/* ASIC Point components. Colours, type, spacing and motion come from assets/v3/tokens.css;
   nothing here names a raw colour, so every component works in every theme.

   The look borrows from the bench, not from software: a drawing title block for page and
   lesson metadata, a transit strip map for the lesson rail, an instrument case with softkeys
   and a graticule screen for runnable code, oscilloscope channel colours for the four tracks,
   and a printed timetable for the problem list. docs/ui-direction.md explains each device. */

/* ---------- base ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0; background: var(--paper); color: var(--ink);
  font: 400 var(--fs-base)/var(--lh-body) var(--sans);
  font-variant-numeric: lining-nums;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--link); text-underline-offset: 3px; text-decoration-thickness: 1px; }
a:hover { text-decoration-thickness: 2px; }
[data-theme="contrast"] a { text-decoration-thickness: 2px; }
code, kbd, pre, samp { font-family: var(--mono); }
:not(pre) > code { font-size: .9em; background: var(--paper-2); border: var(--bw) solid var(--rule); border-radius: var(--r-chip); padding: .02em .32em; overflow-wrap: break-word; }
:focus-visible { outline: var(--focus-w) solid var(--focus); outline-offset: 2px; border-radius: 2px; }
.skip { position: absolute; left: -999px; top: 8px; background: var(--ink); color: var(--paper); padding: 8px 12px; z-index: 30; }
.skip:focus { left: 8px; }
h1, h2, h3 { line-height: var(--lh-head); margin: 0; text-wrap: balance; }
h1, h2 { font-family: var(--display); font-stretch: var(--display-stretch); font-weight: 760; letter-spacing: -.01em; word-spacing: .06em; }
/* A small legend above content: wide Archivo, like a printed front-panel label. */
.eyebrow { font: 600 var(--fs-xs)/1.4 var(--display); font-stretch: var(--legend-stretch); letter-spacing: .02em; color: var(--muted); margin: 0 0 var(--s2); }
.visually-hidden { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.num, .pid, time { font-variant-numeric: tabular-nums; }

/* ---------- header ---------- */
.site-header { position: relative; z-index: 20; display: flex; align-items: center; gap: var(--s5); padding: 12px var(--gutter); border-bottom: var(--bw) solid var(--rule-strong); background: var(--paper); }
.brand { display: inline-flex; align-items: center; gap: 10px; text-decoration: none; color: var(--ink); }
.brand-name { font: 620 19px/1 var(--display); font-stretch: var(--legend-stretch); letter-spacing: .01em; }
/* The mark: a chip in the accent colour, pins in the muted ink, the pulse in on-accent. */
.brand-mark { display: block; width: 34px; height: 34px; margin: -6px 0; flex: none; overflow: visible; }
.brand-mark .bm-hi { stop-color: color-mix(in srgb, #fff 24%, var(--accent)); } .brand-mark .bm-mid { stop-color: var(--accent); } .brand-mark .bm-lo { stop-color: color-mix(in srgb, #000 22%, var(--accent)); }
.brand-mark .bm-pin-hi { stop-color: color-mix(in srgb, var(--muted) 45%, #fff); } .brand-mark .bm-pin-lo { stop-color: var(--muted); }
.brand-mark .bm-body { stroke: color-mix(in srgb, var(--accent) 70%, #000); stroke-width: 1; }
.brand-mark .bm-gloss { opacity: .55; }
.brand-mark .bm-glyph path { fill: none; stroke: var(--on-accent); stroke-width: 2.6; stroke-linejoin: round; stroke-linecap: round; }
.brand-mark .brand-point { fill: var(--on-accent); stroke: none; }
[data-theme="contrast"] .brand-mark .bm-gloss { display: none; }
.site-nav { display: flex; gap: 2px; margin-left: auto; }
.site-nav a { font: 600 var(--fs-sm)/1 var(--sans); color: var(--ink-2); text-decoration: none; padding: 12px 12px; border-radius: var(--r-ctl); }
.site-nav a:hover { background: var(--paper-2); color: var(--ink); }
.site-nav a[aria-current="page"] { color: var(--ink); box-shadow: inset 0 -3px 0 var(--accent); border-radius: 0; }

