/* Layout concept: a flight-deck learning console. Fixed left rail = route of 8 checkpoints;
   main deck = the current view. One bold element per view (the route line / signal orange). */
:root {
  --bg: oklch(97.6% 0.007 250);
  --surface: oklch(99.4% 0.003 250);
  --sunk: oklch(94.6% 0.011 250);
  --ink: oklch(24% 0.045 262);
  --ink-2: oklch(42% 0.03 260);
  --muted: oklch(55% 0.022 258);
  --line: oklch(89.5% 0.014 255);
  --line-strong: oklch(82% 0.02 255);
  --signal: oklch(64% 0.175 48);
  --signal-ink: oklch(50% 0.16 45);
  --signal-soft: oklch(94% 0.045 60);
  --route: oklch(58% 0.14 158);
  --route-soft: oklch(94% 0.05 158);
  --warn: oklch(70% 0.15 85);
  --crit: oklch(56% 0.19 25);
  --code-bg: oklch(22% 0.035 262);
  --code-ink: oklch(92% 0.01 250);
  --code-kw: oklch(78% 0.13 300);
  --code-str: oklch(80% 0.13 150);
  --code-com: oklch(62% 0.03 255);
  --code-num: oklch(80% 0.13 60);
  --code-fn: oklch(80% 0.11 230);
  --shadow: 0 1px 2px oklch(24% 0.05 262 / 0.06), 0 8px 28px oklch(24% 0.05 262 / 0.07);
  --display: "Bricolage Grotesque", "Segoe UI", system-ui, sans-serif;
  --body: "IBM Plex Sans", "Segoe UI", system-ui, -apple-system, sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
  --r: 10px;
  --rail: 264px;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: oklch(18.5% 0.028 262); --surface: oklch(22.5% 0.03 262); --sunk: oklch(16% 0.025 262);
    --ink: oklch(94% 0.01 250); --ink-2: oklch(82% 0.015 250); --muted: oklch(68% 0.02 255);
    --line: oklch(30% 0.03 262); --line-strong: oklch(38% 0.035 262);
    --signal: oklch(72% 0.16 52); --signal-ink: oklch(80% 0.13 58); --signal-soft: oklch(30% 0.06 50);
    --route: oklch(72% 0.14 158); --route-soft: oklch(29% 0.05 158);
    --warn: oklch(80% 0.14 85); --crit: oklch(70% 0.17 25);
    --code-bg: oklch(14.5% 0.025 262);
    --shadow: 0 1px 2px oklch(0% 0 0 / 0.3), 0 10px 30px oklch(0% 0 0 / 0.28);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: oklch(18.5% 0.028 262); --surface: oklch(22.5% 0.03 262); --sunk: oklch(16% 0.025 262);
  --ink: oklch(94% 0.01 250); --ink-2: oklch(82% 0.015 250); --muted: oklch(68% 0.02 255);
  --line: oklch(30% 0.03 262); --line-strong: oklch(38% 0.035 262);
  --signal: oklch(72% 0.16 52); --signal-ink: oklch(80% 0.13 58); --signal-soft: oklch(30% 0.06 50);
  --route: oklch(72% 0.14 158); --route-soft: oklch(29% 0.05 158);
  --warn: oklch(80% 0.14 85); --crit: oklch(70% 0.17 25);
  --code-bg: oklch(14.5% 0.025 262);
  --shadow: 0 1px 2px oklch(0% 0 0 / 0.3), 0 10px 30px oklch(0% 0 0 / 0.28);
  color-scheme: dark;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0; background: var(--bg); color: var(--ink);
  font: 400 15px/1.6 var(--body);
}
body::before { content: ""; position: fixed; inset: 0 0 auto; height: env(safe-area-inset-top, 0px); z-index: 50; background: var(--bg); }
h1, h2, h3, h4 { font-family: var(--display); line-height: 1.15; margin: 0; text-wrap: balance; letter-spacing: -0.01em; }
p { margin: 0; }
a { color: var(--signal-ink); }
button { font: inherit; color: inherit; }
:focus-visible { outline: 2.5px solid var(--signal); outline-offset: 2px; border-radius: 6px; }
.mono { font-family: var(--mono); }
.tnum { font-variant-numeric: tabular-nums; }
.eyebrow { font: 600 11px/1.2 var(--mono); letter-spacing: 0.09em; text-transform: uppercase; color: var(--muted); }
.sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }

/* ---------- shell ---------- */
.shell { display: grid; grid-template-columns: var(--rail) minmax(0, 1fr); min-height: 100vh; }
.rail {
  position: sticky; top: env(safe-area-inset-top, 0px); height: 100vh; overflow-y: auto;
  border-right: 1px solid var(--line); background: var(--surface);
  padding: 20px 14px 24px max(14px, env(safe-area-inset-left, 0px));
  display: flex; flex-direction: column; gap: 18px;
}
.brand { display: flex; align-items: center; gap: 10px; padding: 2px 6px; text-decoration: none; color: var(--ink); }
.brand-mark { width: 30px; height: 30px; flex: none; }
.brand b { font: 700 17px/1 var(--display); display: block; letter-spacing: -0.02em; }
.brand small { font: 500 11px/1.3 var(--mono); color: var(--muted); }
.nav { display: grid; gap: 2px; }
.nav a, .route-link {
  display: flex; align-items: center; gap: 10px; padding: 7px 10px; border-radius: 8px;
  color: var(--ink-2); text-decoration: none; font-weight: 500; font-size: 14px;
}
.nav a:hover, .route-link:hover { background: var(--sunk); color: var(--ink); }
.nav a[aria-current="page"], .route-link[aria-current="page"] { background: var(--signal-soft); color: var(--ink); }
.nav svg { width: 17px; height: 17px; flex: none; stroke: currentColor; fill: none; stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; }
.route { position: relative; display: grid; gap: 2px; }
.route::before { content: ""; position: absolute; left: 22px; top: 18px; bottom: 18px; width: 3px; border-radius: 3px; background: var(--line-strong); }
.route-fill { position: absolute; left: 22px; top: 18px; width: 3px; border-radius: 3px; background: var(--route); transition: height .6s ease; }
.route-link { position: relative; padding-left: 6px; }
.stop {
  position: relative; z-index: 1; width: 34px; height: 24px; flex: none; display: grid; place-items: center;
  border-radius: 999px; border: 2px solid var(--signal); background: var(--surface);
  font: 700 10.5px/1 var(--mono); color: var(--signal-ink);
}
.stop.done { background: var(--route); border-color: var(--route); color: var(--surface); }
.stop.part { border-color: var(--route); color: var(--route); }
.route-link span.t { flex: 1; min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.route-link em { font: 500 11px var(--mono); font-style: normal; color: var(--muted); }
.route-end { font: 600 11px var(--mono); color: var(--route); padding: 2px 10px 0 52px; }
.rail-foot { margin-top: auto; display: grid; gap: 8px; }
.ghost-btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px; padding: 8px 12px; border-radius: 8px;
  border: 1px solid var(--line-strong); background: transparent; cursor: pointer; font-size: 13.5px; font-weight: 500; color: var(--ink-2);
  text-decoration: none;
}
.ghost-btn:hover { background: var(--sunk); color: var(--ink); }
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px; padding: 9px 16px; border-radius: 8px;
  border: 1px solid transparent; background: var(--ink); color: var(--bg); cursor: pointer; font-weight: 600; font-size: 14px; text-decoration: none;
}
.btn:hover { filter: brightness(1.12); }
.btn.signal { background: var(--signal); color: oklch(18% 0.04 50); }
.btn.route-btn { background: var(--route); color: var(--surface); }
.btn:disabled { opacity: .5; cursor: not-allowed; }

.main { min-width: 0; display: flex; flex-direction: column; }
.topbar {
  position: sticky; top: env(safe-area-inset-top, 0px); z-index: 20; background: color-mix(in oklch, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px); border-bottom: 1px solid var(--line);
  padding: 10px max(24px, env(safe-area-inset-right, 0px)) 10px 28px;
  display: flex; align-items: center; gap: 16px; flex-wrap: wrap;
}
.crumb { font: 500 13px var(--mono); color: var(--muted); flex: 1; min-width: 0; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.crumb b { color: var(--ink); font-weight: 600; }
.stat-chip { display: inline-flex; align-items: center; gap: 8px; font: 600 12.5px var(--mono); color: var(--ink-2); }
.xpbar { width: 120px; height: 7px; border-radius: 99px; background: var(--sunk); overflow: hidden; border: 1px solid var(--line); }
.xpbar i { display: block; height: 100%; background: var(--signal); border-radius: 99px; transition: width .6s ease; }
.level-pill { padding: 3px 10px; border-radius: 99px; background: var(--ink); color: var(--bg); font: 600 12px var(--mono); }
.icon-btn { width: 34px; height: 34px; display: grid; place-items: center; border-radius: 8px; border: 1px solid var(--line); background: var(--surface); cursor: pointer; color: var(--ink-2); }
.icon-btn svg { width: 17px; height: 17px; stroke: currentColor; fill: none; stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; }
.menu-btn { display: none; }

.view { padding: 28px max(28px, env(safe-area-inset-right, 0px)) 80px 28px; max-width: 1180px; width: 100%; }
@media (prefers-reduced-motion: no-preference) {
  .view { view-transition-name: deck; }
  ::view-transition-old(deck) { animation: 140ms ease-out both vt-out; }
  ::view-transition-new(deck) { animation: 220ms ease-out both vt-in; }
  @keyframes vt-out { to { opacity: 0; transform: translateY(-4px); } }
  @keyframes vt-in { from { opacity: 0; transform: translateY(6px); } }
}

