/* Interactive lessons (/learn/) and article quizzes (section.learn-quiz):
   pipeline/pages/learn.py, js/learn.js. On top of style.css: .card, .btn,
   .seg, .toggle, .legend, .tip, chart line/bar classes. Colors only through the
   theme variables, so light, paper, graphite and black all work. */

.ln-sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); clip-path: inset(50%); white-space: nowrap; }

/* ---------- lesson page: one calm column ---------- */
.ln-page { --col: 760px; }
.ln-page > * { max-width: var(--col); margin-left: auto; margin-right: auto; }
.ln-intro { padding: 44px 0 20px; gap: 12px; }
.ln-intro h1 { font-size: clamp(32px, 4.8vw, 54px); line-height: 1.02; max-width: 17ch; }
.ln-intro .lead { font-size: clamp(16px, 1.5vw, 19px); }
.ln-meta-line { margin: 0; font-size: 13px; color: var(--muted); font-variant-numeric: tabular-nums; }
.ln-host { scroll-margin-top: 84px; }

/* ---------- the player ---------- */
.ln-player { position: relative; background: var(--surface); border-radius: var(--r); box-shadow: var(--shadow); padding: 18px 28px 0; scroll-margin-top: 84px; }
.ln-top { display: flex; align-items: center; gap: 14px; padding: 2px 0 14px; border-bottom: 1px solid var(--border); }
.ln-bar { flex: 1; min-width: 0; display: flex; gap: 4px; }
.ln-bar i { flex: 1; height: 6px; border-radius: 3px; background: var(--track); transition: background 0.25s ease, box-shadow 0.25s ease; }
.ln-bar i.is-done { background: var(--accent); }
.ln-bar i.is-cur { background: color-mix(in srgb, var(--accent) 35%, var(--track)); box-shadow: inset 0 0 0 1.5px var(--accent); }
.ln-count { font: 600 12.5px var(--mono); color: var(--muted); white-space: nowrap; }
.ln-pts { position: relative; flex: none; font: 600 12.5px/1 var(--mono); color: var(--ink); background: var(--track); border-radius: 999px; padding: 7px 11px; white-space: nowrap; }
.ln-pts b { font-weight: 600; }
.ln-gain { position: absolute; right: 8px; top: -6px; font: 700 13px var(--mono); font-style: normal; color: var(--good); opacity: 0; pointer-events: none; }
.ln-gain.on { animation: ln-gain 1.2s ease-out; }
@keyframes ln-gain { 0% { opacity: 0; transform: translateY(8px); } 18% { opacity: 1; } 100% { opacity: 0; transform: translateY(-18px); } }

.ln-shared { display: flex; align-items: center; gap: 10px; margin: 14px 0 0; padding: 10px 8px 10px 16px; border-radius: 14px; background: var(--accent-soft); color: var(--ink); font-size: 14px; }
.ln-shared[hidden] { display: none; }
.ln-shared p { margin: 0; flex: 1; }
.ln-shared b { font-weight: 650; }
.ln-x { flex: none; width: 32px; height: 32px; border: 0; border-radius: 50%; background: transparent; color: var(--muted); font: 400 20px/1 var(--font); cursor: pointer; }
.ln-x:hover { background: var(--hover); color: var(--ink); }

.ln-stage { padding: 24px 0 22px; min-height: 300px; }
.ln-step.ln-in { animation: ln-in 0.24s ease-out; }
@keyframes ln-in { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }
.ln-kind { margin: 0 0 8px; font: 600 12px/1.4 var(--font); text-transform: uppercase; letter-spacing: 0.12em; color: var(--muted); }
.ln-title { margin: 0 0 10px; font: 700 clamp(24px, 3vw, 31px)/1.12 var(--display); letter-spacing: -0.035em; color: var(--ink); text-wrap: balance; outline: none; }
.ln-text { margin: 0; max-width: 64ch; color: var(--ink-2); font-size: 17px; line-height: 1.62; text-wrap: pretty; }
.ln-text b, .ln-q-text b { color: var(--ink); font-weight: 650; }
.ln-text.ln-title { font: 600 19px/1.5 var(--font); letter-spacing: -0.01em; color: var(--ink); }
.ln-body { margin-top: 20px; display: grid; gap: 18px; min-width: 0; }
.ln-body:empty { display: none; }
.ln-q { display: grid; gap: 12px; padding-top: 18px; border-top: 1px solid var(--border); }
.ln-q-k { margin: 0; font: 600 12px/1.4 var(--font); text-transform: uppercase; letter-spacing: 0.12em; color: var(--accent-ink); }
.ln-q-text { color: var(--ink); font-size: 17px; line-height: 1.55; font-weight: 500; }

