/* =====================================================================
   NEET Physics Notes — shared design system (light theme only)
   Layout: sticky top bar → [section index | reading column]; text ≤ 70ch,
   figures & simulations take the full column width.
   ===================================================================== */
:root {
  color-scheme: light;
  /* neutrals — slightly cool, biased toward the ink-blue */
  --bg: #F5F6F9;
  --surface: #FFFFFF;
  --surface-2: #EEF0F5;
  --ink: #1B2233;
  --ink-2: #454F66;
  --muted: #737C91;
  --line: #E1E4EC;
  --line-2: #CDD2DD;

  /* muted-vibrant palette */
  --teal: #13817E;   --teal-soft: #E2F2F0;
  --indigo: #4B5BD0; --indigo-soft: #E9EBFA;
  --coral: #D6604A;  --coral-soft: #FBE9E4;
  --amber: #C2850E;  --amber-soft: #FAF0DA;
  --plum: #8B4E9F;   --plum-soft: #F3E9F6;
  --green: #2F8A57;  --green-soft: #E3F2E8;
  --water: #3A8CCB;  --water-soft: #E3EFF9;

  --accent: var(--teal);
  --accent-soft: var(--teal-soft);

  --f-display: "Bricolage Grotesque", "Avenir Next", "Segoe UI", system-ui, sans-serif;
  --f-body: "Figtree", "Segoe UI", system-ui, -apple-system, sans-serif;
  --f-mono: "JetBrains Mono", ui-monospace, "SF Mono", Menlo, monospace;

  --r-sm: 6px;
  --r: 10px;
  --r-lg: 16px;
  --shadow: 0 1px 2px rgba(27, 34, 51, .05), 0 4px 16px rgba(27, 34, 51, .05);
  --topbar-h: 56px;
}

body.ch-solids  { --accent: var(--indigo); --accent-soft: var(--indigo-soft); }
body.ch-fluids1 { --accent: var(--water);  --accent-soft: var(--water-soft); }
body.ch-fluids2 { --accent: var(--plum);   --accent-soft: var(--plum-soft); }
body.ch-practice{ --accent: var(--coral);  --accent-soft: var(--coral-soft); }
body.ch-revise  { --accent: var(--green);  --accent-soft: var(--green-soft); }
body.ch-week    { --accent: var(--coral);  --accent-soft: var(--coral-soft); }

*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: calc(var(--topbar-h) + 16px); -webkit-text-size-adjust: 100%; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } *, *::before, *::after { animation: none !important; transition: none !important; } }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--f-body);
  font-size: 17px;
  line-height: 1.65;
}
img, svg, canvas { max-width: 100%; }
a { color: var(--accent); text-underline-offset: 3px; }
a:hover { text-decoration-thickness: 2px; }
:focus-visible { outline: 3px solid color-mix(in srgb, var(--accent) 55%, transparent); outline-offset: 2px; border-radius: 4px; }
h1, h2, h3, h4 { font-family: var(--f-display); line-height: 1.2; text-wrap: balance; color: var(--ink); margin: 0; }
h1 { font-size: clamp(30px, 5vw, 46px); font-weight: 750; letter-spacing: -0.02em; }
h2 { font-size: clamp(24px, 3.4vw, 31px); font-weight: 700; letter-spacing: -0.01em; }
h3 { font-size: clamp(19px, 2.4vw, 22px); font-weight: 650; }
h4 { font-size: 17px; font-weight: 650; }
p { margin: 0; }
strong { font-weight: 650; color: var(--ink); }
code, .mono { font-family: var(--f-mono); font-size: .88em; }
hr { border: 0; border-top: 1px solid var(--line); margin: 8px 0; }

