/* COMP3423 midterm crash course — shared design system
   Self-contained: no external fonts, no network dependencies. */

:root {
  --paper: #f6f3ec;
  --paper-deep: #efeade;
  --surface: #fffdf8;
  --surface-2: #fbf8f1;
  --ink: #1d1b18;
  --ink-soft: #3d3934;
  --muted: #6d675d;
  --faint: #928b7e;
  --line: #e0d9cb;
  --line-strong: #cdc4b2;

  --accent: #0f6b63;
  --accent-soft: #dcefe9;
  --accent-ink: #08443f;

  --ok: #1f7a4d;
  --ok-soft: #e2f3e8;
  --bad: #a8342a;
  --bad-soft: #fae7e3;
  --warn: #8a5a12;
  --warn-soft: #fbf0d9;

  --serif: "Iowan Old Style", "Palatino Linotype", "Book Antiqua", Palatino, Georgia, serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, "SF Mono", "JetBrains Mono", Menlo, Consolas, monospace;

  --measure: 72ch;
  --radius: 14px;
  --shadow-sm: 0 1px 2px rgba(29, 27, 24, .05), 0 6px 18px -12px rgba(29, 27, 24, .25);
  --shadow-md: 0 1px 2px rgba(29, 27, 24, .06), 0 18px 40px -26px rgba(29, 27, 24, .45);
}

html[data-theme="dark"] {
  --paper: #14150f;
  --paper-deep: #191a13;
  --surface: #1c1d16;
  --surface-2: #212218;
  --ink: #f0ecdf;
  --ink-soft: #d8d3c4;
  --muted: #a49e8f;
  --faint: #7d786b;
  --line: #33342a;
  --line-strong: #45463a;

  --accent: #7fd1c2;
  --accent-soft: #1d3b36;
  --accent-ink: #b6ece0;

  --ok: #7ad19f;
  --ok-soft: #17301f;
  --bad: #f0907f;
  --bad-soft: #331b17;
  --warn: #e0b76a;
  --warn-soft: #2e2515;

  --shadow-sm: 0 1px 2px rgba(0, 0, 0, .4), 0 6px 18px -12px rgba(0, 0, 0, .7);
  --shadow-md: 0 1px 2px rgba(0, 0, 0, .5), 0 18px 40px -26px rgba(0, 0, 0, .9);
}

/* per-chapter accents (light + dark) */
body[data-accent="teal"]   { --accent: #0f6b63; --accent-soft: #dcefe9; --accent-ink: #08443f; }
body[data-accent="indigo"] { --accent: #3a4c9c; --accent-soft: #e2e6f7; --accent-ink: #262f6b; }
body[data-accent="amber"]  { --accent: #94620f; --accent-soft: #f8ecd4; --accent-ink: #5f3d05; }
body[data-accent="plum"]   { --accent: #7c3469; --accent-soft: #f5e2ef; --accent-ink: #521f45; }
body[data-accent="moss"]   { --accent: #456b2d; --accent-soft: #e6efd9; --accent-ink: #2c451b; }
body[data-accent="clay"]   { --accent: #a2472c; --accent-soft: #f8e5dd; --accent-ink: #6d2b17; }

html[data-theme="dark"] body[data-accent="teal"]   { --accent: #7fd1c2; --accent-soft: #1d3b36; --accent-ink: #b6ece0; }
html[data-theme="dark"] body[data-accent="indigo"] { --accent: #a3b1f0; --accent-soft: #232a4d; --accent-ink: #ccd5ff; }
html[data-theme="dark"] body[data-accent="amber"]  { --accent: #e2b566; --accent-soft: #382c15; --accent-ink: #f3d9a5; }
html[data-theme="dark"] body[data-accent="plum"]   { --accent: #d99bc5; --accent-soft: #3a1f31; --accent-ink: #f2c8e3; }
html[data-theme="dark"] body[data-accent="moss"]   { --accent: #a9cc80; --accent-soft: #26331b; --accent-ink: #d3e9b7; }
html[data-theme="dark"] body[data-accent="clay"]   { --accent: #e39a80; --accent-soft: #3a231a; --accent-ink: #f5c8b6; }

* { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: 90px; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 16.5px;
  line-height: 1.62;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

@media (max-width: 640px) { body { font-size: 16px; } }

/* ---------- top bar ---------- */

.topbar {
  position: sticky; top: 0; z-index: 50;
  display: flex; align-items: center; gap: 18px;
  padding: 10px clamp(16px, 4vw, 40px);
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: saturate(140%) blur(12px);
  -webkit-backdrop-filter: saturate(140%) blur(12px);
  border-bottom: 1px solid var(--line);
}
.topbar a.home {
  display: inline-flex; align-items: center; gap: 8px;
  font: 600 12.5px/1 var(--sans);
  letter-spacing: .09em; text-transform: uppercase;
  color: var(--muted); text-decoration: none; white-space: nowrap;
}
.topbar a.home:hover { color: var(--accent); }
.topbar a.home .mark {
  width: 18px; height: 18px; border-radius: 5px;
  background: var(--accent); color: var(--surface);
  display: grid; place-items: center;
  font: 700 10px/1 var(--sans); letter-spacing: 0;
}
.topbar .crumb {
  font: 500 13px/1.3 var(--sans); color: var(--faint);
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}
.topbar .spacer { flex: 1; }
.topbar nav.pager { display: flex; gap: 6px; }
.topbar nav.pager a, .topbar button.icon {
  display: grid; place-items: center;
  min-width: 34px; height: 34px; padding: 0 10px;
  border: 1px solid var(--line); border-radius: 9px;
  background: var(--surface); color: var(--muted);
  text-decoration: none; cursor: pointer;
  font: 500 12.5px/1 var(--sans);
  white-space: nowrap;
}
.topbar nav.pager a:hover, .topbar button.icon:hover {
  border-color: var(--accent); color: var(--accent);
}
.topbar nav.pager a[aria-disabled="true"] { opacity: .35; pointer-events: none; }

@media (max-width: 720px) {
  .topbar { gap: 10px; padding-left: 14px; padding-right: 14px; }
  .topbar .crumb { display: none; }
  .topbar a.home { letter-spacing: .05em; }
}

@media (max-width: 480px) {
  .topbar { gap: 8px; }
  .topbar a.home { font-size: 11px; letter-spacing: .03em; gap: 6px; }
  .topbar a.home .mark { width: 16px; height: 16px; border-radius: 4px; }
  .topbar nav.pager a, .topbar button.icon { min-width: 30px; height: 30px; padding: 0 8px; font-size: 11.5px; }
}

/* ---------- page shell ---------- */

.wrap { max-width: 1180px; margin: 0 auto; padding: 0 clamp(16px, 4vw, 40px); }

.hero { padding: clamp(36px, 6vw, 76px) 0 clamp(20px, 3vw, 34px); }
.eyebrow {
  font: 600 12px/1 var(--sans); letter-spacing: .16em;
  text-transform: uppercase; color: var(--accent);
  display: flex; flex-wrap: wrap; align-items: center; gap: 10px;
}
.eyebrow .dot { width: 5px; height: 5px; border-radius: 50%; background: var(--line-strong); }

h1, h2, h3, h4 { font-family: var(--serif); font-weight: 600; letter-spacing: -.012em; }

.hero h1 {
  font-size: clamp(2.1rem, 5.2vw, 3.5rem); line-height: 1.06;
  margin: .35em 0 .3em; max-width: 18ch; text-wrap: balance;
}
.hero .lede {
  font-size: clamp(1.02rem, 1.7vw, 1.18rem); line-height: 1.6;
  color: var(--ink-soft); max-width: 62ch; margin: 0;
}
.hero .lede em { color: var(--ink); font-style: italic; }

.meta-row { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 22px; }
.chip {
  display: inline-flex; align-items: center; gap: 7px;
  padding: 6px 12px; border-radius: 999px;
  border: 1px solid var(--line); background: var(--surface);
  font: 500 12.5px/1.3 var(--sans); color: var(--muted);
}
.chip strong { color: var(--ink); font-weight: 600; }
.chip.accent { border-color: color-mix(in srgb, var(--accent) 35%, var(--line)); background: var(--accent-soft); color: var(--accent-ink); }

