/* Shared design system for the U of T course guides.
   Three surfaces, so content always separates from its background:
   a grey desk (the page), a white sheet (the reading column), and
   recessed or tinted panels on the sheet. Pen-case colour code:
   blue = definitions, indigo = theorems, green = examples, red = warnings. */

:root{
  --desk:#eceef1;--sheet:#ffffff;--well:#f4f5f7;
  --ink:#1f2329;--ink-soft:#525a67;
  --line:#d8dbe1;--line-soft:#e7e9ed;--grid:rgba(42,92,174,.09);
  --blue:#2a5cae;--indigo:#46409f;--green:#2e7d4f;--red:#c03b2d;--amber:#a1741f;
  --tint-blue:#eaf1fa;--tint-indigo:#ededf9;--tint-green:#e9f5ee;
  --tint-red:#faeae7;--tint-amber:#f8f1de;
  --shadow-sheet:0 1px 2px rgba(15,23,42,.05),0 12px 32px rgba(15,23,42,.07);
  --shadow-card:0 1px 3px rgba(15,23,42,.07);
}
[data-theme="dark"]{
  --desk:#0f1115;--sheet:#191d24;--well:#13161c;
  --ink:#e8eaee;--ink-soft:#a5acba;
  --line:#353b46;--line-soft:#272c35;--grid:rgba(125,167,232,.08);
  --blue:#7da7e8;--indigo:#a3a0e6;--green:#6cbd8e;--red:#e08272;--amber:#d2a955;
  --tint-blue:#1c2531;--tint-indigo:#211f31;--tint-green:#1a2b22;
  --tint-red:#2e211d;--tint-amber:#2b2415;
  --shadow-sheet:0 1px 2px rgba(0,0,0,.4),0 14px 36px rgba(0,0,0,.45);
  --shadow-card:0 1px 3px rgba(0,0,0,.4);
}

*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth;scrollbar-gutter:stable both-edges}
a:focus-visible,summary:focus-visible,button:focus-visible,
input:focus-visible{outline:2px solid var(--blue);outline-offset:2px;border-radius:2px}
::selection{background:rgba(42,92,174,.18)}

body{background:var(--desk);color:var(--ink);
  font-family:Charter,"Iowan Old Style","Palatino Linotype",Georgia,serif;
  font-size:17px;line-height:1.65;-webkit-font-smoothing:antialiased;overflow-x:hidden}

/* ---------- theme toggle ---------- */
.theme-toggle{position:fixed;right:14px;top:14px;z-index:50;
  font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:10.5px;font-weight:600;letter-spacing:.08em;text-transform:uppercase;
  color:var(--ink);background:var(--sheet);border:1px solid var(--line);
  border-radius:999px;padding:6px 11px;cursor:pointer;
  box-shadow:var(--shadow-card);transition:border-color .2s,color .2s}
.theme-toggle:hover{border-color:var(--blue);color:var(--blue)}

/* ---------- index layout: sidebar on the desk, main on a sheet ---------- */
.wrap{max-width:1440px;margin:0 auto;padding:0 20px;
  display:grid;grid-template-columns:225px 1fr;gap:44px}
nav.side{position:sticky;top:0;align-self:start;height:100vh;
  padding:40px 0;display:flex;flex-direction:column;gap:4px;z-index:5}
nav.side .brand{font-family:"Avenir Next","Helvetica Neue","Segoe UI",system-ui,sans-serif;
  font-weight:700;font-size:22px;line-height:1.1;margin-bottom:4px;letter-spacing:-.01em}
nav.side .brand span{color:var(--blue)}
nav.side .sub{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:10.5px;color:var(--ink-soft);letter-spacing:.1em;margin-bottom:24px;line-height:1.6}
nav.side a{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:12px;text-transform:uppercase;letter-spacing:.07em;color:var(--ink-soft);
  text-decoration:none;padding:8px 0 8px 16px;border-left:2px solid var(--line);
  transition:color .2s,border-color .2s}
nav.side a:hover{color:var(--ink);border-color:var(--blue)}
nav.side a.active{color:var(--blue);border-color:var(--blue);font-weight:600}
nav.side .foot{margin-top:auto;font-size:10.5px;color:var(--ink-soft);
  font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  line-height:1.7;opacity:.75}

main{min-width:0;margin:26px 0 64px;padding:36px 44px 56px;
  background:var(--sheet);border:1px solid var(--line);border-radius:12px;
  box-shadow:var(--shadow-sheet)}

