72px; margin-inline: auto; display: flex; align-items: center; justify-content: space-between; }
.brand { display: inline-flex; align-items: center; gap: 11px; color: var(--ink); font-size: 1.12rem; font-weight: 800; letter-spacing: -.035em; text-decoration: none; }
.brand-mark { width: 29px; height: 29px; display: inline-flex; align-items: flex-end; justify-content: center; gap: 2px; padding: 5px; border-radius: 8px; background: var(--ink); }
.brand-mark i { width: 3px; border-radius: 3px 3px 1px 1px; background: var(--page); }
.brand-mark i:nth-child(1) { height: 7px; }
.brand-mark i:nth-child(2) { height: 13px; }
.brand-mark i:nth-child(3) { height: 9px; }
.brand-mark i:nth-child(4) { height: 17px; }
.primary-nav { display: flex; align-items: center; gap: 4px; }
.primary-nav > a, .theme-toggle { min-height: 40px; display: inline-flex; align-items: center; justify-content: center; padding: 8px 13px; border: 0; border-radius: 9px; background: transparent; color: var(--muted); font-size: .9rem; font-weight: 650; text-decoration: none; cursor: pointer; }
.primary-nav > a:hover, .primary-nav > a[aria-current="page"] { background: var(--surface); color: var(--ink); box-shadow: var(--shadow-sm); }
.primary-nav > .portfolio-link { margin-right: 6px; border: 1px solid var(--line); color: var(--ink); }
.theme-toggle { width: 42px; margin-left: 6px; border: 1px solid var(--line); background: var(--surface); }
.theme-toggle span { font-size: .72rem; }
.nav-toggle { display: none; min-height: 40px; padding: 8px 12px; border: 1px solid var(--line); border-radius: 9px; background: var(--surface); cursor: pointer; }

/* Shared */
.eyebrow { display: flex; align-items: center; gap: 10px; margin-bottom: 16px; color: var(--teal); font-size: .74rem; font-weight: 800; letter-spacing: .115em; text-transform: uppercase; }
.eyebrow > span { width: 25px; height: 2px; background: currentColor; }
.eyebrow.light { color: #64d2c2; }
.button { min-height: 48px; display: inline-flex; align-items: center; justify-content: center; gap: 12px; padding: 11px 18px; border: 1px solid transparent; border-radius: 10px; font-size: .92rem; font-weight: 760; text-decoration: none; cursor: pointer; transition: transform .18s ease, background .18s ease, border .18s ease; }
.button:hover { transform: translateY(-2px); }
.button.primary { background: var(--primary); color: var(--primary-contrast); box-shadow: 0 8px 22px color-mix(in srgb, var(--primary) 25%, transparent); }
.button.primary:hover { background: var(--primary-dark); }
.button.secondary { border-color: var(--line-strong); background: var(--surface); color: var(--ink); }
.text-link { display: inline-flex; gap: 8px; align-items: center; color: var(--primary); font-weight: 760; text-decoration: none; }
.text-link:hover { text-decoration: underline; text-underline-offset: 4px; }
.section-heading { display: grid; grid-template-columns: minmax(0, 1fr) minmax(280px, 440px); gap: 80px; align-items: end; margin-bottom: 42px; }
.section-heading.compact { display: block; max-width: 700px; }
.section-heading h2 { max-width: 720px; margin-bottom: 0; font-size: clamp(2rem, 4vw, 3.35rem); font-weight: 760; }
.section-heading > p { margin: 0; font-size: 1.02rem; }

/* Home hero */
.home-hero { width: min(1360px, calc(100% - 32px)); min-height: 680px; margin: 16px auto 0; padding: clamp(54px, 7vw, 94px) clamp(24px, 6vw, 84px); display: grid; grid-template-columns: minmax(0, 1.02fr) minmax(460px, .98fr); gap: clamp(48px, 7vw, 100px); align-items: center; overflow: hidden; position: relative; border: 1px solid var(--line); border-radius: 28px; background: linear-gradient(135deg, var(--surface) 0%, color-mix(in srgb, var(--primary-soft) 34%, var(--surface)) 100%); box-shadow: var(--shadow-sm); }
.home-hero::after { content: ""; position: absolute; width: 430px; height: 430px; right: -180px; top: -240px; border-radius: 50%; background: color-mix(in srgb, var(--teal-soft) 70%, transparent); }
.hero-copy { position: relative; z-index: 1; }
.hero-copy h1 { max-width: 760px; margin-bottom: 25px; font-size: clamp(3.25rem, 6.2vw, 6.25rem); line-height: .94; font-weight: 770; letter-spacing: -.07em; }
.hero-copy h1 em { color: var(--primary); font-family: Georgia, serif; font-weight: 500; }
.hero-lede { max-width: 670px; margin-bottom: 30px; font-size: clamp(1.06rem, 1.5vw, 1.24rem); line-height: 1.65; }
.hero-lede strong { color: var(--ink-soft); }
.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; }
.hero-proof { display: flex; flex-wrap: wrap; gap: 24px; margin-top: 38px; padding-top: 24px; border-top: 1px solid var(--line); }
.hero-proof span { display: flex; align-items: baseline; gap: 7px; color: var(--muted); font-size: .83rem; font-weight: 650; }
.hero-proof b { color: var(--ink); font-family: var(--font-mono); font-size: 1rem; }
.continue-card { max-width: 450px; display: grid; grid-template-columns: auto 1fr auto; gap: 13px; align-items: center; margin-top: 28px; padding: 13px 15px; border: 1px solid var(--line); border-radius: 12px; background: color-mix(in srgb, var(--surface) 86%, transparent); color: var(--ink); text-decoration: none; }
.continue-card:hover { border-color: var(--primary); }
.continue-card > span:nth-child(2) { display: flex; flex-direction: column; }
.continue-card small { color: var(--muted); font-size: .72rem; }
.continue-icon { width: 34px; height: 34px; display: grid; place-items: center; border-radius: 9px; background: var(--primary-soft); color: var(--primary); font-weight: 800; }

.hero-demo { min-width: 0; position: relative; z-index: 2; }
.demo-window { padding: 0 22px 20px; overflow: hidden; border: 1px solid #30414d; border-radius: 20px; background: var(--lab); color: var(--lab-text); box-shadow: var(--shadow-lg); transform: rotate(1.2deg); }
.demo-chrome { height: 50px; margin-inline: -22px; padding-inline: 18px; display: flex; align-items: center; gap: 6px; border-bottom: 1px solid #2b3b47; background: #16212b; }
.demo-chrome > span { width: 8px; height: 8px; border-radius: 50%; background: #53636d; }
.demo-chrome > span:first-child { background: #ef7d67; }
.demo-chrome p { flex: 1; margin: 0 0 0 8px; color: #8999a2; font-family: var(--font-mono); font-size: .68rem; }
.demo-chrome b { padding: 3px 7px; border: 1px solid #2a6a62; border-radius: 999px; color: #6fe0cf; font-size: .6rem; letter-spacing: .08em; text-transform: uppercase; }
.demo-context { display: flex; justify-content: space-between; align-items: start; gap: 20px; margin-top: 20px; }
.demo-context > div { display: flex; flex-direction: column; }
.demo-context small { color: #78909c; font-size: .65rem; letter-spacing: .08em; text-transform: uppercase; }
.demo-context strong { font-size: .92rem; }
.demo-context > span { color: #91a3ad; font-family: var(--font-mono); font-size: .66rem; }
.mini-bars { height: 260px; display: flex; gap: 8px; align-items: flex-end; padding: 35px 4px 0; border-bottom: 1px solid #344653; }
.mini-bar { flex: 1; height: var(--bar-height); min-width: 10px; position: relative; border: 1px solid #607a89; border-radius: 5px 5px 1px 1px; background: #354b59; transition: height .28s ease, background .2s ease, transform .2s ease; }
.mini-bar span { width: 100%; position: absolute; top: -22px; left: 0; color: #aebdc5; font-family: var(--font-mono); font-size: .62rem; font-style: normal; text-align: center; }
.mini-bar.is-comparing { border-color: #ffd18a; background: repeating-linear-gradient(135deg, #9b641a 0 6px, #bc7924 6px 12px); }
.mini-bar.is-moving { border-color: #bc9cff; background: #795cc4; transform: translateY(-7px); }
.mini-bar.is-sorted { border-color: #72d8ad; background: #267f62; }
.demo-narration { min-height: 57px; margin-top: 17px; padding: 11px 13px; border-left: 2px solid #5dd5c4; background: #182732; color: #c1cdd3; font-size: .78rem; }
.demo-footer { display: flex; flex-wrap: wrap; gap: 13px; align-items: center; margin-top: 14px; color: #82949e; font-size: .63rem; }
.demo-footer > div { display: flex; gap: 5px; align-items: center; }
.demo-footer button { margin-left: auto; padding: 5px 9px; border: 1px solid #3a4b56; border-radius: 6px; background: transparent; color: #b9c7cd; font-size: .65rem; cursor: pointer; }
.legend-dot { width: 8px; height: 8px; border-radius: 2px; background: #536d7c; }
.legend-dot.compare { background: #d28c2e; }
.legend-dot.move { background: #8969d5; }
.legend-dot.sorted { background: #329a76; }
.floating-note { max-width: 220px; display: flex; gap: 10px; align-items: start; position: absolute; padding: 11px 13px; border: 1px solid var(--line); border-radius: 12px; background: color-mix(in srgb, var(--surface) 94%, transparent); box-shadow: var(--shadow-md); backdrop-filter: blur(10px); }
.floating-note span { color: var(--primary); font-family: var(--font-mono); font-size: .65rem; font-weight: 800; }
.floating-note p { margin: 0; color: var(--muted); font-size: .68rem; line-height: 1.45; }
.floating-note strong { color: var(--ink); }
.note-one { left: -45px; top: 70px; }
.note-two { right: -38px; bottom: 46px; }

