/* UICO Class 4 — design system (light + dark) */

:root {
  --font: "Nunito", ui-rounded, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;

  --bg: #f6f7fb;
  --bg-soft: #eef0f7;
  --surface: #ffffff;
  --surface-2: #f8f9fc;
  --border: #e3e6ef;
  --border-strong: #cfd4e2;
  --text: #1b2236;
  --text-2: #475069;
  --text-3: #7b8398;
  --shadow-1: 0 1px 2px rgba(20, 28, 51, .05), 0 1px 3px rgba(20, 28, 51, .06);
  --shadow-2: 0 6px 18px -6px rgba(20, 28, 51, .14), 0 2px 6px rgba(20, 28, 51, .05);
  --shadow-3: 0 18px 40px -12px rgba(20, 28, 51, .22);

  --brand: #4f46e5;
  --brand-strong: #4338ca;
  --brand-soft: #eef0ff;
  --on-brand: #ffffff;

  --ok: #059669;   --ok-soft: #e7f7f0;   --ok-text: #05603f;
  --bad: #dc2626;  --bad-soft: #fdeceb;  --bad-text: #9b1c1c;
  --warn: #d97706; --warn-soft: #fff5e1; --warn-text: #8a4b06;
  --info: #0284c7; --info-soft: #e6f4fc; --info-text: #075985;

  --computers: #0284c7; --computers-soft: #e6f4fc;
  --maths: #059669;     --maths-soft: #e7f7f0;
  --reasoning: #7c3aed; --reasoning-soft: #f2edff;
  --english: #d97706;   --english-soft: #fff5e1;

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

  --radius-s: 8px;
  --radius-m: 14px;
  --radius-l: 20px;
  --sidebar-w: 272px;
  --topbar-h: 60px;
  --ease: cubic-bezier(.2, .8, .2, 1);
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0e1220; --bg-soft: #141a2b; --surface: #161c2e; --surface-2: #1b2236;
    --border: #262f47; --border-strong: #34405e;
    --text: #e8ebf5; --text-2: #b3bad0; --text-3: #8189a3;
    --shadow-1: 0 1px 2px rgba(0,0,0,.4); --shadow-2: 0 8px 20px -8px rgba(0,0,0,.6); --shadow-3: 0 20px 44px -12px rgba(0,0,0,.7);
    --brand: #8b85ff; --brand-strong: #a5a0ff; --brand-soft: #23244a; --on-brand: #0e1220;
    --ok: #34d399; --ok-soft: #0f2e25; --ok-text: #86efc4;
    --bad: #f87171; --bad-soft: #3a1618; --bad-text: #fecaca;
    --warn: #fbbf24; --warn-soft: #33260c; --warn-text: #fde68a;
    --info: #38bdf8; --info-soft: #0c2a3c; --info-text: #bae6fd;
    --computers: #38bdf8; --computers-soft: #0c2a3c;
    --maths: #34d399; --maths-soft: #0f2e25;
    --reasoning: #a78bfa; --reasoning-soft: #251c45;
    --english: #fbbf24; --english-soft: #33260c;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #0e1220; --bg-soft: #141a2b; --surface: #161c2e; --surface-2: #1b2236;
  --border: #262f47; --border-strong: #34405e;
  --text: #e8ebf5; --text-2: #b3bad0; --text-3: #8189a3;
  --shadow-1: 0 1px 2px rgba(0,0,0,.4); --shadow-2: 0 8px 20px -8px rgba(0,0,0,.6); --shadow-3: 0 20px 44px -12px rgba(0,0,0,.7);
  --brand: #8b85ff; --brand-strong: #a5a0ff; --brand-soft: #23244a; --on-brand: #0e1220;
  --ok: #34d399; --ok-soft: #0f2e25; --ok-text: #86efc4;
  --bad: #f87171; --bad-soft: #3a1618; --bad-text: #fecaca;
  --warn: #fbbf24; --warn-soft: #33260c; --warn-text: #fde68a;
  --info: #38bdf8; --info-soft: #0c2a3c; --info-text: #bae6fd;
  --computers: #38bdf8; --computers-soft: #0c2a3c;
  --maths: #34d399; --maths-soft: #0f2e25;
  --reasoning: #a78bfa; --reasoning-soft: #251c45;
  --english: #fbbf24; --english-soft: #33260c;
  color-scheme: dark;
}

