/* ECE204 online course — site styles */
:root {
  --bg: #f6f5f1; --surface: #ffffff; --surface-2: #f0eee8; --surface-3: #e8e5dd;
  --ink: #1c2228; --ink-2: #434d57; --muted: #737d87; --line: #e2ded5; --line-2: #d3cec2;
  --brand: #17324d; --accent: #2f6fdb; --mc: #2f6fdb;
  --ok: #1f8a4c; --bad: #c43c3c; --warn: #b5651d;
  --c-def: #2f6fdb; --c-rule: #b5651d; --c-key: #7a3fc4; --c-warn: #c43c3c; --c-tip: #1f8a4c;
  --c-sum: #56636f; --c-prac: #0f8a7e; --c-check: #1f8a4c; --c-ex: #3b4a57; --c-hw: #5b4bd1; --c-meta: #17324d;
  --fig-bg: #ffffff;
  --shadow: 0 1px 2px rgba(20, 24, 28, .05), 0 6px 20px -12px rgba(20, 24, 28, .18);
  --radius: 10px;
  --font: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans CJK SC", "Noto Sans SC", "Segoe UI", sans-serif;
  --mono: "SF Mono", "JetBrains Mono", Menlo, Consolas, "Liberation Mono", monospace;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #121518; --surface: #191d21; --surface-2: #20252a; --surface-3: #2a3036;
    --ink: #e5e8eb; --ink-2: #bcc3ca; --muted: #8b959e; --line: #2c3238; --line-2: #3a4148;
    --brand: #cfe0f5; --accent: #6ea0f0;
    --c-def: #6ea0f0; --c-rule: #e0a160; --c-key: #b28cf0; --c-warn: #ef7f7f; --c-tip: #5cc98a;
    --c-sum: #9aa6b1; --c-prac: #4cc4b6; --c-check: #5cc98a; --c-ex: #9fb0bf; --c-hw: #9c90f5; --c-meta: #9fbfe0;
    --fig-bg: #f4f2ee; --shadow: 0 1px 2px rgba(0, 0, 0, .3), 0 8px 24px -14px rgba(0, 0, 0, .6);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #121518; --surface: #191d21; --surface-2: #20252a; --surface-3: #2a3036;
  --ink: #e5e8eb; --ink-2: #bcc3ca; --muted: #8b959e; --line: #2c3238; --line-2: #3a4148;
  --brand: #cfe0f5; --accent: #6ea0f0;
  --c-def: #6ea0f0; --c-rule: #e0a160; --c-key: #b28cf0; --c-warn: #ef7f7f; --c-tip: #5cc98a;
  --c-sum: #9aa6b1; --c-prac: #4cc4b6; --c-check: #5cc98a; --c-ex: #9fb0bf; --c-hw: #9c90f5; --c-meta: #9fbfe0;
  --fig-bg: #f4f2ee; --shadow: 0 1px 2px rgba(0, 0, 0, .3), 0 8px 24px -14px rgba(0, 0, 0, .6);
  color-scheme: dark;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-padding-top: 76px; }
body { margin: 0; background: var(--bg); color: var(--ink); font: 16px/1.78 var(--font); }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }
button { font: inherit; color: inherit; }
kbd { font: 11px/1 var(--mono); border: 1px solid var(--line-2); border-bottom-width: 2px; border-radius: 4px; padding: 2px 5px; color: var(--muted); }
.muted { color: var(--muted); }
[hidden] { display: none !important; }

/* ── top bar ─────────────────────────── */
.topbar { position: sticky; top: 0; z-index: 50; height: 58px; display: flex; align-items: center; gap: 18px; padding: 0 20px;
  background: color-mix(in srgb, var(--bg) 88%, transparent); backdrop-filter: blur(10px); -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line); }
.brand { display: flex; align-items: center; gap: 10px; color: var(--ink); font-weight: 650; letter-spacing: .01em; white-space: nowrap; }
.brand:hover { text-decoration: none; }
.brand-hub { color: var(--muted); font-weight: 600; white-space: nowrap; }
.brand-hub:hover { color: var(--ink); text-decoration: none; }
.brand-sep { color: var(--line-2); margin: 0 -8px; }
.brand-mark { display: inline-grid; place-items: center; width: 34px; height: 28px; border-radius: 7px; background: var(--brand); color: var(--bg);
  font: 700 13px/1 var(--mono); letter-spacing: -.02em; }
.mainnav { display: flex; align-items: center; gap: 2px; flex: 1; }
.nav-link { display: inline-block; padding: 7px 11px; border-radius: 8px; color: var(--ink-2); font-size: 14.5px; background: none; border: 0; cursor: pointer; }
.nav-link:hover { background: var(--surface-2); color: var(--ink); text-decoration: none; }
.nav-link.on, .nav-drop.on > .nav-link { color: var(--ink); font-weight: 600; background: var(--surface-2); }
.nav-drop { position: relative; }
.nav-drop .drop { display: none; position: absolute; top: 100%; left: 0; padding: 8px; min-width: 300px; background: var(--surface);
  border: 1px solid var(--line); border-radius: 12px; box-shadow: var(--shadow); }
.nav-drop:hover .drop, .nav-drop:focus-within .drop { display: block; }
.nav-drop .drop a { display: flex; gap: 10px; padding: 8px 10px; border-radius: 8px; color: var(--ink); font-size: 14.5px; }
.nav-drop .drop a b { font: 600 12px/1.9 var(--mono); color: var(--muted); width: 22px; }
.nav-drop .drop a:hover { background: var(--surface-2); text-decoration: none; }
.top-actions { display: flex; gap: 8px; align-items: center; }
.search-btn { display: flex; align-items: center; gap: 10px; padding: 6px 8px 6px 12px; border: 1px solid var(--line-2); border-radius: 9px;
  background: var(--surface); color: var(--muted); font-size: 14px; cursor: pointer; min-width: 120px; justify-content: space-between; }
.icon-btn { width: 36px; height: 36px; display: grid; place-items: center; border: 1px solid var(--line-2); border-radius: 9px; background: var(--surface);
  cursor: pointer; color: var(--ink-2); font-size: 16px; }
.drawer-btn { display: none; }