.learning-principles { padding-block: 110px 120px; }
.principle-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px; margin-top: 45px; }
.principle-grid article { min-height: 230px; padding: 26px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); box-shadow: var(--shadow-sm); }
.principle-number { display: inline-flex; margin-bottom: 48px; color: var(--primary); font-family: var(--font-mono); font-size: .72rem; font-weight: 800; }
.principle-grid h3 { margin-bottom: 11px; font-size: 1.28rem; }
.principle-grid p { margin: 0; font-size: .91rem; }

/* Learning path */
.learning-path { padding-bottom: 130px; }
.path-list { border-top: 1px solid var(--line-strong); }
.path-stage { display: grid; grid-template-columns: 90px minmax(220px, .8fr) minmax(440px, 1.35fr); gap: 34px; padding: 36px 0; border-bottom: 1px solid var(--line); }
.path-index { display: flex; flex-direction: column; align-items: center; gap: 12px; }
.path-index span { width: 46px; height: 46px; display: grid; place-items: center; border: 1px solid var(--line-strong); border-radius: 50%; background: var(--surface); color: var(--primary); font-family: var(--font-mono); font-size: .72rem; font-weight: 800; }
.path-index i { width: 1px; flex: 1; min-height: 32px; background: var(--line); }
.path-copy > p { margin-bottom: 6px; color: var(--teal); font-size: .7rem; font-weight: 800; letter-spacing: .09em; text-transform: uppercase; }
.path-copy h3 { margin-bottom: 12px; font-size: 1.55rem; }
.path-copy > span { color: var(--muted); font-size: .91rem; }
.path-lessons { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 9px; align-content: start; }
.path-lessons a { min-height: 58px; display: grid; grid-template-columns: auto 1fr auto; gap: 10px; align-items: center; padding: 10px 13px; border: 1px solid var(--line); border-radius: 10px; background: var(--surface); text-decoration: none; }
.path-lessons a:hover { border-color: var(--primary); transform: translateY(-1px); }
.path-lessons a > span { color: var(--faint); font-family: var(--font-mono); font-size: .6rem; }
.path-lessons strong { font-size: .85rem; }
.path-lessons small { color: var(--muted); font-size: .65rem; }

/* Same deck */
.same-deck { padding: 90px 0; position: relative; }
.same-deck::before { content: ""; position: absolute; z-index: -1; inset: 0 calc((100vw - min(1240px, 100vw - 48px)) / -2); background: var(--page-soft); }
.snapshot-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.snapshot-card { padding: 24px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
.snapshot-card.featured { border-color: color-mix(in srgb, var(--teal) 40%, var(--line)); box-shadow: var(--shadow-md); }
.snapshot-card > div:first-child { display: flex; flex-direction: column; margin-bottom: 27px; }
.snapshot-card > div:first-child span { color: var(--muted); font-size: .67rem; letter-spacing: .07em; text-transform: uppercase; }
.snapshot-card a { font-size: 1.16rem; font-weight: 760; text-decoration: none; }
.snapshot-card > strong { display: block; font-family: var(--font-mono); font-size: 2.2rem; line-height: 1; }
.snapshot-card > small { color: var(--muted); }
.metric-track { height: 8px; margin-top: 18px; overflow: hidden; border-radius: 999px; background: var(--page-soft); }
.metric-track i { height: 100%; display: block; border-radius: inherit; background: var(--primary); }
.snapshot-card.featured .metric-track i { background: var(--teal); }
.snapshot-card > p { margin: 10px 0 0; font-family: var(--font-mono); font-size: .7rem; }
.same-deck > .text-link { margin-top: 28px; }

/* Catalog and cards */
.catalog-section { padding: 125px 0 140px; }
.catalog-toolbar { padding: 18px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
.search-field { display: flex; align-items: center; gap: 12px; }
.search-field > span:not(.sr-only) { color: var(--faint); font-size: .72rem; font-weight: 750; text-transform: uppercase; }
.search-field input { width: 100%; min-height: 46px; padding: 9px 12px; border: 1px solid var(--line); border-radius: 9px; background: var(--page); color: var(--ink); }
.filter-chips { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 13px; padding-top: 13px; border-top: 1px solid var(--line); }
.filter-chips button { padding: 7px 10px; border: 1px solid transparent; border-radius: 999px; background: transparent; color: var(--muted); font-size: .75rem; font-weight: 700; cursor: pointer; }
.filter-chips button span { margin-left: 4px; color: var(--faint); font-family: var(--font-mono); font-size: .62rem; }
.filter-chips button:hover, .filter-chips button.is-active { border-color: var(--line); background: var(--page); color: var(--ink); }
.filter-chips button.is-active { border-color: color-mix(in srgb, var(--primary) 30%, var(--line)); background: var(--primary-soft); color: var(--primary); }
.catalog-count { margin: 20px 0 12px; font-size: .76rem; font-weight: 700; }
.algorithm-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.algorithm-card { min-width: 0; min-height: 350px; display: flex; flex-direction: column; padding: 23px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); box-shadow: var(--shadow-sm); transition: transform .2s ease, border .2s ease, box-shadow .2s ease; }
.algorithm-card:hover { transform: translateY(-4px); border-color: color-mix(in srgb, var(--primary) 40%, var(--line)); box-shadow: var(--shadow-md); }
.card-topline { display: flex; justify-content: space-between; align-items: center; gap: 12px; margin-bottom: 22px; }
.family-label { color: var(--teal); font-size: .66rem; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; }
.lesson-time, .explored-mark, .completion-mark { padding: 3px 7px; border-radius: 999px; background: var(--page-soft); color: var(--muted); font-family: var(--font-mono); font-size: .58rem; }
.completion-mark { background: var(--good-soft); color: var(--good); }
.explored-mark { background: var(--primary-soft); color: var(--primary); }
.algorithm-card h3 { margin-bottom: 11px; font-size: 1.35rem; }
.algorithm-card h3 a { text-decoration: none; }
.algorithm-card > p { margin-bottom: 18px; font-size: .87rem; }
.card-facts { display: grid; grid-template-columns: repeat(3, 1fr); gap: 7px; margin-top: auto; }
.card-facts span { display: flex; flex-direction: column; padding: 8px; border-radius: 8px; background: var(--page-soft); color: var(--ink-soft); font-family: var(--font-mono); font-size: .68rem; }
.card-facts small { margin-bottom: 2px; color: var(--faint); font-family: var(--font-sans); font-size: .57rem; text-transform: uppercase; }
.algorithm-card .best-for { margin: 15px 0; font-size: .74rem; line-height: 1.5; }
.best-for strong { color: var(--ink-soft); }
.card-action { display: flex; justify-content: space-between; align-items: center; padding-top: 14px; border-top: 1px solid var(--line); color: var(--primary); font-size: .77rem; font-weight: 760; text-decoration: none; }
.empty-state { padding: 45px; border: 1px dashed var(--line-strong); border-radius: var(--radius); text-align: center; }
.empty-state p { margin: 5px 0 0; }