[data-module="computers"] { --accent: var(--computers); --accent-soft: var(--computers-soft); }
[data-module="maths"]     { --accent: var(--maths);     --accent-soft: var(--maths-soft); }
[data-module="reasoning"] { --accent: var(--reasoning); --accent-soft: var(--reasoning-soft); }
[data-module="english"]   { --accent: var(--english);   --accent-soft: var(--english-soft); }

*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; scroll-padding-top: calc(var(--topbar-h) + 16px); }
body {
  margin: 0; font-family: var(--font); font-size: 17px; line-height: 1.65;
  color: var(--text); background: var(--bg);
  -webkit-font-smoothing: antialiased; transition: background-color .3s var(--ease), color .3s var(--ease);
}
img, svg { max-width: 100%; }
a { color: var(--brand); text-underline-offset: 3px; }
button { font: inherit; color: inherit; }
:focus-visible { outline: 3px solid color-mix(in srgb, var(--brand) 55%, transparent); outline-offset: 2px; border-radius: 6px; }
h1, h2, h3, h4 { line-height: 1.25; letter-spacing: -.01em; margin: 0 0 .5em; }
h1 { font-size: clamp(1.7rem, 3.2vw, 2.3rem); font-weight: 900; }
h2 { font-size: 1.5rem; font-weight: 850; }
h3 { font-size: 1.18rem; font-weight: 800; }
h4 { font-size: 1.02rem; font-weight: 800; }
p { margin: 0 0 1em; }
code, kbd { font-family: var(--font-mono); font-size: .88em; }
kbd {
  display: inline-block; padding: 1px 7px; border-radius: 6px; border: 1px solid var(--border-strong);
  border-bottom-width: 2px; background: var(--surface-2); color: var(--text); white-space: nowrap;
}
.visually-hidden { position: absolute !important; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }

/* ---------- App shell ---------- */
.app { display: flex; min-height: 100vh; }
.sidebar {
  position: fixed; inset: 0 auto 0 0; width: var(--sidebar-w); z-index: 60;
  display: flex; flex-direction: column; background: var(--surface); border-right: 1px solid var(--border);
  transition: transform .3s var(--ease), background-color .3s var(--ease);
}
.brand { display: flex; align-items: center; gap: 12px; padding: 18px 20px; text-decoration: none; color: var(--text); border-bottom: 1px solid var(--border); }
.brand-mark {
  width: 40px; height: 40px; border-radius: 12px; display: grid; place-items: center; flex: none;
  background: linear-gradient(135deg, var(--brand), #06b6d4); color: #fff; font-weight: 900; font-size: 1.05rem;
  box-shadow: 0 6px 14px -4px color-mix(in srgb, var(--brand) 60%, transparent);
}
.brand-name { font-weight: 900; font-size: 1rem; line-height: 1.15; }
.brand-sub { font-size: .74rem; color: var(--text-3); font-weight: 700; letter-spacing: .06em; text-transform: uppercase; }
.nav { flex: 1; overflow-y: auto; padding: 12px 10px 20px; overscroll-behavior: contain; }
.nav-label { font-size: .7rem; font-weight: 800; letter-spacing: .09em; text-transform: uppercase; color: var(--text-3); padding: 14px 12px 6px; }
.nav a, .nav summary {
  display: flex; align-items: center; gap: 10px; padding: 8px 12px; border-radius: 10px; font-size: .93rem;
  font-weight: 700; color: var(--text-2); text-decoration: none; cursor: pointer; list-style: none;
  transition: background-color .15s, color .15s;
}
.nav summary::-webkit-details-marker { display: none; }
.nav a:hover, .nav summary:hover { background: var(--bg-soft); color: var(--text); }
.nav a[aria-current="page"] { background: var(--accent-soft); color: var(--accent); }
.nav .dot { width: 10px; height: 10px; border-radius: 50%; flex: none; background: var(--dot, var(--brand)); }
.nav details > summary::after { content: "›"; margin-left: auto; transition: transform .2s; font-size: 1.1rem; color: var(--text-3); }
.nav details[open] > summary::after { transform: rotate(90deg); }
.nav .sub { padding-left: 22px; margin: 2px 0 6px; border-left: 2px solid var(--border); margin-left: 16px; }
.nav .sub a { font-size: .86rem; font-weight: 650; padding: 6px 10px; }
.nav .sub a .done { margin-left: auto; color: var(--ok); font-weight: 900; }
.nav .num { font-variant-numeric: tabular-nums; color: var(--text-3); font-weight: 800; min-width: 1.2em; }
.sidebar-foot { padding: 14px 16px; border-top: 1px solid var(--border); display: flex; align-items: center; gap: 10px; }
.avatar { width: 36px; height: 36px; border-radius: 50%; display: grid; place-items: center; font-weight: 900; background: var(--warn-soft); color: var(--warn-text); flex: none; }
.who b { display: block; font-size: .9rem; } .who span { font-size: .76rem; color: var(--text-3); }

