/* Course theme for reveal.js -- light and dark share every rule, only tokens differ. */
:root {
  --bg: #fbfaf6;
  --surface: #ffffff;
  --sunken: #f1efe8;
  --ink: #1d2230;
  --muted: #646b7d;
  --line: #dcd8cc;
  --accent: #4338ca;
  --accent-soft: #e6e4fb;
  --warm: #c2410c;
  --warm-soft: #fdebdc;
  --good: #15803d;
  --good-soft: #dff3e4;
  --bad: #b91c1c;
  --bad-soft: #fde4e4;
  --fun: #a16207;
  --fun-soft: #fbf1cc;
  --code-bg: #f4f2ea;
  --code-ink: #24292f;
  --tok-kw: #a626a4;
  --tok-str: #2f7d32;
  --tok-num: #b35900;
  --tok-com: #8a8f9c;
  --tok-fn: #2456c9;
  --tok-builtin: #0e7490;
  --shadow: 0 2px 10px rgba(30, 30, 60, .08);
  --sans: "Inter", "Segoe UI", system-ui, -apple-system, "Helvetica Neue", Arial, sans-serif;
  --mono: "JetBrains Mono", "Fira Code", "Cascadia Code", ui-monospace, "SF Mono", Menlo, Consolas, "DejaVu Sans Mono", monospace;
}
:root[data-theme="dark"] {
  --bg: #11131a;
  --surface: #1a1d27;
  --sunken: #161922;
  --ink: #e7e9f0;
  --muted: #9aa1b4;
  --line: #2e3342;
  --accent: #9aa2ff;
  --accent-soft: #262a4d;
  --warm: #ffa366;
  --warm-soft: #3a2618;
  --good: #6fd08c;
  --good-soft: #17301f;
  --bad: #ff8585;
  --bad-soft: #3a1b1b;
  --fun: #f2cc60;
  --fun-soft: #332b12;
  --code-bg: #171a23;
  --code-ink: #d7dae3;
  --tok-kw: #d59bf6;
  --tok-str: #9ad88a;
  --tok-num: #f5b06b;
  --tok-com: #737a8c;
  --tok-fn: #86b4ff;
  --tok-builtin: #6fd3e0;
  --shadow: 0 2px 12px rgba(0, 0, 0, .4);
}

html, body { background: var(--bg); color: var(--ink); }
body { font-family: var(--sans); }
.reveal { font-family: var(--sans); font-size: 28px; color: var(--ink); }
.reveal-viewport { background: var(--bg); }
.reveal .slides { text-align: left; }
.reveal .slides section { padding: 26px 56px 30px; box-sizing: border-box; height: 100%; }
.reveal h1, .reveal h2, .reveal h3 { font-family: var(--sans); color: var(--ink); text-transform: none; letter-spacing: -.01em; margin: 0; text-wrap: balance; }
.reveal h2 { font-size: 41px; font-weight: 750; line-height: 1.15; padding-bottom: 12px; margin-bottom: 22px; position: relative; }
.reveal h2::after { content: ""; position: absolute; left: 0; bottom: 0; width: 72px; height: 5px; border-radius: 3px; background: var(--accent); }
.reveal h3 { font-size: 30px; font-weight: 700; margin: 0 0 10px; color: var(--accent); }
.reveal p { margin: 0 0 14px; line-height: 1.38; }
.reveal ul, .reveal ol { margin: 0 0 14px 1.1em; display: block; }
.reveal li { margin: 0 0 9px; line-height: 1.34; }
.reveal ul li::marker { color: var(--accent); }
.reveal ol li::marker { color: var(--accent); font-weight: 700; }
.reveal a { color: var(--accent); text-decoration: underline; text-decoration-thickness: 1px; text-underline-offset: 3px; }
.reveal strong, .reveal b { font-weight: 720; }
.reveal em { font-style: italic; }
.reveal small { font-size: .72em; color: var(--muted); }
.reveal .muted { color: var(--muted); }
.reveal .big { font-size: 1.35em; line-height: 1.3; }
.reveal .center { text-align: center; }
.reveal :not(pre) > code { font-family: var(--mono); font-size: .86em; background: var(--sunken); border: 1px solid var(--line); border-radius: 6px; padding: 1px 7px; white-space: nowrap; }
.reveal kbd, .index kbd { font-family: var(--mono); font-size: .8em; background: var(--surface); border: 1px solid var(--line); border-bottom-width: 3px; border-radius: 6px; padding: 1px 8px; white-space: nowrap; }

/* maths */
.reveal .math.display { text-align: center; font-size: 1.3em; margin: 4px 0 20px; }
.reveal .math .katex-display { margin: 0; }
.reveal .katex { font-size: 1.12em; }