/* ---------- shared blocks ---------- */
.panel { background: var(--surface); border: 1px solid var(--line); border-radius: var(--r); padding: 20px; min-width: 0; }
.panel.raised { box-shadow: var(--shadow); border-color: transparent; }
.panel h3 { font-size: 17px; margin-bottom: 4px; }
.sub { color: var(--muted); font-size: 13.5px; }
.grid { display: grid; gap: 16px; }
.cols-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.cols-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.cols-4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.cols-main { grid-template-columns: minmax(0, 1.4fr) minmax(0, 1fr); align-items: start; }
@media (max-width: 1100px) { .cols-main { grid-template-columns: minmax(0, 1fr); } }
.row { display: flex; gap: 12px; align-items: center; flex-wrap: wrap; }
.spread { display: flex; gap: 12px; align-items: center; justify-content: space-between; flex-wrap: wrap; }
.tag {
  display: inline-flex; align-items: center; gap: 5px; padding: 2px 8px; border-radius: 5px; border: 1px solid var(--line);
  font: 600 10.5px/1.6 var(--mono); letter-spacing: .04em; text-transform: uppercase; color: var(--ink-2); background: var(--sunk); white-space: nowrap;
}
.tag.ng { background: var(--signal-soft); border-color: color-mix(in oklch, var(--signal) 40%, transparent); color: var(--signal-ink); }
.tag.free { background: var(--route-soft); border-color: color-mix(in oklch, var(--route) 40%, transparent); color: var(--route); }
.tag.hot { background: var(--ink); color: var(--bg); border-color: var(--ink); }
.track-dot { width: 10px; height: 10px; border-radius: 3px; flex: none; background: oklch(64% 0.15 var(--h)); }
.meter { height: 6px; border-radius: 99px; background: var(--sunk); overflow: hidden; }
.meter i { display: block; height: 100%; background: var(--route); border-radius: 99px; }
.head { display: grid; gap: 8px; margin-bottom: 24px; }
.head h1 { font-size: clamp(28px, 3.6vw, 42px); font-weight: 700; letter-spacing: -0.025em; }
.head p { color: var(--ink-2); max-width: 64ch; font-size: 16px; }
.section-title { display: flex; align-items: baseline; justify-content: space-between; gap: 12px; margin: 34px 0 12px; }
.section-title h2 { font-size: 21px; }
.empty { color: var(--muted); font-size: 14px; padding: 18px; border: 1px dashed var(--line-strong); border-radius: var(--r); text-align: center; }
.toast {
  position: fixed; right: max(20px, env(safe-area-inset-right, 0px)); bottom: calc(20px + env(safe-area-inset-bottom, 0px)); z-index: 80;
  background: var(--ink); color: var(--bg); padding: 10px 16px; border-radius: 10px; font-weight: 600; font-size: 14px; box-shadow: var(--shadow);
  display: flex; align-items: center; gap: 10px;
}
.toast b { color: var(--signal); font-family: var(--mono); }

/* ---------- dashboard ---------- */
.hero { display: grid; grid-template-columns: minmax(0, 1.25fr) minmax(0, 1fr); gap: 16px; margin-bottom: 16px; }
.hero-main { padding: 26px; display: grid; gap: 18px; align-content: start; }
.hero-main h1 { font-size: clamp(30px, 4vw, 48px); font-weight: 700; letter-spacing: -0.03em; }
.hero-main h1 em { font-style: normal; color: var(--signal-ink); }
.lvl-row { display: grid; grid-template-columns: auto minmax(0, 1fr); gap: 6px 16px; align-items: center; }
.lvl-num { font: 700 44px/1 var(--display); letter-spacing: -0.03em; }
.lvl-name { font: 700 18px/1.2 var(--display); }
.ladder { display: flex; gap: 4px; }
.ladder span { flex: 1; height: 8px; border-radius: 3px; background: var(--sunk); border: 1px solid var(--line); }
.ladder span.on { background: var(--signal); border-color: var(--signal); }
.ladder-labels { display: flex; justify-content: space-between; font: 500 10.5px var(--mono); color: var(--muted); }
.kpis { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 10px; }
.kpi { padding: 12px; border-radius: 8px; background: var(--sunk); }
.kpi b { display: block; font: 700 24px/1.1 var(--display); font-variant-numeric: tabular-nums; }
.kpi span { font: 500 11.5px var(--mono); color: var(--muted); }
.continue { display: grid; gap: 10px; padding: 18px; border-radius: var(--r); background: var(--ink); color: var(--bg); text-decoration: none; }
.continue .eyebrow { color: color-mix(in oklch, var(--bg) 65%, transparent); }
.continue h3 { font-size: 21px; }
.continue p { color: color-mix(in oklch, var(--bg) 78%, transparent); font-size: 14px; }
.continue .go { font: 600 13px var(--mono); color: var(--signal); }
.radar-wrap { display: grid; place-items: center; }
.radar { width: 100%; max-width: 440px; height: auto; overflow: visible; }
.radar text { font: 600 15px var(--mono); fill: var(--ink-2); }
.radar .ring { fill: none; stroke: var(--line-strong); stroke-width: 1; }
.radar .axis { stroke: var(--line); stroke-width: 1; }
.radar .area { fill: color-mix(in oklch, var(--signal) 22%, transparent); stroke: var(--signal); stroke-width: 2; stroke-linejoin: round; }
.radar .pt { fill: var(--signal); stroke: var(--surface); stroke-width: 2; }
.radar .ringlab { font: 500 12px var(--mono); fill: var(--muted); }
.track-cards { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 12px; }
.tcard {
  display: grid; gap: 8px; padding: 16px; border-radius: var(--r); border: 1px solid var(--line); background: var(--surface);
  text-decoration: none; color: inherit; align-content: start; transition: border-color .2s, transform .2s;
}
.tcard:hover { border-color: var(--line-strong); transform: translateY(-2px); }
.tcard .num { font: 700 12px var(--mono); color: oklch(55% 0.13 var(--h)); }
:root[data-theme="dark"] .tcard .num { color: oklch(75% 0.12 var(--h)); }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) .tcard .num { color: oklch(75% 0.12 var(--h)); } }
.tcard h3 { font-size: 16px; }
.tcard p { font-size: 13px; color: var(--muted); }
.tcard .bonus { font: 600 10px var(--mono); text-transform: uppercase; letter-spacing: .06em; color: var(--signal-ink); }
.plan { display: grid; gap: 0; }
.plan-row { display: grid; grid-template-columns: 64px 26px minmax(0, 1fr) auto; gap: 12px; align-items: center; padding: 10px 4px; border-bottom: 1px solid var(--line); }
.plan-row:last-child { border-bottom: 0; }
.plan-row .wk { font: 600 12px var(--mono); color: var(--muted); }
.plan-row .what { font-size: 14px; }
.plan-row .what b { font-weight: 600; }
.trait { display: grid; grid-template-columns: auto minmax(0, 1fr); gap: 4px 12px; padding: 12px 0; border-bottom: 1px solid var(--line); align-items: start; }
.trait:last-child { border-bottom: 0; }
.trait input { margin-top: 4px; width: 17px; height: 17px; accent-color: var(--route); }
.trait b { font-weight: 600; font-size: 14.5px; }
.trait p { grid-column: 2; font-size: 13px; color: var(--muted); }
.loop { display: flex; align-items: center; flex-wrap: wrap; gap: 6px; font: 600 13px var(--mono); }
.loop span { padding: 6px 11px; border-radius: 99px; border: 1px solid var(--line-strong); background: var(--surface); }
.loop i { color: var(--signal); font-style: normal; }
.loop span.end { background: var(--route-soft); border-color: var(--route); color: var(--route); }