/* ---------- chapter layout ---------- */

.layout {
  display: grid; grid-template-columns: 212px minmax(0, 1fr);
  gap: clamp(24px, 4vw, 54px);
  padding-bottom: 80px;
  align-items: start;
}
@media (max-width: 900px) { .layout { grid-template-columns: minmax(0, 1fr); } }

.sidenav {
  position: sticky; top: 72px;
  font-size: 13.5px;
  border-left: 1px solid var(--line);
  padding: 4px 0 4px 16px;
  max-height: calc(100vh - 100px); overflow: auto;
}
.sidenav .label {
  font: 600 10.5px/1 var(--sans); letter-spacing: .14em;
  text-transform: uppercase; color: var(--faint);
  margin: 0 0 10px;
}
.sidenav a {
  display: block; padding: 5px 0; color: var(--muted);
  text-decoration: none; line-height: 1.35;
  border-left: 2px solid transparent; margin-left: -18px; padding-left: 16px;
}
.sidenav a:hover { color: var(--ink); }
.sidenav a.active { color: var(--accent); border-left-color: var(--accent); font-weight: 600; }
.sidenav .sub { padding-left: 28px; font-size: 12.5px; color: var(--faint); }
@media (max-width: 900px) {
  .sidenav { position: static; max-height: none; border-left: 0; border-top: 1px solid var(--line); padding: 14px 0 0; }
  .sidenav a { display: inline-block; margin: 0 14px 2px 0; border-left: 0; padding: 2px 0; }
  .sidenav .label { margin-bottom: 6px; }
}

.doc { max-width: var(--measure); min-width: 0; }
.doc > section { padding-top: 14px; }

.doc h2 {
  font-size: clamp(1.45rem, 2.6vw, 1.85rem);
  margin: 2.3em 0 .55em; padding-bottom: .3em;
  border-bottom: 1px solid var(--line);
  scroll-margin-top: 90px;
}
.doc h2 .num {
  font: 600 11px/1 var(--sans); letter-spacing: .12em;
  color: var(--accent); vertical-align: super;
  margin-right: 10px; letter-spacing: .1em;
}
.doc h3 {
  font-size: 1.13rem; margin: 1.9em 0 .45em;
  color: var(--ink); scroll-margin-top: 90px;
}
.doc h4 {
  font: 600 11.5px/1.3 var(--sans); letter-spacing: .12em;
  text-transform: uppercase; color: var(--faint);
  margin: 1.7em 0 .5em;
}
.doc p { margin: 0 0 1em; }
.doc ul, .doc ol { margin: 0 0 1.1em; padding-left: 1.25em; }
.doc li { margin-bottom: .38em; }
.doc li::marker { color: var(--faint); }
.doc strong { font-weight: 650; }
.doc em { font-style: italic; }
a {
  color: var(--accent-ink);
  text-underline-offset: 2px;
  text-decoration-thickness: 1px;
  text-decoration-color: color-mix(in srgb, var(--accent-ink) 40%, transparent);
}
a:hover { text-decoration-color: currentColor; }
table.data td a { white-space: nowrap; }
.doc code, .doc kbd {
  font-family: var(--mono); font-size: .87em;
  background: var(--paper-deep); padding: .12em .38em;
  border-radius: 4px; border: 1px solid var(--line);
}
.doc hr { border: 0; border-top: 1px solid var(--line); margin: 2.4em 0; }

.lead-in {
  font-size: 1.06rem; color: var(--ink-soft);
  border-left: 3px solid var(--accent);
  padding-left: 16px; margin: 0 0 2em;
}

/* key term inline */
.kt {
  font-weight: 600; color: var(--accent-ink);
  background: linear-gradient(transparent 62%, var(--accent-soft) 62%);
  padding: 0 .1em;
}
html[data-theme="dark"] .kt { color: var(--accent); }