/* layout helpers */
.reveal .cols { display: grid; grid-template-columns: 1fr 1fr; gap: 34px; align-items: start; }
.reveal .cols.c3 { grid-template-columns: 1fr 1fr 1fr; gap: 24px; }
.reveal .cols.wide-left { grid-template-columns: 1.45fr 1fr; }
.reveal .cols.wide-right { grid-template-columns: 1fr 1.45fr; }
.reveal .cols { margin-bottom: 22px; }
.reveal .cols > * { min-width: 0; }
.reveal .cols > :last-child, .reveal .cols > div > :last-child { margin-bottom: 0; }
.reveal .card { background: var(--surface); border: 1px solid var(--line); border-radius: 14px; padding: 16px 20px; box-shadow: var(--shadow); }
.reveal .card p:last-child, .reveal .card ul:last-child { margin-bottom: 0; }
.reveal .card { font-size: .88em; line-height: 1.38; }
.reveal .card > b { display: block; font-size: 1.12em; margin-bottom: 8px; color: var(--accent); }
.reveal .card p { line-height: 1.38; margin-bottom: 10px; }
.reveal .card .emoji { font-size: 1.6em; line-height: 1; display: block; margin-bottom: 14px; }
.reveal .cols.c3 .card { height: 100%; box-sizing: border-box; }

/* {dense} slides: for the few pages that carry a long listing */
.reveal section.dense { font-size: 24px; }
.reveal section.dense pre.code { font-size: calc(17px * var(--cz)); }
.reveal .cols.c3 pre.code { font-size: calc(16px * var(--cz)); }
.reveal section.dense pre.output { font-size: 17px; }
.reveal section.dense h2 { margin-bottom: 16px; }

/* title + divider slides */
.reveal section.title-slide, .reveal section.divider { display: flex !important; flex-direction: column; justify-content: center; }
.reveal section.title-slide[hidden], .reveal section.divider[hidden] { display: none !important; }
.reveal h1 { font-size: 76px; font-weight: 800; line-height: 1.05; margin-bottom: 18px; }
.reveal .kicker, .index .kicker { font-size: 22px; letter-spacing: .08em; text-transform: uppercase; color: var(--accent); font-weight: 700; margin-bottom: 18px; }
.reveal .subtitle { font-size: 34px; color: var(--muted); }
.reveal .hint { font-size: 19px; color: var(--muted); margin-top: 40px; }
.reveal section.divider h2 { font-size: 66px; padding-bottom: 20px; }
.reveal section.divider p { font-size: 32px; color: var(--muted); }
.reveal section.divider::before { content: attr(data-part); }

/* callouts */
.reveal .callout { display: flex; gap: 16px; align-items: baseline; border-radius: 12px; padding: 11px 18px; margin: 0 0 14px; border-left: 6px solid var(--accent); background: var(--accent-soft); line-height: 1.38; }
.reveal .callout .tag { flex: none; font-size: 15px; font-weight: 800; letter-spacing: .07em; text-transform: uppercase; color: var(--accent); }
.reveal .callout.ask { border-color: var(--warm); background: var(--warm-soft); }
.reveal .callout.ask .tag { color: var(--warm); }
.reveal .callout.fun { border-color: var(--fun); background: var(--fun-soft); }
.reveal .callout.fun .tag { color: var(--fun); }
.reveal .callout.trap { border-color: var(--bad); background: var(--bad-soft); }
.reveal .callout.trap .tag { color: var(--bad); }
.reveal .callout.answer { border-color: var(--good); background: var(--good-soft); }
.reveal .callout.answer .tag { color: var(--good); }

/* challenge + solution slides */
.reveal section.challenge h2::before { content: "Challenge"; display: block; font-size: 17px; letter-spacing: .1em; text-transform: uppercase; color: var(--warm); margin-bottom: 6px; }
.reveal section.challenge h2::after { background: var(--warm); }
.reveal section.teacher-only h2::before { content: "Teacher only \00B7  solution"; display: block; font-size: 17px; letter-spacing: .1em; text-transform: uppercase; color: var(--good); margin-bottom: 6px; }
.reveal section.teacher-only h2::after { background: var(--good); }

/* tables */
.reveal table { border-collapse: collapse; margin: 0 0 14px; font-size: .84em; width: 100%; }
.reveal table th { text-align: left; font-weight: 720; color: var(--muted); font-size: .8em; letter-spacing: .05em; text-transform: uppercase; border: 0; border-bottom: 2px solid var(--line); padding: 7px 14px 7px 0; }
.reveal table td { border: 0; border-bottom: 1px solid var(--line); padding: 6px 14px 6px 0; vertical-align: top; line-height: 1.3; }
.reveal table.tight td, .reveal table.tight th { padding-top: 5px; padding-bottom: 5px; }
.reveal table.auto { width: auto; }