/* Footer */
.site-footer { border-top: 1px solid var(--line); background: var(--surface); }
.footer-shell { width: var(--shell); min-height: 190px; margin-inline: auto; display: flex; justify-content: space-between; gap: 40px; align-items: center; }
.footer-brand { margin-bottom: 12px; }
.footer-shell p { max-width: 440px; margin: 0; font-size: .84rem; }
.footer-links { display: flex; gap: 22px; }
.footer-links a { color: var(--muted); font-size: .78rem; font-weight: 700; text-decoration: none; }
.footer-links a:hover { color: var(--primary); }
.toast { max-width: min(380px, calc(100vw - 32px)); position: fixed; z-index: 5000; right: 22px; bottom: 22px; padding: 12px 16px; transform: translateY(25px); border: 1px solid var(--line-strong); border-radius: 11px; background: var(--ink); color: var(--page); box-shadow: var(--shadow-lg); font-size: .8rem; font-weight: 650; opacity: 0; pointer-events: none; transition: opacity .2s ease, transform .2s ease; }
.toast.is-visible { transform: none; opacity: 1; }

/* Lesson header */
.lesson-hero { padding: 42px 0 30px; }
.breadcrumbs { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 42px; color: var(--muted); font-size: .72rem; }
.breadcrumbs a { text-decoration: none; }
.breadcrumbs a:hover { color: var(--primary); }
.lesson-hero-grid { display: grid; grid-template-columns: minmax(0, 1.4fr) minmax(300px, .6fr); gap: 80px; align-items: end; }
.lesson-kicker { display: flex; flex-wrap: wrap; gap: 7px; margin-bottom: 17px; }
.lesson-kicker span { padding: 4px 8px; border: 1px solid var(--line); border-radius: 999px; color: var(--muted); font-size: .65rem; font-weight: 720; }
.lesson-hero h1 { margin-bottom: 15px; font-size: clamp(3rem, 6vw, 5.6rem); font-weight: 770; letter-spacing: -.065em; }
.lesson-summary { max-width: 760px; margin-bottom: 22px; font-size: clamp(1.08rem, 1.8vw, 1.28rem); }
.lesson-tags { display: flex; flex-wrap: wrap; gap: 8px; }
.lesson-tags span { padding: 5px 9px; border-radius: 6px; background: var(--page-soft); color: var(--ink-soft); font-family: var(--font-mono); font-size: .65rem; }
.concept-glossary { max-width: 760px; margin-top: 12px; }
.concept-glossary summary { width: max-content; color: var(--primary); font-size: .67rem; font-weight: 750; cursor: pointer; }
.concept-glossary dl { display: grid; grid-template-columns: repeat(2, 1fr); gap: 8px; margin: 11px 0 0; padding: 12px; border: 1px solid var(--line); border-radius: 10px; background: var(--surface); }
.concept-glossary dl div { min-width: 0; }
.concept-glossary dt { color: var(--ink-soft); font-size: .64rem; font-weight: 800; }
.concept-glossary dd { margin: 2px 0 0; color: var(--muted); font-size: .61rem; line-height: 1.45; }
.mental-model-card { padding: 22px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); box-shadow: var(--shadow-sm); }
.mental-model-card > small { display: block; margin-bottom: 8px; color: var(--teal); font-size: .67rem; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; }
.mental-model-card > p { margin-bottom: 20px; color: var(--ink); font-family: Georgia, serif; font-size: 1.3rem; line-height: 1.45; }
.mental-model-card > div { padding-top: 17px; border-top: 1px solid var(--line); }
.mental-model-card > div > span { float: left; margin: 3px 8px 0 0; padding: 2px 6px; border-radius: 4px; background: var(--coral-soft); color: var(--coral-text); font-size: .57rem; font-weight: 800; text-transform: uppercase; }
.mental-model-card strong { display: block; margin-bottom: 4px; font-size: .77rem; }
.mental-model-card div p { margin: 0; font-size: .76rem; }
.lesson-progress-row { display: flex; justify-content: space-between; gap: 30px; align-items: center; margin-top: 40px; padding-top: 20px; border-top: 1px solid var(--line); }
.lesson-progress-row > div:first-child { display: flex; flex-wrap: wrap; align-items: center; gap: 11px; }
.completion-dot { width: 14px; height: 14px; border: 2px solid var(--line-strong); border-radius: 50%; background: var(--surface); }
.completion-dot.is-complete { border-color: var(--good); background: var(--good); box-shadow: inset 0 0 0 3px var(--surface); }
.lesson-progress-row p { display: flex; flex-direction: column; margin: 0; }
.lesson-progress-row strong { color: var(--ink); font-size: .74rem; }
.lesson-progress-row small { color: var(--muted); font-size: .66rem; }
.objective-list { display: flex; flex-wrap: wrap; gap: 5px; margin-left: 8px; }
.objective-list span { display: inline-flex; align-items: center; gap: 5px; padding: 3px 7px; border: 1px solid var(--line); border-radius: 999px; color: var(--muted); font-size: .7rem; font-weight: 750; }
.objective-list i { width: 1em; color: var(--faint); font-style: normal; font-size: .85em; text-align: center; }
.objective-list span.is-complete { border-color: color-mix(in srgb, var(--good) 35%, var(--line)); background: var(--good-soft); color: var(--good); }
.objective-list span.is-complete i { color: currentColor; }
.lesson-nav-links { display: flex; gap: 9px; }
.lesson-nav-links a { display: flex; flex-direction: column; padding: 7px 11px; border: 1px solid var(--line); border-radius: 8px; background: var(--surface); text-decoration: none; }
.lesson-nav-links a:hover { border-color: var(--primary); }
.lesson-nav-links small { color: var(--faint); font-size: .55rem; text-transform: uppercase; }
.lesson-nav-links span { font-size: .72rem; font-weight: 700; }