/* Theme picker: each option is drawn in its own theme. */
.theme-picker { position: relative; }
.theme-button { display: inline-flex; align-items: center; gap: 8px; min-height: 44px; padding: 0 12px 0 8px; border: var(--bw) solid var(--rule-strong); border-radius: var(--r-ctl); background: transparent; color: var(--ink); font: 600 var(--fs-sm)/1 var(--sans); cursor: pointer; }
.theme-button:hover { background: var(--paper-2); }
.theme-chip { display: inline-grid; grid-template-columns: repeat(3, 8px); height: 22px; border: var(--bw) solid var(--rule-strong); border-radius: var(--r-chip); overflow: hidden; }
.theme-chip i { display: block; }
.theme-chip i:nth-child(1) { background: var(--paper); } .theme-chip i:nth-child(2) { background: var(--accent); } .theme-chip i:nth-child(3) { background: var(--wave-signal); }
.theme-menu { position: absolute; right: 0; top: calc(100% + 8px); width: min(340px, calc(100vw - 32px)); padding: 8px; border: var(--bw) solid var(--rule-strong); border-radius: var(--r-case); background: var(--card); box-shadow: var(--shadow-pop); display: grid; gap: 6px; }
.theme-menu-title { margin: 4px 6px 4px; font: 600 var(--fs-xs)/1.3 var(--display); font-stretch: var(--legend-stretch); color: var(--muted); }
.theme-option { display: grid; grid-template-columns: 64px minmax(0, 1fr); align-items: center; gap: 12px; width: 100%; padding: 8px 10px; border: var(--bw) solid var(--rule); border-radius: var(--r-ctl); background: var(--paper); color: var(--ink); text-align: left; cursor: pointer; font: inherit; }
.theme-option:hover { border-color: var(--rule-strong); }
.theme-option[aria-pressed="true"] { border-color: var(--accent); box-shadow: inset 4px 0 0 var(--accent); }
.theme-sample { display: block; height: 32px; border-radius: var(--r-chip); background: var(--screen); padding: 4px; }
.theme-sample svg { display: block; width: 100%; height: 100%; }
.theme-sample-bus { fill: none; stroke: var(--wave-x); stroke-width: 1.6; }
.theme-sample-bit { fill: none; stroke: var(--wave-signal); stroke-width: 1.8; }
.theme-option-text strong { display: block; font: 620 15px/1.2 var(--display); font-stretch: var(--display-stretch); }
.theme-option-text small { display: block; font-size: 12.5px; line-height: 1.35; color: var(--muted); }

/* ---------- footer: a drawing title block ---------- */
.site-footer { margin-top: var(--s9); padding: 0 var(--gutter) var(--s7); }
.title-block { display: grid; grid-template-columns: minmax(180px, auto) minmax(0, 1.4fr) minmax(0, 2fr); border: var(--bw-strong) solid var(--ink); }
.title-block > * { margin: 0; padding: 14px 16px; min-width: 0; }
.title-block > * + * { border-left: var(--bw) solid var(--ink); }
.title-block-brand { display: flex; align-items: center; gap: 10px; color: var(--ink); }
.title-block-note { color: var(--ink-2); font-size: var(--fs-sm); }
.title-block nav { display: flex; flex-wrap: wrap; gap: 6px 18px; align-content: center; font-size: var(--fs-sm); }

/* ---------- buttons ---------- */
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 10px; min-height: 46px; padding: 0 20px; border-radius: var(--r-ctl);
  font: 700 15px/1 var(--sans); text-decoration: none; cursor: pointer; border: var(--bw) solid transparent; }
.btn-primary { background: var(--accent); color: var(--on-accent); }
.btn-primary:hover { filter: brightness(1.08); }
.btn-ghost { background: transparent; color: var(--ink); border-color: var(--rule-strong); }
.btn-ghost:hover { background: var(--paper-2); }
.btn[disabled] { opacity: .55; cursor: progress; }
.btn svg { width: 16px; height: 16px; }
[data-theme="contrast"] .btn { border-width: 2px; }