/* code */
.reveal .codewrap { position: relative; margin: 0 0 14px; }
.reveal pre.code, .reveal pre.output { --cz: 1; width: 100%; margin: 0; box-shadow: none; font-family: var(--mono); font-size: calc(20px * var(--cz)); line-height: 1.4; border-radius: 12px; box-sizing: border-box; }
.reveal pre.code { background: var(--code-bg); border: 1px solid var(--line); max-height: 540px; overflow: auto; }
.reveal pre.code code { font-family: var(--mono); display: block; padding: 11px 16px; max-height: none; overflow: visible; background: transparent; color: var(--code-ink); white-space: pre; tab-size: 4; }
.reveal pre.output { margin: 0 0 14px; padding: 9px 16px 9px 44px; background: var(--sunken); border: 1px dashed var(--line); color: var(--ink); white-space: pre-wrap; position: relative; font-size: 19px; }
.reveal pre.output::before { content: "\25B8"; position: absolute; left: 18px; top: 8px; color: var(--good); }
.reveal .codewrap + pre.output { margin-top: -10px; }
.hljs-ln { border-collapse: collapse; width: auto !important; margin: 0 !important; font-size: 1em !important; }
.hljs-ln td { border: 0 !important; padding: 0 !important; line-height: 1.42; }
.reveal .hljs-ln td.hljs-ln-numbers { color: var(--tok-com); text-align: right; padding-right: 16px !important; user-select: none; min-width: 1.4em; border-right: 1px solid var(--line) !important; }
.reveal .hljs-ln td.hljs-ln-code { padding-left: 16px !important; }
.reveal .hljs.has-highlights tr:not(.highlight-line) { opacity: .35; }
.reveal .hljs tr.highlight-line td { background: var(--accent-soft); }
.hljs-keyword, .hljs-literal, .hljs-meta { color: var(--tok-kw); }
.hljs-string, .hljs-subst, .hljs-regexp { color: var(--tok-str); }
.hljs-subst { color: var(--code-ink); }
.hljs-number { color: var(--tok-num); }
.hljs-comment { color: var(--tok-com); font-style: italic; }
.hljs-title, .hljs-title.function_ { color: var(--tok-fn); }
.hljs-built_in, .hljs-type { color: var(--tok-builtin); }

.code-tools { position: absolute; top: 8px; right: 8px; display: flex; gap: 4px; opacity: 0; transition: opacity .15s; z-index: 3; }
.codewrap:hover .code-tools, .code-tools:focus-within { opacity: 1; }
.code-tools button, .code-tools a, #code-overlay .bar button { font: 600 14px var(--sans); color: var(--ink); background: var(--surface); border: 1px solid var(--line); border-radius: 7px; padding: 4px 9px; cursor: pointer; text-decoration: none; line-height: 1.3; }
.code-tools button:hover, .code-tools a:hover, #code-overlay .bar button:hover { border-color: var(--accent); color: var(--accent); }

#code-overlay { position: fixed; inset: 0; z-index: 100; background: var(--bg); display: none; flex-direction: column; }
#code-overlay.open { display: flex; }
#code-overlay .bar { display: flex; gap: 8px; align-items: center; padding: 10px 16px; border-bottom: 1px solid var(--line); }
#code-overlay .bar span { margin-right: auto; color: var(--muted); font: 14px var(--sans); }
#code-overlay .bar button { font-size: 16px; padding: 6px 14px; }
#code-overlay .stage { flex: 1; overflow: auto; padding: 24px 32px; font-family: var(--mono); font-size: 30px; line-height: 1.45; color: var(--code-ink); white-space: pre; }
#code-overlay .hljs-ln td.hljs-ln-numbers { color: var(--tok-com); text-align: right; padding-right: 18px !important; border-right: 1px solid var(--line) !important; user-select: none; }
#code-overlay .hljs-ln td.hljs-ln-code { padding-left: 18px !important; }