/* ── layout ─────────────────────────── */
.layout { display: grid; gap: 40px; padding: 28px 28px 60px; margin: 0 auto; max-width: 1480px; }
.layout.no-side { grid-template-columns: minmax(0, 1fr); max-width: 1160px; }
.layout.no-side.with-toc { grid-template-columns: minmax(0, 1fr) 220px; max-width: 1180px; }
.layout.with-side { grid-template-columns: 264px minmax(0, 1fr); }
.layout.with-side.with-toc { grid-template-columns: 264px minmax(0, 1fr) 210px; }
.main { min-width: 0; }
.with-side .main > article, .with-toc .main > article { max-width: 800px; margin: 0 auto; }

.sidebar { position: sticky; top: 82px; align-self: start; max-height: calc(100vh - 100px); overflow: auto; padding-right: 6px; font-size: 14px;
  scrollbar-width: thin; }
.side-mod a { display: block; padding: 12px 14px; border-radius: 12px; background: var(--surface); border: 1px solid var(--line); border-left: 4px solid var(--mc);
  color: var(--ink); }
.side-mod a:hover { text-decoration: none; border-color: var(--mc); }
.side-k { display: block; font: 600 11.5px/1.4 var(--mono); color: var(--mc); letter-spacing: .06em; text-transform: uppercase; }
.side-t { display: block; font-weight: 650; font-size: 15px; line-height: 1.45; margin-top: 2px; }
.side-prog, .mod-prog, .mc-p { display: block; height: 4px; border-radius: 4px; background: var(--surface-3); margin-top: 8px; overflow: hidden; }
.side-prog span, .mod-prog span, .mc-p span { display: block; height: 100%; width: 0; background: var(--mc); transition: width .4s; }
.side-list { list-style: none; margin: 10px 0 0; padding: 0; }
.side-list li a { display: flex; gap: 8px; padding: 5px 8px; border-radius: 7px; color: var(--ink-2); line-height: 1.5; }
.side-list li a:hover { background: var(--surface-2); text-decoration: none; color: var(--ink); }
.side-list li.on > a { background: var(--surface); color: var(--ink); font-weight: 600; box-shadow: inset 3px 0 0 var(--mc, var(--accent)); }
.side-list .num { flex: none; min-width: 34px; font: 500 12.5px/1.75 var(--mono); color: var(--muted); }
.side-list li.done .num { color: var(--ok); }
.side-list li.done .num::after { content: " ✓"; }
.side-list.small li a { font-size: 13.5px; }
.side-sec { margin: 18px 8px 4px; font: 600 11.5px/1 var(--mono); letter-spacing: .08em; color: var(--muted); text-transform: uppercase; }
.side-sec.top { margin-top: 0; }

.sidebar.mobile-only, .side-mainnav { display: none; }
.side-mainnav a { display: block; padding: 7px 8px; border-radius: 7px; color: var(--ink); font-size: 15px; }
.side-mainnav a:hover { background: var(--surface-2); text-decoration: none; }
.side-mainnav .side-sec { margin: 12px 8px 4px; }
.page-toc { position: sticky; top: 82px; align-self: start; font-size: 13px; max-height: calc(100vh - 100px); overflow: auto; scrollbar-width: thin; }
.toc-title { font: 600 11.5px/1 var(--mono); letter-spacing: .08em; color: var(--muted); text-transform: uppercase; margin: 4px 0 10px; }
.page-toc ol { list-style: none; margin: 0; padding: 0; border-left: 1px solid var(--line); }
.page-toc li a { display: block; padding: 4px 10px; color: var(--muted); line-height: 1.5; margin-left: -1px; border-left: 2px solid transparent; }
.page-toc li.h3 a { padding-left: 20px; }
.page-toc li a:hover { color: var(--ink); text-decoration: none; }
.page-toc li a.on { color: var(--ink); border-left-color: var(--mc, var(--accent)); }

/* ── page headings ─────────────────────────── */
.crumbs { display: flex; gap: 8px; flex-wrap: wrap; font-size: 13.5px; color: var(--muted); margin-bottom: 6px; }
.crumbs a { color: var(--mc, var(--accent)); font-weight: 550; }
.crumbs span::before { content: "›"; margin-right: 8px; color: var(--line-2); }
.page-title { font-size: 32px; line-height: 1.3; margin: 2px 0 18px; letter-spacing: -.01em; font-weight: 720; }
.page-title .lnum { display: inline-block; font: 650 .62em/1 var(--mono); color: var(--mc, var(--accent)); background: color-mix(in srgb, var(--mc, var(--accent)) 12%, transparent);
  padding: 6px 9px; border-radius: 8px; margin-right: 12px; vertical-align: .22em; }
.lead { font-size: 17px; color: var(--ink-2); }
.sec-h { font-size: 22px; margin: 40px 0 12px; letter-spacing: -.005em; }
.callout { padding: 14px 18px; border-radius: var(--radius); background: color-mix(in srgb, var(--accent) 8%, var(--surface)); border: 1px solid color-mix(in srgb, var(--accent) 22%, var(--line));
  margin: 16px 0 24px; font-size: 15px; }
.callout.warn { background: color-mix(in srgb, var(--warn) 8%, var(--surface)); border-color: color-mix(in srgb, var(--warn) 28%, var(--line)); }