/* ---------- instrument: case, screen, softkeys ---------- */
.instrument { background: var(--case); color: var(--case-ink); border: var(--bw) solid var(--case-2); border-radius: var(--r-case); box-shadow: var(--shadow-case); padding: 18px; position: relative; }
.instrument-head { display: flex; align-items: baseline; flex-wrap: wrap; gap: 6px 14px; margin: 0 4px 12px; }
.instrument-id { font: 650 22px/1 var(--display); font-stretch: var(--legend-stretch); letter-spacing: .02em; white-space: nowrap; }
.instrument-name { font: 600 var(--fs-xs)/1.3 var(--display); font-stretch: var(--legend-stretch); color: var(--case-ink); }
.screen { background: var(--screen); color: var(--screen-ink); border-radius: var(--r-ctl); border: var(--bw) solid var(--screen-rule); overflow: hidden; }
.screen-bar { display: flex; align-items: center; gap: 12px; padding: 9px 14px; border-bottom: var(--bw) solid var(--screen-rule); font: 500 12.5px/1.3 var(--mono); color: var(--screen-muted); }
.screen-bar .grow { flex: 1; }
.led { width: 9px; height: 9px; border-radius: 50%; background: var(--screen-muted); display: inline-block; flex: none; }
.led.on { background: var(--ok); box-shadow: 0 0 8px var(--ok); }
.led.busy { background: var(--busy); box-shadow: 0 0 8px var(--busy); }
.led.err { background: var(--hot); box-shadow: 0 0 8px var(--hot); }
.controls { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; margin-top: 14px; }
.select { min-height: 44px; border-radius: var(--r-ctl); border: var(--bw) solid var(--case-2); background: var(--card); color: var(--ink); font: 500 var(--fs-sm)/1 var(--sans); padding: 0 12px; }

/* ---------- code ---------- */
pre.code { margin: 0; padding: 16px 18px; background: var(--screen); color: var(--screen-ink); border: var(--bw) solid var(--screen-rule); border-radius: var(--r-ctl); overflow-x: auto; font-size: 14px; line-height: 1.6; tab-size: 2; }
.code .k, .editor .k { color: var(--syn-kw); } .code .s, .editor .s { color: var(--syn-str); } .code .c, .editor .c { color: var(--syn-com); font-style: italic; }
.code .n, .editor .n { color: var(--syn-num); } .code .f, .editor .f { color: var(--syn-sys); } .code .m, .editor .m { color: var(--syn-mac); }

/* ---------- editor (playground and examples) ---------- */
.editor { position: relative; display: grid; grid-template-columns: auto 1fr; font: 14px/1.6 var(--mono); background: var(--screen); }
.editor-lines { padding: 14px 10px 14px 14px; color: var(--screen-muted); text-align: right; user-select: none; white-space: pre; border-right: var(--bw) solid var(--screen-rule); }
.editor-area { position: relative; min-height: 220px; min-width: 0; }
.editor-area pre, .editor-area textarea { margin: 0; padding: 14px 16px; font: inherit; white-space: pre; tab-size: 2; overflow: auto; }
.editor-area pre { position: absolute; inset: 0; pointer-events: none; color: var(--screen-ink); }
.editor-area textarea { position: relative; width: 100%; height: 100%; min-height: inherit; resize: vertical; border: 0; outline: none; background: transparent; color: transparent; caret-color: var(--screen-ink); }
.editor-area textarea::selection { background: color-mix(in srgb, var(--syn-kw) 30%, transparent); color: transparent; }
.editor-area:focus-within { box-shadow: inset 0 0 0 2px var(--focus); }
.output { margin: 0; padding: 12px 16px; min-height: 64px; max-height: 260px; overflow: auto; font: 13.5px/1.6 var(--mono); white-space: pre-wrap; color: var(--screen-ink); border-top: var(--bw) solid var(--screen-rule); background: var(--screen-2); }
.output .err { color: var(--hot); } .output .ok { color: var(--ok); } .output .dim { color: var(--screen-muted); } .output .note { color: var(--busy); }
.linklike { border: 0; background: none; padding: 0; font: inherit; color: inherit; text-decoration: underline; cursor: pointer; }