/* ---------- sliders ---------- */
.ln-range { -webkit-appearance: none; appearance: none; display: block; width: 100%; height: 26px; margin: 0; background: transparent; cursor: pointer; --p: 50%; }
.ln-range::-webkit-slider-runnable-track { height: 6px; border-radius: 999px; background: linear-gradient(to right, var(--accent) 0, var(--accent) var(--p), var(--track) var(--p), var(--track) 100%); }
.ln-range::-webkit-slider-thumb { -webkit-appearance: none; width: 26px; height: 26px; margin-top: -10px; border-radius: 50%; background: var(--surface); border: 0; box-shadow: 0 0 0 2.5px var(--accent), 0 2px 8px rgba(0, 0, 0, 0.22); transition: box-shadow 0.15s ease; }
.ln-range::-moz-range-track { height: 6px; border-radius: 999px; background: var(--track); }
.ln-range::-moz-range-progress { height: 6px; border-radius: 999px; background: var(--accent); }
.ln-range::-moz-range-thumb { width: 26px; height: 26px; border: 0; border-radius: 50%; background: var(--surface); box-shadow: 0 0 0 2.5px var(--accent), 0 2px 8px rgba(0, 0, 0, 0.22); }
.ln-range:focus { outline: none; }
.ln-range:focus-visible::-webkit-slider-thumb { box-shadow: 0 0 0 2.5px var(--accent), 0 0 0 8px color-mix(in srgb, var(--accent) 22%, transparent); }
.ln-range:focus-visible::-moz-range-thumb { box-shadow: 0 0 0 2.5px var(--accent), 0 0 0 8px color-mix(in srgb, var(--accent) 22%, transparent); }
.ln-range:active::-webkit-slider-thumb { box-shadow: 0 0 0 2.5px var(--accent), 0 0 0 10px color-mix(in srgb, var(--accent) 18%, transparent); }
.ln-range:disabled { cursor: default; }

/* ---------- predict: a guess on a slider ---------- */
.ln-pred { background: var(--surface-2); border-radius: 20px; padding: 18px 22px 12px; box-shadow: inset 0 0 0 1px var(--border); }
.ln-guess { display: flex; flex-wrap: wrap; align-items: baseline; justify-content: space-between; gap: 4px 14px; }
.ln-guess-v { display: flex; flex-wrap: wrap; align-items: baseline; gap: 4px 16px; font: 600 clamp(32px, 4.4vw, 42px)/1.05 var(--mono); letter-spacing: -0.05em; color: var(--ink); }
.ln-guess-ans { font: 500 14px var(--font); letter-spacing: 0; color: var(--muted); }
.ln-guess-ans b { font: 600 clamp(22px, 3vw, 28px) var(--mono); letter-spacing: -0.04em; color: var(--accent-ink); margin-left: 4px; }
.ln-track { position: relative; padding: 30px 0 30px; }
.ln-ends { display: flex; justify-content: space-between; gap: 10px; margin-top: -18px; font: 500 12px var(--mono); color: var(--muted); }
.ln-mk { position: absolute; top: 43px; width: 0; height: 0; pointer-events: none; }
.ln-mk[hidden] { display: none; }
.ln-mk i { position: absolute; left: -8px; top: -8px; width: 16px; height: 16px; border-radius: 50%; }
.ln-mk b { position: absolute; left: 0; transform: translateX(-50%); white-space: nowrap; font: 600 12px/1 var(--mono); }
.ln-mk.at-l b { transform: translateX(-10px); }
.ln-mk.at-r b { transform: translateX(calc(-100% + 10px)); }
.ln-mk.you i { background: var(--surface); box-shadow: inset 0 0 0 3px var(--ink-2); }
.ln-mk.you b { bottom: 14px; color: var(--ink-2); }
.ln-mk.ans i { background: var(--accent); box-shadow: 0 0 0 3px var(--surface); }
.ln-mk.ans b { top: 14px; color: var(--accent-ink); }
.ln-pred.is-locked .ln-range::-webkit-slider-thumb { opacity: 0; }
.ln-pred.is-locked .ln-range::-moz-range-thumb { opacity: 0; }