/* ---------- track ---------- */
.track-head { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 20px; align-items: end; padding-bottom: 22px; margin-bottom: 22px; border-bottom: 1px solid var(--line); }
.big-num { font: 800 clamp(56px, 8vw, 96px)/0.85 var(--display); letter-spacing: -0.05em; color: oklch(64% 0.15 var(--h)); }
.thesis { font: 500 italic 16px/1.5 var(--body); color: var(--ink-2); border-left: 3px solid var(--signal); padding-left: 12px; max-width: 60ch; }
.lesson-list { display: grid; gap: 10px; }
.lrow {
  display: grid; grid-template-columns: 40px minmax(0, 1fr) auto; gap: 14px; align-items: center; padding: 14px 16px;
  border: 1px solid var(--line); border-radius: var(--r); background: var(--surface); text-decoration: none; color: inherit;
}
.lrow:hover { border-color: var(--line-strong); }
.lrow .n { width: 34px; height: 34px; border-radius: 99px; display: grid; place-items: center; border: 2px solid var(--line-strong); font: 700 12px var(--mono); color: var(--muted); }
.lrow.done .n { background: var(--route); border-color: var(--route); color: var(--surface); }
.lrow h3 { font-size: 16px; }
.lrow p { font-size: 13px; color: var(--muted); display: -webkit-box; -webkit-line-clamp: 1; -webkit-box-orient: vertical; overflow: hidden; }
.res { display: grid; gap: 4px; }
.res a { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 10px; align-items: center; padding: 9px 10px; border-radius: 8px; color: var(--ink); text-decoration: none; font-weight: 500; font-size: 14px; }
.res a:hover { background: var(--sunk); }
.res .tags { display: flex; gap: 4px; flex-wrap: wrap; justify-content: flex-end; }
.cap-steps { list-style: none; padding: 0; margin: 12px 0 0; display: grid; gap: 6px; }
.cap-steps label { display: grid; grid-template-columns: auto minmax(0, 1fr); gap: 10px; align-items: start; font-size: 14px; cursor: pointer; padding: 6px 8px; border-radius: 6px; }
.cap-steps label:hover { background: var(--sunk); }
.cap-steps input { width: 17px; height: 17px; margin-top: 2px; accent-color: var(--route); }
.cap-steps input:checked + span { color: var(--muted); text-decoration: line-through; text-decoration-color: var(--route); }
.done-when { margin: 12px 0 0; padding: 10px 12px; border-radius: 8px; background: var(--sunk); font-size: 13px; color: var(--ink-2); }
.done-when b { font: 600 11px var(--mono); text-transform: uppercase; letter-spacing: .06em; color: var(--muted); display: block; margin-bottom: 4px; }