.main { flex: 1; min-width: 0; margin-left: var(--sidebar-w); display: flex; flex-direction: column; }
.topbar {
  position: sticky; top: 0; z-index: 50; height: var(--topbar-h); display: flex; align-items: center; gap: 12px;
  padding: 0 22px; background: color-mix(in srgb, var(--surface) 86%, transparent);
  backdrop-filter: saturate(1.4) blur(12px); -webkit-backdrop-filter: saturate(1.4) blur(12px); border-bottom: 1px solid var(--border);
}
.crumbs { display: flex; gap: 8px; align-items: center; font-size: .88rem; color: var(--text-3); font-weight: 700; min-width: 0; overflow: hidden; white-space: nowrap; text-overflow: ellipsis; }
.crumbs a { color: var(--text-2); text-decoration: none; } .crumbs a:hover { color: var(--brand); }
.topbar-actions { margin-left: auto; display: flex; gap: 8px; align-items: center; }
.icon-btn {
  width: 40px; height: 40px; border-radius: 12px; display: grid; place-items: center; cursor: pointer;
  background: var(--surface); border: 1px solid var(--border); color: var(--text-2); transition: all .15s;
}
.icon-btn:hover { color: var(--text); border-color: var(--border-strong); background: var(--surface-2); }
.icon-btn svg { width: 20px; height: 20px; }
.icon-btn[aria-pressed="true"] { background: var(--brand); border-color: var(--brand); color: var(--on-brand); }
.menu-btn { display: none; }
.reading-progress { position: absolute; left: 0; bottom: -1px; height: 3px; width: 0; background: var(--accent); transition: width .1s linear; }

.content { width: 100%; max-width: 980px; margin: 0 auto; padding: 32px 28px 96px; position: relative; }
.content.wide { max-width: 1180px; }

@media (max-width: 1000px) {
  .sidebar { transform: translateX(-102%); box-shadow: none; }
  .sidebar.open { transform: none; box-shadow: var(--shadow-3); }
  .main { margin-left: 0; }
  .menu-btn { display: grid; }
  .content { padding: 22px 16px 80px; }
}
.scrim { position: fixed; inset: 0; background: rgba(8, 10, 20, .4); z-index: 55; opacity: 0; pointer-events: none; transition: opacity .25s; }
.scrim.show { opacity: 1; pointer-events: auto; }