/* ---------- build-time waveform figures (tools/templates/v3/trace-svg.mjs) ---------- */
.figure { margin: 28px 0; }
.figure-title { font: 620 var(--fs-sm)/1.4 var(--display); font-stretch: var(--display-stretch); color: var(--ink-2); margin-bottom: 8px; }
.figure-caption { font-size: 15px; color: var(--muted); margin: 8px 0 0; }
.trace-scroll { overflow-x: auto; background: var(--wave-bg); border: var(--bw) solid var(--screen-rule); border-radius: var(--r-ctl); padding: 8px 6px 2px; }
.trace-svg { display: block; max-width: none; }
.tr-grid { stroke: var(--wave-grid); stroke-width: 1; }
.tr-cycle { fill: var(--wave-muted); font: 10.5px var(--mono); }
.tr-name { fill: var(--wave-text); font: 12.5px var(--mono); }
.tr-bit { stroke: var(--wave-signal); stroke-width: 2; fill: none; }
.tr-z { stroke: var(--wave-z); stroke-width: 2; stroke-dasharray: 5 4; }
.tr-x { stroke: var(--wave-x); stroke-width: 1; }
.tr-x-bg { fill: var(--wave-x-bg); } .tr-x-ln { stroke: var(--wave-x); stroke-width: 1.3; opacity: .6; }
.tr-bus { fill: var(--wave-bus-fill); stroke: var(--wave-signal); stroke-width: 1.5; }
.tr-bus.x { stroke: var(--wave-x); } .tr-bus.z { stroke: var(--wave-z); }
.tr-val { fill: var(--wave-text); font: 12px var(--mono); }
.tr-val.x { fill: var(--wave-x); font-weight: 600; } .tr-val.z { fill: var(--wave-z); font-weight: 600; }
.tr-tag { fill: var(--wave-bg); }
.tr-mark { stroke: var(--wave-cursor); stroke-width: 1.4; stroke-dasharray: 4 3; }
.tr-mark-label { fill: var(--wave-cursor); font: 600 11px var(--mono); }

/* ---------- tables, compare, notes, steps ---------- */
.table-scroll { overflow-x: auto; }
table { border-collapse: collapse; width: 100%; font-size: 15.5px; font-variant-numeric: tabular-nums; }
th, td { text-align: left; padding: 9px 12px; border-bottom: var(--bw) solid var(--rule); vertical-align: top; }
thead th { font: 620 var(--fs-xs)/1.3 var(--display); font-stretch: var(--legend-stretch); color: var(--muted); border-bottom: var(--bw-strong) solid var(--ink); }
.compare { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 16px; }
.compare-side { border-top: 3px solid var(--rule-strong); padding-top: 10px; min-width: 0; }
.compare-side.bad { border-top-color: var(--bad); } .compare-side.good { border-top-color: var(--good); }
.compare-title { font: 700 var(--fs-sm)/1.4 var(--sans); margin: 0 0 8px; }
.compare-side.bad .compare-title { color: var(--bad); } .compare-side.good .compare-title { color: var(--good); }
.compare-verdict { font-size: 15px; color: var(--ink-2); margin: 8px 0 0; }
.compare .figure-caption { grid-column: 1 / -1; }
.note { margin: 24px 0; padding: 14px 18px; border-left: 3px solid var(--accent); background: var(--card); }
.note.simulator { border-left-style: dashed; border-left-color: var(--rule-strong); }
.note.warning { border-left-color: var(--bad); }
.note-label { font: 620 var(--fs-xs)/1.3 var(--display); font-stretch: var(--legend-stretch); color: var(--muted); margin: 0 0 4px; }
.note p:last-child { margin-bottom: 0; }
/* Steps: numbered callout balloons, as on a service-manual figure. */
.steps { counter-reset: step; list-style: none; padding: 0; margin: 24px 0; display: grid; gap: 14px; }
.steps > li { counter-increment: step; position: relative; padding-left: 46px; min-width: 0; overflow-wrap: anywhere; }
.steps > li::before { content: counter(step); position: absolute; left: 0; top: 0; width: 30px; height: 30px; border-radius: 50%; border: var(--bw-strong) solid var(--ink); display: grid; place-items: center; font: 620 14px var(--display); }
.step-title { font-weight: 700; margin: 2px 0 4px; }
.step-values { width: auto; margin-top: 6px; font-size: 14px; }
.step-values th { font: 500 14px var(--sans); color: var(--muted); }
.list { padding-left: 1.2em; }

