/* Shared LeeVis visual system. Algorithm-specific renderers keep their own
   geometry and state colors; this layer owns surfaces, hierarchy and controls. */
:root {
  --paper: #f5f6f8;
  --surface: #ffffff;
  --surface-2: #eef0f4;
  --soft: #eef0f4;
  --ink: #202329;
  --muted: #606674;
  --line: #dce0e6;
  --primary: #5846c7;
  --primary-dark: #4835b2;
  --action: #624cda;
  --action-hover: #523dc3;
  --mint: #167454;
  --primary-soft: #efecfc;
  --success-soft: #e8f4ee;
  --stage: #fafbfc;
  --stage-dot: #dfe3e9;
  --code: #1b1d20;
  --code-ink: #e4e6ed;
  --code-muted: #b0b6c4;
  --shadow: 0 4px 18px #20232906;
  --sidebar: 236px;
  --radius: 14px;
  background: var(--paper);
  color: var(--ink);
  font-family: "DM Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.6;
}
:root[data-theme="dark"] {
  --paper: #0b0d0d;
  --surface: #141717;
  --surface-2: #1e2221;
  --soft: #1e2221;
  --ink: #eef0ef;
  --muted: #a8b1ae;
  --line: #2d3432;
  --primary: #b7a8ff;
  --primary-dark: #d0c6ff;
  --action: #ae9bf7;
  --action-hover: #c2b3ff;
  --mint: #91d9b4;
  --primary-soft: #2c283d;
  --success-soft: #20372d;
  --stage: #0f1211;
  --stage-dot: #2a302e;
  --code: #080a09;
  --code-ink: #e4e9e6;
  --code-muted: #a8b5af;
  --shadow: 0 4px 24px #00000012;
  background: var(--paper);
}
body { background: var(--paper); }
button, input, select, textarea { color: var(--ink); background: var(--surface); }
input::placeholder, textarea::placeholder { color: var(--muted); opacity: 1; }
input, select, textarea { accent-color: var(--primary); }
h1, h2, h3, h4 { text-wrap: balance; letter-spacing: -.035em; }
h1 { font-size: clamp(1.9rem, 3.4vw, 2.7rem); }
:is(a, button, input, select, textarea, summary):focus-visible { outline: 3px solid var(--primary); outline-offset: 3px; }
.eyebrow { font: 650 .7rem/1.5 var(--mono); letter-spacing: .1em; color: var(--primary); }
.btn, [data-theme="dark"] .btn { background: var(--surface); color: var(--ink); border-color: var(--line); border-radius: 9px; min-height: 44px; padding: 10px 16px; box-shadow: none; }
.btn:hover { background: var(--surface-2); transform: none; }
.btn.primary, [data-theme="dark"] .btn.primary { background: var(--action); color: #fff; border-color: transparent; box-shadow: none; }
[data-theme="dark"] .btn.primary { color: #201a35; }
.btn.primary:hover, [data-theme="dark"] .btn.primary:hover { background: var(--action-hover); }
.btn.secondary, [data-theme="dark"] .btn.secondary { color: var(--ink); background: var(--surface); }
.icon-button { min-width: 36px; min-height: 36px; }
.icon-button:hover, [data-theme="dark"] .icon-button:hover { background: var(--primary-soft); color: var(--primary); }
.icon-button.saved svg { fill: var(--primary-soft); }
.text-button, [data-theme="dark"] .text-button { background: transparent; }
.text-link { color: var(--primary); }
.sidebar, [data-theme="dark"] .sidebar { background: var(--surface); padding: 30px 16px 20px; overflow-y: auto; scrollbar-width: thin; }
.brand { padding: 0 12px; font-size: 1.4rem; gap: 11px; }
.brand-mark, [data-theme="dark"] .brand-mark { background: var(--action); color: #fff; width: 36px; height: 36px; border-radius: 11px; box-shadow: none; }
[data-theme="dark"] .brand-mark { color: #201a35; }
.brand-sub, [data-theme="dark"] .brand-sub { margin: 10px 0 26px 12px; font-size: .76rem; color: var(--muted); }
.nav-heading { margin: 24px 0 10px; font: 600 .7rem var(--mono); letter-spacing: .12em; color: var(--muted); }
.nav-links { gap: 4px; }
.nav-links a, [data-theme="dark"] .nav-links a { color: var(--muted); border: 1px solid transparent; font-size: .86rem; padding: 10px 12px; min-height: 44px; }
.nav-links a:hover, [data-theme="dark"] .nav-links a:hover { color: var(--ink); background: var(--surface-2); }