/* ---------- Buttons, chips ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px; min-height: 44px; padding: 0 18px;
  border-radius: 12px; border: 1px solid transparent; font-weight: 800; font-size: .95rem; text-decoration: none;
  cursor: pointer; transition: transform .12s var(--ease), background-color .15s, box-shadow .15s, border-color .15s;
  background: var(--surface); color: var(--text); border-color: var(--border-strong); white-space: nowrap;
}
.btn:hover { border-color: var(--text-3); }
.btn:active { transform: scale(.97); }
.btn-primary { background: var(--accent); border-color: var(--accent); color: #fff; box-shadow: 0 6px 14px -6px color-mix(in srgb, var(--accent) 70%, transparent); }
:root[data-theme="dark"] .btn-primary { color: #0e1220; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) .btn-primary { color: #0e1220; } }
.btn-primary:hover { filter: brightness(1.06); border-color: var(--accent); }
.btn-ghost { background: transparent; border-color: transparent; color: var(--text-2); }
.btn-ghost:hover { background: var(--bg-soft); border-color: transparent; }
.btn-sm { min-height: 36px; padding: 0 12px; font-size: .86rem; border-radius: 10px; }
.btn[disabled] { opacity: .45; pointer-events: none; }
.chip {
  display: inline-flex; align-items: center; gap: 6px; padding: 3px 10px; border-radius: 999px; font-size: .78rem;
  font-weight: 800; background: var(--bg-soft); color: var(--text-2); white-space: nowrap;
}
.chip.accent { background: var(--accent-soft); color: var(--accent); }
.chip.ok { background: var(--ok-soft); color: var(--ok-text); }
.chip.bad { background: var(--bad-soft); color: var(--bad-text); }
.chip.warn { background: var(--warn-soft); color: var(--warn-text); }

/* ---------- Hero ---------- */
.hero {
  position: relative; overflow: hidden; border-radius: var(--radius-l); padding: 34px 32px; margin-bottom: 28px;
  background: var(--surface); border: 1px solid var(--border); box-shadow: var(--shadow-1);
}
.hero::before {
  content: ""; position: absolute; inset: 0; pointer-events: none;
  background:
    radial-gradient(600px 240px at 100% 0%, color-mix(in srgb, var(--accent) 16%, transparent), transparent 70%),
    radial-gradient(400px 200px at 0% 100%, color-mix(in srgb, var(--accent) 8%, transparent), transparent 70%);
}
.hero > * { position: relative; }
.eyebrow { display: inline-flex; gap: 8px; align-items: center; font-size: .78rem; font-weight: 900; letter-spacing: .08em; text-transform: uppercase; color: var(--accent); margin-bottom: 10px; }
.hero p.lead { font-size: 1.08rem; color: var(--text-2); max-width: 720px; }
.hero-meta { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 14px; }
.hero-art { position: absolute; right: 28px; top: 50%; transform: translateY(-50%); width: 140px; height: 140px; opacity: .95; color: var(--accent); }
@media (min-width: 761px) { .hero:has(.hero-art) { padding-right: 200px; } }
@media (max-width: 760px) { .hero-art { display: none; } .hero { padding: 24px 20px; } }

/* ---------- Cards & grids ---------- */
.grid { display: grid; gap: 18px; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); }
.grid-2 { display: grid; gap: 18px; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); }
.card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-m); padding: 20px;
  box-shadow: var(--shadow-1); transition: transform .2s var(--ease), box-shadow .2s var(--ease), border-color .2s;
  position: relative;
}
a.card { color: inherit; text-decoration: none; display: block; }
a.card:hover, .card.hover:hover { transform: translateY(-3px); box-shadow: var(--shadow-2); border-color: color-mix(in srgb, var(--accent) 40%, var(--border)); }
.card h3 { margin-bottom: 6px; }
.card p { color: var(--text-2); font-size: .95rem; margin-bottom: 0; }
.card .card-top { display: flex; justify-content: space-between; align-items: center; margin-bottom: 12px; gap: 8px; }
.card-icon { width: 46px; height: 46px; border-radius: 14px; display: grid; place-items: center; background: var(--accent-soft); color: var(--accent); }
.card-icon svg { width: 26px; height: 26px; }
.card .bar { height: 6px; border-radius: 99px; background: var(--bg-soft); overflow: hidden; margin-top: 14px; }
.card .bar > i { display: block; height: 100%; width: 0; background: var(--accent); border-radius: inherit; transition: width .8s var(--ease); }