/* step-by-step player */
.reveal .tracer { display: grid; grid-template-columns: 1.35fr 1fr; grid-template-rows: auto auto 1fr; gap: 12px 26px; align-items: start; margin: 0 0 14px; }
.reveal .tracer > .codewrap { grid-column: 1; grid-row: 1; }
.reveal .tracer > .tracer-panel { grid-column: 2; grid-row: 1 / 4; }
.reveal .tracer .codewrap { margin: 0; }
.reveal .tracer-bar { grid-column: 1; grid-row: 2; display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }
.reveal .tracer-bar button { font: 600 17px var(--sans); color: var(--ink); background: var(--surface); border: 1px solid var(--line); border-radius: 8px; padding: 6px 15px; cursor: pointer; }
.reveal .tracer-bar button:hover { border-color: var(--accent); color: var(--accent); }
.reveal .tracer-info { margin-left: 10px; font-size: 18px; color: var(--muted); }
.reveal .tracer-panel { background: var(--surface); border: 1px solid var(--line); border-radius: 12px; padding: 10px 16px 12px; box-shadow: var(--shadow); }
.reveal .tracer-vars { font-family: var(--mono); font-size: 20px; margin-bottom: 10px; }
.reveal .tracer-vars td:first-child { width: 45%; color: var(--accent); }
.reveal .tracer-vars tr.unset td { color: var(--muted); opacity: .55; }
.reveal .tracer-vars tr.changed td:last-child { color: var(--warm); font-weight: 700; background: var(--warm-soft); }
.reveal .tracer-label { font-size: 13px !important; font-weight: 720; letter-spacing: .05em; text-transform: uppercase; color: var(--muted); margin: 0 0 4px !important; }
.reveal .tracer-panel pre.output { margin: 0; font-size: 18px; }
.reveal .tracer .hljs tr.now td { background: var(--accent-soft); }
.reveal .tracer .hljs tr.now td.hljs-ln-numbers { color: var(--accent); font-weight: 800; box-shadow: inset 4px 0 0 var(--accent); }
.reveal .tracer-event { display: block; font: 650 16px var(--mono); padding: 3px 10px; border-radius: 7px; margin: 0 0 8px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; color: var(--muted); background: var(--sunken); }
.reveal .tracer-event.call { color: var(--accent); background: var(--accent-soft); }
.reveal .tracer-event.ret { color: var(--good); background: var(--good-soft); }
.reveal .tracer-event.err { color: var(--bad); background: var(--bad-soft); }
/* call stack in the table view */
.reveal .tracer-vars.stack { font-size: 18px; }
.reveal .tracer-vars tr.frame td { font: 700 14px var(--sans); letter-spacing: .04em; text-transform: uppercase; color: var(--muted); background: var(--bg); padding-top: 6px; border-top: 2px solid var(--line); }
.reveal .tracer-vars tr.frame.top td { color: var(--accent); border-top-color: var(--accent); }
.reveal .tracer-vars tr.ret td { color: var(--good) !important; font-style: italic; }
/* heap view: frames on the left, objects on the right, arrows between */
.reveal .tracer.heap { grid-template-columns: 1fr 1.25fr; }
.reveal .hv { position: relative; display: grid; grid-template-columns: auto 1fr; gap: 10px 44px; align-items: start; margin-bottom: 10px; font-family: var(--mono); font-size: 18px; }
.reveal .hv-frames, .reveal .hv-col { display: flex; flex-direction: column; gap: 10px; align-items: flex-start; }
.reveal .hv-heap { display: flex; gap: 40px; align-items: flex-start; }
.reveal .hv-frame { min-width: 150px; border: 1px solid var(--line); border-radius: 8px; padding: 4px 10px 6px; background: var(--bg); }
.reveal .hv-frame.top { border-color: var(--accent); box-shadow: inset 4px 0 0 var(--accent); }
.reveal .hv-title { font: 700 13px var(--sans); text-transform: uppercase; letter-spacing: .05em; color: var(--muted); margin-bottom: 2px; }
.reveal .hv-frame.top .hv-title { color: var(--accent); }
.reveal .hv-row { display: flex; justify-content: space-between; align-items: center; gap: 14px; line-height: 1.55; }
.reveal .hv-name { color: var(--accent); }
.reveal .hv-row.ret .hv-name { color: var(--good); font-style: italic; }
.reveal .hv-val.changed { color: var(--warm); font-weight: 700; }
.reveal .ptr { display: inline-block; width: 13px; height: 13px; border-radius: 50%; background: var(--ink); margin: 0 4px; }
.reveal .ptr.changed { background: var(--warm); }
.reveal .hv-obj { border: 1px solid var(--line); border-radius: 8px; background: var(--bg); padding: 2px 6px 6px; }
.reveal .hv-type { font: 700 12px var(--sans); color: var(--muted); text-transform: uppercase; letter-spacing: .05em; }
.reveal .hv-seq { display: flex; flex-wrap: wrap; max-width: 330px; }
.reveal .hv-cell { display: flex; flex-direction: column; align-items: center; justify-content: flex-end; min-width: 38px; padding: 0 7px 2px; border: 1px solid var(--line); margin: 0 -1px -1px 0; background: var(--surface); }
.reveal .hv-cell small { font-size: 11px; color: var(--muted); line-height: 1.2; }
.reveal .t-tuple .hv-cell { background: var(--accent-soft); }
.reveal .t-set .hv-cell { border-radius: 12px; margin-right: 4px; }
.reveal .hv-map { display: grid; grid-template-columns: auto auto; }
.reveal .hv-map > .hv-key, .reveal .hv-map > .hv-v { border: 1px solid var(--line); margin: 0 -1px -1px 0; padding: 1px 8px; background: var(--surface); }
.reveal .hv-key { color: var(--accent); }
.reveal .hv-empty { color: var(--muted); font-style: italic; font-size: 15px; padding: 2px 6px; }
.reveal svg.hv-arrows { position: absolute; left: 0; top: 0; pointer-events: none; overflow: visible; }
.reveal .hv-line { fill: none; stroke: var(--ink); stroke-width: 2; opacity: .75; }
.reveal .hv-line.changed { stroke: var(--warm); opacity: 1; }
.reveal .hv-head { fill: var(--ink); }
/* bar chart for sorting */
.reveal .tracer-bars { display: flex; align-items: flex-end; gap: 6px; height: 140px; margin: 2px 0 12px; }
.reveal .tb-col { flex: 1 1 0; min-width: 0; display: flex; flex-direction: column; align-items: stretch; height: 100%; justify-content: flex-end; }
.reveal .tb-bar { min-height: 5px; background: var(--accent-soft); border: 1px solid var(--accent); border-radius: 4px 4px 0 0; transition: height .25s; }
.reveal .tb-bar.marked { background: var(--accent); }
.reveal .tb-bar.changed { background: var(--warm); border-color: var(--warm); }
.reveal .tb-val, .reveal .tb-mark { font: 600 15px var(--mono); text-align: center; line-height: 1.3; white-space: nowrap; overflow: visible; }
.reveal .tb-mark { color: var(--accent); min-height: 1.3em; }