.nav-links a.active, [data-theme="dark"] .nav-links a.active { background: var(--primary-soft); color: var(--primary); border-color: color-mix(in srgb, var(--primary) 22%, transparent); }
.nav-links a.active svg { color: var(--primary); }
.nav-count, [data-theme="dark"] .nav-count { background: var(--surface); color: var(--primary); font: .68rem/1.9 var(--mono); padding: 0 5px; }
.topic-nav a { font-size: .8rem; min-height: 36px; padding-block: 7px; }
.topic-nav i { background: var(--muted); opacity: .65; width: 4px; height: 4px; }
.sidebar-bottom { padding-top: 24px; }
.local-badge { font-size: .76rem; padding-top: 16px; }
.sidebar-bottom p, [data-theme="dark"] .sidebar-bottom p { color: var(--muted); font-size: .72rem; }
.local-badge i, .live-dot { background: var(--mint); }
.topbar, [data-theme="dark"] .topbar { height: 72px; background: color-mix(in srgb, var(--paper) 93%, transparent); padding: 0 36px; }
.topbar-location { display: flex; align-items: center; gap: 12px; min-width: 0; }
.breadcrumb { min-width: 0; font-size: .8rem; }
.breadcrumb strong, [data-theme="dark"] .breadcrumb strong { color: var(--ink); font-weight: 600; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.topbar-right { flex-shrink: 0; }
.avatar, [data-theme="dark"] .avatar { background: var(--primary-soft); color: var(--primary); border: 1px solid var(--line); box-shadow: none; font-size: .7rem; }
.text-size-label { font-size: .75rem; }
.text-size-label select { font-size: .75rem; padding: 7px 10px; }
.theme-toggle { font-size: .78rem; padding: 8px 12px; }
.nav-toggle, .nav-close { display: none; }
.nav-backdrop[hidden] { display: none; }
.main { padding: 30px 36px 44px; max-width: 1600px; }
.hero, .ai-hero, [data-theme="dark"] .hero {
  border: 1px solid var(--line); border-radius: 18px;
  background: var(--surface); padding: clamp(24px, 3vw, 44px);
  gap: 36px; grid-template-columns: 1.15fr 1fr;
  position: relative; overflow: hidden;
}
.hero:before, .ai-hero:before { content: ""; position: absolute; left: 0; top: 30px; bottom: 30px; width: 3px; background: var(--primary); opacity: .8; }
.hero h1 { font-size: clamp(2rem, 3.1vw, 3rem); line-height: 1.17; margin: 18px 0; max-width: 620px; }
.hero .eyebrow { font-size: .7rem; letter-spacing: .08em; }
.hero p, [data-theme="dark"] .hero p { font-size: .95rem; color: var(--muted); max-width: 430px; margin-bottom: 26px; }
.hero-actions { gap: 10px; flex-wrap: wrap; }
.hero-demo, [data-theme="dark"] .hero-demo { transform: none; background: var(--stage); border: 1px solid var(--line); border-radius: 12px; padding: 22px; box-shadow: none; }
.demo-kicker { display: flex; align-items: center; gap: 6px; color: var(--muted); font: .7rem var(--mono); letter-spacing: .04em; margin-bottom: 18px; }
.demo-kicker > span:last-child { margin-left: auto; }
.live-dot { width: 5px; height: 5px; border-radius: 50%; flex-shrink: 0; }
.demo-header { color: var(--ink); font-size: .9rem; }
.demo-header span, [data-theme="dark"] .demo-header span { background: var(--surface-2); color: var(--muted); font: .68rem var(--mono); border: 1px solid var(--line); }
.demo-array { gap: 10px; padding: 30px 0 18px; }
.demo-cell { width: 52px; }
.demo-cell b, [data-theme="dark"] .demo-cell b { font-family: var(--mono); border-color: var(--line); color: var(--ink); background: var(--surface); height: 52px; }
.demo-cell.active b, [data-theme="dark"] .demo-cell.active b { background: var(--primary-soft); border-color: var(--primary); color: var(--primary); }
.demo-cell.found b, [data-theme="dark"] .demo-cell.found b { background: var(--success-soft); color: var(--mint); border-color: var(--mint); }
.demo-cell small, [data-theme="dark"] .demo-cell small { color: var(--muted); font: .7rem var(--mono); margin-top: 8px; }
.demo-terminal { background: var(--code); border: 1px solid var(--line); color: var(--code-ink); font-size: .8rem; padding: 12px; }