/* ── prose ─────────────────────────── */
.prose { font-size: 16.5px; }
.prose h2 { font-size: 24px; margin: 46px 0 14px; padding-top: 6px; }
.prose h3 { font-size: 21px; margin: 44px 0 12px; padding-bottom: 8px; border-bottom: 1px solid var(--line); letter-spacing: -.005em; }
.prose h4 { font-size: 17.5px; margin: 28px 0 8px; }
.prose p { margin: 12px 0; }
.prose ul, .prose ol { padding-left: 1.6em; margin: 10px 0; }
.prose li { margin: 4px 0; }
.prose li > p { margin: 4px 0; }
.prose strong { font-weight: 650; }
.prose code { font: .88em var(--mono); background: var(--surface-2); border: 1px solid var(--line); border-radius: 5px; padding: 1px 5px; }
.prose pre code { background: none; border: 0; padding: 0; }
.prose blockquote { margin: 14px 0; padding: 4px 16px; border-left: 3px solid var(--line-2); color: var(--ink-2); }
.prose hr { border: 0; border-top: 1px solid var(--line); margin: 30px 0; }
a.xref { border-bottom: 1px dashed color-mix(in srgb, var(--accent) 50%, transparent); }
a.xref:hover { text-decoration: none; border-bottom-style: solid; }

.table-wrap { overflow-x: auto; margin: 16px 0; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
.table-wrap table { border-collapse: collapse; width: 100%; font-size: 15px; }
.table-wrap th, .table-wrap td { padding: 7px 12px; border-bottom: 1px solid var(--line); border-right: 1px solid var(--line); vertical-align: top; }
.table-wrap th:last-child, .table-wrap td:last-child { border-right: 0; }
.table-wrap tr:last-child td { border-bottom: 0; }
.table-wrap thead th { background: var(--surface-2); font-weight: 650; white-space: nowrap; }
.table-wrap tbody tr:hover { background: color-mix(in srgb, var(--surface-2) 60%, transparent); }

.katex { font-size: 1.06em; }
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 4px 0; margin: 14px 0; }

/* figures: a light card so line art stays readable in dark mode */
.fig { margin: 22px 0; text-align: center; }
.fig-frame { display: inline-block; max-width: 100%; width: 100%; background: var(--fig-bg); border-radius: var(--radius); padding: 14px; border: 1px solid var(--line); }
.fig img { width: var(--w, 60%); max-width: 100%; height: auto; }
.fig figcaption { font-size: 14px; color: var(--muted); margin-top: 8px; }
.fig figcaption b { color: var(--ink-2); font-weight: 600; }

/* code */
pre.code { position: relative; background: #1a2027; color: #d9e1e8; border-radius: var(--radius); padding: 14px 16px; overflow: auto; font: 13.6px/1.6 var(--mono); margin: 16px 0; }
pre.code::before { content: attr(data-lang); position: absolute; top: 6px; right: 58px; font: 11px/1 var(--mono); color: #7f8c99; text-transform: uppercase; letter-spacing: .06em; }
pre.code .copy { position: absolute; top: 4px; right: 6px; font: 11.5px/1 var(--font); background: #2a333c; color: #c5d0da; border: 1px solid #3a4550; border-radius: 6px; padding: 5px 8px; cursor: pointer; }
pre.code .copy:hover { background: #34404b; }
.hljs-keyword, .hljs-built_in { color: #ff9e7a; }
.hljs-type { color: #8fc7ff; }
.hljs-number { color: #f2cc60; }
.hljs-string { color: #a6e3a1; }
.hljs-comment { color: #7d8a96; font-style: italic; }
.hljs-meta, .hljs-variable, .hljs-attr { color: #d4a5ff; }
.hljs-title { color: #8fd4c7; }

/* ── content boxes (from the notes) ─────────────────────────── */
.prose div.def, .prose div.rule, .prose div.key, .prose div.warn, .prose div.tip, .prose div.summary,
.prose div.practice, .prose div.check, .prose div.example, .prose div.hw, .prose div.goal, .prose div.tool, .prose div.checkoff, .prose div.deliver {
  --c: var(--c-def); margin: 20px 0; padding: 14px 18px; border-radius: var(--radius); background: color-mix(in srgb, var(--c) 6%, var(--surface));
  border: 1px solid color-mix(in srgb, var(--c) 20%, var(--line)); border-left: 4px solid var(--c); }
.prose div.rule { --c: var(--c-rule); }
.prose div.key { --c: var(--c-key); }
.prose div.warn { --c: var(--c-warn); }
.prose div.tip { --c: var(--c-tip); }
.prose div.summary { --c: var(--c-sum); }
.prose div.practice { --c: var(--c-prac); }
.prose div.check { --c: var(--c-check); }
.prose div.example { --c: var(--c-ex); background: var(--surface); }
.prose div.hw { --c: var(--c-hw); }
.prose div.goal { --c: var(--c-def); }
.prose div.tool { --c: var(--c-tip); }
.prose div.checkoff { --c: var(--c-check); }
.prose div.deliver { --c: var(--c-rule); }
.prose div > p:first-child { margin-top: 0; }
.prose div > :last-child { margin-bottom: 0; }
.prose div.def > p:first-child > strong:first-child, .prose div.rule > p:first-child > strong:first-child,
.prose div.key > p:first-child > strong:first-child, .prose div.warn > p:first-child > strong:first-child,
.prose div.tip > p:first-child > strong:first-child, .prose div.summary > p:first-child > strong:first-child,
.prose div.practice > p:first-child > strong:first-child, .prose div.example > p:first-child > strong:first-child,
.prose div.hw > p:first-child > strong:first-child, .prose div.goal > p:first-child > strong:first-child,
.prose div.tool > p:first-child > strong:first-child, .prose div.deliver > p:first-child > strong:first-child { color: var(--c); }
.prose div.example > p:first-child > strong:first-child { font-size: 1.04em; }
.prose div.practice ol > li { margin: 10px 0; }