/* ---------- choose: options as cards ---------- */
.ln-opts { margin: 0; padding: 0; border: 0; min-width: 0; display: grid; gap: 10px; }
.ln-opt { position: relative; display: flex; align-items: center; gap: 14px; padding: 13px 16px; border-radius: 16px; background: var(--surface-2); box-shadow: inset 0 0 0 1.5px var(--border); color: var(--ink); font-size: 16px; line-height: 1.4; cursor: pointer; transition: box-shadow 0.15s ease, background 0.15s ease, opacity 0.15s ease; }
.ln-opt:hover { box-shadow: inset 0 0 0 1.5px var(--axis); }
.ln-opt input { position: absolute; opacity: 0; width: 1px; height: 1px; margin: 0; pointer-events: none; }
.ln-letter { flex: none; width: 30px; height: 30px; display: grid; place-items: center; border-radius: 9px; background: var(--track); color: var(--ink-2); font: 600 13px var(--mono); transition: background 0.15s ease, color 0.15s ease; }
.ln-opt-t { min-width: 0; }
.ln-opt:has(input:checked) { background: var(--surface); box-shadow: inset 0 0 0 2px var(--ink); }
.ln-opt:has(input:checked) .ln-letter { background: var(--ink); color: var(--surface); }
.ln-opt:has(input:focus-visible) { outline: 2px solid var(--accent); outline-offset: 2px; }
.ln-opts.is-locked .ln-opt { cursor: default; }
.ln-opts.is-locked .ln-opt:not(.is-right):not(.is-wrong) { opacity: 0.5; }
.ln-opts.is-locked .ln-opt.is-right { background: var(--good-soft); box-shadow: inset 0 0 0 2px var(--good); }
.ln-opts.is-locked .ln-opt.is-right .ln-letter { background: var(--good); color: var(--surface); }
.ln-opts.is-locked .ln-opt.is-wrong { background: var(--bad-soft); box-shadow: inset 0 0 0 2px var(--bad); }
.ln-opts.is-locked .ln-opt.is-wrong .ln-letter { background: var(--bad); color: var(--surface); }