.demo-terminal span { color: var(--code-muted); }
.demo-terminal b { color: #a7e6c5; }
.demo-footer, [data-theme="dark"] .demo-footer { color: var(--muted); font-size: .7rem; gap: 6px; }
.stats-strip { background: var(--surface); border: 1px solid var(--line); border-radius: 12px; margin: 18px 0 34px; padding: 16px 20px; justify-content: space-between; gap: 16px; }
.stat { font-size: .78rem; gap: 8px; }
.stat svg { color: var(--muted); }
.stat:not(:last-child) { padding-right: 24px; }
.section-line h2 { font-size: 1.3rem; }
.section-subtitle { font-size: .85rem; }
.filter-bar, .ai-filters { padding: 16px; background: var(--surface); border: 1px solid var(--line); border-radius: 12px; }
.search-wrap, [data-theme="dark"] .search-wrap { background: var(--stage); border-color: var(--line); color: var(--muted); }
.search-wrap input, [data-theme="dark"] .search-wrap input { background: transparent; color: var(--ink); min-height: 44px; }
.search-wrap input::placeholder { color: var(--muted); }
.search-hint { font: .7rem var(--mono); color: var(--muted); }
.segmented, .view-toggle, [data-theme="dark"] :is(.segmented, .view-toggle) { background: var(--surface-2); border-color: var(--line); }
.segmented button, [data-theme="dark"] .segmented button { background: transparent; min-height: 36px; color: var(--muted); }
.segmented button.selected, .view-toggle button.selected, .mode-button.selected,
[data-theme="dark"] :is(.segmented button.selected, .view-toggle button.selected, .mode-button.selected, .filter-bookmark.selected) { background: var(--primary-soft); color: var(--primary); }
:is(.filter-row select, .topic-picker summary, .filter-bookmark), [data-theme="dark"] :is(.filter-row select, .topic-picker summary, .filter-bookmark) { color: var(--muted); background: var(--surface); min-height: 42px; height: auto; border-radius: 8px; }
.filter-bookmark.selected { color: var(--primary); background: var(--primary-soft); }
.filter-row .text-button { min-height: 42px; }
.topic-menu { max-height: 360px; overflow: auto; box-shadow: 0 12px 30px #0002; }
.results-toolbar { margin: 0 0 18px; flex-wrap: wrap; }
#sort, [data-theme="dark"] #sort { color: var(--ink); background: transparent; }
.view-toggle button { min-width: 36px; min-height: 36px; }
.library-layout { grid-template-columns: minmax(0, 1fr) 240px; gap: 24px; }
.problem-grid { gap: 18px; }
.problem-card, [data-theme="dark"] .problem-card { padding: 20px 20px 0; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); box-shadow: var(--shadow); }
.problem-card:hover, .ai-card:hover { transform: none; border-color: color-mix(in srgb, var(--primary) 55%, var(--line)); box-shadow: var(--shadow); }
.card-top { margin-bottom: 18px; }
.card-top .bookmark { min-width: 36px; min-height: 36px; }
.badge { font-size: .7rem; padding: 3px 8px; border-radius: 5px; }
.problem-number, [data-theme="dark"] .problem-number { font-size: .72rem; color: var(--muted); }
.card-identity { display: flex; align-items: center; gap: 11px; margin-bottom: 12px; }
.card-glyph { display: grid; place-items: center; flex-shrink: 0; width: 36px; height: 36px; border: 1px solid var(--line); border-radius: 10px; color: var(--primary); background: var(--primary-soft); }
.main .card-title { margin: 0; font-size: 1rem; line-height: 1.45; }
.card-description, [data-theme="dark"] .card-description { color: var(--muted); font-size: .84rem; line-height: 1.7; }
.tags span, .main .tags span, [data-theme="dark"] .tags span { font-size: .68rem; background: var(--surface-2); color: var(--muted); border-color: transparent; border-radius: 5px; padding: 3px 7px; }
.card-pattern, [data-theme="dark"] .card-pattern { color: var(--muted); font-size: .72rem; gap: 8px; }
.card-meta, [data-theme="dark"] .card-meta { color: var(--muted); font-size: .72rem; margin: 17px 0; }
.status.in-progress { color: #936411; }