/* Interactive lab */
.lab-section { padding: 74px 0 90px; background: var(--lab); color: var(--lab-text); }
.lab-section button:focus-visible, .lab-section input:focus-visible, .lab-section select:focus-visible { outline-color: #8cf3e3; }
.lab-heading { display: flex; justify-content: space-between; gap: 40px; align-items: end; margin-bottom: 28px; }
.lab-heading h2 { margin-bottom: 12px; font-size: clamp(2rem, 4vw, 3.2rem); }
.lab-heading p:not(.eyebrow) { max-width: 670px; margin: 0; color: var(--lab-muted); }
.mode-switch { display: flex; padding: 4px; border: 1px solid var(--lab-line); border-radius: 10px; background: #0c141b; }
.mode-switch button { min-width: 84px; padding: 7px 12px; border: 0; border-radius: 7px; background: transparent; color: var(--lab-muted); font-size: .72rem; font-weight: 750; cursor: pointer; }
.mode-switch button.is-active { background: var(--lab-soft); color: var(--lab-text); }
.lab-card { overflow: hidden; border: 1px solid var(--lab-line); border-radius: 18px; background: #121d26; box-shadow: 0 30px 70px rgba(0, 0, 0, .25); }
.lab-card:not([data-mode="explore"]) .explore-only { display: none; }
.lab-card:not([data-mode="guided"]) .guided-only { display: none; }
.lab-card:not([data-mode="practice"]) .practice-only { display: none; }
.dataset-panel { display: grid; grid-template-columns: minmax(0, 1.5fr) 190px minmax(290px, .9fr); gap: 22px; align-items: end; padding: 18px 20px; border-bottom: 1px solid var(--lab-line); background: #16232d; }
.dataset-presets > span, .size-field > span, .custom-input > label { display: block; margin-bottom: 8px; color: #93a6af; font-size: .64rem; font-weight: 750; letter-spacing: .06em; text-transform: uppercase; }
.dataset-presets button { margin: 0 4px 4px 0; padding: 7px 9px; border: 1px solid #3b4b57; border-radius: 7px; background: transparent; color: #b9c6cc; font-size: .68rem; cursor: pointer; }
.dataset-presets button:hover, .dataset-presets button.is-active { border-color: #5bc8ba; background: #1d3c3b; color: #75dfd0; }
.size-field output { color: #77ddd0; font-family: var(--font-mono); }
.size-field input { width: 100%; accent-color: #62d3c4; }
.custom-input > div { display: flex; }
.custom-input input { width: 100%; min-height: 38px; padding: 7px 9px; border: 1px solid #3b4b57; border-right: 0; border-radius: 7px 0 0 7px; background: #0e1820; color: var(--lab-text); font-family: var(--font-mono); font-size: .7rem; }
.custom-input button { padding: 7px 11px; border: 1px solid #5d56c5; border-radius: 0 7px 7px 0; background: #4d47af; color: white; font-size: .68rem; font-weight: 750; cursor: pointer; }
.custom-input small { display: block; margin-top: 4px; color: #718590; font-size: .57rem; }
.guided-banner { display: flex; gap: 14px; align-items: center; padding: 13px 20px; border-bottom: 1px solid var(--lab-line); background: #17262e; }
.guided-banner > span { padding: 4px 7px; border-radius: 5px; background: #204743; color: #70d8ca; font-size: .59rem; font-weight: 800; text-transform: uppercase; }
.guided-banner p { flex: 1; margin: 0; color: #aebdc4; font-size: .7rem; }
.guided-banner strong { color: #e3eaed; }
.guided-banner b { display: block; margin-top: 3px; color: #77ddd0; font-family: var(--font-mono); font-size: .61rem; }
.guided-banner button { border: 0; background: transparent; color: #76d9cd; font-size: .68rem; font-weight: 750; cursor: pointer; }
.playback-bar { display: grid; grid-template-columns: auto minmax(220px, 1fr) auto auto; gap: 18px; align-items: center; padding: 15px 20px; border-bottom: 1px solid var(--lab-line); background: #0e1820; }
.transport-controls { display: flex; align-items: center; gap: 5px; }
.transport-controls button, .share-button { min-height: 36px; display: inline-flex; align-items: center; gap: 5px; padding: 7px 9px; border: 1px solid #344753; border-radius: 7px; background: #172530; color: #c3d0d5; font-size: .66rem; cursor: pointer; }
.transport-controls button:hover, .share-button:hover { border-color: #667c89; color: white; }
.transport-controls button:disabled { opacity: .35; cursor: not-allowed; }
.transport-controls .play-button { min-width: 68px; justify-content: center; border-color: #5f58cb; background: #514ab7; color: white; font-weight: 800; }
.transport-controls .play-button.is-playing { border-color: #ba715f; background: #a35747; }
.transport-controls small { font-size: .58rem; }
.timeline-field { min-width: 0; display: grid; grid-template-columns: auto 1fr; gap: 13px; align-items: center; }
.timeline-field > span { display: flex; flex-direction: column; min-width: 60px; }
.timeline-field strong { font-family: var(--font-mono); font-size: .63rem; }
.timeline-field small { color: #748893; font-size: .55rem; }
.timeline-field input { width: 100%; height: 4px; accent-color: #6b63de; background: linear-gradient(90deg, #7169df var(--timeline-progress, 0%), #33444f var(--timeline-progress, 0%)); }
.speed-field { display: flex; align-items: center; gap: 7px; }
.speed-field span { color: #7f929c; font-size: .58rem; text-transform: uppercase; }
.speed-field select { padding: 6px 24px 6px 8px; border: 1px solid #344753; border-radius: 7px; background: #172530; color: #cad5da; font-size: .65rem; }
.share-button { white-space: nowrap; }
.visual-grid { display: grid; grid-template-columns: minmax(0, 1.55fr) minmax(290px, .45fr); min-height: 480px; }
.visual-column { min-width: 0; padding: 20px; border-right: 1px solid var(--lab-line); }
.visual-label { display: flex; justify-content: space-between; gap: 20px; align-items: center; margin-bottom: 14px; }
.visual-label > span { color: #82949e; font-size: .62rem; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; }
.visual-label > div { display: flex; flex-wrap: wrap; gap: 9px; }
.state-key { display: flex; align-items: center; gap: 5px; color: #879aa3; font-size: .56rem; }
.state-key::before { content: ""; width: 8px; height: 8px; border: 1px solid #67808d; border-radius: 2px; background: #36505f; }
.state-key.compare::before { border-color: #e6ad56; background: repeating-linear-gradient(135deg, #9b641a 0 2px, #c9872c 2px 4px); }
.state-key.move::before { border-color: #bca3ff; background: #7557c4; }
.state-key.sorted::before { border-color: #6ad4a8; background: #24775d; }
.array-stage { height: 360px; min-width: 0; display: flex; align-items: stretch; gap: clamp(3px, .7vw, 9px); overflow-x: auto; padding: 38px 13px 22px; border: 1px solid #30434f; border-radius: 12px; background: linear-gradient(180deg, #0d171f, #111e27); box-shadow: inset 0 -30px 60px rgba(0, 0, 0, .14); }
.array-item { flex: 1 1 26px; min-width: 20px; height: 100%; display: flex; flex-direction: column; justify-content: flex-end; align-items: center; position: relative; opacity: 1; transition: opacity .2s ease, transform .2s ease; }
.item-state { min-height: 17px; position: absolute; top: -25px; left: 50%; transform: translateX(-50%); color: #95a8b1; font-size: .48rem; font-weight: 800; letter-spacing: .06em; text-transform: uppercase; white-space: nowrap; opacity: 0; }
.item-value { margin-bottom: 5px; color: #c6d2d8; font-family: var(--font-mono); font-size: clamp(.5rem, .9vw, .73rem); white-space: nowrap; }
.item-bar { width: min(100%, 44px); height: var(--bar-height); min-height: 8px; position: relative; border: 1px solid #5d7785; border-radius: 5px 5px 2px 2px; background: #36505f; box-shadow: inset 0 1px rgba(255, 255, 255, .08); transition: height .23s ease, transform .2s ease, background .2s ease, border .2s ease; }
.item-index { margin-top: 6px; color: #617681; font-family: var(--font-mono); font-size: .5rem; }
.array-item.is-muted { opacity: .31; }
.array-item.is-active .item-state, .array-item.is-comparing .item-state, .array-item.is-moving .item-state, .array-item.is-sorted .item-state { opacity: 1; }
.array-item.is-active .item-bar { border: 2px solid #5dd4c5; background: #246e69; box-shadow: 0 0 0 3px rgba(93, 212, 197, .13); }
.array-item.is-active .item-value { color: #76e0d2; }
.array-item.is-comparing .item-bar { border: 2px solid #edbd72; background: repeating-linear-gradient(135deg, #8a591a 0 7px, #bd7c29 7px 14px); box-shadow: 0 0 0 3px rgba(237, 189, 114, .12); }
.array-item.is-comparing .item-value { color: #ffd69a; }
.array-item.is-moving { transform: translateY(-8px); }
.array-item.is-moving .item-bar { border: 2px dashed #c6b1ff; background: #7253c1; box-shadow: 0 8px 25px rgba(114, 83, 193, .3); }
.array-item.is-moving .item-value { color: #d9ccff; }
.array-item.is-sorted .item-bar { border: 2px solid #67d1a6; background: #27775e; }
.array-item.is-sorted .item-value { color: #83e2bc; }
.auxiliary-stage { margin-top: 12px; padding: 13px; overflow-x: auto; border: 1px solid #30434f; border-radius: 10px; background: #0e1921; }
.aux-lane { display: grid; grid-template-columns: 100px minmax(max-content, 1fr); gap: 10px; align-items: start; padding: 6px 0; }
.aux-lane + .aux-lane { border-top: 1px solid #263945; }
.aux-lane > span { padding-top: 5px; color: #7f929d; font-size: .57rem; font-weight: 750; text-transform: uppercase; }
.aux-lane > div { display: flex; flex-wrap: wrap; gap: 4px; }
.aux-lane i { min-width: 28px; min-height: 28px; display: grid; place-items: center; padding: 3px 5px; border: 1px solid #3c5160; border-radius: 5px; background: #182833; color: #c5d2d8; font-family: var(--font-mono); font-size: .59rem; font-style: normal; }
.aux-lane i.is-empty { color: #526975; }
.narration-panel { display: flex; flex-direction: column; padding: 24px; background: #16232d; }
.phase-row { display: flex; justify-content: space-between; gap: 12px; align-items: center; margin-bottom: 24px; }
.phase-row > span { padding: 4px 7px; border: 1px solid #2f6d66; border-radius: 5px; background: #1b3938; color: #6bd5c7; font-size: .58rem; font-weight: 800; letter-spacing: .07em; text-transform: uppercase; }
.phase-row button { border: 0; background: transparent; color: #9b91ee; font-size: .61rem; font-weight: 750; cursor: pointer; }
.narration-panel h3 { margin-bottom: 11px; font-size: 1.45rem; line-height: 1.2; }
.narration-panel > p { min-height: 73px; margin-bottom: 18px; color: #aebec6; font-size: .83rem; }
.prediction-panel { margin: 0 0 18px; padding: 13px; border: 1px solid #6f64cc; border-radius: 10px; background: #1f2541; }
.prediction-panel > p { margin: 0 0 9px; color: white; font-size: .72rem; font-weight: 750; }
.prediction-panel > div { display: grid; gap: 6px; }
.prediction-panel button { padding: 7px 9px; border: 1px solid #4b5278; border-radius: 6px; background: #252e4d; color: #cbd0e9; font-size: .65rem; text-align: left; cursor: pointer; }
.prediction-panel button:hover { border-color: #978df0; }
.prediction-panel button.is-correct { border-color: #55c797; background: #173f32; color: #82ddb8; }
.prediction-panel button.is-wrong { border-color: #d66f6f; background: #49292d; color: #ffacac; }
.prediction-panel > span { display: block; margin-top: 8px; color: #abb7d8; font-size: .62rem; }
.variable-list { display: flex; flex-wrap: wrap; gap: 7px; min-height: 44px; margin-bottom: 18px; }
.variable-list span { min-width: 70px; display: flex; flex-direction: column; padding: 6px 8px; border: 1px solid #334753; border-radius: 7px; background: #111c24; }
.variable-list small { color: #6e838e; font-size: .52rem; text-transform: uppercase; }
.variable-list strong { color: #dce5e8; font-family: var(--font-mono); font-size: .68rem; }
.live-metrics { display: grid; grid-template-columns: repeat(2, 1fr); gap: 7px; margin-top: auto; }
.live-metrics div { padding: 9px; border: 1px solid #324551; border-radius: 8px; background: #111c24; }
.live-metrics span { display: block; color: #708691; font-size: .54rem; text-transform: uppercase; }
.live-metrics strong { color: #e5ecef; font-family: var(--font-mono); font-size: .82rem; }
.metric-note { min-height: auto !important; margin: 11px 0 0 !important; color: #6e828d !important; font-size: .57rem !important; line-height: 1.45; }
.code-trace { border-top: 1px solid var(--lab-line); background: #0c151c; }
.code-heading { display: flex; justify-content: space-between; gap: 20px; align-items: center; padding: 13px 20px; border-bottom: 1px solid #283a45; }
.code-heading > div { display: flex; gap: 12px; align-items: baseline; }
.code-heading span { color: #8ea1aa; font-size: .6rem; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; }
.code-heading strong { color: #70848e; font-size: .62rem; font-weight: 500; }
.keyboard-hint { letter-spacing: 0 !important; text-transform: none !important; }
kbd { padding: 1px 4px; border: 1px solid #40535f; border-bottom-width: 2px; border-radius: 4px; background: #17242d; color: #b8c6cc; font-size: .55rem; }
#pseudocode-list { max-height: 330px; margin: 0; padding: 13px 0; overflow-y: auto; list-style: none; counter-reset: none; }
#pseudocode-list li { min-height: 31px; display: grid; grid-template-columns: 48px 1fr; align-items: center; padding: 4px 20px; border-left: 2px solid transparent; color: #9babb3; }
#pseudocode-list li > span { color: #506773; font-family: var(--font-mono); font-size: .58rem; }
#pseudocode-list code { white-space: pre-wrap; font-size: .71rem; }
#pseudocode-list li.is-active { border-left-color: #6ed8ca; background: #162b31; color: #e4eeee; }
#pseudocode-list li.is-active > span { color: #70d7ca; }