/* ---------- top bar ---------- */
.topbar {
  position: sticky; top: env(safe-area-inset-top, 0px); z-index: 50;
  background: color-mix(in srgb, var(--surface) 92%, transparent);
  backdrop-filter: saturate(1.4) blur(10px);
  -webkit-backdrop-filter: saturate(1.4) blur(10px);
  border-bottom: 1px solid var(--line);
}
.topbar-inner {
  max-width: 1280px; margin: 0 auto; padding-inline: 16px;
  min-height: var(--topbar-h); display: flex; align-items: center; gap: 16px;
}
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; color: var(--ink); flex-shrink: 0; }
.brand-mark {
  width: 30px; height: 30px; border-radius: 8px; display: grid; place-items: center;
  background: var(--ink); color: #fff; font-family: var(--f-display); font-weight: 800; font-size: 15px;
}
.brand-name { font-family: var(--f-display); font-weight: 700; font-size: 16px; line-height: 1.1; }
.brand-name small { display: block; font-family: var(--f-body); font-weight: 500; font-size: 11.5px; color: var(--muted); letter-spacing: .02em; }
.nav { display: flex; gap: 4px; overflow-x: auto; scrollbar-width: none; margin-left: auto; min-width: 0; }
.nav::-webkit-scrollbar { display: none; }
.nav a {
  white-space: nowrap; text-decoration: none; color: var(--ink-2); font-weight: 550; font-size: 14.5px;
  padding: 7px 12px; border-radius: 999px; transition: background .15s, color .15s;
}
.nav a:hover { background: var(--surface-2); color: var(--ink); }
.nav a[aria-current="page"] { background: var(--accent-soft); color: var(--accent); }
@media (max-width: 720px) {
  .topbar-inner { flex-wrap: wrap; gap: 4px 12px; padding-block: 8px 6px; }
  .brand-name small { display: none; }
  .nav { order: 3; width: 100%; margin-left: -8px; margin-right: -16px; padding-right: 16px; }
  .nav a { padding: 6px 10px; font-size: 14px; }
}

/* ---------- page frame ---------- */
.frame { max-width: 1280px; margin: 0 auto; padding-inline: 16px; padding-block: 0 80px; }
@media (min-width: 720px) { .frame { padding-inline: 28px; } }
.with-toc { display: grid; grid-template-columns: minmax(0, 1fr); gap: 40px; }
@media (min-width: 1100px) { .with-toc { grid-template-columns: 230px minmax(0, 1fr); gap: 48px; } }
.content { min-width: 0; max-width: 900px; }

/* section index (desktop sidebar / mobile collapsible) */
.toc { min-width: 0; }
.toc details { background: var(--surface); border: 1px solid var(--line); border-radius: var(--r); padding: 10px 14px; }
.toc summary { cursor: pointer; font-weight: 650; font-size: 14px; color: var(--ink-2); list-style: none; display: flex; justify-content: space-between; }
.toc summary::after { content: "▾"; color: var(--muted); }
.toc details[open] summary::after { content: "▴"; }
.toc ol { list-style: none; margin: 10px 0 2px; padding: 0; display: grid; gap: 1px; }
.toc a {
  display: flex; gap: 8px; text-decoration: none; color: var(--ink-2); font-size: 14px; line-height: 1.35;
  padding: 6px 8px; border-radius: var(--r-sm);
}
.toc a .n { font-family: var(--f-mono); font-size: 11.5px; color: var(--muted); min-width: 30px; padding-top: 2px; }
.toc a:hover { background: var(--surface-2); color: var(--ink); }
.toc a.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.toc a.active .n { color: var(--accent); }
@media (min-width: 1100px) {
  .toc { position: sticky; top: calc(var(--topbar-h) + 20px); align-self: start; max-height: calc(100vh - var(--topbar-h) - 40px); overflow-y: auto; padding-top: 28px; }
  .toc details { background: transparent; border: 0; padding: 0; }
  .toc summary { pointer-events: none; font-size: 12px; text-transform: uppercase; letter-spacing: .08em; color: var(--muted); }
  .toc summary::after { content: none; }
}
@media (max-width: 1099px) { .toc { margin-top: 16px; } }

/* ---------- chapter hero ---------- */
.hero { padding-block: 32px 8px; display: grid; gap: 14px; }
.eyebrow { font-family: var(--f-mono); font-size: 12px; letter-spacing: .1em; text-transform: uppercase; color: var(--accent); font-weight: 600; }
.lede { font-size: 19px; color: var(--ink-2); max-width: 62ch; }
.chips { display: flex; flex-wrap: wrap; gap: 8px; }
.chip {
  display: inline-flex; align-items: center; gap: 6px; font-size: 13px; font-weight: 600; line-height: 1;
  padding: 6px 10px; border-radius: 999px; background: var(--surface-2); color: var(--ink-2); white-space: nowrap;
}
.chip.accent { background: var(--accent-soft); color: var(--accent); }
.chip.coral { background: var(--coral-soft); color: var(--coral); }
.chip.amber { background: var(--amber-soft); color: var(--amber); }
.chip.green { background: var(--green-soft); color: var(--green); }
.chip.indigo { background: var(--indigo-soft); color: var(--indigo); }
.chip.plum { background: var(--plum-soft); color: var(--plum); }
.chip.water { background: var(--water-soft); color: var(--water); }