.section-head { display: flex; align-items: baseline; justify-content: space-between; gap: 12px; margin: 36px 0 16px; }
.section-head h2 { margin: 0; }
.section-head p { margin: 0; color: var(--text-3); font-weight: 700; font-size: .9rem; }

/* ---------- Lesson prose ---------- */
.lesson { counter-reset: sec; }
.lesson > section { margin: 0 0 40px; }
.lesson h2 { display: flex; align-items: center; gap: 12px; padding-top: 8px; margin-top: 8px; }
.lesson h2 .n {
  flex: none; width: 36px; height: 36px; border-radius: 11px; display: grid; place-items: center; font-size: 1rem;
  background: var(--accent-soft); color: var(--accent); font-weight: 900;
}
.lesson h3 { margin-top: 1.4em; }
.lesson ul, .lesson ol { padding-left: 1.3em; margin: 0 0 1em; }
.lesson li { margin: .3em 0; }
.lesson li::marker { color: var(--accent); font-weight: 800; }
.lesson strong { color: var(--text); font-weight: 850; }
.lesson .lead { font-size: 1.1rem; color: var(--text-2); }
.hl { background: linear-gradient(transparent 55%, color-mix(in srgb, var(--warn) 35%, transparent) 55%); padding: 0 2px; }

.callout {
  border-radius: var(--radius-m); padding: 16px 18px 16px 18px; margin: 18px 0; border: 1px solid;
  background: var(--c-soft); border-color: color-mix(in srgb, var(--c) 30%, transparent); color: var(--text);
  --c: var(--info); --c-soft: var(--info-soft);
}
.callout > :last-child { margin-bottom: 0; }
.callout-title { display: flex; gap: 8px; align-items: center; font-weight: 900; color: var(--c); margin-bottom: 6px; font-size: .95rem; letter-spacing: .01em; }
.callout.tip { --c: var(--ok); --c-soft: var(--ok-soft); }
.callout.trap { --c: var(--bad); --c-soft: var(--bad-soft); }
.callout.fact { --c: var(--warn); --c-soft: var(--warn-soft); }
.callout.example { --c: var(--brand); --c-soft: var(--brand-soft); }
.callout.remember { --c: var(--reasoning); --c-soft: var(--reasoning-soft); }

.key-points { list-style: none; padding: 0 !important; display: grid; gap: 8px; }
.key-points li { padding: 10px 14px 10px 42px; border-radius: 12px; background: var(--surface); border: 1px solid var(--border); position: relative; margin: 0; }
.key-points li::before { content: "✓"; position: absolute; left: 14px; top: 10px; color: var(--ok); font-weight: 900; }

.steps { list-style: none; counter-reset: step; padding: 0 !important; }
.steps li { counter-increment: step; position: relative; padding: 4px 0 12px 46px; margin: 0; }
.steps li::before {
  content: counter(step); position: absolute; left: 0; top: 2px; width: 30px; height: 30px; border-radius: 50%;
  display: grid; place-items: center; font-weight: 900; font-size: .88rem; background: var(--accent); color: #fff;
}
.steps li:not(:last-child)::after { content: ""; position: absolute; left: 14px; top: 36px; bottom: 2px; width: 2px; background: var(--border); }

dl.glossary { display: grid; grid-template-columns: max-content 1fr; gap: 8px 18px; margin: 0 0 1em; }
dl.glossary dt { font-weight: 900; color: var(--accent); }
dl.glossary dd { margin: 0; color: var(--text-2); }
@media (max-width: 600px) { dl.glossary { grid-template-columns: 1fr; } dl.glossary dd { margin-bottom: 8px; } }

.memory-tip {
  display: flex; gap: 14px; align-items: flex-start; padding: 16px 18px; border-radius: var(--radius-m); margin: 18px 0;
  background: repeating-linear-gradient(-45deg, var(--reasoning-soft), var(--reasoning-soft) 10px, color-mix(in srgb, var(--reasoning-soft) 70%, var(--surface)) 10px, color-mix(in srgb, var(--reasoning-soft) 70%, var(--surface)) 20px);
  border: 1px dashed color-mix(in srgb, var(--reasoning) 45%, transparent);
}
.memory-tip::before { content: "🧠"; font-size: 1.5rem; line-height: 1; }