/* Lesson content */
.lesson-content { display: grid; grid-template-columns: minmax(0, 1fr) 250px; gap: 80px; padding: 110px 0 130px; }
.content-main { min-width: 0; }
.lesson-block { padding: 0 0 90px; margin-bottom: 90px; border-bottom: 1px solid var(--line); }
.lesson-block:last-child { margin-bottom: 0; }
.lesson-block h2 { max-width: 780px; margin-bottom: 32px; font-size: clamp(2rem, 4vw, 3.3rem); }
.mechanism-steps { margin: 0; padding: 0; border-top: 1px solid var(--line); list-style: none; }
.mechanism-steps li { display: grid; grid-template-columns: 60px 1fr; gap: 16px; align-items: center; padding: 22px 0; border-bottom: 1px solid var(--line); }
.mechanism-steps span { color: var(--primary); font-family: var(--font-mono); font-size: .7rem; }
.mechanism-steps p { margin: 0; color: var(--ink-soft); font-size: 1.04rem; }
.invariant-block { display: grid; grid-template-columns: minmax(0, 1fr) 280px; gap: 60px; align-items: center; }
.invariant-block h2 { margin-bottom: 18px; }
.invariant-block > div > p:last-child { max-width: 670px; font-size: 1.05rem; }
.invariant-block aside { padding: 23px; border-radius: var(--radius); background: var(--primary-soft); }
.invariant-block aside small { display: block; margin-bottom: 10px; color: var(--primary); font-size: .62rem; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; }
.invariant-block aside strong { font-family: Georgia, serif; font-size: 1.22rem; font-weight: 500; line-height: 1.45; }
.complexity-cards { display: grid; grid-template-columns: repeat(4, 1fr); gap: 10px; }
.complexity-cards article { padding: 17px; border: 1px solid var(--line); border-radius: 12px; background: var(--surface); }
.complexity-cards span { display: block; margin-bottom: 12px; color: var(--muted); font-size: .65rem; text-transform: uppercase; }
.complexity-cards strong { color: var(--primary); font-family: var(--font-mono); font-size: 1.06rem; }
.complexity-context { margin: 22px 0 0; padding: 14px 17px; border-left: 3px solid var(--teal); background: var(--teal-soft); color: var(--ink-soft); }
.teaching-note { margin: 12px 0 0; padding: 12px 16px; border-left: 3px solid var(--gold); background: color-mix(in srgb, var(--gold) 10%, var(--surface)); color: var(--ink-soft); font-size: .7rem; }
.input-experiment { margin-top: 28px; overflow: hidden; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
.experiment-prompt { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 32px; align-items: end; padding: 24px; }
.experiment-prompt > div > span { display: block; margin-bottom: 7px; color: var(--teal); font-size: .72rem; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; }
.experiment-prompt h3 { margin-bottom: 8px; font-size: 1.35rem; }
.experiment-prompt p { max-width: 650px; margin: 0; font-size: .78rem; }
.experiment-prompt form { min-width: 205px; display: grid; gap: 6px; }
.experiment-prompt label { color: var(--muted); font-size: .7rem; font-weight: 750; text-transform: uppercase; }
.experiment-prompt select, .experiment-prompt button { min-height: 39px; padding: 7px 10px; border: 1px solid var(--line-strong); border-radius: 8px; background: var(--page); color: var(--ink); font-size: .72rem; }
.experiment-prompt button { border-color: var(--primary); background: var(--primary); color: var(--primary-contrast); font-weight: 760; cursor: pointer; }
.experiment-results { padding: 21px 24px; border-top: 1px solid var(--line); background: var(--page-soft); }
.experiment-row { display: grid; grid-template-columns: 105px minmax(100px, 1fr) 52px minmax(170px, auto); gap: 11px; align-items: center; padding: 6px 0; }
.experiment-row strong { font-size: .67rem; }
.experiment-row > span { height: 8px; overflow: hidden; border-radius: 999px; background: var(--line); }
.experiment-row i { height: 100%; display: block; border-radius: inherit; background: var(--primary); }
.experiment-row b { font-family: var(--font-mono); font-size: .67rem; }
.experiment-row small { color: var(--muted); font-size: .66rem; }
.experiment-results > p { margin: 15px 0 9px; color: var(--ink-soft); font-size: .74rem; }
.experiment-counterexample { padding: 0; border: 0; background: transparent; cursor: pointer; }
.experiment-caution { margin: 0; padding: 12px 24px; border-top: 1px solid var(--line); background: color-mix(in srgb, var(--gold) 8%, var(--surface)); color: var(--muted); font-size: .7rem; }
.tradeoff-block { display: grid; grid-template-columns: repeat(2, 1fr); gap: 12px; }
.tradeoff-column { min-height: 180px; padding: 22px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
.tradeoff-column > span, .misconception > span { display: block; margin-bottom: 30px; color: var(--muted); font-size: .64rem; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; }
.tradeoff-column.good { border-top: 3px solid var(--good); }
.tradeoff-column.caution { border-top: 3px solid var(--coral); }
.tradeoff-column h3 { margin: 0; font-size: 1.22rem; line-height: 1.35; }
.misconception { grid-column: 1 / -1; padding: 19px 22px; border-radius: 12px; background: var(--coral-soft); }
.misconception > span { margin-bottom: 7px; color: var(--coral-text); }
.misconception p { margin: 0; color: var(--ink-soft); }
.stability-lab { display: grid; grid-template-columns: 1fr auto; gap: 50px; align-items: end; padding: 35px; border: 1px solid var(--line); border-radius: var(--radius-lg); background: var(--surface); }
.stability-lab h2 { margin-bottom: 16px; }
.stability-lab p:last-child { max-width: 680px; margin: 0; }
.knowledge-check { padding: 35px; border: 1px solid var(--line); border-radius: var(--radius-lg); background: var(--surface); }
.knowledge-check > p:not(.eyebrow) { max-width: 700px; margin-top: -18px; }
#quiz-root { display: grid; gap: 12px; margin-top: 24px; }
.quiz-question { padding: 20px; border: 1px solid var(--line); border-radius: 13px; background: var(--page); }
.quiz-question > div:first-child { display: grid; grid-template-columns: 38px 1fr; align-items: start; margin-bottom: 13px; }
.quiz-question > div:first-child > span { color: var(--primary); font-family: var(--font-mono); font-size: .62rem; font-weight: 800; }
.quiz-question h3 { margin: 0; font-size: 1rem; line-height: 1.35; }
.quiz-options { display: grid; gap: 9px; }
.quiz-options button { display: grid; grid-template-columns: 34px 1fr; gap: 11px; align-items: center; padding: 12px 14px; border: 1px solid var(--line); border-radius: 10px; background: var(--page); color: var(--ink-soft); text-align: left; cursor: pointer; }
.quiz-options button span { width: 30px; height: 30px; display: grid; place-items: center; border-radius: 7px; background: var(--surface); color: var(--primary); font-family: var(--font-mono); font-size: .68rem; font-weight: 800; }
.quiz-options button:hover { border-color: var(--primary); }
.quiz-options button:disabled { cursor: default; }
.quiz-options button.is-correct { border-color: var(--good); background: var(--good-soft); }
.quiz-options button.is-wrong { border-color: var(--danger); background: var(--danger-soft); }
.quiz-result { min-height: 28px; margin-top: 15px; color: var(--muted); font-size: .83rem; }
.quiz-result.is-correct strong { color: var(--good); }
.quiz-result.is-wrong strong { color: var(--danger); }
.quiz-feedback { min-height: 22px; margin: 10px 0 0; color: var(--muted); font-size: .7rem; }
.quiz-feedback strong { color: var(--ink-soft); }
.quiz-result button { padding: 2px 5px; border: 0; background: transparent; color: var(--primary); font-weight: 750; text-decoration: underline; text-underline-offset: 3px; cursor: pointer; }
.lesson-sidebar { min-width: 0; }
.lesson-sidebar > nav { position: sticky; top: 100px; display: flex; flex-direction: column; padding-left: 18px; border-left: 1px solid var(--line-strong); }
.lesson-sidebar nav strong { margin-bottom: 12px; font-size: .72rem; }
.lesson-sidebar nav a { padding: 6px 0; color: var(--muted); font-size: .72rem; text-decoration: none; }
.lesson-sidebar nav a:hover { color: var(--primary); }
.sidebar-tip { margin-top: 28px; padding: 15px; border-radius: 11px; background: var(--teal-soft); }
.sidebar-tip span { color: var(--teal); font-size: .61rem; font-weight: 800; text-transform: uppercase; }
.sidebar-tip p { margin: 6px 0 0; color: var(--ink-soft); font-size: .7rem; }
.related-section { padding: 90px 0 110px; background: var(--page-soft); }
.related-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }

/* Comparison page */
.compare-hero { padding: 100px 0 65px; }
.compare-hero h1 { max-width: 900px; margin-bottom: 25px; font-size: clamp(3.5rem, 8vw, 7.2rem); line-height: .92; font-weight: 770; letter-spacing: -.07em; }
.compare-hero > p:last-child { max-width: 750px; font-size: 1.15rem; }
.comparison-builder { padding-bottom: 110px; }
.builder-card { overflow: hidden; border: 1px solid var(--line); border-radius: var(--radius-lg); background: var(--surface); box-shadow: var(--shadow-md); }
.builder-heading { display: flex; justify-content: space-between; gap: 30px; align-items: center; padding: 25px 28px; border-bottom: 1px solid var(--line); }
.builder-heading > div > span { display: block; margin-bottom: 4px; color: var(--teal); font-size: .64rem; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; }
.builder-heading h2 { margin: 0; font-size: 1.75rem; }
.builder-heading button { min-height: 43px; padding: 9px 15px; border: 0; border-radius: 9px; background: var(--primary); color: var(--primary-contrast); font-weight: 760; cursor: pointer; }
.builder-controls { display: grid; grid-template-columns: repeat(5, 1fr); gap: 14px; padding: 22px 28px; }
.builder-controls label { display: flex; flex-direction: column; gap: 6px; }
.builder-controls label > span { color: var(--muted); font-size: .62rem; font-weight: 750; text-transform: uppercase; }
.builder-controls select, .builder-controls input { width: 100%; min-height: 41px; padding: 7px 9px; border: 1px solid var(--line); border-radius: 8px; background: var(--page); color: var(--ink); font-size: .75rem; }
.comparison-results { margin-top: 22px; }
.shared-deck { display: grid; grid-template-columns: 90px 1fr auto; gap: 18px; align-items: end; padding: 17px 20px; border: 1px solid var(--line); border-radius: 13px; background: var(--surface); }
.shared-deck > span { align-self: center; color: var(--muted); font-size: .64rem; font-weight: 800; text-transform: uppercase; }
.shared-deck > div { height: 80px; display: flex; gap: 4px; align-items: end; }
.shared-deck i { flex: 1; height: var(--height); min-width: 5px; position: relative; border-radius: 3px 3px 0 0; background: var(--teal); font-style: normal; }
.shared-deck i small { position: absolute; top: -17px; left: 50%; transform: translateX(-50%); color: var(--muted); font-family: var(--font-mono); font-size: .45rem; }
.shared-deck p { align-self: center; margin: 0; font-size: .67rem; }
.result-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 15px; margin-top: 15px; }
.result-card { padding: 22px; border: 1px solid var(--line); border-top: 4px solid var(--primary); border-radius: var(--radius); background: var(--surface); }
.result-card.accent-two { border-top-color: var(--coral); }
.result-card.accent-three { border-top-color: var(--teal); }
.result-card > div:first-child { display: flex; flex-direction: column; margin-bottom: 20px; }
.result-card > div:first-child span { color: var(--muted); font-size: .6rem; text-transform: uppercase; }
.result-card > div:first-child a { font-size: 1.25rem; font-weight: 760; text-decoration: none; }
.result-card dl { display: grid; grid-template-columns: repeat(2, 1fr); gap: 7px; margin: 0 0 21px; }
.result-card dl div { padding: 9px; border-radius: 8px; background: var(--page-soft); }
.result-card dt { color: var(--muted); font-size: .56rem; text-transform: uppercase; }
.result-card dd { margin: 2px 0 0; font-family: var(--font-mono); font-size: .8rem; font-weight: 800; }
.result-bars { display: grid; gap: 8px; }
.result-bars p { display: grid; grid-template-columns: 75px 1fr; gap: 8px; align-items: center; margin: 0; }
.result-bars span { font-size: .58rem; }
.result-bars i { height: 7px; overflow: hidden; border-radius: 999px; background: var(--page-soft); }
.result-bars b { height: 100%; display: block; border-radius: inherit; background: var(--primary); }
.accent-two .result-bars b { background: var(--coral); }
.accent-three .result-bars b { background: var(--teal); }
.result-note { margin: 18px 0 0; padding-top: 12px; border-top: 1px solid var(--line); font-size: .67rem; }
.comparison-disclaimer { margin: 15px 0 0; padding: 13px 16px; border-left: 3px solid var(--gold); background: color-mix(in srgb, var(--coral-soft) 60%, var(--surface)); color: var(--ink-soft); font-size: .76rem; }
.growth-section { padding-bottom: 110px; }
.growth-card { overflow: hidden; border: 1px solid var(--line); border-radius: var(--radius-lg); background: var(--surface); box-shadow: var(--shadow-sm); }
.growth-controls { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)) auto; gap: 12px; align-items: end; padding: 22px 24px; border-bottom: 1px solid var(--line); background: var(--page-soft); }
.growth-controls label { min-width: 0; display: grid; gap: 5px; }
.growth-controls label > span { color: var(--muted); font-size: .7rem; font-weight: 760; text-transform: uppercase; }
.growth-controls select, .growth-controls button { width: 100%; min-height: 41px; padding: 7px 9px; border: 1px solid var(--line-strong); border-radius: 8px; background: var(--surface); color: var(--ink); font-size: .7rem; }
.growth-controls button { padding-inline: 15px; border-color: var(--primary); background: var(--primary); color: var(--primary-contrast); font-weight: 760; white-space: nowrap; cursor: pointer; }
.growth-results { padding: 25px; }
.growth-summary { display: grid; grid-template-columns: repeat(3, 1fr); gap: 9px; margin-bottom: 22px; }
.growth-summary div { padding: 12px 14px; border-radius: 9px; background: var(--page-soft); }
.growth-summary span { display: block; color: var(--muted); font-size: .7rem; text-transform: uppercase; }
.growth-summary strong { display: block; margin-top: 4px; color: var(--ink); font-family: var(--font-mono); font-size: .73rem; }
.growth-bars { display: grid; gap: 9px; }
.growth-bars > div { display: grid; grid-template-columns: 54px 1fr 50px; gap: 10px; align-items: center; }
.growth-bars span { color: var(--muted); font-family: var(--font-mono); font-size: .7rem; }
.growth-bars i { height: 13px; overflow: hidden; border-radius: 999px; background: var(--page-soft); }
.growth-bars b { height: 100%; display: block; border-radius: inherit; background: linear-gradient(90deg, var(--primary), var(--teal)); }
.growth-bars strong { font-family: var(--font-mono); font-size: .65rem; text-align: right; }
.growth-reading { display: flex; justify-content: space-between; gap: 25px; align-items: center; margin-top: 20px; padding-top: 17px; border-top: 1px solid var(--line); }
.growth-reading p { max-width: 700px; margin: 0; font-size: .67rem; }
.growth-reading a { flex: 0 0 auto; font-size: .7rem; }
.scenario-section { padding: 105px 0; }
.scenario-layout { display: grid; grid-template-columns: minmax(360px, .8fr) minmax(0, 1.2fr); overflow: hidden; border: 1px solid var(--line); border-radius: var(--radius-lg); background: var(--surface); }
.scenario-buttons { padding: 10px; border-right: 1px solid var(--line); background: var(--page-soft); }
.scenario-buttons button { width: 100%; display: grid; grid-template-columns: 38px 1fr; column-gap: 9px; padding: 15px; border: 0; border-radius: 10px; background: transparent; color: var(--ink); text-align: left; cursor: pointer; }
.scenario-buttons button + button { margin-top: 4px; }
.scenario-buttons button.is-active { background: var(--surface); box-shadow: var(--shadow-sm); }
.scenario-buttons span { grid-row: 1 / 3; color: var(--primary); font-family: var(--font-mono); font-size: .67rem; }
.scenario-buttons strong { font-size: .85rem; }
.scenario-buttons small { color: var(--muted); font-size: .66rem; }
.scenario-answer { min-height: 360px; display: flex; flex-direction: column; justify-content: center; padding: clamp(34px, 6vw, 78px); }
.scenario-answer > span { color: var(--teal); font-size: .65rem; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; }
.scenario-answer h3 { max-width: 600px; margin: 13px 0 18px; font-size: clamp(2rem, 4vw, 3.25rem); }
.scenario-answer p { max-width: 680px; }
.scenario-answer > div { display: flex; flex-wrap: wrap; gap: 9px; margin-top: 15px; }
.comparison-catalog { padding: 110px 0 130px; background: var(--page-soft); }
.matrix-toolbar { display: grid; grid-template-columns: 1fr auto auto; gap: 14px; align-items: end; margin-bottom: 14px; padding: 15px; border: 1px solid var(--line); border-radius: 12px; background: var(--surface); }
.checkbox-filter { display: flex; align-items: center; gap: 8px; min-height: 46px; padding: 0 11px; border: 1px solid var(--line); border-radius: 9px; color: var(--muted); font-size: .7rem; font-weight: 720; }
.checkbox-filter input { accent-color: var(--primary); }
.matrix-family { display: flex; flex-direction: column; gap: 4px; }
.matrix-family span { color: var(--muted); font-size: .56rem; text-transform: uppercase; }
.matrix-family select { min-height: 38px; padding: 7px 29px 7px 9px; border: 1px solid var(--line); border-radius: 8px; background: var(--page); color: var(--ink); font-size: .7rem; }
.matrix-wrap { overflow-x: auto; border: 1px solid var(--line); border-radius: 13px; background: var(--surface); }
.comparison-matrix { width: 100%; min-width: 1020px; border-collapse: collapse; font-size: .72rem; }
.comparison-matrix th, .comparison-matrix td { padding: 13px 12px; border-bottom: 1px solid var(--line); text-align: left; vertical-align: middle; }
.comparison-matrix thead th { position: sticky; top: 0; background: var(--page-soft); color: var(--muted); font-size: .58rem; letter-spacing: .06em; text-transform: uppercase; }
.comparison-matrix tbody tr:last-child th, .comparison-matrix tbody tr:last-child td { border-bottom: 0; }
.comparison-matrix tbody tr:hover { background: color-mix(in srgb, var(--primary-soft) 35%, transparent); }
.comparison-matrix tbody th { min-width: 145px; }
.comparison-matrix tbody th a { display: block; color: var(--ink); font-size: .79rem; text-decoration: none; }
.comparison-matrix tbody th small { color: var(--muted); font-size: .57rem; font-weight: 500; }
.comparison-matrix td:last-child { min-width: 260px; color: var(--muted); }
.table-status { display: inline-flex; padding: 3px 7px; border-radius: 999px; font-size: .58rem; font-weight: 800; }
.table-status.positive { background: var(--good-soft); color: var(--good); }
.table-status.negative { background: var(--danger-soft); color: var(--danger); }
.table-status.neutral { background: var(--page-soft); color: var(--muted); }
.matrix-empty { padding: 25px; text-align: center; }