/* memory diagrams (name -> object) */
.reveal .mem { display: grid; gap: 10px; margin: 0 0 18px; font-family: var(--mono); font-size: 23px; }
.reveal .mem-row { display: grid; grid-template-columns: 150px 90px auto; align-items: center; justify-content: start; }
.reveal .mem-name { background: var(--accent-soft); border: 2px solid var(--accent); border-radius: 8px; padding: 5px 12px; text-align: center; }
.reveal .mem-arrow { height: 2px; background: var(--muted); position: relative; margin: 0 6px; }
.reveal .mem-arrow::after { content: ""; position: absolute; right: -2px; top: -6px; border: 7px solid transparent; border-left-color: var(--muted); border-right: 0; }
.reveal .mem-obj { background: var(--surface); border: 2px solid var(--line); border-radius: 22px; padding: 5px 16px; box-shadow: var(--shadow); }
.reveal .mem-obj small { margin-left: 12px; color: var(--warm); font-size: .7em; }

/* flowcharts */
.reveal svg.flow { display: block; margin: 0 auto; max-width: 100%; height: auto; font-family: var(--sans); }
svg.flow .n { stroke-width: 2.5; }
svg.flow .T { fill: var(--good-soft); stroke: var(--good); }
svg.flow .P { fill: var(--surface); stroke: var(--muted); }
svg.flow .IO { fill: var(--accent-soft); stroke: var(--accent); }
svg.flow .D { fill: var(--warm-soft); stroke: var(--warm); }
svg.flow text { fill: var(--ink); font-size: 18px; text-anchor: middle; dominant-baseline: central; }
svg.flow text.lbl { fill: var(--muted); font-size: 16px; font-weight: 700; }
svg.flow .edge { fill: none; stroke: var(--ink); stroke-width: 2.2; }
svg.flow .head { fill: var(--ink); }

/* widgets */
.reveal .widget { background: var(--surface); border: 1px solid var(--line); border-radius: 14px; padding: 18px 22px; box-shadow: var(--shadow); margin-bottom: 18px; }
.reveal .widget button { font: 600 18px var(--sans); color: var(--ink); background: var(--sunken); border: 1px solid var(--line); border-radius: 8px; padding: 6px 16px; cursor: pointer; }
.reveal .widget button:hover { border-color: var(--accent); color: var(--accent); }
.bits-row { display: flex; gap: 8px; justify-content: center; }
.bits-row .bit { display: flex; flex-direction: column; align-items: center; gap: 6px; }
.bits-row .bit small { font-family: var(--mono); }
.bits-row .bit button { width: 68px; height: 72px; font: 700 40px var(--mono) !important; padding: 0 !important; }
.bits-row .bit button.on { background: var(--accent) !important; color: var(--bg) !important; border-color: var(--accent) !important; }
.bits-out { text-align: center; margin: 16px 0 0 !important; font-family: var(--mono); font-size: 26px; }
.bits-out b { color: var(--accent); font-size: 1.5em; }
.tm-tape { display: flex; justify-content: center; margin: 4px 0 26px; }
.tm-cell { width: 62px; height: 62px; border: 2px solid var(--line); margin-left: -2px; display: grid; place-items: center; font: 700 32px var(--mono); position: relative; background: var(--sunken); }
.tm-cell.head { border-color: var(--warm); background: var(--warm-soft); z-index: 1; }
.tm-cell.head::after { content: "\25B2  head"; position: absolute; top: 66px; left: 50%; transform: translateX(-50%); font: 700 15px var(--sans); color: var(--warm); white-space: nowrap; }
.tm-status { display: flex; gap: 14px; align-items: center; justify-content: center; font-size: 22px; flex-wrap: wrap; }
.tm-status .state { font-family: var(--mono); font-weight: 700; color: var(--accent); }
.tm-rules { font-size: 19px !important; margin: 14px 0 0 !important; }
.tm-rules tr.active td { background: var(--accent-soft); font-weight: 700; }