/* ---------- order: drag cards into place ---------- */
.ln-order-box { display: grid; gap: 8px; }
.ln-order-end { margin: 0; font: 600 11.5px/1.4 var(--font); text-transform: uppercase; letter-spacing: 0.12em; color: var(--muted); }
.ln-order { position: relative; margin: 0; padding: 0; list-style: none; display: grid; gap: 8px; }
.ln-item { position: relative; display: grid; grid-template-columns: 30px minmax(0, 1fr) auto 30px; align-items: center; gap: 12px; padding: 11px 8px 11px 12px; border-radius: 16px; background: var(--surface); box-shadow: inset 0 0 0 1.5px var(--border), 0 1px 2px rgba(0, 0, 0, 0.04); color: var(--ink); cursor: grab; user-select: none; -webkit-user-select: none; }
.ln-item:hover { box-shadow: inset 0 0 0 1.5px var(--axis), 0 1px 2px rgba(0, 0, 0, 0.04); }
.ln-item:focus { outline: none; }
.ln-item:focus-visible { box-shadow: inset 0 0 0 2px var(--accent), 0 1px 2px rgba(0, 0, 0, 0.04); }
.ln-item.is-drag { z-index: 3; cursor: grabbing; box-shadow: inset 0 0 0 2px var(--ink), var(--shadow-lg); transition: none !important; }
.ln-rank { width: 30px; height: 30px; display: grid; place-items: center; border-radius: 9px; background: var(--track); font: 600 13px var(--mono); color: var(--ink-2); }
.ln-item-t { min-width: 0; font-size: 16px; line-height: 1.35; }
.ln-item-t b { font-weight: 650; }
.ln-item-t small { display: block; margin-top: 1px; font-size: 13px; color: var(--muted); }
.ln-item-v { display: grid; justify-items: end; gap: 1px; font-size: 12px; color: var(--muted); text-align: right; }
.ln-item-v:empty { display: none; }
.ln-item-v b { font: 600 16px/1.2 var(--mono); letter-spacing: -0.03em; color: var(--ink); }
.ln-grip { width: 30px; height: 38px; display: grid; place-items: center; border-radius: 9px; color: var(--muted); touch-action: none; cursor: grab; }
.ln-grip svg { width: 10px; height: 16px; fill: currentColor; }
.ln-item:hover .ln-grip { color: var(--ink-2); }
.ln-order-box.is-locked .ln-item { cursor: default; grid-template-columns: 30px minmax(0, 1fr) auto; padding-right: 14px; }
.ln-order-box.is-locked .ln-grip { display: none; }
.ln-item.is-right .ln-rank { background: var(--good); color: var(--surface); }
.ln-item.is-wrong .ln-rank { background: var(--bad); color: var(--surface); }
.ln-item.is-wrong .ln-item-v span { color: var(--bad); }
.ln-hint { margin: 2px 0 0; font-size: 13px; color: var(--muted); }

/* ---------- figures and charts ---------- */
.ln-figs { display: grid; gap: 14px; min-width: 0; }
.ln-fig { margin: 0; min-width: 0; }
.ln-plot .legend, .ln-draw .legend { margin: 0 0 6px; }
.ln-legend[hidden] { display: none; }
.ln-svgbox { position: relative; }
.ln-svgbox svg { display: block; width: 100%; height: auto; overflow: visible; outline: none; touch-action: pan-y; }
.ln-svgbox svg:focus-visible { box-shadow: 0 0 0 2px var(--accent); border-radius: 10px; }
.ln-svgbox .tip { min-width: 190px; }
.ln-cap { margin: 6px 0 0; font-size: 12px; line-height: 1.45; color: var(--muted); }
.ln-cap[hidden] { display: none; }
.ln-reads { display: flex; flex-wrap: wrap; gap: 8px 26px; }
.ln-reads[hidden] { display: none; }
.ln-read { display: grid; gap: 3px; align-content: start; }
.ln-read .label { font-size: 12px; }
.ln-read b { font: 600 24px/1.1 var(--mono); letter-spacing: -0.045em; color: var(--ink); }
.ln-read.sub b { font-size: 18px; color: var(--ink-2); }
.ln-read .pill { justify-self: start; padding: 5px 9px; font-size: 12px; }
.ln-reads:has(.ln-read.on) .ln-read:not(.on) b { color: var(--ink-2); font-size: 20px; }
.ln-read.on b { font-size: 26px; }
.ln-ref { stroke: var(--axis); stroke-width: 1.2; stroke-dasharray: 3 4; }
.ln-ref-t { fill: var(--muted); font: 500 11px var(--font); }
.ln-vline { stroke: var(--ink-2); stroke-width: 1; stroke-dasharray: 2 3; opacity: 0.55; }
.ln-vlab { fill: var(--ink-2); font: 600 11px var(--mono); font-variant-numeric: tabular-nums; }
.ln-mk-t { fill: var(--ink); font: 600 12px var(--mono); }
.ln-faint { opacity: 0.4; }
.bar.ln-on { filter: brightness(1.12); }
.ln-plot .bar.muted { opacity: 0.35; }