/* Tables */
.table-wrap { overflow-x: auto; margin: 16px 0 20px; border-radius: var(--radius-m); border: 1px solid var(--border); background: var(--surface); }
table.table { width: 100%; border-collapse: collapse; font-size: .94rem; }
table.table th { text-align: left; background: var(--surface-2); color: var(--text-2); font-weight: 900; font-size: .8rem; letter-spacing: .04em; text-transform: uppercase; padding: 12px 14px; border-bottom: 1px solid var(--border); }
table.table td { padding: 11px 14px; border-bottom: 1px solid var(--border); vertical-align: top; }
table.table tr:last-child td { border-bottom: 0; }
table.table tbody tr:hover td { background: color-mix(in srgb, var(--accent-soft) 45%, transparent); }

/* Figures & media */
figure.figure { margin: 22px 0; padding: 18px; border-radius: var(--radius-m); background: var(--surface); border: 1px solid var(--border); text-align: center; }
figure.figure svg, figure.figure img { display: block; margin: 0 auto; max-height: 420px; height: auto; }
figure.figure img { border-radius: 10px; }
figure.figure.photo { padding: 10px; }
figure.figure figcaption { margin-top: 12px; font-size: .88rem; color: var(--text-2); }
figure.figure .credit { display: block; margin-top: 2px; font-size: .74rem; color: var(--text-3); }
figure.figure .credit a { color: inherit; }
.figure-row { display: grid; gap: 16px; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); margin: 22px 0; }
.figure-row figure.figure { margin: 0; }
:root[data-theme="dark"] figure.figure img.diagram-light { filter: invert(.9) hue-rotate(180deg); }

.media-links { display: grid; gap: 10px; grid-template-columns: repeat(auto-fill, minmax(250px, 1fr)); margin: 16px 0 8px; padding: 0 !important; list-style: none; }
.media-links li { margin: 0; }
.media-link {
  display: flex; gap: 12px; align-items: center; padding: 12px 14px; border-radius: 12px; text-decoration: none;
  background: var(--surface); border: 1px solid var(--border); color: var(--text); transition: all .15s;
}
.media-link:hover { border-color: var(--accent); transform: translateY(-2px); box-shadow: var(--shadow-2); }
.media-link .mi { flex: none; width: 38px; height: 38px; border-radius: 10px; display: grid; place-items: center; font-size: 1.1rem; background: var(--bg-soft); }
.media-link[data-kind="video"] .mi { background: var(--bad-soft); color: var(--bad); }
.media-link[data-kind="photo"] .mi { background: var(--info-soft); color: var(--info); }
.media-link[data-kind="interactive"] .mi { background: var(--ok-soft); color: var(--ok); }
.media-link[data-kind="article"] .mi { background: var(--warn-soft); color: var(--warn); }
.media-link b { display: block; font-size: .92rem; line-height: 1.3; }
.media-link small { color: var(--text-3); font-weight: 700; font-size: .76rem; }

.video { margin: 22px 0; border-radius: var(--radius-m); overflow: hidden; background: var(--surface); border: 1px solid var(--border); box-shadow: var(--shadow-1); }
.video-poster, .video iframe { display: block; width: 100%; aspect-ratio: 16 / 9; border: 0; padding: 0; position: relative; background: #000; cursor: pointer; }
.video-poster img { width: 100%; height: 100%; object-fit: cover; display: block; opacity: .9; transition: opacity .2s; }
.video-poster:hover img { opacity: 1; }
.video-poster .play { position: absolute; left: 50%; top: 50%; transform: translate(-50%, -50%); width: 72px; height: 72px; border-radius: 50%; display: grid; place-items: center; background: rgba(220, 38, 38, .92); color: #fff; box-shadow: 0 8px 24px rgba(0,0,0,.35); transition: transform .2s var(--ease); }
.video-poster:hover .play { transform: translate(-50%, -50%) scale(1.08); }
.video-poster .play svg { width: 34px; height: 34px; margin-left: 4px; }
.video-cap { padding: 12px 16px; }
.video-cap b { display: block; font-size: .95rem; }
.video-cap small { color: var(--text-3); font-weight: 700; }
.video-row { display: grid; gap: 16px; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); margin: 22px 0; }
.video-row .video { margin: 0; }