/* figures */
.reveal figure.comic { margin: 0 auto 10px; text-align: center; }
.reveal figure.comic img { max-height: 470px; max-width: 100%; background: #fff; border-radius: 10px; padding: 12px; border: 1px solid var(--line); margin: 0; box-sizing: border-box; }
.reveal figure.comic.tall img { max-height: 520px; }
.reveal figure.comic figcaption { font-size: 15px; color: var(--muted); margin-top: 6px; }
.reveal figure.photo { margin: 0 0 14px; text-align: center; }
.reveal figure.photo img { max-height: 400px; max-width: 100%; border-radius: 12px; border: 1px solid var(--line); margin: 0; background: #fff; box-sizing: border-box; }
.reveal figure.photo.wide img { max-height: 330px; }
.reveal figure.photo figcaption { font-size: 17px; color: var(--muted); margin-top: 6px; line-height: 1.35; }
.reveal figure.photo figcaption span { font-size: 13px; opacity: .85; white-space: nowrap; }
.reveal .hw { display: grid; grid-template-columns: 1fr 1.25fr 1fr; gap: 18px; align-items: center; text-align: center; margin-bottom: 18px; }
.reveal .hw .card b { display: block; color: var(--accent); margin-bottom: 4px; }
.reveal .hw .card { font-size: .8em; }
.reveal .spiral svg { width: 100%; max-height: 360px; }
.reveal .spiral polyline { fill: none; stroke: var(--accent); stroke-width: 1.2; }
.reveal .steps { display: flex; gap: 12px; align-items: stretch; margin-bottom: 18px; }
.reveal .steps > div { flex: 1; background: var(--surface); border: 1px solid var(--line); border-radius: 12px; padding: 14px 16px; font-size: .78em; position: relative; line-height: 1.35; }
.reveal .steps > div b { display: block; color: var(--accent); margin-bottom: 4px; font-size: 1.1em; }
.reveal .steps > div:not(:last-child)::after { content: "\2192"; position: absolute; right: -14px; top: 50%; transform: translate(50%, -50%); color: var(--muted); font-size: 22px; z-index: 2; }

/* chrome */
.deck-footer { position: fixed; left: 18px; bottom: 12px; z-index: 5; font: 13px var(--sans); color: var(--muted); }
.deck-footer a { color: inherit; text-decoration: none; }
.reveal .slide-number { background: transparent; color: var(--muted); font: 14px var(--sans); right: 96px; bottom: 12px; }
.reveal .slide-number a { color: inherit; text-decoration: none; }
.reveal .progress { color: var(--accent); }
.reveal .controls { color: var(--accent); }
.theme-toggle { position: fixed; top: 12px; right: 14px; z-index: 6; width: 38px; height: 38px; border-radius: 50%; border: 1px solid var(--line); background: var(--surface); color: var(--ink); font-size: 20px; cursor: pointer; opacity: .55; }
.theme-toggle:hover { opacity: 1; }
body.teacher:not(.index-page)::before { content: "TEACHER EDITION"; position: fixed; top: 20px; right: 64px; z-index: 6; font: 800 12px var(--sans); letter-spacing: .1em; color: var(--good); border: 1px solid var(--good); border-radius: 5px; padding: 3px 8px; }

/* index page */
.index { max-width: 860px; margin: 0 auto; padding: 56px 16px 80px; }
.index h1 { font-size: clamp(32px, 6vw, 52px); line-height: 1.08; margin: 0 0 12px; font-weight: 800; letter-spacing: -.02em; }
.index .kicker { font-size: 14px; }
.index .subtitle { color: var(--muted); font-size: 20px; margin: 0 0 32px; }
.index .lectures { list-style: none; padding: 0; margin: 0 0 28px; display: grid; gap: 12px; }
.index .lectures a { display: flex; gap: 18px; align-items: center; padding: 16px 20px; background: var(--surface); border: 1px solid var(--line); border-radius: 14px; text-decoration: none; color: var(--ink); box-shadow: var(--shadow); }
.index .lectures a:hover { border-color: var(--accent); }
.index .lectures .n { font: 800 26px var(--mono); color: var(--accent); }
.index .lectures b { display: block; font-size: 19px; }
.index .lectures small { color: var(--muted); font-size: 15px; }
.index .lectures .count { margin-left: auto; color: var(--muted); font-size: 14px; white-space: nowrap; }
.index .hint { color: var(--muted); font-size: 15px; line-height: 1.7; }
.index code { font-family: var(--mono); background: var(--sunken); padding: 1px 6px; border-radius: 5px; }

/* Backdrops: each kind of slide has its own tint and a large faint glyph.
   reveal.js puts the current slide's data-state on <body>. */
body { --k-tint: transparent; --k-ink: var(--accent); --k-glyph: none; transition: background-color .25s; }
body.k-title, section.k-title { --k-tint: var(--accent-soft); --k-ink: var(--accent); --k-glyph: "01"; }
body.k-divider, section.k-divider { --k-tint: var(--accent-soft); --k-ink: var(--accent); --k-glyph: "{ }"; }
body.k-question, section.k-question { --k-tint: var(--warm-soft); --k-ink: var(--warm); --k-glyph: "?"; }
body.k-challenge, section.k-challenge { --k-tint: var(--warm-soft); --k-ink: var(--warm); --k-glyph: "</>"; }
body.k-aside, section.k-aside { --k-tint: var(--fun-soft); --k-ink: var(--fun); --k-glyph: "\2726"; }
body.k-solution, section.k-solution { --k-tint: var(--good-soft); --k-ink: var(--good); --k-glyph: "\2713"; }
body.k-explain, section.k-explain { --k-tint: var(--accent-soft); --k-glyph: none; }
body.reveal-viewport { background-color: var(--bg); background-image: radial-gradient(120% 90% at 100% 0%, var(--k-tint), transparent 62%), radial-gradient(70% 60% at 0% 100%, var(--k-tint), transparent 70%); }
body.reveal-viewport.k-explain { background-image: radial-gradient(60% 50% at 100% 0%, var(--k-tint), transparent 70%); }
body.reveal-viewport.k-title, body.reveal-viewport.k-divider, body.reveal-viewport.k-challenge { background-image: linear-gradient(135deg, var(--k-tint), transparent 70%), radial-gradient(60% 70% at 100% 100%, var(--k-tint), transparent 70%); }
body.reveal-viewport::after { content: var(--k-glyph); position: fixed; right: 3vw; bottom: -7vh; z-index: 0; font: 800 62vh/1 var(--mono); letter-spacing: -.06em; color: var(--k-ink); opacity: .07; pointer-events: none; white-space: nowrap; }
body.k-title::after, body.k-divider::after { opacity: .1; }
.reveal { z-index: 1; }
.reveal .callout.ask { box-shadow: var(--shadow); }
body.k-question .reveal .callout.ask, body.k-challenge .reveal .callout.ask { background: var(--surface); }
.reveal .slides section.k-divider h2::after { background: var(--k-ink); }