/* ---------- sections & prose ---------- */
.content > section { padding-top: 44px; display: grid; gap: 18px; }
.content > section + section { border-top: 1px solid var(--line); margin-top: 44px; }
.sec-head { display: grid; gap: 6px; }
.sec-head .num { font-family: var(--f-mono); font-size: 13px; color: var(--accent); font-weight: 600; letter-spacing: .04em; display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
.level { font-family: var(--f-body); font-size: 11.5px; font-weight: 700; letter-spacing: .06em; text-transform: uppercase; padding: 3px 8px; border-radius: 999px; }
.level.basic { background: var(--green-soft); color: var(--green); }
.level.core { background: var(--water-soft); color: var(--water); }
.level.exam { background: var(--coral-soft); color: var(--coral); }
.prose { display: grid; gap: 14px; max-width: 70ch; }
.prose ul, .prose ol { margin: 0; padding-left: 1.3em; display: grid; gap: 6px; }
.prose li::marker { color: var(--accent); }
.hl { background: linear-gradient(transparent 58%, color-mix(in srgb, var(--amber) 28%, transparent) 58%); padding-inline: 1px; }
.term { font-weight: 650; color: var(--accent); }

/* ---------- callouts ---------- */
.callout {
  border-radius: var(--r); padding: 14px 16px; display: grid; gap: 8px; max-width: 78ch;
  background: var(--surface); border: 1px solid var(--line);
}
.callout > .label { font-size: 12px; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; display: flex; align-items: center; gap: 8px; }
.callout > .label::before { content: ""; width: 8px; height: 8px; border-radius: 50%; background: currentColor; }
.callout.def   { background: var(--accent-soft); border-color: transparent; }
.callout.def > .label { color: var(--accent); }
.callout.tip   { background: var(--green-soft); border-color: transparent; }
.callout.tip > .label { color: var(--green); }
.callout.trap  { background: var(--coral-soft); border-color: transparent; }
.callout.trap > .label { color: var(--coral); }
.callout.exam  { background: var(--amber-soft); border-color: transparent; }
.callout.exam > .label { color: var(--amber); }
.callout.life  { background: var(--surface); }
.callout.life > .label { color: var(--ink-2); }
.callout ul { margin: 0; padding-left: 1.2em; display: grid; gap: 4px; }

/* formula card */
.formula {
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--r); padding: 16px 18px;
  display: grid; gap: 10px; box-shadow: var(--shadow); overflow-x: auto; max-width: 100%;
}
.formula .f-title { font-size: 12px; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--muted); }
.formula .f-main { font-size: 1.15em; text-align: center; padding-block: 4px; }
.formula .f-where { font-size: 14.5px; color: var(--ink-2); }
.formula-grid { display: grid; gap: 12px; grid-template-columns: repeat(auto-fit, minmax(min(100%, 240px), 1fr)); }

/* tables */
.table-wrap { overflow-x: auto; border: 1px solid var(--line); border-radius: var(--r); background: var(--surface); }
table { border-collapse: collapse; width: 100%; font-size: 15px; font-variant-numeric: tabular-nums; }
th, td { text-align: left; padding: 10px 12px; border-bottom: 1px solid var(--line); vertical-align: top; }
th { font-size: 12.5px; text-transform: uppercase; letter-spacing: .06em; color: var(--muted); font-weight: 700; background: var(--surface-2); }
tr:last-child td { border-bottom: 0; }

/* two-column comparison blocks */
.compare { display: grid; gap: 12px; grid-template-columns: repeat(auto-fit, minmax(min(100%, 220px), 1fr)); }
.compare > div { background: var(--surface); border: 1px solid var(--line); border-radius: var(--r); padding: 14px 16px; display: grid; gap: 6px; align-content: start; }
.compare h4 { color: var(--accent); }

/* ---------- static figures ---------- */
figure { margin: 0; }
.fig { background: var(--surface); border: 1px solid var(--line); border-radius: var(--r-lg); padding: 14px; display: grid; gap: 10px; }
.fig svg { display: block; width: 100%; height: auto; }
figcaption { font-size: 14px; color: var(--muted); }