/* ---------- playground ---------- */
.playground .editor-area { min-height: 300px; }
.playground.full .editor-area { min-height: 46vh; }
.pg-templates { display: flex; flex-wrap: wrap; gap: 6px; }
.pg-template { min-height: 36px; padding: 0 12px; border-radius: var(--r-pill); border: var(--bw) solid var(--case-2); background: var(--card); color: var(--ink); font: 600 13px var(--sans); cursor: pointer; }
.pg-template[aria-pressed="true"] { background: var(--ink); color: var(--paper); border-color: var(--ink); }
.pg-status { font: 500 12.5px var(--mono); color: var(--case-ink); }
.pg-tabs { display: flex; gap: 2px; padding: 6px 8px 0; border-top: var(--bw) solid var(--screen-rule); background: var(--screen-2); }
.pg-tab { min-height: 34px; padding: 0 12px; border: 0; border-radius: var(--r-ctl) var(--r-ctl) 0 0; background: transparent; color: var(--screen-muted); font: 600 13px var(--sans); cursor: pointer; }
.pg-tab[aria-selected="true"] { background: var(--screen); color: var(--screen-ink); box-shadow: inset 0 2px 0 var(--accent); }
.pg-tab[disabled] { opacity: .45; cursor: default; }
.screen-bar .pg-state { flex: 1 1 auto; min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.screen-bar .pg-file { flex: none; }
.pg-engine { flex: 1 1 220px; min-width: 0; max-width: 100%; }
.pg-actions { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 10px; }
.pg-actions .btn { min-height: 40px; padding: 0 14px; font-size: 14px; background: var(--card); }
.pg-actions .btn[disabled] { cursor: not-allowed; }
.pg-notice { margin-top: 12px; padding: 10px 14px; border: var(--bw) solid var(--case-2); border-left: 3px solid var(--accent); border-radius: var(--r-ctl); background: var(--card); color: var(--ink); font-size: 15px; }
.pg-notice p { margin: 0; }
.pg-notice-actions { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 8px; }
.pg-notice-actions .btn { min-height: 36px; padding: 0 12px; font-size: 14px; }
.pg-link { display: block; width: 100%; margin-top: 8px; min-height: 40px; padding: 0 10px; font: 13px var(--mono); border: var(--bw) solid var(--rule-strong); border-radius: var(--r-ctl); background: var(--paper); color: var(--ink); }
.pg-start { margin: 16px 4px 8px; color: var(--case-ink); }
.page-pad { padding: 0 var(--gutter); }

/* ---------- page heads (catalog, playground, 404) ---------- */
.learn-head { padding: clamp(32px, 5vw, 64px) var(--gutter) var(--s2); }
.learn-head h1 { font-size: var(--fs-3xl); line-height: var(--lh-tight); }
.learn-head p { font-size: var(--fs-md); color: var(--ink-2); max-width: 60ch; }