/* ---------- callouts ---------- */

.callout {
  margin: 1.6em 0; padding: 15px 18px 15px 16px;
  background: var(--surface-2);
  border: 1px solid var(--line);
  border-left: 3px solid var(--accent);
  border-radius: 0 var(--radius) var(--radius) 0;
  font-size: .95rem;
}
.callout > :first-child { margin-top: 0; }
.callout > :last-child { margin-bottom: 0; }
.callout .tag {
  display: block; font: 600 10.5px/1 var(--sans);
  letter-spacing: .13em; text-transform: uppercase;
  color: var(--accent); margin-bottom: 8px;
}
.callout.warn { border-left-color: var(--warn); background: var(--warn-soft); }
.callout.warn .tag { color: var(--warn); }
.callout.exam { border-left-color: var(--bad); background: var(--bad-soft); }
.callout.exam .tag { color: var(--bad); }

/* ---------- formula ---------- */

.formula {
  margin: 1.5em 0; padding: 20px 22px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  text-align: center;
}
.formula .eq {
  font-family: var(--serif); font-size: 1.35rem;
  letter-spacing: .01em; margin: 0 0 10px;
}
.formula .eq i { font-style: italic; }
.formula .legend {
  font-size: .83rem; color: var(--muted); line-height: 1.5;
  text-align: left; max-width: 54ch; margin: 0 auto;
}
.formula .legend b { color: var(--ink); font-weight: 600; }

/* ---------- tables ---------- */

.table-wrap { overflow-x: auto; margin: 1.5em 0; border-radius: var(--radius); border: 1px solid var(--line); }
table.data {
  width: 100%; border-collapse: collapse; font-size: .91rem;
  background: var(--surface); min-width: 480px;
}
table.data th, table.data td {
  padding: 10px 14px; text-align: left; vertical-align: top;
  border-bottom: 1px solid var(--line);
}
table.data th {
  font: 600 11px/1.3 var(--sans); letter-spacing: .09em;
  text-transform: uppercase; color: var(--faint);
  background: var(--surface-2);
}
table.data tr:last-child td { border-bottom: 0; }
table.data td b, table.data td strong { color: var(--ink); }

/* ---------- figures ---------- */

.figure {
  margin: 1.8em 0; padding: 18px;
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); text-align: center;
}
.figure svg { max-width: 100%; height: auto; }
.figure figcaption {
  margin-top: 12px; font-size: .82rem; color: var(--muted);
  text-align: left; line-height: 1.5;
}
.figure figcaption b { color: var(--ink); }

/* ---------- code block ---------- */

pre.snippet {
  margin: 1.3em 0; padding: 14px 16px; overflow-x: auto;
  background: var(--paper-deep); border: 1px solid var(--line);
  border-radius: 10px; font: 400 12.8px/1.6 var(--mono); color: var(--ink-soft);
}
pre.snippet .c { color: var(--faint); }

/* ---------- quiz ---------- */

.quiz { margin: 1.4em 0 0; }
.quiz-head {
  display: flex; flex-wrap: wrap; align-items: baseline; gap: 10px 16px;
  margin: 0 0 18px;
}
.quiz-head .score {
  font: 600 12px/1 var(--sans); letter-spacing: .06em;
  color: var(--muted); background: var(--surface);
  border: 1px solid var(--line); border-radius: 999px; padding: 7px 12px;
}
.quiz-head .score b { color: var(--accent); }