.toc { margin: 0 0 32px; padding: 18px 22px; border-radius: var(--radius-m); background: var(--surface); border: 1px solid var(--border); }
.toc b { display: block; font-size: .74rem; letter-spacing: .08em; text-transform: uppercase; color: var(--text-3); margin-bottom: 8px; }
.toc ol { margin: 0; padding-left: 1.3em; columns: 2 240px; column-gap: 28px; }
.toc li { margin: 3px 0; break-inside: avoid; }
.toc li::marker { color: var(--accent); font-weight: 900; }
.toc a { color: var(--text-2); text-decoration: none; font-weight: 700; }
.toc a:hover { color: var(--accent); }

/* Quick check (inline practice) */
.quick-check { margin: 22px 0; padding: 18px; border-radius: var(--radius-m); background: var(--surface); border: 1px solid var(--border); box-shadow: var(--shadow-1); }
.quick-check .qc-label { font-size: .74rem; letter-spacing: .08em; font-weight: 900; text-transform: uppercase; color: var(--accent); margin-bottom: 6px; }
.quick-check .qc-q { font-weight: 800; margin-bottom: 12px; }
.quick-check .qc-options { list-style: none; padding: 0 !important; margin: 0; display: grid; gap: 8px; grid-template-columns: 1fr 1fr; }
@media (max-width: 520px) { .quick-check .qc-options { grid-template-columns: 1fr; } }
.quick-check .qc-options li { margin: 0; }
.opt {
  width: 100%; text-align: left; display: flex; gap: 12px; align-items: center; min-height: 48px; padding: 10px 14px;
  border-radius: 12px; border: 1.5px solid var(--border); background: var(--surface); cursor: pointer; font-weight: 700;
  transition: border-color .15s, background-color .15s, transform .1s;
}
.opt:hover:not([disabled]) { border-color: var(--accent); background: var(--accent-soft); }
.opt:active:not([disabled]) { transform: scale(.99); }
.opt .letter {
  flex: none; width: 30px; height: 30px; border-radius: 9px; display: grid; place-items: center; font-weight: 900; font-size: .88rem;
  background: var(--bg-soft); color: var(--text-2);
}
.opt .opt-body { flex: 1; min-width: 0; }
.opt .opt-body svg { max-height: 110px; width: auto; display: block; }
.opt.selected { border-color: var(--brand); background: var(--brand-soft); }
.opt.selected .letter { background: var(--brand); color: var(--on-brand); }
.opt.correct { border-color: var(--ok); background: var(--ok-soft); }
.opt.correct .letter { background: var(--ok); color: #fff; }
.opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.opt.wrong .letter { background: var(--bad); color: #fff; }
.opt[disabled] { cursor: default; }
.feedback { margin-top: 12px; padding: 12px 14px; border-radius: 12px; font-size: .95rem; animation: pop .3s var(--ease); }
.feedback.ok { background: var(--ok-soft); color: var(--ok-text); }
.feedback.bad { background: var(--bad-soft); color: var(--bad-text); }
.feedback b { display: block; margin-bottom: 2px; }

/* Lesson footer */
.lesson-end { margin-top: 48px; padding: 24px; border-radius: var(--radius-l); background: var(--surface); border: 1px solid var(--border); display: grid; gap: 16px; }
.lesson-end .row { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; justify-content: space-between; }
.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 18px; }
.pager a { padding: 14px 16px; border-radius: 14px; border: 1px solid var(--border); background: var(--surface); text-decoration: none; color: var(--text); font-weight: 800; }
.pager a small { display: block; color: var(--text-3); font-size: .75rem; letter-spacing: .06em; text-transform: uppercase; }
.pager a.next { text-align: right; grid-column: 2; }
.pager a:hover { border-color: var(--accent); }
.done-toggle[aria-pressed="true"] { background: var(--ok); border-color: var(--ok); color: #fff; }