/* ---------- chapter layout: one sheet on the desk ---------- */
.container{max-width:960px;margin:28px auto 64px;padding:36px 44px 56px;
  background:var(--sheet);border:1px solid var(--line);border-radius:12px;
  box-shadow:var(--shadow-sheet)}

/* ---------- hero: title over faint graph paper ---------- */
header.hero{position:relative;margin-bottom:30px;padding:26px 0 30px;
  background:
    linear-gradient(180deg,rgba(0,0,0,0) 0%,var(--sheet) 92%),
    linear-gradient(var(--grid) 1px,transparent 1px),
    linear-gradient(90deg,var(--grid) 1px,transparent 1px);
  background-size:auto,24px 24px,24px 24px}
.kicker{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:11.5px;letter-spacing:.24em;text-transform:uppercase;color:var(--blue);
  margin-bottom:12px}
h1{font-family:"Avenir Next","Helvetica Neue","Segoe UI",system-ui,sans-serif;
  font-weight:650;font-size:clamp(30px,4.4vw,46px);line-height:1.05;
  letter-spacing:-.015em;max-width:calc(100% - 250px)}
h1 em{font-style:italic;color:var(--blue)}
.lede{margin-top:14px;max-width:70ch;font-size:17px;color:var(--ink-soft)}
.curve{position:absolute;right:-10px;top:-2px;width:230px;height:150px;opacity:.95}
.curve path{fill:none;stroke:var(--blue);stroke-width:2.4;
  stroke-dasharray:1400;stroke-dashoffset:1400;animation:draw 2.4s .3s ease forwards}
.curve .axis{stroke:var(--line);stroke-width:1.4;stroke-dasharray:none;stroke-dashoffset:0;animation:none}
.curve circle{fill:var(--red);opacity:0;animation:pop .5s 2.3s ease forwards}
@keyframes draw{to{stroke-dashoffset:0}}
@keyframes pop{to{opacity:1}}

/* ---------- strategy note ---------- */
.note{background:var(--tint-blue);border:1px solid var(--line-soft);
  border-left:3px solid var(--blue);border-radius:6px;
  padding:20px 24px;margin-bottom:32px}
.note h3{font-family:"Avenir Next","Helvetica Neue","Segoe UI",system-ui,sans-serif;
  font-weight:650;font-size:19px;margin-bottom:8px}
.note p{font-size:16px;max-width:78ch;color:var(--ink)}
.note .tag{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:11px;letter-spacing:.2em;text-transform:uppercase;color:var(--blue);
  font-weight:600;margin-bottom:12px}
.note a{color:var(--blue);text-decoration:underline;text-underline-offset:3px}

/* ---------- section heads ---------- */
section{margin-bottom:38px;scroll-margin-top:24px}
.sec-head{display:flex;align-items:baseline;gap:14px;
  border-bottom:2px solid var(--ink);padding-bottom:10px;margin-bottom:6px}
.sec-head h2{font-family:"Avenir Next","Helvetica Neue","Segoe UI",system-ui,sans-serif;
  font-weight:650;font-size:clamp(22px,2.8vw,29px);letter-spacing:-.012em}
.sec-head .no{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:13px;color:var(--blue);font-weight:600}
.sec-sub{color:var(--ink-soft);font-size:16px;margin:10px 0 18px;max-width:75ch}

/* ---------- chips ---------- */
.chips{display:flex;flex-wrap:wrap;gap:9px;margin:0 0 20px}
.chip{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:12px;font-weight:600;letter-spacing:.04em;padding:7px 12px;
  border:1px solid var(--line-soft);border-radius:4px;background:var(--well);
  display:flex;gap:8px;align-items:center}
.chip b{color:var(--blue)}.chip.teal b{color:var(--green)}
.chip small{font-weight:400;color:var(--ink-soft);
  font-family:Charter,"Iowan Old Style",Georgia,serif;font-size:13px}