/* ?pdf export: one slide per 1280x720 page, no reveal.js positioning */
html.pdf-export, html.pdf-export body { width: 1280px !important; height: auto !important; overflow: visible !important; position: static !important; -webkit-print-color-adjust: exact; print-color-adjust: exact; }
html.pdf-export .reveal { position: static; width: 1280px; height: auto; overflow: visible; }
html.pdf-export .reveal .slides { position: static !important; display: block !important; width: 1280px !important; height: auto !important; margin: 0 !important; transform: none !important; zoom: 1 !important; perspective: none; counter-reset: page; }
html.pdf-export .reveal .slides > section { display: block !important; position: relative !important; top: auto !important; left: auto !important; width: 1280px !important; height: 720px !important; transform: none !important; opacity: 1 !important; visibility: visible !important; overflow: hidden; break-after: page; break-inside: avoid; background: var(--bg); counter-increment: page; }
html.pdf-export .reveal .slides > section.title-slide, html.pdf-export .reveal .slides > section.divider { display: flex !important; }
html.pdf-export .reveal .slides > section::after { content: counter(page); position: absolute; right: 22px; bottom: 12px; font: 13px var(--sans); color: var(--muted); }
html.pdf-export .reveal .fragment { opacity: 1 !important; visibility: visible !important; }
html.pdf-export .reveal pre.code { max-height: none; overflow: hidden; }
html.pdf-export .reveal .hint, html.pdf-export .reveal .controls, html.pdf-export .reveal .progress, html.pdf-export .reveal .slide-number, html.pdf-export .reveal .backgrounds, html.pdf-export .reveal aside.notes, html.pdf-export .code-tools, html.pdf-export .theme-toggle, html.pdf-export .deck-footer, html.pdf-export #code-overlay { display: none !important; }
html.pdf-export body.teacher::before { display: none; }
html.pdf-export .reveal .slides > section { padding: 34px 72px 34px !important; background-color: var(--bg); background-image: radial-gradient(120% 90% at 100% 0%, var(--k-tint, transparent), transparent 62%); }
html.pdf-export .reveal .slides > section::before { content: var(--k-glyph, ""); position: absolute; right: 30px; bottom: 0; transform: translateY(50px); font: 800 440px/1 var(--mono); letter-spacing: -.06em; color: var(--k-ink); opacity: .07; white-space: nowrap; }
html.pdf-export .reveal .slides > section:last-of-type { break-after: auto; height: 716px !important; }
html.pdf-export body > :not(.reveal) { display: none !important; }
html.pdf-export, html.pdf-export body { margin: 0 !important; padding: 0 !important; }
html.pdf-export .reveal .speaker-notes, html.pdf-export body::after { display: none !important; }
html.pdf-export body.reveal-viewport { background-image: none; }
.reveal section.center h2::after { left: 50%; transform: translateX(-50%); }
html.pdf-export .reveal > :not(.slides) { display: none !important; }
html.pdf-export .reveal .slides > :not(section) { display: none !important; }
html.pdf-export .reveal .tracer-bar button { display: none; }
.reveal .tracer .hljs-ln { width: 100% !important; }
.reveal .tracer .hljs-ln td.hljs-ln-code { width: 100%; }