.meta { font-size: 14.5px; padding: 14px 18px; margin: 0 0 18px; border-radius: var(--radius); background: var(--surface); border: 1px solid var(--line);
  display: grid; grid-template-columns: 1fr; gap: 2px; }
.meta p { margin: 2px 0; }
.meta strong { color: var(--mc, var(--c-meta)); font-weight: 600; }

.ex-toggle { display: block; width: 100%; margin: 12px 0 2px; padding: 9px 12px; border: 1px dashed color-mix(in srgb, var(--c-ex) 45%, var(--line-2)); border-radius: 8px;
  background: var(--surface-2); color: var(--ink-2); font-size: 14.5px; cursor: pointer; text-align: center; }
.ex-toggle:hover { border-style: solid; color: var(--ink); }
.ex-sol.hide { display: none; }
.example.open .ex-toggle { display: none; }

details.sol { margin: 6px 0 4px; }
details.sol > summary { display: inline-block; cursor: pointer; font-size: 13.5px; color: var(--c-prac); padding: 2px 10px; border-radius: 999px; list-style: none;
  border: 1px solid color-mix(in srgb, var(--c-prac) 35%, var(--line)); background: var(--surface); user-select: none; }
details.sol > summary::-webkit-details-marker { display: none; }
details.sol[open] > summary { background: color-mix(in srgb, var(--c-prac) 12%, var(--surface)); }
.sol-body { margin-top: 8px; padding: 10px 14px; border-radius: 8px; background: var(--surface); border: 1px solid var(--line); font-size: 15.5px; }

.box-title { font-weight: 650; color: var(--c-check); }
.box-title .hint { font-weight: 400; color: var(--muted); font-size: 13.5px; margin-left: 8px; }
.checklist { list-style: none; padding: 0 !important; margin: 8px 0 0; }
.checklist li { margin: 4px 0; }
.checklist label { display: flex; gap: 10px; align-items: flex-start; cursor: pointer; padding: 4px 6px; border-radius: 7px; }
.checklist label:hover { background: color-mix(in srgb, var(--c-check) 8%, transparent); }
.checklist input { margin-top: .42em; width: 17px; height: 17px; accent-color: var(--c-check); flex: none; }
.checklist input:checked + span { color: var(--muted); }

.lesson-tools { display: flex; gap: 12px; align-items: center; margin: -4px 0 8px; font-size: 13.5px; color: var(--muted); }
.tool-btn { border: 1px solid var(--line-2); background: var(--surface); border-radius: 7px; padding: 4px 10px; font-size: 13px; cursor: pointer; color: var(--ink-2); }
.tool-btn:hover { color: var(--ink); border-color: var(--muted); }

/* loop panel + done */
.loop-panel { margin: 40px 0 18px; padding: 18px 20px; border-radius: 14px; background: var(--surface); border: 1px solid var(--line); box-shadow: var(--shadow); }
.loop-head { font-weight: 700; margin-bottom: 10px; }
.loop-row { display: grid; grid-template-columns: 52px 1fr; gap: 10px; padding: 8px 0; border-top: 1px solid var(--line); align-items: start; }
.loop-k { font: 600 13px/2 var(--font); color: var(--muted); }
.res-list { list-style: none; margin: 0; padding: 0; font-size: 14.5px; }
.res-list li { padding: 3px 0; }
.res-list .src { color: var(--muted); font-size: 12.5px; margin-left: 8px; }
.chip { display: inline-flex; align-items: center; gap: 6px; padding: 5px 11px; margin: 3px 6px 3px 0; border-radius: 999px; border: 1px solid var(--line-2);
  background: var(--surface); color: var(--ink); font-size: 14px; line-height: 1.4; }
.chip:hover { text-decoration: none; border-color: var(--mc, var(--accent)); }
.chip i { font-style: normal; color: var(--c-prac); }
.chip.drill { border-color: color-mix(in srgb, var(--c-prac) 35%, var(--line)); }
.chip.hw { border-color: color-mix(in srgb, var(--c-hw) 40%, var(--line)); color: var(--c-hw); }
.chip.lab { border-color: color-mix(in srgb, var(--c-rule) 40%, var(--line)); }
.chip.lab.done::after, .chip.done::after { content: "✓"; color: var(--ok); }
.done-bar { display: flex; justify-content: center; margin: 26px 0; }
.done-btn { padding: 11px 22px; border-radius: 999px; border: 1px solid var(--line-2); background: var(--surface); cursor: pointer; font-weight: 600; font-size: 15px; }
.done-btn:hover { border-color: var(--ok); }
.done-btn .d1 { display: none; }
.done-btn.on { background: color-mix(in srgb, var(--ok) 12%, var(--surface)); border-color: var(--ok); color: var(--ok); }
.done-btn.on .d0 { display: none; }
.done-btn.on .d1 { display: inline; }

.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin: 26px 0 10px; }
.pg { display: flex; flex-direction: column; padding: 12px 16px; border: 1px solid var(--line); border-radius: 12px; background: var(--surface); color: var(--ink); }
.pg:hover { border-color: var(--mc, var(--accent)); text-decoration: none; }
.pg span { font-size: 12.5px; color: var(--muted); }
.pg b { font-weight: 600; font-size: 15px; }
.pg.next { text-align: right; }