.fatal-error { min-height: 100vh; display: grid; place-items: center; padding: 30px; }
.fatal-error > div { max-width: 520px; padding: 35px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); text-align: center; box-shadow: var(--shadow-md); }
.fatal-error > div > span { width: 50px; height: 50px; display: grid; place-items: center; margin: 0 auto 18px; border-radius: 50%; background: var(--danger-soft); color: var(--danger); font-size: 1.5rem; font-weight: 800; }
.fatal-error button { padding: 9px 15px; border: 0; border-radius: 8px; background: var(--primary); color: var(--primary-contrast); cursor: pointer; }

/* Responsive */
@media (max-width: 1100px) {
    .home-hero { grid-template-columns: 1fr; padding-bottom: 110px; }
    .hero-copy { max-width: 820px; }
    .hero-demo { width: min(700px, 90%); margin-inline: auto; }
    .note-one { left: -55px; }
    .note-two { right: -55px; }
    .algorithm-grid { grid-template-columns: repeat(2, 1fr); }
    .path-stage { grid-template-columns: 70px minmax(190px, .65fr) minmax(390px, 1.35fr); }
    .lesson-hero-grid { gap: 40px; }
    .playback-bar { grid-template-columns: auto 1fr auto; }
    .share-button { grid-column: 1 / -1; justify-self: end; }
    .visual-grid { grid-template-columns: minmax(0, 1.35fr) minmax(270px, .65fr); }
    .dataset-panel { grid-template-columns: 1fr 180px; }
    .custom-input { grid-column: 1 / -1; }
    .lesson-content { gap: 45px; }
    .builder-controls { grid-template-columns: repeat(3, 1fr); }
    .growth-controls { grid-template-columns: repeat(2, 1fr); }
    .growth-controls button { grid-column: 1 / -1; }
}