/* utf8 widget */
.reveal .utf8 input, .reveal .hashtable input { font: 500 26px var(--mono); padding: 6px 14px; border: 2px solid var(--line); border-radius: 10px; background: var(--surface); color: var(--ink); width: 100%; box-sizing: border-box; }
.reveal .utf8 input:focus, .reveal .hashtable input:focus { outline: none; border-color: var(--accent); }
.reveal .utf8-table { margin: 14px 0 6px; font-family: var(--mono); font-size: 20px; }
.reveal .utf8-table th { font: 700 14px var(--sans); text-transform: uppercase; letter-spacing: .04em; color: var(--muted); text-align: left; white-space: nowrap; }
.reveal .utf8-table td { text-align: center; }
.reveal .utf8-table tr.r0 td { font-size: 30px; }
.reveal .utf8-table td.b2 { color: var(--accent); font-weight: 700; }
.reveal .utf8-table td.b3 { color: var(--warm); font-weight: 700; }
.reveal .utf8-table td.b4 { color: var(--bad); font-weight: 700; }
.reveal .utf8-sum { font-size: 22px; margin: 6px 0 0 !important; }
.reveal .utf8-sum b { color: var(--accent); }
/* hash table widget */
.reveal .ht-form { display: flex; gap: 10px; }
.reveal .ht-form input { flex: 1; font-size: 22px; }
.reveal .ht-form button, .reveal .ct-bar button { font: 600 18px var(--sans); color: var(--ink); background: var(--surface); border: 1px solid var(--line); border-radius: 8px; padding: 6px 16px; cursor: pointer; white-space: nowrap; }
.reveal .ht-form button:hover, .reveal .ct-bar button:hover { border-color: var(--accent); color: var(--accent); }
.reveal .ht-how { font: 18px var(--mono); margin: 10px 0 !important; min-height: 1.5em; }
.reveal .ht-how .slot { color: var(--accent); font-size: 1.2em; }
.reveal .ht-how .clash, .reveal .ht-key.clash { color: var(--warm); }
.reveal .ht-how .ok { color: var(--good); font-weight: 700; }
.reveal .ht-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 6px 24px; }
.reveal .ht-row { display: flex; align-items: center; gap: 10px; font-family: var(--mono); font-size: 19px; }
.reveal .ht-row.hit .ht-idx { background: var(--accent); color: var(--bg); }
.reveal .ht-idx { width: 34px; height: 34px; display: grid; place-items: center; border-radius: 8px; background: var(--sunken); font-weight: 700; flex: none; }
.reveal .ht-chain { display: flex; gap: 6px; flex-wrap: wrap; }
.reveal .ht-key { padding: 2px 10px; border: 1px solid var(--line); border-radius: 6px; background: var(--surface); }
.reveal .ht-key.clash::before { content: "→ "; color: var(--muted); }
.reveal .ht-key.new { border-color: var(--accent); background: var(--accent-soft); }
.reveal .ht-empty { color: var(--muted); opacity: .6; font-size: 16px; }
/* growth widget */
.reveal .growth input[type=range] { width: 100%; accent-color: var(--accent); }
.reveal .gr-n { font-size: 22px; margin: 0 0 4px !important; }
.reveal .gr-n b { color: var(--accent); font-size: 1.3em; }
.reveal .gr-n small { color: var(--muted); font-size: 16px; }
.reveal .gr-rows { display: grid; gap: 8px; margin-top: 12px; }
.reveal .gr-row { display: grid; grid-template-columns: 130px 1fr 330px; gap: 14px; align-items: center; font-size: 19px; }
.reveal .gr-name { font: 700 19px var(--mono); }
.reveal .gr-track { height: 22px; background: var(--sunken); border-radius: 6px; overflow: hidden; }
.reveal .gr-bar { height: 100%; background: var(--accent); border-radius: 6px; transition: width .2s; }
.reveal .gr-bar.hot { background: var(--bad); }
.reveal .gr-val { font: 16px var(--mono); color: var(--muted); }
/* call tree widget */
.reveal .ct-svg svg { width: 100%; max-height: 430px; }
.reveal svg.ct line { stroke: var(--line); stroke-width: 2; }
.reveal svg.ct line.gone { opacity: .25; stroke-dasharray: 4 4; }
.reveal svg.ct rect { fill: var(--surface); stroke: var(--accent); stroke-width: 1.6; }
.reveal svg.ct text { font: 600 15px var(--mono); fill: var(--ink); text-anchor: middle; }
.reveal svg.ct g.cached rect { fill: var(--good-soft); stroke: var(--good); }
.reveal svg.ct g.gone { opacity: .2; }
.reveal .ct-bar { display: flex; justify-content: space-between; align-items: center; gap: 16px; }
.reveal .ct-info { font-size: 22px; margin: 6px 0 0 !important; }
.reveal .ct-info b { color: var(--accent); }
.reveal .ct-bar button.on { background: var(--good-soft); border-color: var(--good); color: var(--good); }
.reveal .hv-frame + .hv-frame .hv-title, .reveal .tracer-vars tr.frame.fn td { font: 700 16px var(--mono); text-transform: none; letter-spacing: 0; }
.reveal .tracer-vars tr.call td:first-child { width: auto; white-space: nowrap; }
.reveal .tracer-vars tr.call.top td:first-child { color: var(--accent); font-weight: 700; box-shadow: inset 4px 0 0 var(--accent); }
.reveal .tracer-vars tr.call.ret td:last-child { color: var(--good); font-weight: 700; }
.reveal th .katex, .reveal th .math { text-transform: none; }
.reveal section.smallcode pre.code { font-size: calc(15px * var(--cz)); }
.reveal section.smallcode pre.output { font-size: 15px; }