[data-theme="dark"] .status.in-progress { color: #dfbd74; }
.card-open, [data-theme="dark"] .card-open { border-color: var(--line); color: var(--primary); font-size: .78rem; padding: 14px 0; }
.list-view .card-identity { margin-bottom: 0; }
.list-view .card-glyph { display: none; }
.progress-panel, .continue-card, .pattern-card, .panel, .roadmap-item, .lesson-card,
[data-theme="dark"] :is(.progress-panel, .continue-card, .pattern-card, .panel, .roadmap-item, .lesson-card) { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow); }
.progress-panel { padding: 22px; }
.progress-panel h3, [data-theme="dark"] .progress-panel h3 { color: var(--ink); font-size: .9rem; }
.progress-summary strong { font-family: Manrope, sans-serif; letter-spacing: -.06em; font-size: 2.8rem; }
.progress-summary > span, [data-theme="dark"] .progress-summary > span { font-size: .74rem; color: var(--muted); }
.progress-track, [data-theme="dark"] .progress-track { background: var(--surface-2); height: 5px; }
.progress-track span { background: var(--mint); }
.difficulty-progress { font-size: .76rem; }
.continue-card, [data-theme="dark"] .continue-card { border-top: 2px solid var(--mint); padding: 22px; }
.continue-card .eyebrow, [data-theme="dark"] .continue-card .eyebrow { font-size: .7rem; color: var(--muted); }
.continue-card p { font-size: .8rem; }
.continue-card .btn { width: 100%; padding-inline: 10px; font-size: .76rem; }
.continue-icon { background: var(--primary-soft); color: var(--primary); box-shadow: none; }
.side-note { padding: 18px 8px; }
.side-note h3, [data-theme="dark"] .side-note h3 { color: var(--ink); font-size: .88rem; }
.side-note p { font-size: .8rem; }
.page-heading { padding: 14px 0 28px; }
.page-heading p { color: var(--muted); max-width: 760px; }
.pattern-card { padding: 26px; }
.pattern-card p { color: var(--muted); }
.roadmap-item:hover { background: var(--surface-2); }
.roadmap-index { background: var(--primary-soft); color: var(--primary); font-family: var(--mono); }
.recent-link { border-color: var(--line); }
.progress-page { gap: 24px; }
.footer { color: var(--muted); border-color: var(--line); font-size: .75rem; }
/* Lesson workbenches: the stage has a quieter texture than the surrounding UI. */
.problem-back { color: var(--muted); font-size: .78rem; margin-bottom: 12px; }
.problem-heading { padding-block: 12px 10px; margin-bottom: 8px; }
.problem-heading h1 { margin-block: 10px; }
.problem-heading p { max-width: 800px; color: var(--muted); font-size: .95rem; }
.heading-meta { color: var(--muted); font-size: .76rem; }
.objective-row { margin: 8px 0 20px; padding: 4px 0 10px; font-size: .8rem; color: var(--muted); }
.lab, [data-theme="dark"] .lab { background: var(--surface); border-color: var(--line); border-radius: 16px; box-shadow: var(--shadow); }
.lab-header, [data-theme="dark"] .lab-header { background: var(--surface); border-color: var(--line); padding: 20px 24px; }
.lab-header h2 { font-size: 1.05rem; }
.lab-header > span { color: var(--muted); font-size: .76rem; }
.learning-toolbar { background: var(--stage); padding: 12px 24px; gap: 16px; }
.learning-toolbar .btn { font-size: .78rem; }
.input-form { gap: 12px; padding: 22px 24px 12px; }
.input-form label, [data-theme="dark"] .input-form label { font-size: .78rem; color: var(--muted); }
.input-form input, [data-theme="dark"] .input-form input { border-radius: 8px; background: var(--stage); color: var(--ink); min-height: 44px; font-family: var(--mono); }
.input-error:empty { display: none; }
.mode-row { padding-top: 12px; padding-inline: 24px; gap: 8px; flex-wrap: wrap; }
.mode-row > span { font: .7rem var(--mono); letter-spacing: .07em; }
.mode-button, [data-theme="dark"] .mode-button { background: var(--surface); color: var(--muted); border-color: var(--line); min-height: 42px; border-radius: 7px; }