/* ---------- unit index list ---------- */
.units{list-style:none;counter-reset:c}
.units li{counter-increment:c;border-top:1px solid var(--line-soft)}
.units a,.units .soon{display:grid;grid-template-columns:46px 1fr auto;gap:16px;
  align-items:baseline;padding:13px 12px 13px 0;text-decoration:none;color:inherit;
  max-width:640px;transition:padding .2s,background .2s}
.units a:hover{padding-left:10px;background:var(--tint-blue)}
.units a::before,.units .soon::before{content:counter(c,decimal-leading-zero);
  font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:13px;font-weight:600;color:var(--blue)}
.units h4{font-family:"Avenir Next","Helvetica Neue","Segoe UI",system-ui,sans-serif;
  font-weight:600;font-size:17.5px;margin-bottom:2px}
.units p{font-size:14.5px;color:var(--ink-soft)}
.units .go{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:11px;letter-spacing:.1em;text-transform:uppercase;color:var(--blue)}
.units .soon{opacity:.5}
.units .soon .go{color:var(--ink-soft)}

/* ---------- prologue / epilogue bookend links ---------- */
.bookend{display:flex;justify-content:space-between;align-items:center;gap:16px;
  padding:14px 18px;margin:4px 0 8px;border:1px solid var(--line-soft);
  border-left:3px solid var(--blue);border-radius:6px;background:var(--well);
  text-decoration:none;color:inherit;transition:border-color .2s,background .2s}
.bookend:hover{border-color:var(--blue);background:var(--tint-blue)}
.bookend h4{font-family:"Avenir Next","Helvetica Neue","Segoe UI",system-ui,sans-serif;
  font-weight:600;font-size:17.5px;margin-bottom:2px}
.bookend p{font-size:14.5px;color:var(--ink-soft);margin:0}
.bookend .go{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:11px;letter-spacing:.1em;text-transform:uppercase;color:var(--blue);white-space:nowrap}

/* ---------- term divider ---------- */
.term{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:12px;letter-spacing:.16em;text-transform:uppercase;color:var(--blue);
  margin:22px 0 4px;font-weight:600;display:flex;align-items:center;gap:14px}
.term::after{content:"";flex:1;height:1px;background:var(--line)}
.term:first-of-type{margin-top:8px}

/* ---------- breadcrumb + chapter title ---------- */
.crumb{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:12px;letter-spacing:.08em;text-transform:uppercase;color:var(--ink-soft);
  margin-bottom:16px;display:flex;gap:10px;align-items:center}
.crumb a{color:var(--blue);text-decoration:none}
.crumb a:hover{text-decoration:underline}
.unit-no{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:12.5px;letter-spacing:.2em;text-transform:uppercase;color:var(--blue);
  font-weight:600;margin-bottom:8px}
.ch-title{font-family:"Avenir Next","Helvetica Neue","Segoe UI",system-ui,sans-serif;
  font-weight:650;font-size:clamp(26px,3.6vw,38px);line-height:1.08;
  letter-spacing:-.015em;margin-bottom:12px}
.ch-intro{font-size:17px;color:var(--ink-soft);max-width:72ch;margin-bottom:10px}

/* ---------- goals ---------- */
.goals{background:var(--well);border:1px solid var(--line-soft);border-radius:6px;
  padding:14px 18px;margin:18px 0 26px}
.goals .gl{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:11px;letter-spacing:.18em;text-transform:uppercase;color:var(--blue);
  font-weight:600;margin-bottom:8px}
.goals ul{list-style:none;display:flex;flex-direction:column;gap:6px}
.goals li{padding-left:22px;position:relative;font-size:16px}
.goals li::before{content:"→";position:absolute;left:0;color:var(--blue)}

/* ---------- content blocks ---------- */
.block{margin:22px 0}
.block[id]{scroll-margin-top:24px}
.block>h3{font-family:"Avenir Next","Helvetica Neue","Segoe UI",system-ui,sans-serif;
  font-weight:650;font-size:20px;margin-bottom:8px;letter-spacing:-.008em}
.block p{margin:10px 0;max-width:72ch}
.block ul,.block ol{margin:10px 0 10px 22px}
.block li{margin:5px 0;max-width:70ch}

/* boxed environments: definition / theorem / example / pitfall.
   Tinted just enough to separate from the white sheet. */
.box{border-radius:6px;padding:13px 16px;margin:14px 0;
  border:1px solid var(--line-soft)}
.box .bl{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:11px;letter-spacing:.16em;text-transform:uppercase;font-weight:600;
  margin-bottom:6px;display:flex;gap:10px;align-items:center}
.box .bl b{font-family:Charter,"Iowan Old Style",Georgia,serif;font-style:italic;
  font-weight:600;text-transform:none;letter-spacing:0;font-size:14.5px;color:var(--ink)}
.box p{margin:6px 0;max-width:70ch}
.def{border-left:3px solid var(--blue);background:var(--tint-blue)}.def .bl{color:var(--blue)}
.thm{border-left:3px solid var(--indigo);background:var(--tint-indigo)}.thm .bl{color:var(--indigo)}
.eg{border-left:3px solid var(--green);background:var(--tint-green)}.eg .bl{color:var(--green)}
.warn{border-left:3px solid var(--red);background:var(--tint-red)}.warn .bl{color:var(--red)}
.eg .step{margin:7px 0;padding-left:14px;border-left:2px solid var(--line);
  font-size:16px;max-width:70ch}