/* the seesaw */
.ln-see-ground { stroke: var(--axis); stroke-width: 1.5; }
.ln-see-pivot { fill: var(--track); stroke: var(--axis); stroke-width: 1.2; stroke-linejoin: round; }
.ln-see-beam { stroke: var(--ink-2); stroke-width: 6; stroke-linecap: round; }
.ln-see-hub { fill: var(--surface); stroke: var(--ink-2); stroke-width: 2; }
.ln-see-end rect { fill: var(--surface); stroke-width: 2; }
.ln-see-end.y rect { stroke: var(--accent); }
.ln-see-end.p rect { stroke: var(--bond); }
.ln-see-k { fill: var(--muted); font: 600 9.5px var(--font); text-transform: uppercase; letter-spacing: 0.1em; }
.ln-see-v { fill: var(--ink); font: 600 14px var(--mono); font-variant-numeric: tabular-nums; }

/* ---------- draw ---------- */
.ln-draw { min-width: 0; }
.ln-draw .ln-svgbox svg { touch-action: none; cursor: crosshair; }
.ln-draw.is-locked .ln-svgbox svg { touch-action: pan-y; cursor: default; }
.ln-zone { fill: color-mix(in srgb, var(--accent) 6%, transparent); stroke: color-mix(in srgb, var(--accent) 40%, transparent); stroke-width: 1.2; stroke-dasharray: 4 5; }
.ln-zone-t { fill: var(--accent-ink); font: 600 14px var(--font); pointer-events: none; }
.ln.ln-mine { stroke: var(--ink); stroke-width: 2.8; }
.ln.ln-mine.done { stroke-width: 2; stroke-dasharray: 5 5; opacity: 0.75; }
.ln-cursor { fill: none; stroke: var(--accent); stroke-width: 2.2; }
.ln-reveal { stroke-dasharray: 1; stroke-dashoffset: 1; animation: ln-draw 1.3s ease-out forwards; }
@keyframes ln-draw { to { stroke-dashoffset: 0; } }

/* ---------- controls of a manipulate step ---------- */
.ln-ctls { display: grid; grid-template-columns: repeat(auto-fit, minmax(min(100%, 240px), 1fr)); gap: 12px 28px; padding: 16px 20px; border-radius: 20px; background: var(--surface-2); box-shadow: inset 0 0 0 1px var(--border); }
.ln-ctl { display: grid; gap: 6px; min-width: 0; }
.ln-ctl-h { display: flex; justify-content: space-between; align-items: baseline; gap: 10px; }
.ln-ctl-h output { font: 600 18px var(--mono); letter-spacing: -0.03em; color: var(--ink); }
.ln-ctl-seg, .ln-ctl-toggle { display: flex; flex-wrap: wrap; align-items: center; gap: 8px 12px; }
.ln-ctl .seg { background: var(--track); }

/* ---------- feedback ---------- */
.ln-fbbox { margin-top: 20px; display: grid; gap: 16px; }
.ln-fbbox:empty { display: none; }
.ln-fb { --v: var(--ink); border-radius: 18px; padding: 16px 20px 18px; scroll-margin-bottom: 96px; }
.ln-fb.is-right { --v: var(--good); background: var(--good-soft); }
.ln-fb.is-close { --v: var(--gold-ink); background: color-mix(in srgb, var(--gold) 15%, var(--surface)); }
.ln-fb.is-wrong { --v: var(--bad); background: var(--bad-soft); }
.ln-fb.is-in { animation: ln-in 0.2s ease-out; }
.ln-fb-h { display: flex; align-items: center; gap: 10px; font: 700 19px/1.2 var(--display); letter-spacing: -0.015em; color: var(--v); }
.ln-fb-h svg { flex: none; width: 26px; height: 26px; padding: 4px; border-radius: 50%; background: var(--v); fill: none; stroke: var(--surface); stroke-width: 2.8; stroke-linecap: round; stroke-linejoin: round; }
.ln-fb-pts { margin-left: auto; font: 600 13px var(--mono); color: var(--v); }
.ln-fb p { margin: 8px 0 0; color: var(--ink-2); font-size: 15.5px; line-height: 1.58; text-wrap: pretty; }
.ln-fb p b { color: var(--ink); font-weight: 650; }
.ln-fb-why { color: var(--ink) !important; }
.ln-after { padding: 4px 0 0; }