.mcq {
  margin: 0 0 18px; padding: 20px 22px;
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); box-shadow: var(--shadow-sm);
}
.mcq .q {
  font-family: var(--serif); font-size: 1.04rem; line-height: 1.45;
  margin: 0 0 14px;
}
.mcq .q .qno {
  font: 600 10.5px/1 var(--sans); letter-spacing: .12em;
  color: var(--accent); display: block; margin-bottom: 8px;
}
.opts { display: grid; gap: 7px; margin: 0 0 14px; }
.opts label {
  display: flex; gap: 11px; align-items: flex-start;
  padding: 10px 13px; border: 1px solid var(--line);
  border-radius: 9px; cursor: pointer;
  font-size: .94rem; line-height: 1.45;
  background: var(--surface-2);
  transition: border-color .15s, background .15s, transform .1s;
}
.opts label:hover { border-color: var(--line-strong); }
.opts input { position: absolute; opacity: 0; pointer-events: none; }
.opts label .key {
  flex: 0 0 auto; width: 21px; height: 21px; border-radius: 6px;
  display: grid; place-items: center;
  border: 1px solid var(--line-strong); background: var(--surface);
  font: 600 11px/1 var(--sans); color: var(--muted);
  margin-top: .1em;
}
.opts label.sel { border-color: var(--accent); background: var(--accent-soft); }
.opts label.sel .key { background: var(--accent); border-color: var(--accent); color: var(--surface); }
.opts label.correct { border-color: var(--ok); background: var(--ok-soft); }
.opts label.correct .key { background: var(--ok); border-color: var(--ok); color: #fff; }
.opts label.wrong { border-color: var(--bad); background: var(--bad-soft); }
.opts label.wrong .key { background: var(--bad); border-color: var(--bad); color: #fff; }
.opts label.locked { cursor: default; }

.mcq .actions { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.btn {
  appearance: none; border: 1px solid var(--ink); background: var(--ink);
  color: var(--paper); border-radius: 9px; cursor: pointer;
  font: 600 12.5px/1 var(--sans); letter-spacing: .04em;
  padding: 10px 16px;
  transition: transform .1s, opacity .15s, background .15s;
}
.btn:hover { opacity: .88; }
.btn:active { transform: translateY(1px); }
.btn.ghost {
  background: transparent; color: var(--muted); border-color: var(--line-strong);
  font-weight: 500;
}
.btn.ghost:hover { color: var(--ink); border-color: var(--ink); }
.btn:disabled { opacity: .4; cursor: default; }

.feedback {
  margin: 13px 0 0; padding: 12px 15px; border-radius: 9px;
  font-size: .9rem; line-height: 1.55; display: none;
}
.feedback.show { display: block; }
.feedback.ok { background: var(--ok-soft); color: var(--ok); }
.feedback.bad { background: var(--bad-soft); color: var(--bad); }
.feedback .verdict { font-weight: 700; display: block; margin-bottom: 4px; letter-spacing: .02em; }
.feedback .body { color: var(--ink-soft); }
.feedback .body b { color: var(--ink); }

/* ---------- open questions ---------- */

.qa {
  margin: 0 0 18px; padding: 20px 22px;
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); box-shadow: var(--shadow-sm);
}
.qa .qhead {
  display: flex; flex-wrap: wrap; align-items: baseline; gap: 8px 14px;
  margin-bottom: 10px;
}
.qa .qtag {
  font: 600 10.5px/1 var(--sans); letter-spacing: .11em;
  text-transform: uppercase; color: var(--bad);
}
.qa .marks {
  font: 600 11px/1 var(--sans); color: var(--faint);
  border: 1px solid var(--line); border-radius: 999px; padding: 5px 9px;
}
.qa .stem { font-size: .96rem; }
.qa .stem > :last-child { margin-bottom: 0; }
.qa details { margin-top: 14px; border-top: 1px dashed var(--line); padding-top: 12px; }
.qa summary {
  cursor: pointer; list-style: none; display: inline-flex; align-items: center; gap: 8px;
  font: 600 12.5px/1 var(--sans); color: var(--accent);
  border: 1px solid color-mix(in srgb, var(--accent) 40%, var(--line));
  background: var(--accent-soft);
  border-radius: 8px; padding: 9px 14px;
  user-select: none;
}
.qa summary::-webkit-details-marker { display: none; }
.qa summary::before { content: "▸"; font-size: 11px; }
.qa details[open] summary::before { content: "▾"; }
.qa summary:hover { filter: brightness(.98); }
.qa .answer { margin-top: 14px; font-size: .93rem; }
.qa .answer > :first-child { margin-top: 0; }
.qa .answer > :last-child { margin-bottom: 0; }
.qa .answer h4 { margin-top: 1.2em; }