/* ---------- interactive simulation ---------- */
.sim {
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--r-lg);
  box-shadow: var(--shadow); overflow: hidden; display: grid;
}
.sim-head { display: flex; align-items: center; gap: 10px; padding: 12px 16px; border-bottom: 1px solid var(--line); flex-wrap: wrap; }
.sim-head .tag { font-family: var(--f-mono); font-size: 11px; letter-spacing: .1em; text-transform: uppercase; color: #fff; background: var(--accent); padding: 3px 7px; border-radius: 5px; font-weight: 600; }
.sim-head h4 { font-size: 16px; }
.sim-stage { position: relative; background: linear-gradient(180deg, #FBFCFE, #F4F6FA); }
.sim-stage canvas { display: block; width: 100%; touch-action: pan-y; }
.sim-body { display: grid; gap: 0; grid-template-columns: minmax(0, 1fr); }
@media (min-width: 860px) { .sim-body.side { grid-template-columns: minmax(0, 1fr) 260px; } .sim-body.side .sim-panel { border-top: 0; border-left: 1px solid var(--line); } }
.sim-panel { padding: 14px 16px; display: grid; gap: 14px; border-top: 1px solid var(--line); align-content: start; }
.controls { display: grid; gap: 12px; grid-template-columns: repeat(auto-fit, minmax(min(100%, 190px), 1fr)); }
.ctrl { display: grid; gap: 4px; }
.ctrl label { display: flex; justify-content: space-between; gap: 8px; font-size: 13.5px; color: var(--ink-2); font-weight: 550; }
.ctrl output { font-family: var(--f-mono); font-size: 12.5px; color: var(--accent); font-weight: 600; white-space: nowrap; }
input[type="range"] { width: 100%; accent-color: var(--accent); height: 28px; margin: 0; }
.seg { display: inline-flex; flex-wrap: wrap; gap: 4px; background: var(--surface-2); padding: 3px; border-radius: 9px; }
.seg button { border: 0; background: transparent; font: inherit; font-size: 13.5px; font-weight: 600; color: var(--ink-2); padding: 6px 10px; border-radius: 7px; cursor: pointer; }
.seg button[aria-pressed="true"] { background: var(--surface); color: var(--accent); box-shadow: 0 1px 3px rgba(27,34,51,.12); }
.readouts { display: grid; gap: 8px; grid-template-columns: repeat(auto-fit, minmax(min(100%, 130px), 1fr)); }
.readout { background: var(--surface-2); border-radius: 8px; padding: 8px 10px; display: grid; gap: 2px; }
.readout .k { font-size: 11.5px; color: var(--muted); font-weight: 600; text-transform: uppercase; letter-spacing: .05em; }
.readout .v { font-family: var(--f-mono); font-size: 15px; font-weight: 600; color: var(--ink); font-variant-numeric: tabular-nums; }
.readout.hi { background: var(--accent-soft); }
.readout.hi .v { color: var(--accent); }
.sim-note { font-size: 14px; color: var(--ink-2); }
.btn {
  font: inherit; font-size: 14px; font-weight: 600; border-radius: 8px; padding: 8px 14px; cursor: pointer;
  border: 1px solid var(--line-2); background: var(--surface); color: var(--ink);
}
.btn:hover { border-color: var(--accent); color: var(--accent); }
.btn.primary { background: var(--accent); color: #fff; border-color: var(--accent); }
.btn.primary:hover { filter: brightness(1.06); color: #fff; }
.btn-row { display: flex; gap: 8px; flex-wrap: wrap; }

/* ---------- worked examples ---------- */
.eg { background: var(--surface); border: 1px solid var(--line); border-radius: var(--r); overflow: hidden; }
.eg-q { padding: 14px 16px; display: grid; gap: 8px; }
.eg-q .eg-tag { font-size: 12px; font-weight: 700; letter-spacing: .06em; text-transform: uppercase; color: var(--accent); display: flex; gap: 8px; flex-wrap: wrap; align-items: center; }
.eg details { border-top: 1px dashed var(--line-2); }
.eg summary { cursor: pointer; padding: 10px 16px; font-weight: 650; font-size: 14.5px; color: var(--accent); list-style: none; }
.eg summary::-webkit-details-marker { display: none; }
.eg summary::before { content: "＋ "; }
.eg details[open] summary::before { content: "－ "; }
.eg .eg-a { padding: 0 16px 16px; display: grid; gap: 8px; }
.steps { margin: 0; padding-left: 1.4em; display: grid; gap: 6px; }
.steps li::marker { font-family: var(--f-mono); color: var(--accent); font-size: .85em; }
.answer { font-weight: 700; color: var(--green); }