/* ---------- the action bar: sticks to the bottom of the screen on long steps ---------- */
.ln-actions { position: sticky; bottom: 0; z-index: 4; display: flex; align-items: center; gap: 12px; margin: 0 -28px; padding: 14px 28px; padding-bottom: calc(14px + env(safe-area-inset-bottom, 0px)); background: color-mix(in srgb, var(--surface) 94%, transparent); -webkit-backdrop-filter: blur(12px); backdrop-filter: blur(12px); border-top: 1px solid var(--border); border-radius: 0 0 var(--r) var(--r); }
.ln-actions .btn { padding: 13px 22px; }
.ln-go { margin-left: auto; min-width: 148px; justify-content: center; }
.ln-player .btn:focus-visible, .ln-player .ln-x:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; }
.ln-go:disabled { opacity: 0.45; cursor: default; filter: none; }
.ln-back[hidden] { display: none; }
.ln-need { min-width: 0; font-size: 13px; line-height: 1.3; color: var(--bad); }
.ln-key { font: 500 12px var(--mono); color: var(--muted); white-space: nowrap; }
@media (hover: none) { .ln-key { display: none; } }

/* ---------- the end: score, recap, share ---------- */
.ln-end { display: grid; gap: 14px; }
.ln-end-h { margin: 0; font: 700 clamp(24px, 3vw, 31px)/1.12 var(--display); letter-spacing: -0.035em; color: var(--ink); outline: none; }
.ln-score { display: flex; align-items: baseline; flex-wrap: wrap; gap: 4px 12px; }
.ln-score .big { font-size: clamp(60px, 8vw, 84px); }
.ln-score-of { color: var(--muted); font-weight: 500; }
.ln-score-line, .ln-best { margin: -6px 0 0; color: var(--ink-2); font-variant-numeric: tabular-nums; }
.ln-best { margin: -10px 0 0; font-size: 14px; color: var(--muted); }
.ln-sub { margin: 10px 0 0; font: 600 12px/1.4 var(--font); text-transform: uppercase; letter-spacing: 0.12em; color: var(--muted); }
.ln-recap { margin: 0; padding-left: 20px; display: grid; gap: 8px; color: var(--ink-2); line-height: 1.55; }
.ln-recap li::marker { color: var(--accent); }
.ln-marks { margin: 0; padding: 0; list-style: none; display: grid; gap: 2px; }
.ln-marks button { display: flex; align-items: center; gap: 12px; width: 100%; padding: 8px 10px; border: 0; border-radius: 10px; background: transparent; color: var(--ink); font: 500 15px/1.35 var(--font); text-align: left; cursor: pointer; }
.ln-marks button:hover, .ln-marks button:focus-visible { background: var(--hover); outline: none; }
.ln-marks i { flex: none; width: 10px; height: 10px; border-radius: 50%; background: var(--track); box-shadow: inset 0 0 0 1.5px var(--axis); }
.ln-marks .is-right i { background: var(--good); box-shadow: none; }
.ln-marks .is-close i { background: var(--gold); box-shadow: none; }
.ln-marks .is-wrong i { background: var(--bad); box-shadow: none; }
.ln-share { display: grid; gap: 8px; margin-top: 6px; padding: 16px 18px; border-radius: 18px; background: var(--surface-2); box-shadow: inset 0 0 0 1px var(--border); }
.ln-share-t { margin: 0; color: var(--ink); font-weight: 500; }
.ln-share-row { display: flex; flex-wrap: wrap; gap: 8px; }
.ln-share-url { flex: 1 1 220px; min-width: 0; padding: 11px 16px; border: 1.5px solid var(--border); border-radius: 999px; background: var(--surface); color: var(--ink-2); font: 500 13px var(--mono); }
.ln-share-url:focus { outline: none; border-color: var(--accent); }
.ln-share .btn { padding: 11px 18px; font-size: 14px; }
.ln-again { justify-self: start; }
.ln-qz-lesson { margin: 4px 0 0; color: var(--ink-2); }
.ln-actions.is-summary .ln-key { display: none; }