/* ---------- lesson ---------- */
.lesson { display: grid; grid-template-columns: minmax(0, 1fr) 210px; gap: 32px; align-items: start; }
.lesson-body { display: grid; gap: 14px; min-width: 0; }
.toc { position: sticky; top: calc(76px + env(safe-area-inset-top, 0px)); display: grid; gap: 2px; font-size: 13px; }
.toc a { display: flex; gap: 8px; padding: 5px 8px; border-radius: 6px; color: var(--ink-2); text-decoration: none; }
.toc a:hover { background: var(--sunk); }
.toc a i { font: 600 11px var(--mono); font-style: normal; color: var(--signal-ink); width: 16px; }
.toc .toc-actions { margin-top: 14px; display: grid; gap: 8px; }
.sec { background: var(--surface); border: 1px solid var(--line); border-radius: var(--r); padding: 20px 22px; scroll-margin-top: 80px; min-width: 0; }
.sec-h { display: flex; align-items: center; gap: 10px; margin-bottom: 10px; }
.sec-h i { font: 700 11px var(--mono); font-style: normal; width: 24px; height: 24px; border-radius: 6px; display: grid; place-items: center; background: var(--signal-soft); color: var(--signal-ink); flex: none; }
.sec-h h2 { font-size: 17px; }
.sec p { max-width: 70ch; }
.sec.k-analogy { background: var(--ink); color: var(--bg); border-color: var(--ink); }
.sec.k-analogy p { font: 500 19px/1.5 var(--display); letter-spacing: -0.005em; max-width: 60ch; }
.sec.k-analogy .sec-h i { background: var(--signal); color: oklch(18% 0.04 50); }
.sec.k-core p { font-size: 16.5px; }
.sec.k-why { border-left: 4px solid var(--crit); }
.parts { display: grid; grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); gap: 10px; }
.part { padding: 12px 14px; border-radius: 8px; background: var(--sunk); }
.part b { display: block; font: 600 14px var(--body); margin-bottom: 3px; }
.part span { font-size: 13.5px; color: var(--ink-2); }
.diagram { overflow-x: auto; padding: 12px; border-radius: 8px; background: var(--sunk); min-height: 120px; display: grid; place-items: center; }
.diagram svg { max-width: 100%; height: auto; }
.diagram pre { margin: 0; font: 12.5px/1.5 var(--mono); white-space: pre; color: var(--ink-2); }
.code { position: relative; border-radius: 8px; background: var(--code-bg); color: var(--code-ink); }
.code pre { margin: 0; padding: 16px 18px; overflow-x: auto; font: 13px/1.6 var(--mono); tab-size: 4; }
.code .copy { position: absolute; top: 8px; right: 8px; padding: 4px 10px; border-radius: 6px; border: 1px solid oklch(40% 0.03 262); background: oklch(28% 0.035 262); color: var(--code-ink); font: 600 11.5px var(--mono); cursor: pointer; }
.code .copy:hover { background: oklch(34% 0.04 262); }
.tk-k { color: var(--code-kw); } .tk-s { color: var(--code-str); } .tk-c { color: var(--code-com); font-style: italic; }
.tk-n { color: var(--code-num); } .tk-f { color: var(--code-fn); } .tk-d { color: var(--code-num); }
.mistakes { margin: 0; padding: 0; list-style: none; display: grid; gap: 8px; }
.mistakes li { display: grid; grid-template-columns: 22px minmax(0, 1fr); gap: 8px; font-size: 14.5px; }
.mistakes li::before { content: "✕"; font: 700 13px var(--mono); color: var(--crit); line-height: 1.6; }
.sec.k-practice { border: 2px solid var(--route); background: var(--route-soft); }
.sec.k-practice .sec-h i { background: var(--route); color: var(--surface); }
.lesson-foot { display: flex; gap: 10px; flex-wrap: wrap; justify-content: space-between; align-items: center; margin-top: 6px; }

/* ---------- play ---------- */
.seg { display: inline-flex; flex-wrap: wrap; gap: 4px; padding: 4px; border-radius: 10px; background: var(--sunk); border: 1px solid var(--line); }
.seg button { border: 0; background: transparent; padding: 6px 12px; border-radius: 7px; cursor: pointer; font-size: 13px; font-weight: 500; color: var(--ink-2); }
.seg button[aria-pressed="true"] { background: var(--surface); color: var(--ink); box-shadow: var(--shadow); }
.qcard { max-width: 760px; display: grid; gap: 16px; }
.qprog { display: flex; gap: 4px; }
.qprog span { flex: 1; height: 5px; border-radius: 99px; background: var(--line); }
.qprog span.ok { background: var(--route); } .qprog span.no { background: var(--crit); } .qprog span.cur { background: var(--signal); }
.qtext { font: 600 21px/1.35 var(--display); letter-spacing: -0.01em; }
.opts { display: grid; gap: 8px; }
.opt {
  text-align: left; padding: 13px 16px; border-radius: 9px; border: 1.5px solid var(--line-strong); background: var(--surface); cursor: pointer;
  font-size: 15px; display: grid; grid-template-columns: 26px minmax(0, 1fr); gap: 10px; align-items: start;
}
.opt:hover:not(:disabled) { border-color: var(--ink-2); }
.opt kbd { font: 600 12px var(--mono); color: var(--muted); border: 1px solid var(--line); border-radius: 5px; text-align: center; padding: 1px 0; background: var(--sunk); }
.opt.right { border-color: var(--route); background: var(--route-soft); }
.opt.wrong { border-color: var(--crit); background: color-mix(in oklch, var(--crit) 12%, var(--surface)); }
.opt:disabled { cursor: default; }
.explain { padding: 12px 14px; border-radius: 8px; background: var(--sunk); font-size: 14px; }
.explain b { font-family: var(--display); }
.score-big { font: 800 64px/1 var(--display); letter-spacing: -0.04em; }
.flash-wrap { display: grid; gap: 16px; max-width: 680px; }
.flash {
  min-height: 250px; border-radius: 14px; padding: 28px; display: grid; align-content: center; gap: 12px; cursor: pointer;
  background: var(--surface); border: 1px solid var(--line); box-shadow: var(--shadow); text-align: left; width: 100%;
}
.flash .front { font: 700 26px/1.2 var(--display); letter-spacing: -0.02em; }
.flash .back { font-size: 16.5px; color: var(--ink-2); }
.flash.flipped { background: var(--ink); color: var(--bg); border-color: var(--ink); }
.flash.flipped .back { color: color-mix(in oklch, var(--bg) 85%, transparent); }
.boxes { display: flex; gap: 6px; flex-wrap: wrap; }
.boxes span { font: 600 11.5px var(--mono); padding: 4px 9px; border-radius: 6px; background: var(--sunk); border: 1px solid var(--line); color: var(--ink-2); }
.inc-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 12px; }
.inc {
  text-align: left; display: grid; gap: 8px; padding: 16px; border-radius: var(--r); border: 1px solid var(--line); background: var(--surface); cursor: pointer;
  border-top: 4px solid var(--warn); align-content: start;
}
.inc[data-sev="SEV1"] { border-top-color: var(--crit); }
.inc[data-sev="SEV3"] { border-top-color: var(--line-strong); }
.inc.solved { border-top-color: var(--route); }
.inc .ih { display: block; font: 700 15.5px/1.25 var(--display); }
.inc > span { min-width: 0; }
.inc .ip { font-size: 13px; color: var(--muted); display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }
.sev { font: 700 10.5px var(--mono); letter-spacing: .06em; }
.pager { font: 600 12px var(--mono); color: var(--muted); }
textarea, input[type="text"], select {
  width: 100%; font: inherit; color: var(--ink); background: var(--surface); border: 1.5px solid var(--line-strong); border-radius: 9px; padding: 12px 14px;
}
textarea { min-height: 220px; resize: vertical; line-height: 1.55; }
textarea:focus, input[type="text"]:focus, select:focus { outline: none; border-color: var(--signal); }
.rubric { list-style: none; margin: 0; padding: 0; display: grid; gap: 6px; }
.rubric li { display: grid; grid-template-columns: 26px minmax(0, 1fr); gap: 8px; font-size: 14px; padding: 8px 10px; border-radius: 7px; background: var(--sunk); }
.rubric li .mk { font: 700 13px var(--mono); }
.rubric li.pass .mk { color: var(--route); } .rubric li.fail .mk { color: var(--crit); }
.rubric li small { display: block; color: var(--muted); font-size: 12.5px; }
.chat { display: grid; gap: 12px; }
.msgs { display: grid; gap: 12px; }
.msg { padding: 14px 16px; border-radius: 12px; max-width: 100%; min-width: 0; overflow-wrap: anywhere; }
.msg.user { background: var(--ink); color: var(--bg); justify-self: end; max-width: 80%; }
.msg.bot { background: var(--surface); border: 1px solid var(--line); }
.msg.bot .md h1, .msg.bot .md h2, .msg.bot .md h3 { font-size: 16px; margin: 14px 0 6px; }
.msg.bot .md p { margin: 6px 0; }
.msg.bot .md ul, .msg.bot .md ol { margin: 6px 0; padding-left: 22px; }
.msg.bot .md code { font: 13px var(--mono); background: var(--sunk); padding: 1px 5px; border-radius: 4px; }
.msg.bot .md .code code { background: none; padding: 0; }
.composer { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 10px; align-items: end; }
.composer textarea { min-height: 56px; height: 56px; }
.chips { display: flex; flex-wrap: wrap; gap: 6px; }
.chip { padding: 6px 11px; border-radius: 99px; border: 1px solid var(--line-strong); background: var(--surface); cursor: pointer; font-size: 13px; color: var(--ink-2); }
.chip:hover { border-color: var(--signal); color: var(--ink); }
.prompt-box { font: 12.5px/1.55 var(--mono); white-space: pre-wrap; background: var(--code-bg); color: var(--code-ink); border-radius: 8px; padding: 16px; max-height: 300px; overflow: auto; }
.filters { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 14px; }