/* ── home ─────────────────────────── */
.kind-home .layout { max-width: 1160px; }
.hero { display: grid; grid-template-columns: minmax(0, 1fr) 300px; gap: 40px; align-items: center; padding: 30px 0 18px; }
.hero-k { font: 600 12.5px/1 var(--mono); letter-spacing: .1em; text-transform: uppercase; color: var(--accent); }
.hero h1 { font-size: 42px; line-height: 1.22; margin: 14px 0 14px; letter-spacing: -.02em; font-weight: 760; }
.hero p { font-size: 17.5px; color: var(--ink-2); max-width: 40em; }
.hero-cta { display: flex; gap: 12px; flex-wrap: wrap; margin-top: 22px; }
.btn { display: inline-flex; align-items: center; padding: 11px 20px; border-radius: 10px; border: 1px solid var(--line-2); background: var(--surface); color: var(--ink); font-weight: 600; cursor: pointer; }
.btn:hover { text-decoration: none; border-color: var(--ink-2); }
.btn.primary { background: var(--brand); border-color: var(--brand); color: var(--bg); }
.btn.primary:hover { filter: brightness(1.1); }
.hero-side { background: var(--surface); border: 1px solid var(--line); border-radius: 18px; padding: 22px; box-shadow: var(--shadow); }
.ring { position: relative; width: 150px; margin: 0 auto 14px; }
.ring svg { transform: rotate(-90deg); display: block; }
.ring circle { fill: none; stroke-width: 3.2; }
.ring .r0 { stroke: var(--surface-3); }
.ring .r1 { stroke: var(--accent); stroke-linecap: round; transition: stroke-dasharray .6s; }
.ring-t { position: absolute; inset: 0; display: grid; place-content: center; text-align: center; }
.ring-t b { font-size: 28px; line-height: 1.1; }
.ring-t span { font-size: 12.5px; color: var(--muted); }
.hero-stats { display: grid; grid-template-columns: repeat(3, 1fr); gap: 6px; text-align: center; font-size: 13px; color: var(--muted); }
.hero-stats b { font-size: 19px; color: var(--ink); }
.hero-stats span { display: block; }

.loop-steps { display: grid; grid-template-columns: repeat(5, 1fr); gap: 12px; counter-reset: s; }
.ls { position: relative; padding: 16px 16px 14px; background: var(--surface); border: 1px solid var(--line); border-radius: 14px; }
.ls b { display: inline-grid; place-items: center; width: 34px; height: 34px; border-radius: 10px; background: var(--brand); color: var(--bg); font-size: 16px; }
.ls span { margin-left: 8px; font-weight: 650; }
.ls p { margin: 10px 0 0; font-size: 14px; color: var(--ink-2); line-height: 1.65; }
.ls:not(:last-child)::after { content: "→"; position: absolute; right: -11px; top: 22px; color: var(--muted); font-size: 14px; }

.weeks { display: grid; gap: 14px; margin-top: 14px; }
.week { background: var(--surface); border: 1px solid var(--line); border-radius: 14px; border-left: 4px solid var(--mc); overflow: hidden; }
.week-head { display: flex; align-items: center; gap: 12px; padding: 12px 18px; cursor: pointer; user-select: none; }
.week-n { font: 650 13px/1 var(--mono); color: var(--mc); white-space: nowrap; }
.week-t { font-weight: 680; font-size: 16.5px; flex: 1; }
.week-m { font: 600 11.5px/1 var(--mono); color: var(--muted); border: 1px solid var(--line-2); padding: 3px 6px; border-radius: 5px; }
.week-p { font-size: 13px; color: var(--muted); min-width: 56px; text-align: right; }
.week.complete .week-p { color: var(--ok); }
.week-body { display: grid; grid-template-columns: minmax(0, 1.25fr) minmax(0, 1fr); gap: 22px; padding: 4px 18px 16px; }
.week.collapsed .week-body { display: none; }
.wk { font: 600 12px/1 var(--mono); color: var(--muted); letter-spacing: .08em; margin: 10px 0 6px; }
.wlist { list-style: none; margin: 0; padding: 0; font-size: 14.5px; columns: 1; }
.wlist li a { display: flex; gap: 8px; padding: 3px 6px; border-radius: 6px; color: var(--ink); }
.wlist li a:hover { background: var(--surface-2); text-decoration: none; }
.wlist .num { font: 500 12.5px/1.9 var(--mono); color: var(--muted); min-width: 34px; }
.wlist li.done .num { color: var(--ok); }
.wlist li.done a { color: var(--muted); }

.mod-cards, .cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 14px; }
.mod-card, .card { display: flex; flex-direction: column; gap: 6px; padding: 16px 18px; background: var(--surface); border: 1px solid var(--line); border-radius: 14px;
  border-top: 4px solid var(--mc); color: var(--ink); position: relative; }
.mod-card:hover, .card:hover { text-decoration: none; box-shadow: var(--shadow); border-color: var(--mc); }
.mc-k, .card-k { font: 600 11.5px/1.3 var(--mono); color: var(--mc); letter-spacing: .06em; text-transform: uppercase; }
.mc-t, .card-t { font-weight: 680; font-size: 17px; line-height: 1.4; }
.mc-d, .card-d { font-size: 14px; color: var(--ink-2); line-height: 1.65; flex: 1; }
.card-icon { position: absolute; top: 14px; right: 16px; font-size: 22px; color: var(--mc); opacity: .8; }
.card-tags { display: flex; flex-wrap: wrap; gap: 5px; }
.tag { font-size: 12px; padding: 2px 8px; border-radius: 999px; background: var(--surface-2); color: var(--ink-2); border: 1px solid var(--line); white-space: nowrap; }
.card-foot { font-size: 13px; color: var(--muted); display: flex; justify-content: space-between; margin-top: 4px; }
.card .tick { display: none; color: var(--ok); }
.card.done .tick { display: inline; }
.home-foot-links { display: flex; flex-wrap: wrap; gap: 22px; margin: 40px 0 0; padding-top: 20px; border-top: 1px solid var(--line); font-size: 14.5px; }