.stage-container { padding: 18px; }
.stage-top { font: .7rem var(--mono); padding: 4px 4px 12px; margin-bottom: 8px; border-color: var(--line); color: var(--muted); }
.stage-top b, [data-theme="dark"] .stage-top b { color: var(--ink); font-weight: 500; }
.visual-stage, [data-theme="dark"] .visual-stage { background-color: var(--stage); background-image: radial-gradient(var(--stage-dot) .7px, transparent .7px); background-size: 20px 20px; min-height: 320px; border-color: var(--line); }
.visual-stage.focus-stage { background: var(--stage); }
.inspector, [data-theme="dark"] .inspector { background: var(--stage); border-color: var(--line); }
.inspector-label { font: .68rem var(--mono); letter-spacing: .07em; }
.step-explanation h3 { color: var(--ink); }
.step-explanation p { color: var(--muted); }
.state-terminal, .code-panel, [data-theme="dark"] :is(.state-terminal, .code-panel) { background: var(--code); color: var(--code-ink); border: 1px solid var(--line); border-radius: 10px; box-shadow: none; }
.state-terminal span, [data-theme="dark"] .state-terminal span { color: var(--code-muted); }
.legend, [data-theme="dark"] .legend { background: var(--surface); color: var(--muted); font-size: .72rem; padding: 16px 24px; }
.animation-controls, [data-theme="dark"] .animation-controls { background: var(--surface); border-color: var(--line); padding: 16px 24px; gap: 16px; }
.playback-buttons { background: var(--surface-2); padding: 4px; border-radius: 10px; gap: 3px; }
.playback-buttons .icon-button { min-width: 40px; min-height: 40px; color: var(--ink); }
.play-button { min-width: 92px; }
.step-count { color: var(--ink); font: .75rem var(--mono); }
.speed-label { font-size: .75rem; color: var(--muted); }
.speed-label select { color: var(--ink); border-radius: 7px; min-height: 40px; }
.learning-companion { background: var(--surface); padding: 24px; }
.trace-variable { background: var(--stage); }
.code-top, .code-tabs, [data-theme="dark"] :is(.code-top, .code-tabs) { background: var(--code); border-color: #3a403e; color: var(--code-ink); }
.code-copy, [data-theme="dark"] .code-copy { color: var(--code-muted); background: transparent; min-height: 40px; }
.code-tabs button, [data-theme="dark"] .code-tabs button { color: var(--code-muted); background: transparent; min-height: 40px; }
.code-tabs button.selected, [data-theme="dark"] .code-tabs button.selected { color: #d9d1ff; border-color: #b7a8ff; background: #2d283e; }
.code-mode-caption, [data-theme="dark"] .code-mode-caption { color: var(--code-muted); border-color: #3a403e; }
.code-panel pre { color: var(--code-ink); padding-block: 20px; }
.lesson-card { padding: 26px; }
.lesson-card h2 { font-size: 1.15rem; margin-bottom: 20px; }
.lesson-card p, .lesson-card li, [data-theme="dark"] :is(.lesson-card p, .lesson-card li) { color: var(--muted); font-size: .94rem; line-height: 1.85; }
.pseudocode, .complexity-box, [data-theme="dark"] :is(.pseudocode, .complexity-box) { background: var(--stage); color: var(--ink); border-color: var(--line); }
.quiz-option, [data-theme="dark"] .quiz-option { background: var(--stage); color: var(--ink); border: 1px solid var(--line); padding: 12px; border-radius: 8px; }
.quiz-option:has(input:checked) { background: var(--primary-soft); border-color: var(--primary); }
.quiz-option input { accent-color: var(--primary); }
.lesson-nav a { background: var(--surface); border-color: var(--line); }
/* AI Lab shares the workspace; its plots and neural/tree diagrams retain
   independent data, prediction, error and optimum encodings. */
.ai-hero { margin-bottom: 18px; }
.ai-hero h1 { font-size: clamp(2.7rem, 4vw, 4rem); margin: 12px 0 18px; }
.ai-hero p { font-size: .95rem; }
.ai-hero-diagram { background: var(--stage); border-radius: 12px; box-shadow: none; padding: 24px; gap: 18px; }
.ai-loop { display: grid; grid-template-columns: 1fr 20px 1fr; align-items: center; gap: 12px 8px; }