dialog { border: 0; border-radius: 14px; padding: 0; background: var(--surface); color: var(--ink); box-shadow: var(--shadow); width: min(560px, calc(100vw - 32px)); }
dialog::backdrop { background: oklch(15% 0.03 262 / 0.5); }
.dlg { padding: 22px; display: grid; gap: 14px; }
.dlg textarea { min-height: 140px; font: 12px/1.5 var(--mono); }

/* ---------- responsive ---------- */
@media (max-width: 1100px) {
  .track-cards { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .lesson { grid-template-columns: minmax(0, 1fr); }
  .toc { display: none; }
  .inc-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 860px) {
  .shell { grid-template-columns: minmax(0, 1fr); }
  .rail {
    position: fixed; inset: 0 auto 0 0; z-index: 60; width: min(300px, 86vw); transform: translateX(-102%); transition: transform .25s ease;
    padding-top: calc(20px + env(safe-area-inset-top, 0px)); box-shadow: var(--shadow); height: 100%;
  }
  .rail.open { transform: none; }
  .scrim { position: fixed; inset: 0; z-index: 55; background: oklch(15% 0.03 262 / 0.45); }
  .menu-btn { display: grid; }
  .topbar { padding-left: max(16px, env(safe-area-inset-left, 0px)); padding-right: max(16px, env(safe-area-inset-right, 0px)); gap: 10px; }
  .view { padding: 20px max(16px, env(safe-area-inset-right, 0px)) 72px max(16px, env(safe-area-inset-left, 0px)); }
  .hero, .cols-2, .cols-3 { grid-template-columns: minmax(0, 1fr); }
  .kpis { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .track-head { grid-template-columns: minmax(0, 1fr); }
  .xpbar { width: 70px; }
}
@media (max-width: 560px) {
  .track-cards, .inc-grid, .cols-4 { grid-template-columns: minmax(0, 1fr); }
  .stat-chip .lbl { display: none; }
  .topbar { flex-wrap: nowrap; }
  .crumb { visibility: hidden; }
  .xpbar { display: none; }
  .plan-row { grid-template-columns: 48px 20px minmax(0, 1fr); }
  .plan-row .tag { display: none; }
  .sec { padding: 16px; }
  .qtext { font-size: 18px; }
  .lrow { grid-template-columns: 36px minmax(0, 1fr); }
  .lrow .tag { display: none; }
}
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { transition: none !important; animation: none !important; }
}