@media (max-width: 860px) {
    :root { --shell: min(100% - 32px, 760px); }
    .nav-toggle { display: inline-flex; }
    .primary-nav { display: none; width: min(360px, calc(100vw - 32px)); position: absolute; top: 62px; right: 16px; padding: 10px; flex-direction: column; align-items: stretch; border: 1px solid var(--line); border-radius: 12px; background: var(--surface); box-shadow: var(--shadow-lg); }
    .primary-nav.is-open { display: flex; }
    .primary-nav > a { justify-content: flex-start; }
    .primary-nav > .portfolio-link { margin-right: 0; }
    .theme-toggle { width: 100%; margin: 4px 0 0; }
    .home-hero { width: calc(100% - 16px); margin-top: 8px; border-radius: 22px; }
    .section-heading { grid-template-columns: 1fr; gap: 20px; }
    .principle-grid, .snapshot-grid { grid-template-columns: 1fr; }
    .principle-grid article { min-height: auto; }
    .principle-number { margin-bottom: 30px; }
    .path-stage { grid-template-columns: 55px 1fr; gap: 20px; }
    .path-lessons { grid-column: 2; }
    .lesson-hero-grid { grid-template-columns: 1fr; }
    .mental-model-card { max-width: 620px; }
    .lesson-progress-row { align-items: flex-start; }
    .lesson-nav-links { flex-direction: column; }
    .lab-heading { align-items: flex-start; flex-direction: column; }
    .playback-bar { grid-template-columns: 1fr; }
    .share-button { grid-column: auto; justify-self: stretch; justify-content: center; }
    .transport-controls { justify-content: center; }
    .speed-field { justify-content: center; }
    .visual-grid { grid-template-columns: 1fr; }
    .visual-column { border-right: 0; border-bottom: 1px solid var(--lab-line); }
    .narration-panel { min-height: 380px; }
    .lesson-content { grid-template-columns: 1fr; }
    .lesson-sidebar { display: none; }
    .invariant-block { grid-template-columns: 1fr; }
    .experiment-prompt { grid-template-columns: 1fr; }
    .experiment-prompt form { min-width: 0; }
    .experiment-row { grid-template-columns: 90px 1fr 44px; }
    .experiment-row small { grid-column: 2 / -1; }
    .complexity-cards { grid-template-columns: repeat(2, 1fr); }
    .stability-lab { grid-template-columns: 1fr; }
    .result-grid { grid-template-columns: 1fr; }
    .growth-reading { align-items: flex-start; flex-direction: column; }
    .scenario-layout { grid-template-columns: 1fr; }
    .scenario-buttons { border-right: 0; border-bottom: 1px solid var(--line); }
    .matrix-toolbar { grid-template-columns: 1fr 1fr; }
    .matrix-toolbar .search-field { grid-column: 1 / -1; }
    .footer-shell { padding-block: 45px; align-items: flex-start; flex-direction: column; }
}

@media (max-width: 640px) {
    :root { --shell: calc(100% - 24px); }
    .nav-shell { height: 62px; }
    .home-hero { min-height: auto; padding: 52px 20px 95px; gap: 60px; }
    .hero-copy h1 { font-size: clamp(3.25rem, 17vw, 4.8rem); }
    .hero-actions .button { width: 100%; }
    .hero-proof { gap: 11px 20px; }
    .hero-demo { width: 100%; }
    .demo-window { padding-inline: 13px; transform: none; }
    .demo-chrome { margin-inline: -13px; }
    .mini-bars { height: 210px; gap: 4px; }
    .floating-note { max-width: 185px; }
    .note-one { left: -8px; top: -44px; }
    .note-two { right: -5px; bottom: -58px; }
    .learning-principles { padding-block: 100px 90px; }
    .learning-path, .catalog-section { padding-bottom: 100px; }
    .path-stage { grid-template-columns: 40px 1fr; gap: 12px; }
    .path-index span { width: 38px; height: 38px; }
    .path-lessons { grid-template-columns: 1fr; }
    .algorithm-grid, .related-grid { grid-template-columns: 1fr; }
    .algorithm-card { min-height: 330px; }
    .filter-chips { flex-wrap: nowrap; overflow-x: auto; padding-bottom: 4px; }
    .filter-chips button { flex: 0 0 auto; }
    .lesson-hero { padding-top: 25px; }
    .breadcrumbs { margin-bottom: 26px; }
    .lesson-hero h1 { font-size: clamp(3rem, 16vw, 4.7rem); }
    .concept-glossary dl { grid-template-columns: 1fr; }
    .lesson-progress-row { flex-direction: column; }
    .objective-list { width: 100%; margin-left: 0; padding-left: 25px; }
    .lesson-nav-links { width: 100%; flex-direction: row; }
    .lesson-nav-links a { flex: 1; }
    .lab-section { padding-block: 55px 65px; }
    .mode-switch { width: 100%; }
    .mode-switch button { flex: 1; }
    .dataset-panel { grid-template-columns: 1fr; }
    .custom-input { grid-column: auto; }
    .guided-banner { align-items: flex-start; flex-wrap: wrap; }
    .guided-banner p { flex-basis: calc(100% - 65px); }
    .guided-banner button { margin-left: 60px; }
    .playback-bar { padding-inline: 12px; }
    .transport-controls button { flex: 1; justify-content: center; }
    .transport-controls button:first-child { max-width: 68px; }
    .visual-column { padding: 13px; }
    .visual-label { align-items: flex-start; flex-direction: column; }
    .array-stage { height: 290px; padding-inline: 7px; }
    .array-item { min-width: 18px; }
    .item-index { display: none; }
    .aux-lane { grid-template-columns: 72px 1fr; }
    .narration-panel { padding: 19px; }
    .code-heading { align-items: flex-start; flex-direction: column; }
    .keyboard-hint { display: none; }
    #pseudocode-list li { grid-template-columns: 36px 1fr; padding-inline: 13px; }
    .lesson-content { padding-block: 80px 100px; }
    .lesson-block { padding-bottom: 65px; margin-bottom: 65px; }
    .complexity-cards { grid-template-columns: 1fr 1fr; }
    .tradeoff-block { grid-template-columns: 1fr; }
    .misconception { grid-column: auto; }
    .stability-lab, .knowledge-check { padding: 23px; }
    .experiment-prompt, .experiment-results { padding-inline: 17px; }
    .experiment-row { grid-template-columns: 78px 1fr 38px; gap: 7px; }
    .compare-hero { padding-top: 70px; }
    .compare-hero h1 { font-size: clamp(3.3rem, 17vw, 5rem); }
    .builder-heading { align-items: flex-start; flex-direction: column; }
    .builder-heading button { width: 100%; }
    .builder-controls { grid-template-columns: 1fr; }
    .growth-controls { grid-template-columns: 1fr; }
    .growth-summary { grid-template-columns: 1fr; }
    .shared-deck { grid-template-columns: 1fr; }
    .shared-deck > div { order: 3; }
    .scenario-buttons button { grid-template-columns: 31px 1fr; padding: 12px; }
    .matrix-toolbar { grid-template-columns: 1fr; }
    .matrix-toolbar .search-field { grid-column: auto; }
    .footer-links { flex-direction: column; gap: 9px; }
}

@media (prefers-reduced-motion: reduce) {
    html { scroll-behavior: auto; }
    *, *::before, *::after { scroll-behavior: auto !important; transition-duration: .001ms !important; animation-duration: .001ms !important; animation-iteration-count: 1 !important; }
}

@media (forced-colors: active) {
    .item-bar, .mini-bar { forced-color-adjust: none; }
    .array-item.is-comparing .item-bar { background: CanvasText; }
    .array-item.is-moving .item-bar { border-style: dashed; }
    .array-item.is-sorted .item-bar { border-width: 4px; }
}