/* ---------- figures: math gets drawn on graph paper ---------- */
.figure{margin:16px 0;background:var(--well);border:1px solid var(--line-soft);
  border-radius:6px;padding:14px 16px;overflow:hidden}
.figure .fig-title{font-family:"Avenir Next","Helvetica Neue","Segoe UI",system-ui,sans-serif;
  font-weight:600;font-size:16px;margin-bottom:3px}
.figure .fig-note{font-size:13.5px;color:var(--ink-soft);margin:0 0 12px;max-width:68ch}
.figure svg{display:block;width:100%;height:auto;border:1px solid var(--line);
  border-radius:4px;background-color:var(--sheet);
  background-image:linear-gradient(var(--grid) 1px,transparent 1px),
    linear-gradient(90deg,var(--grid) 1px,transparent 1px);
  background-size:22px 22px}
.figure svg text{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:11px;fill:var(--ink-soft)}
.figure svg .axis{stroke:var(--ink-soft);stroke-width:1.2}
.figure svg .guide{stroke:var(--line);stroke-width:1;stroke-dasharray:5 5}
.figure svg .curve-line{fill:none;stroke:var(--blue);stroke-width:3}
.figure svg .focus-line{fill:none;stroke:var(--red);stroke-width:2.5}
.figure svg .secondary-line{fill:none;stroke:var(--amber);stroke-width:2;stroke-dasharray:6 4}
.figure svg .focus-point{fill:var(--red);stroke:var(--sheet);stroke-width:2}
.figure svg .secondary-point{fill:var(--amber);stroke:var(--sheet);stroke-width:2}
.figure svg .input-band{fill:rgba(42,92,174,.16)}
.figure svg .output-band{fill:rgba(192,59,45,.13)}
.controls{display:flex;flex-wrap:wrap;align-items:center;gap:10px 16px;margin-top:14px}
.controls label{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:11px;letter-spacing:.08em;text-transform:uppercase;color:var(--indigo);font-weight:600}
.controls input[type="range"]{accent-color:var(--blue);min-width:220px;flex:1}
.controls output{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:12px;color:var(--ink);background:var(--sheet);border:1px solid var(--line);
  padding:5px 8px;border-radius:4px}
.controls button{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:11px;letter-spacing:.08em;text-transform:uppercase;color:var(--sheet);
  background:var(--blue);border:0;border-radius:4px;padding:8px 12px;cursor:pointer}
.controls button:hover{background:var(--indigo)}
[data-theme="dark"] .controls button{color:var(--desk)}
.exh-row{display:flex;gap:18px;align-items:center;flex-wrap:wrap}
.exh-row svg{flex:1 1 320px;width:auto;min-width:0}
.exh-row .calc-panel{flex:1 1 360px;margin-top:0}
.calc-panel{margin-top:12px;font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:12.5px;line-height:1.95;color:var(--ink);border:1px solid var(--line);
  border-radius:4px;padding:11px 14px;overflow-x:auto;background-color:var(--sheet);
  background-image:linear-gradient(var(--grid) 1px,transparent 1px),
    linear-gradient(90deg,var(--grid) 1px,transparent 1px);
  background-size:22px 22px}
.calc-panel div{white-space:nowrap}
.calc-panel .res{color:var(--blue);font-weight:600}
.calc-panel .pi{color:var(--red);font-weight:600}
.proof-map{display:grid;grid-template-columns:1fr auto 1fr;gap:10px;align-items:stretch;margin-top:14px}
.proof-map .choice{background:var(--well);border:1px solid var(--line-soft);
  padding:13px 14px;border-radius:6px}
.proof-map .choice b{display:block;
  font-family:"Avenir Next","Helvetica Neue","Segoe UI",system-ui,sans-serif;
  font-weight:600;font-size:15.5px;margin-bottom:3px}
.proof-map .choice span{display:block;font-size:13.5px;color:var(--ink-soft);line-height:1.5}
.proof-map .arrow{align-self:center;color:var(--blue);
  font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;font-weight:600}
.logic-table{width:100%;border-collapse:collapse;margin:15px 0;font-size:15px;background:var(--sheet)}
.logic-table th,.logic-table td{padding:8px 10px;border:1px solid var(--line);text-align:center}
.logic-table th{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:10.5px;letter-spacing:.08em;text-transform:uppercase;color:var(--indigo);
  background:var(--well)}
.logic-table .false{color:var(--red);font-weight:600}
.logic-table .true{color:var(--green);font-weight:600}
.checkpoint{border:1px solid var(--line-soft);border-left:3px solid var(--indigo);
  border-radius:6px;padding:11px 14px;margin:14px 0;background:var(--tint-indigo);font-size:15px}
.checkpoint b{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:10.5px;letter-spacing:.12em;text-transform:uppercase;color:var(--indigo);
  display:block;margin-bottom:4px}