/* ======================= v2: resources, finder, search, polish ======================= */
/* Search trigger in the top bar */
.search-btn {
  display: inline-flex; align-items: center; gap: 10px; min-width: 0; width: min(340px, 34vw); height: 36px; padding: 0 8px 0 12px;
  border-radius: 9px; border: 1px solid var(--line); background: var(--surface); color: var(--muted); cursor: pointer; font-size: 13.5px; text-align: left;
  transition: border-color .15s, box-shadow .15s;
}
.search-btn:hover { border-color: var(--line-strong); box-shadow: var(--shadow); color: var(--ink-2); }
.search-btn svg { width: 16px; height: 16px; flex: none; stroke: currentColor; fill: none; stroke-width: 2; stroke-linecap: round; }
.search-lbl { flex: 1; min-width: 0; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
kbd { font: 600 11px/1 var(--mono); padding: 3px 6px; border-radius: 5px; border: 1px solid var(--line); border-bottom-width: 2px; background: var(--sunk); color: var(--ink-2); white-space: nowrap; }

/* Command palette */
dialog.cmd { width: min(640px, calc(100vw - 32px)); margin-top: max(10vh, 24px); overflow: hidden; }
.cmd-box { display: grid; grid-template-rows: auto minmax(0, 1fr) auto; max-height: min(70vh, 560px); }
.cmd-input { display: flex; align-items: center; gap: 10px; padding: 14px 16px; border-bottom: 1px solid var(--line); }
.cmd-input svg { width: 18px; height: 18px; flex: none; stroke: var(--muted); fill: none; stroke-width: 2; stroke-linecap: round; }
.cmd-input input { flex: 1; min-width: 0; border: 0; padding: 4px 0; background: transparent; font-size: 16px; }
.cmd-input input:focus { outline: none; border: 0; }
.cmd-list { overflow-y: auto; padding: 6px; overscroll-behavior: contain; }
.cmd-item { display: grid; grid-template-columns: 92px minmax(0, 1fr) auto auto; gap: 10px; align-items: center; padding: 9px 10px; border-radius: 8px; color: var(--ink); text-decoration: none; font-size: 14px; }
.cmd-item[aria-selected="true"], .cmd-item:hover { background: var(--signal-soft); }
.cmd-kind { font: 600 10.5px var(--mono); letter-spacing: .05em; text-transform: uppercase; color: var(--muted); }
.cmd-label { min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; font-weight: 500; }
.cmd-meta { font: 500 11.5px var(--mono); color: var(--muted); white-space: nowrap; max-width: 180px; overflow: hidden; text-overflow: ellipsis; }
.cmd-ext { color: var(--muted); font-size: 12px; }
.cmd-foot { display: flex; gap: 16px; flex-wrap: wrap; padding: 10px 16px; border-top: 1px solid var(--line); font-size: 12px; color: var(--muted); background: var(--sunk); }
.cmd-foot kbd { margin-right: 3px; }

/* Resource finder */
.finder { display: grid; gap: 10px; }
.finder-h { display: flex; align-items: baseline; gap: 10px; flex-wrap: wrap; min-width: 0; }
.finder-q { font-style: italic; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; min-width: 0; max-width: 100%; }
.finder-row { display: flex; flex-wrap: wrap; gap: 6px; }
.find-btn {
  display: inline-flex; align-items: center; gap: 7px; height: 32px; padding: 0 11px; border-radius: 8px; border: 1px solid var(--line-strong);
  background: var(--surface); color: var(--ink-2); font-size: 13px; font-weight: 500; text-decoration: none; cursor: pointer; white-space: nowrap;
  transition: border-color .15s, color .15s, background .15s;
}
.find-btn svg { width: 16px; height: 16px; flex: none; stroke: currentColor; fill: none; stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; }
.find-btn:hover { color: var(--ink); border-color: var(--ink-2); }
.find-btn.yt svg { color: var(--crit); }
.find-btn.dl svg { color: var(--signal-ink); }
.find-btn.save { border-style: dashed; color: var(--route); border-color: color-mix(in oklch, var(--route) 55%, transparent); }
.find-btn.save:hover { background: var(--route-soft); }
.mine-block { margin-top: 18px; padding-top: 16px; border-top: 1px solid var(--line); display: grid; gap: 10px; }
.mine-block + .finder { margin-top: 18px; padding-top: 16px; border-top: 1px solid var(--line); }
.go-deeper { display: grid; gap: 0; }
.finder-panel { display: grid; gap: 12px; margin-bottom: 18px; }
.finder-search input { max-width: 520px; }
.ghost-btn.sm { padding: 5px 10px; font-size: 12.5px; }
.ghost-btn.danger { color: var(--crit); border-color: color-mix(in oklch, var(--crit) 45%, transparent); }
.ghost-btn.danger:hover { background: color-mix(in oklch, var(--crit) 10%, var(--surface)); }
.icon-btn.sm { width: 30px; height: 30px; }
.icon-btn.sm svg { width: 15px; height: 15px; }

/* My resources list */
.myres { list-style: none; margin: 0; padding: 0; display: grid; gap: 4px; }
.myres li { display: grid; grid-template-columns: auto minmax(0, 1fr) auto; gap: 12px; align-items: start; padding: 10px; border-radius: 8px; }
.myres li:hover { background: var(--sunk); }
.myres input[type="checkbox"] { width: 17px; height: 17px; margin-top: 3px; accent-color: var(--route); }
.myres-main { display: grid; gap: 4px; min-width: 0; }
.myres-main a { color: var(--ink); font-weight: 600; text-decoration: none; overflow-wrap: anywhere; }
.myres-main a:hover { text-decoration: underline; text-decoration-color: var(--signal); text-underline-offset: 3px; }
.myres li.is-done .myres-main a { color: var(--muted); text-decoration: line-through; text-decoration-color: var(--route); }
.myres-meta { display: flex; gap: 6px; flex-wrap: wrap; align-items: center; }
.myres-notes { font-size: 13px; color: var(--ink-2); }
.tag.mine { background: color-mix(in oklch, var(--signal) 14%, var(--surface)); border-color: color-mix(in oklch, var(--signal) 35%, transparent); color: var(--signal-ink); }
.empty-state { display: grid; gap: 10px; justify-items: start; padding: 22px 6px; max-width: 60ch; }