/* module page */
.mod-hero { padding: 20px 22px; border-radius: 16px; background: var(--surface); border: 1px solid var(--line); border-top: 5px solid var(--mc); margin-bottom: 20px; }
.mod-k { font: 600 12px/1 var(--mono); color: var(--mc); letter-spacing: .08em; text-transform: uppercase; }
.mod-hero .page-title { margin: 10px 0 8px; }
.mod-intro p { margin: 8px 0; color: var(--ink-2); }
.mod-book { font-size: 13.5px; color: var(--muted); margin-top: 8px; }
.mod-loop { display: grid; grid-template-columns: repeat(5, 1fr); gap: 10px; }
.ml-step { padding: 12px 14px; background: var(--surface); border: 1px solid var(--line); border-radius: 12px; font-size: 13.5px; }
.ml-k { font: 650 12px/1 var(--mono); color: var(--mc); letter-spacing: .04em; }
.ml-t { font-weight: 650; font-size: 15px; margin: 6px 0 4px; }
.ml-d { color: var(--ink-2); line-height: 1.6; }
.lcards { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 8px; }
.lcard { display: flex; gap: 10px; align-items: baseline; padding: 10px 12px; border-radius: 10px; background: var(--surface); border: 1px solid var(--line); color: var(--ink); font-size: 14.5px; }
.lcard:hover { text-decoration: none; border-color: var(--mc); }
.lcard .num { font: 600 13px/1 var(--mono); color: var(--mc); min-width: 34px; }
.lcard .lt { flex: 1; line-height: 1.5; }
.lcard .tick { color: var(--ok); visibility: hidden; }
.lcard.done .tick { visibility: visible; }

/* homework index */
.hw-rows { display: grid; gap: 10px; margin: 20px 0; }
.hw-row { display: grid; grid-template-columns: 70px 1fr auto auto; gap: 16px; align-items: center; padding: 14px 18px; border-radius: 12px; background: var(--surface);
  border: 1px solid var(--line); border-left: 4px solid var(--mc); color: var(--ink); }
.hw-row:hover { text-decoration: none; border-color: var(--mc); }
.hw-n { font: 700 17px/1 var(--mono); color: var(--mc); }
.hw-a, .hw-m { font-size: 13.5px; color: var(--muted); }

/* labs */
.lab-meta { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin: -6px 0 18px; font-size: 14px; color: var(--muted); }
.lab-meta > span:first-child { margin-right: 6px; }

/* resources */
.res-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 12px; }
.res-card { padding: 14px 16px; background: var(--surface); border: 1px solid var(--line); border-radius: 12px; }
.res-top { display: flex; justify-content: space-between; gap: 8px; align-items: baseline; }
.res-name { font-weight: 650; }
.res-desc { font-size: 14px; color: var(--ink-2); margin: 6px 0; line-height: 1.65; }
.res-ls { font-size: 13px; color: var(--muted); }
.hdl-table td:first-child { white-space: nowrap; font-weight: 600; }
.hdl-table .chip { font-size: 12.5px; padding: 2px 9px; }

/* search */
.search-modal { position: fixed; inset: 0; z-index: 100; background: rgba(10, 14, 18, .45); display: flex; justify-content: center; align-items: flex-start; padding-top: 10vh; }
.search-box { width: min(640px, calc(100vw - 32px)); background: var(--surface); border-radius: 14px; box-shadow: 0 30px 80px -20px rgba(0, 0, 0, .5); overflow: hidden; border: 1px solid var(--line); }
.search-box input { width: 100%; border: 0; border-bottom: 1px solid var(--line); padding: 16px 18px; font: 17px var(--font); background: var(--surface); color: var(--ink); outline: none; }
.search-results { list-style: none; margin: 0; padding: 6px; max-height: 55vh; overflow: auto; }
.search-results li a { display: block; padding: 9px 12px; border-radius: 9px; color: var(--ink); }
.search-results li a small { display: block; color: var(--muted); font-size: 12.5px; }
.search-results li.sel a, .search-results li a:hover { background: var(--surface-2); text-decoration: none; }
.search-results mark { background: color-mix(in srgb, var(--accent) 25%, transparent); color: inherit; border-radius: 3px; }
.search-foot { padding: 8px 14px; font-size: 12px; color: var(--muted); border-top: 1px solid var(--line); }

.foot { text-align: center; font-size: 13px; color: var(--muted); padding: 26px 20px 70px; border-top: 1px solid var(--line); }
.foot-sub { font-size: 12px; margin-top: 4px; }