/* ---------- quiz cards ---------- */
.quiz-list { display: grid; gap: 16px; }
.qcard { background: var(--surface); border: 1px solid var(--line); border-radius: var(--r-lg); padding: 16px; display: grid; gap: 12px; box-shadow: var(--shadow); min-width: 0; }
.qcard.done-right { border-color: color-mix(in srgb, var(--green) 45%, var(--line)); }
.qcard.done-wrong { border-color: color-mix(in srgb, var(--coral) 45%, var(--line)); }
.qmeta { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; }
.qmeta .src { font-family: var(--f-mono); font-size: 12px; font-weight: 600; color: var(--ink-2); margin-right: 4px; }
.qtext { display: grid; gap: 8px; }
.qtext .qfig { background: #FAFBFD; border: 1px solid var(--line); border-radius: var(--r); padding: 10px; overflow-x: auto; }
.qtext .qfig svg { display: block; margin: 0 auto; max-width: 520px; width: 100%; height: auto; }
.ar { display: grid; gap: 6px; }
.ar p strong { color: var(--accent); }
.opts { display: grid; gap: 8px; grid-template-columns: minmax(0, 1fr); }
@media (min-width: 640px) { .opts.short { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
.opt {
  font: inherit; text-align: left; display: flex; gap: 10px; align-items: flex-start; cursor: pointer;
  padding: 10px 12px; border-radius: 10px; border: 1.5px solid var(--line); background: var(--surface); color: var(--ink);
  transition: border-color .15s, background .15s; min-width: 0;
}
.opt:hover:not(:disabled) { border-color: var(--accent); background: var(--accent-soft); }
.opt .on { font-family: var(--f-mono); font-weight: 700; font-size: 13px; color: var(--muted); min-width: 18px; padding-top: 2px; }
.opt .ot { min-width: 0; overflow-x: auto; }
.opt.right { border-color: var(--green); background: var(--green-soft); }
.opt.right .on { color: var(--green); }
.opt.wrong { border-color: var(--coral); background: var(--coral-soft); }
.opt.wrong .on { color: var(--coral); }
.opt:disabled { cursor: default; }
.qactions { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; }
.verdict { font-weight: 700; font-size: 14.5px; }
.verdict.ok { color: var(--green); }
.verdict.no { color: var(--coral); }
.sol { border-top: 1px dashed var(--line-2); padding-top: 12px; display: grid; gap: 10px; }
.sol h5 { margin: 0; font-family: var(--f-display); font-size: 15px; color: var(--accent); }
.sol .why-opts { font-size: 15px; color: var(--ink-2); }
.sol .concept { font-size: 14px; }

/* match-the-column tables in questions */
.mtc { width: 100%; font-size: 14.5px; }
.mtc td { padding: 6px 10px; }

/* ---------- home / cards ---------- */
.grid-cards { display: grid; gap: 16px; grid-template-columns: repeat(auto-fit, minmax(min(100%, 260px), 1fr)); }
.card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--r-lg); padding: 18px; display: grid; gap: 10px; align-content: start; text-decoration: none; color: var(--ink); transition: border-color .15s, transform .15s; }
a.card:hover { border-color: var(--accent); transform: translateY(-2px); }
.card .card-k { font-family: var(--f-mono); font-size: 12px; letter-spacing: .08em; text-transform: uppercase; font-weight: 600; }
.card p { color: var(--ink-2); font-size: 15.5px; }
.ch-card { border-top: 4px solid var(--c); }
.ch-card .card-k { color: var(--c); }
.ch-card .chip { white-space: normal; max-width: 100%; }
.chapter-volume { display: grid; gap: 16px; margin-block: 24px; }
.chapter-volume .grid-cards { grid-template-columns: repeat(auto-fit, minmax(min(100%, 300px), 1fr)); }
.chapter-volume .volume-heading { color: var(--ink-2); font-size: 20px; }
.chapter-card-link { display: grid; gap: 10px; color: var(--ink); text-decoration: none; }
.chapter-card-link:hover h3 { color: var(--c); }
.chapter-card-progress { border-top: 1px solid var(--line); padding-top: 12px; display: grid; gap: 8px; }
.ch-card progress { accent-color: var(--c); }