/* ---------- no JavaScript: the lesson as a list of steps ---------- */
.ln-outline { margin: 0; padding: 0; list-style: none; display: grid; gap: 14px; }
.ln-o-step { padding: 22px 26px; border-radius: var(--r); background: var(--surface); box-shadow: var(--shadow); color: var(--ink-2); }
.ln-o-step h2 { margin: 0 0 8px; font-size: clamp(21px, 2.4vw, 25px); color: var(--ink); }
.ln-o-step p { margin: 0 0 10px; }
.ln-o-kind { margin: 0 0 6px !important; font: 600 12px/1.4 var(--font); text-transform: uppercase; letter-spacing: 0.12em; color: var(--muted); }
.ln-o-opts { margin: 0 0 10px; padding-left: 22px; }
.ln-ans summary { cursor: pointer; font-weight: 600; color: var(--accent-ink); }
.ln-ans[open] summary { margin-bottom: 8px; }
.ln-ans .table-wrap { box-shadow: none; background: var(--surface-2); margin: 0 0 10px; max-width: 320px; }

/* ---------- after the lesson: related pages, method ---------- */
.ln-more { margin-top: 52px; }
.ln-more h2, .ln-method h2 { font-size: clamp(22px, 2.6vw, 28px); }
.ln-rel-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(min(100%, 300px), 1fr)); gap: 12px; }
.ln-rel { display: grid; align-content: start; gap: 4px; padding: 18px 20px; }
.ln-rel-k { font: 600 11px/1.4 var(--font); text-transform: uppercase; letter-spacing: 0.12em; color: var(--muted); }
.ln-rel-t { font-size: 17px; font-weight: 650; line-height: 1.3; color: var(--ink); }
.ln-rel-d { font-size: 14px; line-height: 1.45; color: var(--ink-2); }
.ln-method { margin-top: 40px; }

/* ---------- the hub ---------- */
.ln-cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(min(100%, 340px), 1fr)); gap: 16px; margin-top: 30px; }
.ln-card { display: flex; flex-direction: column; gap: 8px; padding: 22px; }
.ln-card-thumb { display: block; overflow: hidden; margin: 0 0 8px; padding: 16px 0 0; border-radius: 16px; background: var(--surface-2); }
.ln-card-thumb svg { display: block; width: 100%; height: 100px; }
.ln-card-thumb .ln { stroke-width: 2.6; }
.ln-card-thumb .area { opacity: 0.16; }
.ln-card-k { font-size: 12.5px; font-weight: 500; color: var(--muted); font-variant-numeric: tabular-nums; }
.ln-card-t { font: 700 27px/1.08 var(--display); letter-spacing: -0.035em; color: var(--ink); }
.ln-card-d { color: var(--ink-2); font-size: 15px; line-height: 1.5; }
.ln-card-p { margin-top: auto; padding-top: 12px; display: flex; align-items: center; gap: 12px; }
.ln-card-bar { flex: 1; height: 6px; overflow: hidden; border-radius: 3px; background: var(--track); }
.ln-card-bar i { display: block; width: 0; height: 100%; border-radius: 3px; background: var(--accent); }
.ln-card-s { font: 600 13px var(--font); color: var(--accent-ink); white-space: nowrap; }
.ln-card.is-done .ln-card-bar i { background: var(--good); }
.ln-card.is-done .ln-card-s { color: var(--good); }
.ln-how ul { margin: 0; padding: 0; list-style: none; display: grid; grid-template-columns: repeat(auto-fit, minmax(min(100%, 160px), 1fr)); gap: 12px; }
.ln-how li { display: grid; gap: 4px; padding: 18px 20px; border-radius: 20px; background: var(--surface); box-shadow: var(--shadow); }
.ln-how b { font-size: 16px; color: var(--ink); }
.ln-how span { font-size: 14px; line-height: 1.5; color: var(--ink-2); }
.ln-hub-note { margin: -4px 0 14px; color: var(--ink-2); }
.ln-qz-list { margin: 0; padding: 0; list-style: none; display: grid; gap: 8px; }
.ln-qz-list li { display: flex; flex-wrap: wrap; align-items: baseline; justify-content: space-between; gap: 4px 14px; padding: 14px 18px; border-radius: 16px; background: var(--surface); box-shadow: var(--shadow); }
.ln-qz-list a { font-weight: 600; color: var(--ink); text-decoration: none; }
.ln-qz-list a:hover { color: var(--accent-ink); }
.ln-qz-n { font-size: 13px; color: var(--muted); }