/* LOGO lab (legacy interactive, restyled) */
.logo-lab { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-l); padding: 18px; margin: 22px 0; }
.logo-lab canvas { width: 100%; max-width: 520px; background: #fff; border-radius: 12px; border: 1px solid var(--border); display: block; margin: 0 auto 12px; }
.logo-lab .row { display: flex; gap: 8px; flex-wrap: wrap; }
.logo-lab input { flex: 1; min-width: 180px; min-height: 44px; border-radius: 12px; border: 1px solid var(--border-strong); background: var(--surface-2); color: var(--text); padding: 0 12px; font-family: var(--font-mono); }

/* Flashcards */
.flip { perspective: 900px; min-height: 150px; cursor: pointer; }
.flip-inner { position: relative; width: 100%; height: 100%; min-height: 150px; transition: transform .5s var(--ease); transform-style: preserve-3d; }
.flip.on .flip-inner { transform: rotateY(180deg); }
.flip-face { position: absolute; inset: 0; backface-visibility: hidden; -webkit-backface-visibility: hidden; border-radius: var(--radius-m); padding: 18px; display: flex; flex-direction: column; justify-content: center; border: 1px solid var(--border); background: var(--surface); box-shadow: var(--shadow-1); }
.flip-face.back { transform: rotateY(180deg); background: var(--accent-soft); }
.flip-face small { color: var(--text-3); font-weight: 800; font-size: .72rem; letter-spacing: .08em; text-transform: uppercase; }

/* Toast */
.toast { position: fixed; left: 50%; bottom: 24px; transform: translate(-50%, 30px); opacity: 0; z-index: 200; background: var(--text); color: var(--bg); padding: 10px 18px; border-radius: 12px; font-weight: 800; font-size: .92rem; transition: all .3s var(--ease); pointer-events: none; }
.toast.show { opacity: 1; transform: translate(-50%, 0); }

/* Motion */
@keyframes pop { from { transform: scale(.97); opacity: 0; } to { transform: none; opacity: 1; } }
@keyframes rise { from { transform: translateY(14px); opacity: 0; } to { transform: none; opacity: 1; } }
.reveal { opacity: 0; transform: translateY(14px); transition: opacity .6s var(--ease), transform .6s var(--ease); }
.reveal.in { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: .01ms !important; transition-duration: .01ms !important; scroll-behavior: auto !important; }
  .reveal { opacity: 1; transform: none; }
}

/* Print */
@media print {
  .sidebar, .topbar, .lesson-end, .ink-toolbar, .ink-layer, .scrim { display: none !important; }
  .main { margin: 0; } body { background: #fff; color: #000; font-size: 12pt; }
  .card, .callout, figure.figure { break-inside: avoid; box-shadow: none; }
}

/* Chapter overview lesson list */
.lesson-list { display: grid; gap: 12px; }
.lesson-row { display: flex; align-items: center; gap: 16px; padding: 16px 18px; }
.lesson-num { flex: none; width: 44px; height: 44px; border-radius: 14px; display: grid; place-items: center; font-weight: 900; font-size: 1.1rem; background: var(--accent-soft); color: var(--accent); }
.lesson-num.done { background: var(--ok); color: #fff; }
.lesson-info { flex: 1; min-width: 0; }
.lesson-info h3 { margin: 0 0 2px; font-size: 1.08rem; }
.lesson-info h3 a { color: var(--text); text-decoration: none; }
.lesson-info h3 a:hover { color: var(--accent); }
.lesson-info small { color: var(--text-3); font-weight: 700; }
.lesson-actions { display: flex; gap: 8px; }
@media (max-width: 560px) { .lesson-row { flex-wrap: wrap; } .lesson-actions { width: 100%; } .lesson-actions .btn { flex: 1; } }
.home-steps li b { color: var(--text); }

html.auth-pending body { visibility: hidden; }
.sidebar-foot .logout { margin-left: auto; }