.ai-loop > div { padding: 14px 10px; border: 1px solid var(--line); border-radius: 8px; background: var(--surface); display: grid; gap: 8px; }
.ai-loop small { margin: 0; font: .7rem var(--mono); color: var(--muted); }
.ai-loop b { color: var(--ai-fit); font: 600 .85rem var(--mono); }
.ai-loop > span { color: var(--muted); text-align: center; }
.ai-loop .loop-update b { color: var(--ai-optimum); }
.ai-loop .loop-loss b { color: var(--ai-error); }
.ai-loop-footer { font: .7rem var(--mono); color: var(--muted); padding-top: 12px; border-top: 1px solid var(--line); }
.ai-summary { padding: 16px 20px; border: 1px solid var(--line); border-radius: 12px; background: var(--surface); font-size: .78rem; margin-bottom: 28px; gap: 16px; }
.ai-summary strong { color: var(--ink); font-weight: 600; }
.ai-summary > span { margin-left: auto; }
.ai-area-browser { margin-bottom: 30px; border-block: 1px solid var(--line); }
.ai-page .ai-area-browser > summary { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; padding: 18px 4px; font-size: .85rem; }
.ai-area-browser > summary:before { content: "+"; font: 1.1rem var(--mono); color: var(--primary); }
.ai-area-browser[open] > summary:before { content: "−"; }
.ai-area-browser > summary small { margin-left: auto; color: var(--muted); font-size: .75rem; font-weight: 400; }
.ai-categories { gap: 16px; margin-bottom: 24px; }
.ai-categories .ai-panel { padding: 22px; margin: 0; background: transparent; }
.ai-panel, .ai-equation { background: var(--surface); border-color: var(--line); border-radius: var(--radius); box-shadow: var(--shadow); }
.ai-categories p { font-size: .83rem; }
.ai-categories h2 { font-size: 1.05rem; }
.ai-filters { margin-top: 22px; gap: 16px; }
.ai-page input:not([type="range"]):not([type="checkbox"]):not([type="radio"]), .ai-page select { background: var(--stage); border-color: var(--line); color: var(--ink); min-height: 44px; border-radius: 8px; }
.ai-filters label { font-size: .75rem; }
#ai-count { font-size: .8rem; color: var(--muted); margin-block: 18px; }
.ai-cards { gap: 18px; }
.ai-card { padding: 22px; transition: border-color .15s; }
.ai-available { border-color: var(--line); }
.ai-card-signature { display: flex; align-items: center; justify-content: space-between; margin: 10px 0 12px; color: var(--primary); }
.ai-card-signature > span { font: .7rem var(--mono); color: var(--muted); letter-spacing: .04em; }
.ai-card h3 { font-size: 1.05rem; margin-top: 0; }
.ai-card p { font-size: .84rem; }
.ai-card .ai-muted { font-size: .72rem; color: var(--primary); }
.ai-card .btn.primary { background: var(--primary-soft); border: 1px solid color-mix(in srgb, var(--primary) 25%, var(--line)); color: var(--primary); font-size: .78rem; }
.ai-card .btn.primary:hover { background: var(--surface-2); }
.ai-card small { font-size: .72rem; }
.ai-card-top { font-size: .68rem; }
.ai-lesson-heading { padding: 18px 0 26px; }
.ai-lesson-heading h1 { font-size: clamp(1.9rem, 3vw, 2.7rem); }
.ai-tabs { gap: 8px; margin-bottom: 24px; }
.ai-tabs button, [data-theme="dark"] .ai-tabs button { background: transparent; color: var(--muted); min-height: 48px; padding: 12px 18px; white-space: nowrap; }
.ai-tabs [aria-selected="true"], [data-theme="dark"] .ai-tabs [aria-selected="true"] { color: var(--primary); background: var(--primary-soft); border-radius: 8px 8px 0 0; }
.ai-chart, .ai-math, .ai-metrics > div, .pca-placeholder { background: var(--stage); border: 1px solid var(--line); border-radius: 10px; }
.ai-chart-grid { gap: 24px; }
.ai-chart-grid figcaption { color: var(--ink); font-size: .88rem; }
.ai-controls, .nn-primary-controls { padding: 18px; border: 1px solid var(--line); background: var(--stage); border-radius: 10px; }
.ai-playback { margin-top: 20px; background: var(--stage); border: 1px solid var(--line); border-radius: 10px; padding: 14px; }