/* ---------- practice ---------- */
.prac-intro{font-size:14px;color:var(--ink-soft);margin:5px 0 12px;max-width:72ch}
.prac{display:flex;flex-direction:column;gap:9px;margin-top:6px}
.q{background:var(--well);border:1px solid var(--line-soft);border-left:3px solid var(--blue);
  padding:11px 14px;border-radius:6px}
.q .ql{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:10px;letter-spacing:.16em;text-transform:uppercase;color:var(--blue);
  font-weight:600;margin-bottom:4px}
.q p{font-size:16px;color:var(--ink);max-width:70ch}
details{margin-top:7px}
details summary{cursor:pointer;
  font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:11.5px;letter-spacing:.08em;text-transform:uppercase;color:var(--blue);
  list-style:none;display:inline-flex;align-items:center;gap:6px;
  background:var(--sheet);border:1px solid var(--line);padding:4px 10px;
  border-radius:4px;transition:background .2s,color .2s}
details summary::-webkit-details-marker{display:none}
details summary::before{content:"+";font-weight:600}
details[open] summary::before{content:"–"}
details summary:hover{background:var(--blue);color:var(--sheet);border-color:var(--blue)}
[data-theme="dark"] details summary:hover{color:var(--desk)}
details .ans{margin-top:8px;font-size:15px;color:var(--ink);padding-left:12px;
  border-left:2px solid var(--line);max-width:68ch}

.math-rendered{font-family:"STIX Two Math","Cambria Math","Times New Roman",serif;
  font-size:1.08em;color:var(--ink);vertical-align:-.08em}
.math-rendered[display="block"]{display:block;margin:16px 0;padding:8px 12px;
  overflow-x:auto;text-align:center;font-size:1.16em}
.math-rendered mtext{font-family:Charter,"Iowan Old Style",Georgia,serif}
.unit-offset-seven{counter-reset:c 6}

/* ---------- prev/next ---------- */
.navrow{display:flex;justify-content:space-between;gap:14px;margin-top:36px;
  border-top:2px solid var(--ink);padding-top:16px}
.navrow a{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:12px;letter-spacing:.06em;text-transform:uppercase;color:var(--blue);
  text-decoration:none;max-width:45%}
.navrow a:hover{color:var(--indigo)}
.navrow a.n{text-align:right;margin-left:auto}
.navrow span{display:block;font-family:Charter,"Iowan Old Style",Georgia,serif;
  text-transform:none;letter-spacing:0;font-size:15px;color:var(--ink);margin-top:3px}

/* ---------- misc ---------- */
.bp{display:grid;grid-template-columns:repeat(2,1fr);gap:14px}
.bp .card{background:var(--well);border:1px solid var(--line-soft);border-radius:6px;
  padding:16px 18px;transition:border-color .2s,transform .2s}
.bp .card:hover{transform:translateY(-3px);border-color:var(--blue)}
.bp .card .n{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:12px;color:var(--blue);font-weight:600;letter-spacing:.12em}
.bp .card h4{font-family:"Avenir Next","Helvetica Neue","Segoe UI",system-ui,sans-serif;
  font-weight:600;font-size:16.5px;margin:5px 0}
.bp .card p{font-size:15px;color:var(--ink-soft)}
.src{font-size:15px;color:var(--ink-soft);line-height:1.85}
.src a{color:var(--blue);text-decoration:none;border-bottom:1px solid var(--line)}
.src a:hover{border-color:var(--blue)}
.lic{margin-top:18px;font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:11.5px;color:var(--ink-soft);line-height:1.8;background:var(--well);
  border:1px dashed var(--line);padding:14px 16px;border-radius:6px}