/* Library toolbar */
.lib-bar { display: flex; gap: 12px; align-items: center; justify-content: space-between; flex-wrap: wrap; margin-bottom: 12px; }
.lib-tools { display: flex; gap: 8px; align-items: center; flex: 1 1 320px; justify-content: flex-end; min-width: 0; }
.lib-tools input { max-width: 300px; padding: 9px 12px; }
.seg .cnt { font: 600 11px var(--mono); color: var(--muted); margin-left: 4px; }
.chip[aria-pressed="true"] { border-color: var(--signal); color: var(--ink); background: var(--signal-soft); }
input[type="search"] { width: 100%; font: inherit; color: var(--ink); background: var(--surface); border: 1.5px solid var(--line-strong); border-radius: 9px; padding: 10px 14px; }
input[type="search"]:focus, input[type="url"]:focus { outline: none; border-color: var(--signal); }

/* Resource form + :user-invalid (Modern Web Guidance: validate-input-after-interaction) */
.res-form { gap: 16px; }
.field { display: grid; gap: 6px; min-width: 0; }
.field label { font-weight: 600; font-size: 13.5px; }
.field .hint { font-size: 12.5px; color: var(--muted); }
.field .opt-lbl { font-weight: 400; color: var(--muted); font-size: 12px; }
.field-row { display: grid; grid-template-columns: minmax(0, 1.6fr) minmax(0, 1fr); gap: 12px; }
.res-form input[type="url"], .res-form input[type="text"], .res-form select { padding: 10px 12px; width: 100%; font: inherit; color: var(--ink); background: var(--surface); border: 1.5px solid var(--line-strong); border-radius: 9px; }
.res-form textarea { min-height: 84px; font: inherit; }
.error-msg { display: none; font-size: 12.5px; font-weight: 500; color: var(--crit); }
.res-form :is(input, select, textarea):user-invalid,
.res-form .user-invalid-fallback { border-color: var(--crit); background: color-mix(in oklch, var(--crit) 6%, var(--surface)); }
.res-form input:user-invalid ~ .error-msg,
.res-form .user-invalid-fallback ~ .error-msg { display: block; }

/* Lesson: active TOC + reading progress (scroll-driven, progressive enhancement) */
.toc a.on { background: var(--signal-soft); color: var(--ink); font-weight: 600; }
.readbar { position: fixed; left: 0; right: 0; top: env(safe-area-inset-top, 0px); height: 3px; z-index: 30; background: var(--signal); transform-origin: 0 50%; transform: scaleX(0); pointer-events: none; display: none; }
@supports (animation-timeline: scroll()) {
  @media (prefers-reduced-motion: no-preference) {
    body:has(.lesson) .readbar { display: block; }
    .readbar { animation: read-progress linear both; animation-timeline: scroll(root block); }
    @keyframes read-progress { to { transform: scaleX(1); } }
  }
}

/* Container queries: components adapt to the space they get (Modern Web Guidance: size-aware-styling) */
.panel, .hero-main, .tcard { container-type: inline-size; }
@container (max-width: 520px) {
  .kpis { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .res a { grid-template-columns: minmax(0, 1fr); gap: 4px; }
  .res .tags { justify-content: flex-start; }
  .field-row { grid-template-columns: minmax(0, 1fr); }
}
@container (max-width: 380px) {
  .find-btn span { font-size: 12.5px; }
  .cap-steps label { font-size: 13.5px; }
}

/* Professional polish */
.panel.raised, .hero-main { border: 1px solid var(--line); box-shadow: var(--shadow); }
.tcard { box-shadow: 0 1px 0 var(--line); }
.tcard:hover { box-shadow: var(--shadow); }
.lrow { transition: border-color .15s, box-shadow .15s; }
.lrow:hover { box-shadow: var(--shadow); }
.topbar { min-height: 57px; }
.crumb { flex: 1 1 120px; }
.head h1 { letter-spacing: -0.03em; }
::selection { background: color-mix(in oklch, var(--signal) 30%, transparent); }

@media (max-width: 860px) {
  .search-btn { width: 36px; padding: 0; justify-content: center; flex: none; }
  .search-lbl, .search-btn kbd { display: none; }
}
@media (max-width: 560px) {
  .cmd-item { grid-template-columns: minmax(0, 1fr) auto; }
  .cmd-kind, .cmd-meta { display: none; }
  .lib-tools { justify-content: stretch; }
  .lib-tools input { max-width: none; }
  dialog.cmd { margin-top: 16px; }
}
.level-pill { white-space: nowrap; }
.search-btn { width: clamp(200px, 24vw, 320px); }
.crumb { flex: 1 1 180px; }
@media (max-width: 1240px) { .stat-chip .lbl { display: none; } .xpbar { width: 80px; } }
@media (max-width: 560px) { #xpnum { display: none; } .topbar { gap: 8px; } }
@media (max-width: 860px) { .search-btn { width: 36px; } }
.topbar { flex-wrap: nowrap; }
.crumb { flex: 1 1 0; min-width: 0; }