/* ── drills ─────────────────────────── */
.drill { margin-top: 18px; }
.dr-bar { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; justify-content: space-between; margin-bottom: 12px; }
.dr-modes { display: flex; flex-wrap: wrap; gap: 6px; }
.dr-mode { padding: 6px 12px; border-radius: 999px; border: 1px solid var(--line-2); background: var(--surface); cursor: pointer; font-size: 14px; color: var(--ink-2); }
.dr-mode.on { background: var(--brand); border-color: var(--brand); color: var(--bg); }
.dr-stats { font-size: 13.5px; color: var(--muted); display: flex; gap: 14px; }
.dr-stats b { color: var(--ink); }
.dr-card { background: var(--surface); border: 1px solid var(--line); border-radius: 16px; padding: 22px 24px; box-shadow: var(--shadow); }
.dr-q { font-size: 18px; line-height: 1.8; }
.dr-q .big { font: 600 24px/1.4 var(--mono); letter-spacing: .04em; display: inline-block; padding: 2px 10px; border-radius: 8px; background: var(--surface-2); }
.dr-in { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; margin: 16px 0 6px; }
.dr-in input[type=text] { flex: 1; min-width: 200px; padding: 10px 14px; border: 1px solid var(--line-2); border-radius: 10px; font: 18px var(--mono); background: var(--bg); color: var(--ink); }
.dr-in input[type=text]:focus { outline: 2px solid color-mix(in srgb, var(--accent) 45%, transparent); border-color: var(--accent); }
.dr-in select { padding: 9px 10px; border-radius: 10px; border: 1px solid var(--line-2); background: var(--bg); color: var(--ink); font: 15px var(--font); }
.dr-btns { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 12px; }
.dr-btn { padding: 9px 18px; border-radius: 10px; border: 1px solid var(--line-2); background: var(--surface); cursor: pointer; font-weight: 600; font-size: 15px; }
.dr-btn.primary { background: var(--brand); color: var(--bg); border-color: var(--brand); }
.dr-btn:hover { filter: brightness(1.06); }
.dr-fb { margin-top: 16px; padding: 12px 16px; border-radius: 10px; font-size: 15.5px; line-height: 1.75; }
.dr-fb.ok { background: color-mix(in srgb, var(--ok) 10%, var(--surface)); border: 1px solid color-mix(in srgb, var(--ok) 35%, var(--line)); }
.dr-fb.bad { background: color-mix(in srgb, var(--bad) 8%, var(--surface)); border: 1px solid color-mix(in srgb, var(--bad) 30%, var(--line)); }
.dr-fb.info { background: var(--surface-2); border: 1px solid var(--line); }
.dr-fb .t { font-weight: 700; }
.dr-steps { margin-top: 10px; font-size: 14.5px; }
.dr-steps pre, .mono { font: 14px/1.6 var(--mono); white-space: pre; overflow-x: auto; background: var(--surface-2); border-radius: 8px; padding: 10px 12px; margin: 8px 0; }
.dr-help { font-size: 13.5px; color: var(--muted); margin-top: 6px; }
.dr-help code { font: 12.5px var(--mono); background: var(--surface-2); padding: 1px 5px; border-radius: 4px; }
.dr-tt { border-collapse: collapse; font: 15px var(--mono); margin: 10px 0; }
.dr-tt th, .dr-tt td { border: 1px solid var(--line-2); padding: 4px 12px; text-align: center; }
.dr-tt th { background: var(--surface-2); font-weight: 600; }
.dr-tt td.cell { cursor: pointer; min-width: 44px; font-weight: 700; user-select: none; }
.dr-tt td.cell:hover { background: var(--surface-2); }
.dr-tt td.cell.v1 { color: var(--accent); }
.dr-tt td.cell.v0 { color: var(--ink-2); }
.dr-tt td.cell.right { background: color-mix(in srgb, var(--ok) 14%, transparent); }
.dr-tt td.cell.wrong { background: color-mix(in srgb, var(--bad) 16%, transparent); }
.kmap { border-collapse: collapse; font: 16px var(--mono); margin: 12px 0; }
.kmap td, .kmap th { width: 52px; height: 46px; text-align: center; border: 1px solid var(--line-2); }
.kmap th { background: var(--surface-2); font-weight: 600; font-size: 13.5px; color: var(--ink-2); }
.kmap th.corner { background: none; border: 0; font-size: 12.5px; position: relative; }
.kmap td { font-weight: 700; position: relative; background: var(--surface); }
.kmap td small { position: absolute; left: 4px; top: 2px; font-size: 10px; color: var(--muted); font-weight: 400; }
.kmap td.edit { cursor: pointer; }
.kmap td.edit:hover { background: var(--surface-2); }
.kmap td.v1 { color: var(--accent); }
.kmap td.vx { color: var(--warn); }
.kmap td.v0 { color: var(--muted); font-weight: 400; }
.kmap td.hl { box-shadow: inset 0 0 0 3px var(--hlc, var(--accent)); }
.wave svg { display: block; max-width: 100%; height: auto; }
.wave .seg { cursor: pointer; }
.wave .seg:hover rect { fill: color-mix(in srgb, var(--accent) 14%, transparent); }
.fsm-tbl td input { width: 56px; padding: 4px 6px; font: 15px var(--mono); border: 1px solid var(--line-2); border-radius: 6px; background: var(--bg); color: var(--ink); text-align: center; }
.seqrow { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; margin: 6px 0; }
.seqrow .lab { width: 76px; font-size: 14px; color: var(--muted); }
.seqrow input { width: 48px; padding: 6px 4px; text-align: center; font: 15px var(--mono); border: 1px solid var(--line-2); border-radius: 7px; background: var(--bg); color: var(--ink); }
.seqrow .given { width: 48px; text-align: center; font: 600 15px var(--mono); padding: 6px 0; background: var(--surface-2); border-radius: 7px; }
.seqrow input.right { border-color: var(--ok); background: color-mix(in srgb, var(--ok) 10%, var(--bg)); }
.seqrow input.wrong { border-color: var(--bad); background: color-mix(in srgb, var(--bad) 10%, var(--bg)); }
.radio-row { display: flex; gap: 14px; flex-wrap: wrap; font-size: 15.5px; }
.radio-row label { display: flex; gap: 6px; align-items: center; cursor: pointer; }