/* ---------- index cards ---------- */

.section-head {
  display: flex; align-items: baseline; justify-content: space-between;
  gap: 16px; flex-wrap: wrap;
  margin: clamp(38px, 5vw, 60px) 0 20px;
  border-bottom: 1px solid var(--line); padding-bottom: 10px;
}
.section-head h2 { font-size: clamp(1.35rem, 2.4vw, 1.7rem); margin: 0; }
.section-head .aside { font-size: .84rem; color: var(--faint); }

.cards { display: grid; gap: 16px; grid-template-columns: repeat(2, minmax(0, 1fr)); }
@media (max-width: 760px) { .cards { grid-template-columns: minmax(0, 1fr); } }
.card {
  display: flex; flex-direction: column;
  padding: 24px 24px 20px;
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); box-shadow: var(--shadow-sm);
  text-decoration: none; color: inherit;
  transition: transform .18s ease, box-shadow .18s ease, border-color .18s ease;
  position: relative; overflow: hidden;
}
.card::after {
  content: ""; position: absolute; inset: 0 0 auto 0; height: 3px;
  background: var(--accent); opacity: .85;
}
.card:hover { transform: translateY(-3px); box-shadow: var(--shadow-md); border-color: var(--line-strong); }
.card .cnum {
  font: 600 11px/1 var(--sans); letter-spacing: .14em;
  text-transform: uppercase; color: var(--accent); margin-bottom: 10px;
}
.card h3 { font-size: 1.3rem; line-height: 1.2; margin: 0 0 8px; }
.card .weeks { font-size: .8rem; color: var(--faint); margin: 0 0 12px; letter-spacing: .02em; }
.card p { font-size: .92rem; color: var(--ink-soft); margin: 0 0 16px; }
.card .topics { display: flex; flex-wrap: wrap; gap: 6px; margin: auto 0 0; }
.card .topics span {
  font-size: 11px; color: var(--muted); background: var(--paper-deep);
  border: 1px solid var(--line); border-radius: 999px; padding: 4px 9px;
}
.card .foot {
  display: flex; align-items: center; justify-content: space-between;
  margin-top: 16px; padding-top: 12px; border-top: 1px solid var(--line);
  font: 500 12px/1 var(--sans); color: var(--faint);
}
.card .foot .arrow { color: var(--accent); font-weight: 600; }

.card.wide { grid-column: 1 / -1; flex-direction: row; align-items: center; gap: 24px; }
.card.wide .body { flex: 1; }
.card.wide .cta {
  font: 600 12.5px/1 var(--sans); color: var(--paper); background: var(--ink);
  padding: 12px 18px; border-radius: 9px; white-space: nowrap;
}
@media (max-width: 640px) { .card.wide { flex-direction: column; align-items: flex-start; } }

/* progress bar on cards */
.mini-progress {
  height: 4px; border-radius: 4px; background: var(--paper-deep);
  overflow: hidden; margin: 14px 0 0;
}
.mini-progress i { display: block; height: 100%; background: var(--accent); width: 0; transition: width .4s ease; }

/* ---------- plan / checklist ---------- */

.plan { display: grid; gap: 12px; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); margin: 20px 0 0; }
.plan .step {
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 18px 20px;
}
.plan .step .n {
  font: 600 10.5px/1 var(--sans); letter-spacing: .14em;
  text-transform: uppercase; color: var(--accent); margin-bottom: 8px; display: block;
}
.plan .step h3 { font-size: 1.02rem; margin: 0 0 6px; font-family: var(--sans); font-weight: 650; letter-spacing: 0; }
.plan .step p { font-size: .89rem; color: var(--ink-soft); margin: 0; }

.factlist { margin: 18px 0 0; padding: 0; list-style: none; counter-reset: f; }
.factlist li {
  position: relative; padding: 12px 16px 12px 46px;
  border: 1px solid var(--line); border-radius: 10px;
  background: var(--surface); margin-bottom: 8px; font-size: .93rem;
}
.factlist li::before {
  counter-increment: f; content: counter(f);
  position: absolute; left: 14px; top: 12px;
  width: 22px; height: 22px; border-radius: 50%;
  background: var(--accent-soft); color: var(--accent-ink);
  display: grid; place-items: center;
  font: 600 11px/1 var(--sans);
}
.factlist li b { color: var(--ink); }