/* context / story panel */
.context{margin:22px 0;border:1px solid var(--line-soft);border-radius:6px;
  background:var(--well);overflow:hidden}
.context .ctxh{font-family:"Avenir Next","Helvetica Neue","Segoe UI",system-ui,sans-serif;
  font-weight:600;font-size:15.5px;padding:10px 18px;color:var(--ink);
  border-bottom:1px solid var(--line-soft);display:flex;align-items:center;gap:10px;
  background-color:var(--sheet);
  background-image:linear-gradient(var(--grid) 1px,transparent 1px),
    linear-gradient(90deg,var(--grid) 1px,transparent 1px);
  background-size:22px 22px}
.context .ctxh::before{content:"❖";font-size:12px;color:var(--blue)}
.context .ci{padding:11px 18px;border-top:1px solid var(--line-soft)}
.context .ci:first-of-type{border-top:none}
.context .cl{font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:10.5px;letter-spacing:.16em;text-transform:uppercase;color:var(--blue);
  font-weight:600;margin-bottom:5px}
.context .ci p{font-size:16px;color:var(--ink);margin:0;max-width:72ch;line-height:1.6}

.reveal{opacity:0;transform:translateY(14px);animation:rise .6s cubic-bezier(.2,.7,.2,1) forwards}
@keyframes rise{to{opacity:1;transform:none}}
footer.end{border-top:2px solid var(--ink);padding-top:20px;
  font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:11.5px;color:var(--ink-soft);display:flex;justify-content:space-between;
  flex-wrap:wrap;gap:12px}

.assessment-bank{border-top:3px solid var(--indigo);padding-top:32px;margin-top:56px}
.assessment-bank .assessment-note{max-width:72ch;margin:10px 0 24px;color:var(--ink-soft);font-size:16px}
.assessment-bank .q{border-left-color:var(--indigo)}
.assessment-bank .q .ql{color:var(--indigo)}

@media(max-width:880px){
  .wrap{grid-template-columns:1fr;gap:0;padding:0 10px}
  main{margin:0 0 40px;padding:22px 18px 40px;border-radius:8px}
  .container{margin:10px 10px 40px;padding:22px 18px 40px;border-radius:8px;max-width:none}
  nav.side{position:static;height:auto;flex-direction:row;flex-wrap:wrap;gap:8px 14px;
    padding:22px 8px;border-bottom:none}
  nav.side .brand,nav.side .sub{width:100%}nav.side .sub{margin-bottom:6px}
  nav.side a{border-left:none;border-bottom:2px solid var(--line);padding:4px 0}
  nav.side .foot{display:none}.curve{display:none}.bp{grid-template-columns:1fr}
  h1{max-width:none}
  .units a,.units .soon{grid-template-columns:36px 1fr;gap:12px}
  .units .go{display:none}
}
/* ---------- code, for the programming courses ---------- */
.code{margin:10px 0;border:1px solid var(--line);border-left:3px solid var(--indigo);
  border-radius:6px;background:var(--well);overflow:hidden}
.code .cl{padding:5px 10px;border-bottom:1px solid var(--line-soft);
  background:var(--sheet);color:var(--indigo);
  font:700 10px/1.3 ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  letter-spacing:.1em;text-transform:uppercase}
.code pre{margin:0;padding:10px 12px;overflow-x:auto;
  font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:13px;line-height:1.55;color:var(--ink);tab-size:4}
.code pre b{font-weight:700;color:var(--indigo)}
.code pre i{font-style:normal;color:var(--green)}
.code pre s{text-decoration:none;color:var(--ink-soft)}
.code + .code{margin-top:6px}
p code,li code,.step code,.ans code{padding:1px 5px;border:1px solid var(--line-soft);
  border-radius:4px;background:var(--well);color:var(--indigo);
  font-family:ui-monospace,"SF Mono",SFMono-Regular,Menlo,Consolas,monospace;
  font-size:.88em}

@media(max-width:600px){
  .proof-map{grid-template-columns:1fr}.proof-map .arrow{transform:rotate(90deg);justify-self:center}
  .controls input[type="range"]{min-width:100%;width:100%}
  .logic-table{display:block;overflow-x:auto;white-space:nowrap}
}
@media(prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  .reveal{opacity:1;transform:none;animation:none}
  .curve path,.curve circle{animation:none}
}