/* ── responsive ─────────────────────────── */
@media (max-width: 1279px) {
  .layout.with-side.with-toc { grid-template-columns: 250px minmax(0, 1fr); }
  .layout.no-side.with-toc { grid-template-columns: minmax(0, 1fr); }
  .page-toc { display: none; }
}
@media (max-width: 1080px) {
  .loop-steps, .mod-loop { grid-template-columns: repeat(2, 1fr); }
  .ls:not(:last-child)::after { display: none; }
}
@media (max-width: 960px) {
  .drawer-btn { display: grid; }
  .layout, .layout.with-side, .layout.with-side.with-toc { grid-template-columns: minmax(0, 1fr); padding: 18px 16px 50px; gap: 0; }
  .sidebar { position: fixed; top: 58px; left: 0; bottom: 0; width: 300px; max-height: none; height: calc(100vh - 58px); z-index: 60; background: var(--bg); padding: 16px;
    border-right: 1px solid var(--line); transform: translateX(-105%); transition: transform .22s; box-shadow: var(--shadow); }
  body.drawer-open .sidebar { transform: none; }
  .mainnav { display: none; }
  .sidebar.mobile-only { display: block; }
  .side-mainnav { display: block; margin-bottom: 14px; padding-bottom: 10px; border-bottom: 1px solid var(--line); }
  .hero { grid-template-columns: 1fr; }
  .hero h1 { font-size: 32px; }
  .week-body { grid-template-columns: 1fr; gap: 0; }
}
@media (max-width: 640px) {
  body { font-size: 15.5px; }
  .topbar { padding: 0 12px; gap: 10px; }
  .brand-hub, .brand-sep { display: none; }
  .search-btn { min-width: 0; }
  .search-btn kbd { display: none; }
  .page-title { font-size: 25px; }
  .prose { font-size: 16px; }
  .prose h3 { font-size: 19px; }
  .fig img { width: min(100%, calc(var(--w, 60%) * 1.7)); }
  .fig-frame { padding: 8px; }
  .prose div.def, .prose div.rule, .prose div.key, .prose div.warn, .prose div.tip, .prose div.summary,
  .prose div.practice, .prose div.check, .prose div.example, .prose div.hw, .prose div.goal, .prose div.tool, .prose div.checkoff, .prose div.deliver { padding: 12px 13px; }
  .prose ul, .prose ol { padding-left: 1.3em; }
  .loop-steps, .mod-loop { grid-template-columns: 1fr; }
  .pager { grid-template-columns: 1fr; }
  .hw-row { grid-template-columns: 56px 1fr; }
  .hw-a, .hw-m { grid-column: 2; }
  .dr-card { padding: 16px; }
  .dr-q .big { font-size: 19px; }
  .kmap td, .kmap th { width: 42px; height: 40px; }
  .hero h1 { font-size: 28px; }
  .layout { padding: 16px 16px 40px; }
}
@media print {
  .topbar, .sidebar, .page-toc, .foot, .loop-panel, .done-bar, .pager, .lesson-tools, .ex-toggle { display: none !important; }
  .ex-sol.hide { display: block !important; }
  .layout { display: block; padding: 0; }
}

/* lab file blocks */
.file-head { display: flex; justify-content: space-between; align-items: center; margin: 18px 0 -10px; padding: 7px 12px; border-radius: 10px 10px 0 0;
  background: #252d36; color: #c5d0da; font: 13px var(--mono); }
.file-head + pre.code, .file-head + p + pre.code { border-top-left-radius: 0; border-top-right-radius: 0; }
.file-head .dl { color: #9cc4ff; font-family: var(--font); font-size: 13px; }
.prose div.goal ul, .prose div.checkoff ul { margin-bottom: 0; }
.prose div.checkoff .checklist { margin-top: 4px; }

/* boolean overline used by drills */
.ov { border-top: 1.5px solid currentColor; line-height: 1; }
.dr-q .big .ov { border-top-width: 2px; }
.sol-k .kmap { margin: 8px 0; }
.kgrp { cursor: pointer; font-family: var(--mono); }

pre.code .run-code { position: absolute; top: 4px; right: 62px; font: 11.5px/1 var(--font); background: #2a333c; color: #9fd8a8; border: 1px solid #3a4550; border-radius: 6px; padding: 5px 8px; cursor: pointer; }
pre.code .run-code:hover { background: #34404b; }
pre.code:has(.run-code)::before { right: 190px; }

.account { display: flex; align-items: center; gap: 8px; font-size: 13px; color: var(--muted); white-space: nowrap; }
.account a, .account button { font: inherit; color: var(--ink-2, inherit); background: none; border: 1px solid var(--line-2); border-radius: 8px; padding: 5px 9px; cursor: pointer; text-decoration: none; }
.account a:hover, .account button:hover { background: var(--surface-2, rgba(0,0,0,.04)); }
@media (max-width: 720px) { .account-name { display: none; } }

/* homework: the original problem, the guide folded under it */
.hwq { margin: 0 0 22px; padding: 16px 20px 12px; border: 1px solid var(--line); border-radius: var(--radius, 12px); background: var(--surface); }
.hwq .problem > :first-child { margin-top: 0; }
.problem img.hw-fig, .orig img.orig-img { display: block; max-width: 100%; height: auto; margin: 12px auto 4px; background: #fff; border-radius: 6px; padding: 6px; }
.problem img.hw-fig + p, .problem p > em:only-child { color: var(--muted); font-size: 14px; }
.hw-guide, .lab-notes { margin-top: 10px; border-top: 1px dashed var(--line-2); padding-top: 8px; }
.hw-guide > summary, .lab-notes > summary { cursor: pointer; color: var(--accent); font-weight: 600; font-size: 15px; padding: 4px 0; }
.hw-guide[open] > summary, .lab-notes[open] > summary { margin-bottom: 8px; }
.hw-guide-body > :first-child { margin-top: 0; }
.hw-page .prose > h2 { margin-top: 28px; }
/* labs: the handout's own prelab / postlab questions */
.orig { margin: 10px 0 14px; padding: 14px 18px; border: 1px solid var(--line); border-left: 4px solid var(--mc, var(--accent)); border-radius: 10px; background: var(--surface); }
.orig-h { font-size: 12px; letter-spacing: .06em; text-transform: uppercase; color: var(--muted); margin-bottom: 6px; }
.orig > :nth-child(2) { margin-top: 0; }
.lab-notes { margin-bottom: 14px; }
.orig img.orig-img { max-width: 100%; display: inline-block; vertical-align: top; margin: 8px 6px 4px 0; }
.problem img.hw-fig { max-width: min(100%, 520px); }