/* ---------- footer ---------- */

footer.pagefoot {
  border-top: 1px solid var(--line);
  padding: 26px 0 60px; margin-top: 20px;
  font-size: .84rem; color: var(--faint);
}
footer.pagefoot .row { display: flex; flex-wrap: wrap; gap: 10px 22px; justify-content: space-between; }
footer.pagefoot a { color: var(--muted); }

.pager-bottom { display: flex; gap: 12px; justify-content: space-between; margin: 48px 0 0; }
.pager-bottom a {
  flex: 1; padding: 16px 18px; border: 1px solid var(--line);
  border-radius: var(--radius); background: var(--surface);
  text-decoration: none; color: inherit;
}
.pager-bottom a:hover { border-color: var(--accent); }
.pager-bottom .dir { font: 600 10.5px/1 var(--sans); letter-spacing: .12em; text-transform: uppercase; color: var(--faint); }
.pager-bottom .ttl { display: block; margin-top: 6px; font-family: var(--serif); font-size: 1.02rem; }
.pager-bottom a.next { text-align: right; }

/* ---------- mock paper ---------- */

.paper-head {
  border: 1px solid var(--line); border-radius: var(--radius);
  background: var(--surface); padding: 26px 28px; margin: 26px 0 10px;
  box-shadow: var(--shadow-sm);
}
.paper-head .inst {
  font: 600 11px/1.5 var(--sans); letter-spacing: .12em;
  text-transform: uppercase; color: var(--faint); margin-bottom: 14px;
}
.paper-head h2 { font-family: var(--serif); font-size: 1.5rem; margin: 0 0 4px; border: 0; padding: 0; }
.paper-head .sub { color: var(--muted); font-size: .9rem; margin: 0 0 18px; }
.paper-grid {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 12px; border-top: 1px solid var(--line); padding-top: 16px;
}
.paper-grid div { font-size: .85rem; color: var(--muted); }
.paper-grid b { display: block; color: var(--ink); font: 600 11px/1.6 var(--sans); letter-spacing: .08em; text-transform: uppercase; }

.section-band {
  display: flex; align-items: baseline; gap: 14px; flex-wrap: wrap;
  margin: 44px 0 6px; padding: 12px 16px;
  background: var(--ink); color: var(--paper); border-radius: 10px;
}
.section-band h2 { font-family: var(--serif); font-size: 1.15rem; margin: 0; border: 0; padding: 0; color: inherit; }
.section-band .m { font: 500 12px/1 var(--sans); color: color-mix(in srgb, var(--paper) 65%, var(--ink)); margin-left: auto; }

.sticky-tools {
  position: sticky; top: 57px; z-index: 40;
  display: flex; gap: 8px; flex-wrap: wrap; align-items: center;
  padding: 10px 0; margin-bottom: 8px;
  background: color-mix(in srgb, var(--paper) 92%, transparent);
  backdrop-filter: blur(8px);
}
@media (max-width: 640px) { .sticky-tools { position: static; } }

.sticky-tools .tally {
  font: 500 12px/1 var(--sans); color: var(--muted);
  border: 1px solid var(--line); background: var(--surface);
  border-radius: 999px; padding: 8px 12px;
}
.sticky-tools .tally b { color: var(--accent); }

/* MC answer sheet style in mock */
.mcq.paper-q .q { margin-bottom: 12px; }

/* utility */
.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}
.nowrap { white-space: nowrap; }
.small { font-size: .86rem; color: var(--muted); }

@media print {
  .topbar, .sidenav, .sticky-tools, .pager-bottom, .btn, .quiz-head .score { display: none !important; }
  body { background: #fff; color: #000; font-size: 11pt; }
  .layout { grid-template-columns: 1fr; }
  .card, .mcq, .qa, .callout, .figure, .formula { box-shadow: none; break-inside: avoid; }
  .qa details { display: block; }
  .qa details > summary { display: none; }
  .qa .answer { display: block !important; }
  a { color: #000; text-decoration: none; }
}