.ai-playback .btn { font-size: .8rem; }
.ai-metrics dt { font-size: .74rem; }
.ai-metrics dd { font-size: 1.05rem; }
.ai-code { background: var(--code); color: var(--code-ink); border-color: var(--line); }
.ai-question label { background: var(--stage); border: 1px solid var(--line); padding: 12px; border-radius: 8px; }
.ai-question label:has(input:checked) { background: var(--primary-soft); border-color: var(--primary); }
.nn-parameter-details, .nn-layer-editor, .nn-neuron-editor, .nn-stage-strip { background: var(--stage); border-color: var(--line); }
.ai-page table th { color: var(--ink); background: var(--stage); }
.ai-page table td { color: var(--ink); }
.ai-update { background: var(--stage); }
.skip-link { background: var(--surface); color: var(--ink); border: 1px solid var(--line); }
@media (min-width: 1500px) {
  .problem-grid:not(.list-view) { grid-template-columns: repeat(3, minmax(0, 1fr)); }
}
@media (max-width: 1200px) {
  :root { --sidebar: 218px; }
  .main { padding-inline: 26px; }
  .topbar { padding-inline: 26px; }
  .library-layout { grid-template-columns: minmax(0, 1fr); }
  .library-aside { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; }
  .library-aside > * { margin: 0; }
  .library-aside .side-note { display: none; }
  .hero, [data-theme="dark"] .hero, .ai-hero { gap: 24px; }
  .demo-kicker > span:last-child { display: none; }
}
@media (min-width: 761px) and (max-width: 1000px) {
  :root { --sidebar: 192px; }
  .sidebar { padding-inline: 10px; }
  .nav-links a { font-size: .78rem; gap: 8px; }
  .hero, [data-theme="dark"] .hero, .ai-hero { grid-template-columns: minmax(0, 1fr); }
  .hero-demo, [data-theme="dark"] .hero-demo { max-width: 520px; width: 100%; }
  .ai-hero-diagram { display: grid; }
}
@media (max-width: 760px) {
  :root { --sidebar: 0px; }
  .navigation-open { overflow: hidden; }
  .sidebar, [data-theme="dark"] .sidebar { position: fixed; width: min(300px, 86vw); height: 100dvh; inset: 0 auto 0 0; z-index: 60; padding: 28px 16px; border-right: 1px solid var(--line); transform: translateX(-101%); visibility: hidden; transition: transform .18s ease, visibility .18s; }
  .sidebar.is-open { transform: translateX(0); visibility: visible; }
  .sidebar .brand-sub, .sidebar .nav-heading, .sidebar .sidebar-bottom { display: block; }
  .sidebar .topic-nav { display: grid; }
  .sidebar .nav-links { display: grid; overflow: visible; margin-top: 0; gap: 4px; }
  .sidebar .nav-links a { font-size: .86rem; }
  .sidebar .nav-count { display: inline; }
  .sidebar .brand { margin-top: 8px; }
  .nav-close { display: grid; position: absolute; top: 14px; right: 14px; font-size: 1.4rem; }
  .nav-toggle { display: inline-flex; font-size: .75rem; min-height: 44px; padding: 8px; gap: 5px; }
  .nav-backdrop { position: fixed; inset: 0; z-index: 55; background: #0009; border: 0; backdrop-filter: blur(3px); }
  .topbar, [data-theme="dark"] .topbar { height: auto; min-height: 68px; padding: 12px 18px; gap: 10px; flex-wrap: wrap; }
  .topbar-location { flex: 1; }
  .breadcrumb { font-size: .74rem; gap: 6px; }
  .topbar-right { gap: 8px; }
  .topbar .avatar { display: none; }
  .text-size-label { font-size: 0; gap: 0; }
  .text-size-label select { max-width: 120px; font-size: .7rem; min-height: 44px; }
  .theme-toggle { padding: 8px 10px; min-height: 44px; }
  .main { padding: 22px 18px 32px; }
  .hero, [data-theme="dark"] .hero, .ai-hero { grid-template-columns: minmax(0, 1fr); padding: 24px; gap: 26px; border-radius: 14px; }
  .hero h1 { font-size: 2.1rem; margin-block: 16px; }
  .hero p { font-size: .9rem; }
  .hero .eyebrow { font-size: .7rem; }
  .hero-demo, [data-theme="dark"] .hero-demo { display: block; padding: 18px; transform: none; }
  .demo-cell { width: 48px; }
  .demo-cell b { height: 48px; }