/* ---------- a quiz inside an article ---------- */
.learn-quiz { margin-top: 56px; scroll-margin-top: 84px; }
.learn-quiz:empty, .learn-quiz[hidden] { display: none; }
.ln-player.is-quiz { padding: 22px 26px 0; }
.ln-qz-head { margin: 0 0 14px; }
.ln-qz-h { margin: 0; font: 700 clamp(22px, 2.6vw, 28px)/1.1 var(--display); letter-spacing: -0.03em; color: var(--ink); }
.ln-qz-sub { margin: 4px 0 0; font-size: 14px; color: var(--muted); }
.is-quiz .ln-stage { min-height: 0; padding: 20px 0 20px; }
.is-quiz .ln-actions { position: static; margin: 0 -26px; padding: 14px 26px; }
.is-quiz .ln-kind { display: none; }

/* ---------- phones ---------- */
@media (max-width: 640px) {
  .ln-intro { padding-top: 30px; }
  .ln-player, .ln-player.is-quiz { padding: 14px 16px 0; border-radius: 22px; }
  .ln-actions, .is-quiz .ln-actions { margin: 0 -16px; padding: 12px 16px; padding-bottom: calc(12px + env(safe-area-inset-bottom, 0px)); border-radius: 0 0 22px 22px; gap: 8px; }
  .ln-actions .btn { padding: 13px 16px; }
  .ln-go { min-width: 0; flex: 1 1 auto; }
  .ln-need { position: absolute; left: 16px; right: 16px; bottom: calc(100% + 6px); padding: 8px 12px; border-radius: 12px; background: var(--surface); box-shadow: var(--shadow-lg); }
  .ln-need:empty { display: none; }
  .ln-top { gap: 10px; }
  .ln-stage { padding: 18px 0 18px; min-height: 260px; }
  .ln-title { font-size: 24px; }
  .ln-text, .ln-q-text { font-size: 16px; }
  .ln-text.ln-title { font-size: 17.5px; }
  .ln-pred { padding: 14px 16px 8px; }
  .ln-ctls { padding: 14px 16px; }
  .ln-opt { gap: 12px; padding: 12px 13px; font-size: 15.5px; }
  .ln-item { grid-template-columns: 28px minmax(0, 1fr) 34px; gap: 10px; padding: 10px 4px 10px 10px; }
  .ln-item .ln-item-v { grid-column: 2 / -1; justify-items: start; text-align: left; display: flex; flex-wrap: wrap; gap: 2px 10px; align-items: baseline; }
  .ln-order-box.is-locked .ln-item { grid-template-columns: 28px minmax(0, 1fr); }
  .ln-rank { width: 28px; height: 28px; }
  .ln-fb { padding: 14px 16px 16px; }
  .ln-fb-h { font-size: 17.5px; }
  .ln-fb p { font-size: 15px; }
  .ln-read b { font-size: 21px; }
  .ln-read.on b { font-size: 22px; }
  .ln-reads { gap: 8px 18px; }
  .ln-o-step { padding: 18px; }
}

@media (prefers-reduced-motion: reduce) {
  .ln-step.ln-in, .ln-gain.on, .ln-fb.is-in { animation: none; }
  .ln-reveal { animation: none; stroke-dashoffset: 0; }
  .ln-bar i, .ln-opt, .ln-letter, .ln-range::-webkit-slider-thumb { transition: none; }
}