.bar { height: 8px; background: var(--surface-2); border-radius: 99px; overflow: hidden; }
.bar > span { display: block; height: 100%; background: var(--accent); border-radius: 99px; }

/* MathJax sizing */
mjx-container { max-width: 100%; }
mjx-container[display="true"] { overflow-x: auto; overflow-y: hidden; padding-block: 2px; margin: 0.4em 0 !important; }
.ot mjx-container, .qtext mjx-container { font-size: 103%; }

/* small helpers */
.muted { color: var(--muted); }
.small { font-size: 14px; }
.center { text-align: center; }
.stack { display: grid; gap: 12px; }
.row { display: flex; gap: 12px; flex-wrap: wrap; align-items: center; }
.chapter-progress { margin: 18px 0; padding: 16px; border: 1px solid var(--line); border-radius: var(--r); background: var(--surface); display: grid; gap: 8px; }
.chapter-progress p { margin: 0; }
.section-study { border-top: 1px dashed var(--line-2); padding-top: 12px; margin-top: 14px; }
.section-study .btn[aria-pressed="true"] { color: var(--green); background: var(--green-soft); border-color: var(--green); }
.study-card progress, .chapter-progress progress { width: 100%; height: 12px; accent-color: var(--accent); }
.toc a.studied::after { content: '✓'; color: var(--green); margin-left: auto; font-weight: 700; }
.study-card a { overflow-wrap: anywhere; }
[hidden] { display: none !important; }
.sr { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; border: 0; }
.footer { border-top: 1px solid var(--line); margin-top: 60px; padding-block: 24px; color: var(--muted); font-size: 14px; }

/* =====================================================================
   Print (browser print, or '#print' / '#printq' for PDF export)
   A4 portrait; interactive controls removed; solutions expanded.
   ===================================================================== */
.answer-key { padding-top: 24px; display: grid; gap: 12px; }
.ak-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(min(100%, 150px), 1fr)); gap: 4px 12px; font-size: 13px; font-variant-numeric: tabular-nums; }
.ak b { font-family: var(--f-mono); font-weight: 600; color: var(--ink-2); margin-right: 4px; }
.print-group { display: grid; gap: 14px; padding-top: 20px; }
.print-only { display: none; }

@page { size: A4; margin: 14mm 13mm 16mm; }
@media print {
  html { scroll-behavior: auto; }
  body { font-size: 11.5pt; line-height: 1.5; -webkit-print-color-adjust: exact; print-color-adjust: exact; }
}
html.print body { background: #fff; }
html.print .topbar, html.print .toc, html.print .filters, html.print .qactions,
html.print .controls, html.print .seg, html.print .btn-row, html.print .btn,
html.print .eg summary, html.print .footer a.btn, html.print .verdict,
html.print .home-hero .row, html.print .quiz > p.small { display: none !important; }
html.print .print-only { display: block; }
html.print .chapter-progress, html.print .section-study { display: none !important; }
html.print .frame { padding-inline: 0; padding-block: 0; max-width: none; }
html.print .with-toc { display: block; }
html.print .content { max-width: none !important; }
html.print .hero { padding-block: 0 4px; }
html.print .content > section { padding-top: 18px; gap: 12px; }
html.print .content > section + section { margin-top: 18px; }
html.print .content > section { break-before: auto; }
html.print .sec-head { break-after: avoid; }
html.print h2, html.print h3 { break-after: avoid; }
html.print .formula, html.print .callout, html.print .eg, html.print .qcard,
html.print figure, html.print .compare > div, html.print .pattern, html.print tr,
html.print .fx, html.print .traps > div, html.print .check-list li, html.print .checklist li { break-inside: avoid; }
html.print .sim, html.print .qcard, html.print .formula { box-shadow: none; }
html.print .sim-body.side { grid-template-columns: minmax(0, 1fr) !important; }
html.print .sim-body.side .sim-panel { border-left: 0 !important; border-top: 1px solid var(--line); }
html.print .sim-head .tag::after { content: " · shown at default settings"; text-transform: none; letter-spacing: 0; }
html.print .sim-stage canvas { max-height: 360px; object-fit: contain; }
html.print .eg details { border-top: 1px dashed var(--line-2); }
html.print .eg .eg-a { padding-top: 10px; }
html.print .opt { padding: 6px 10px; border-width: 1px; }
html.print .opts.short { grid-template-columns: repeat(2, minmax(0, 1fr)); }
html.print .qcard { padding: 12px 14px; gap: 8px; }
html.print .quiz-list { gap: 10px; }
html.print-questions .sol { display: none !important; }
html.print .answer-key { break-before: page; }
html.print .print-group { break-before: page; }
html.print .print-group:first-child { break-before: auto; }
html.print a { color: inherit; text-decoration: none; }
html.print .table-wrap { overflow: visible; }
html.print mjx-container[display="true"] { overflow: visible; }