  .demo-terminal { font-size: .78rem; }
  .hero .btn { font-size: .78rem; min-height: 44px; padding: 10px 13px; }
  .ai-hero-diagram { display: grid; padding: 18px; }
  .ai-summary { gap: 12px; }
  .ai-summary > span { margin-left: 0; }
  .stats-strip { flex-wrap: wrap; padding: 16px; gap: 12px 18px; }
  .stat { font-size: .74rem; }
  .stat:not(:last-child) { padding-right: 0; border-right: 0; }
  .section-line { flex-wrap: wrap; align-items: flex-start; }
  .section-line h2 { font-size: 1.2rem; }
  .filter-bar, .ai-filters { padding: 12px; }
  .filter-row { gap: 8px; }
  .search-wrap { padding-inline: 10px; }
  .search-hint { display: none; }
  .segmented { width: auto; }
  .segmented button { font-size: .75rem; padding: 6px 10px; min-height: 38px; }
  .filter-row select { max-width: 100%; flex: 1 1 130px; }
  .topic-picker summary, .filter-bookmark { min-height: 44px; }
  .results-toolbar { gap: 8px; }
  .results-toolbar .sort-label { display: none; }
  .result-count { font-size: .75rem; flex: 1 1 100%; }
  .problem-grid { gap: 14px; }
  .problem-card { padding: 18px 18px 0; }
  .library-aside { grid-template-columns: minmax(0, 1fr); }
  .problem-heading h1 { font-size: 1.85rem; }
  .heading-actions { flex-wrap: wrap; }
  .heading-actions .btn { font-size: .76rem; }
  .objective-row { gap: 12px; }
  .lab-header { padding: 18px; flex-wrap: wrap; gap: 8px; }
  .learning-toolbar, .learning-companion, .input-form, .mode-row { padding-inline: 16px; }
  .input-form { gap: 12px; }
  .stage-top { padding: 16px; }
  .visual-stage, [data-theme="dark"] .visual-stage { min-height: 300px; padding-inline: 16px; }
  .legend { padding-inline: 16px; }
  .inspector { display: block; padding: 18px; }
  .animation-controls, [data-theme="dark"] .animation-controls { padding: 12px 16px; gap: 12px; }
  .lesson-card { padding: 22px; }
  .lesson-card h2 { font-size: 1.08rem; }
  .ai-controls, .nn-primary-controls { padding: 12px; }
  .ai-panel, .ai-equation { padding: 18px; }
  .ai-categories { gap: 12px; }
  .ai-playback { padding: 12px; gap: 8px; }
  .ai-tabs button { padding-inline: 14px; }
  .footer { flex-wrap: wrap; gap: 8px; }
}
@media (max-width: 520px) {
  .topbar-location { flex-basis: 100%; }
  .topbar-right { width: 100%; justify-content: flex-end; }
  .text-size-label { margin-right: auto; }
  .problem-grid { grid-template-columns: minmax(0, 1fr); }
  .hero, [data-theme="dark"] .hero { padding: 22px 18px; }
  .hero h1 { font-size: 1.9rem; }
  .hero-demo, [data-theme="dark"] .hero-demo { margin: 0; }
  .demo-footer { flex-wrap: wrap; }
  .demo-footer a { margin-left: auto; }
  .list-view .problem-card { display: flex; }
  .list-view .card-identity { margin-bottom: 12px; }
  .list-view .card-meta { margin-block: 14px; }
  .list-view .card-open { display: flex; }
  .ai-controls, .nn-primary-controls { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .nn-primary-controls > label:first-child { grid-column: 1 / -1; }
  .ai-area-browser > summary small { margin-left: 0; }
  .ai-page h1 { font-size: 1.85rem; }
  .ai-hero h1 { font-size: 2.8rem; }
}
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; transition: none !important; animation: none !important; }
}

.viz-type { color: var(--muted); border-color: var(--line); font-size: .72rem; }
.card-open:hover { color: var(--primary-dark); }

@media (max-width: 360px) { .ai-controls, .nn-primary-controls { grid-template-columns: minmax(0, 1fr); } }
.difficulty-label.easy { color: var(--mint); }
.difficulty-label.medium { color: #8d5f0c; }
.difficulty-label.hard { color: #aa4058; }
[data-theme="dark"] .difficulty-label.medium { color: #e3bf77; }
[data-theme="dark"] .difficulty-label.hard { color: #eca1b3; }
.quiz-feedback { color: var(--mint); }
.quiz-feedback.incorrect { color: #b14055; }
[data-theme="dark"] .quiz-feedback.incorrect { color: #f0a8b4; }