/* Expanded Class 11 catalogue and models */
.ch-mechanics { --accent: var(--indigo); --accent-soft: #eef0fc; }
.content > section { margin-block: 28px; }
.model-content { padding: 16px; display: grid; gap: 12px; }
.model-content label { display: grid; gap: 6px; font-weight: 600; }
.model-content input { width: 100%; min-width: 0; }
.model-content svg { display: block; width: 100%; height: auto; border: 1px solid var(--line); border-radius: 10px; background: var(--surface); }
.model-readout { font-family: var(--f-mono); font-size: 15px; padding: 10px; border-radius: 8px; background: var(--accent-soft); overflow-wrap: anywhere; }
.model-content .controls { display: grid; grid-template-columns: repeat(auto-fit,minmax(min(100%,190px),1fr)); gap: 14px; }
.table-wrap { overflow-x: auto; }
.formula .f-main { overflow-x: auto; max-width: 100%; }
@media print { .concept-model { display: none; } }
.qcard > * { min-width: 0; }
.qmeta .chip { max-width: 100%; white-space: normal; overflow-wrap: anywhere; }
.qmeta .src { overflow-wrap: anywhere; }

/* Original direct chapter tabs, wrapped so every link remains visible. */
.topbar-inner { min-height: 56px; }
.nav { overflow: visible; flex-wrap: wrap; }
.ch-home .content, body[data-page="chapters"] .content { max-width: 1120px; margin-inline: auto; }
@media (max-width: 1000px) {
  :root { --topbar-h: 132px; }
  .topbar-inner { display: grid; grid-template-columns: minmax(0,1fr); gap: 8px; padding-block: 10px; }
  .nav { display: grid; grid-template-columns: repeat(5,minmax(0,1fr)); gap: 4px; width: 100%; margin: 0; padding: 0; }
  .nav a { padding: 8px 4px; font-size: 14px; text-align: center; }
}
@media (max-width: 560px) {
  .nav { grid-template-columns: repeat(3,minmax(0,1fr)); }
}
@media (max-width: 420px) {
  .nav a { font-size: 12.5px; padding-inline: 2px; }
}
@media (max-width: 360px) {
  .nav a { font-size: 11.5px; }
}

/* ---------- link to the one-page fluids summary ---------- */
.quick-banner {
  display: flex; align-items: center; gap: 14px; margin-bottom: 18px; padding: 12px 16px;
  background: var(--green-soft); border: 1px solid color-mix(in srgb, var(--green) 30%, transparent);
  border-radius: var(--r); color: var(--ink); text-decoration: none; max-width: 760px;
}
.quick-banner:hover { border-color: var(--green); }
.quick-banner .qb-tag { flex: none; font-family: var(--f-mono); font-size: 11px; font-weight: 600; letter-spacing: .08em; text-transform: uppercase; color: #fff; background: var(--green); border-radius: 6px; padding: 4px 8px; }
.quick-banner .qb-text { display: grid; gap: 2px; min-width: 0; line-height: 1.35; }
.quick-banner .qb-text strong { color: var(--green); font-size: 16.5px; }
.quick-banner .qb-text span { font-size: 14px; color: var(--ink-2); }
.quick-banner .qb-go { margin-left: auto; font-size: 22px; font-weight: 700; color: var(--green); }
@media (max-width: 480px) { .quick-banner { flex-wrap: wrap; gap: 8px; } .quick-banner .qb-go { display: none; } }

/* "This week" tab: the current weekly syllabus page */
.nav a[href="this-week.html"]:not([aria-current]) { color: var(--coral); }
.nav a[href="this-week.html"]::before { content: ""; display: inline-block; width: 6px; height: 6px; border-radius: 50%; background: var(--coral); margin-right: 6px; vertical-align: 2px; }