/* ---------- lesson ---------- */
.lesson-layout { --track: var(--accent); display: grid; grid-template-columns: 250px minmax(0, 1fr) 210px; gap: clamp(20px, 3vw, 44px); padding: 32px var(--gutter) 0; align-items: start; }
[data-track="sv"] { --track: var(--ch-sv); } [data-track="sva"] { --track: var(--ch-sva); }
[data-track="coverage"] { --track: var(--ch-cov); } [data-track="uvm"] { --track: var(--ch-uvm); }
.lesson-rail { position: sticky; top: 16px; font-size: 14.5px; }
.rail-module { font: 650 21px/1.1 var(--display); font-stretch: var(--display-stretch); margin: 4px 0 14px; }
/* The rail is a strip map: the module is a line, each lesson a station on it. */
.rail-list { list-style: none; padding: 0; margin: 0; }
.rail-list li { position: relative; }
.rail-list li::before { content: ''; position: absolute; left: 7px; top: 0; bottom: 0; width: 4px; background: var(--track); }
.rail-list li:first-child::before { top: 16px; }
.rail-list li:last-child::before { bottom: calc(100% - 16px); }
.rail-list li:only-child::before { display: none; }
.rail-list a { position: relative; display: block; padding: 6px 0 8px 30px; color: var(--ink-2); text-decoration: none; line-height: 1.35; }
.rail-list a::before { content: ''; position: absolute; left: 2px; top: 8px; width: 14px; height: 14px; border-radius: 50%; background: var(--paper); border: 3px solid var(--track); }
.rail-list a:hover { color: var(--ink); text-decoration: underline; }
.rail-list a[aria-current="page"] { color: var(--ink); font-weight: 700; }
.rail-list a[aria-current="page"]::before { left: -2px; top: 4px; width: 22px; height: 22px; border-width: 4px; background: var(--paper); box-shadow: inset 0 0 0 3px var(--paper), inset 0 0 0 9px var(--track); }
.rail-list .num { display: block; font: 600 12px var(--mono); color: var(--muted); }
.rail-all { margin-top: 18px; font-size: var(--fs-sm); }
.lesson-main { min-width: 0; max-width: var(--measure); }
.lesson-head h1 { font-size: var(--fs-3xl); line-height: var(--lh-tight); margin-top: 2px; }
.lesson-lead { font-size: 20px; color: var(--ink-2); margin: 16px 0 10px; }
/* Lesson metadata as a drawing title block: labelled cells in a ruled grid. */
.spec-block { display: grid; grid-template-columns: repeat(auto-fit, minmax(120px, 1fr)); margin: 20px 0 8px; border: var(--bw-strong) solid var(--ink); }
.spec-block > div { padding: 7px 12px 8px; border-right: var(--bw) solid var(--ink); min-width: 0; margin-right: -1px; }
.spec-block dt { font: 600 11.5px/1.3 var(--display); font-stretch: var(--legend-stretch); color: var(--muted); }
.spec-block dd { margin: 2px 0 0; font: 700 15px/1.3 var(--sans); }
.spec-block .spec-id dd { font: 650 19px/1.2 var(--display); font-stretch: var(--display-stretch); color: var(--track); }
.prose > p, .prose li { max-width: var(--measure); }
.prose h2 { font-size: var(--fs-2xl); line-height: 1.05; margin: 56px 0 14px; padding-top: 14px; border-top: var(--bw) solid var(--rule); }
.prose h3 { font: 700 20px/1.3 var(--sans); margin: 30px 0 8px; }
.hook { font-size: 18.5px; }
.lesson-toc { position: sticky; top: 16px; font-size: 14px; border-left: var(--bw) solid var(--rule); padding-left: 14px; }
.lesson-toc a { display: block; color: var(--muted); text-decoration: none; padding: 5px 0; }
.lesson-toc a:hover { color: var(--ink); text-decoration: underline; }
.example { margin: 30px 0; }
.keypoints { margin: 40px 0; padding: 20px 22px; border: var(--bw-strong) solid var(--ink); border-radius: 0; background: var(--card); }
.keypoints h2 { margin-top: 0 !important; padding-top: 0 !important; border-top: 0 !important; font-size: var(--fs-xl) !important; }
.keypoints ul { margin: 8px 0 0; padding-left: 1.2em; }
.keypoints li { margin: 6px 0; }
.lesson-nav { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin: 48px 0 0; }
.lesson-nav a { display: block; padding: 14px 16px; border: var(--bw) solid var(--rule-strong); border-radius: var(--r-ctl); text-decoration: none; color: var(--ink); font-weight: 600; }
.lesson-nav a:hover { background: var(--card); border-color: var(--ink); }
.lesson-nav .dir { display: block; font: 600 var(--fs-xs) var(--display); font-stretch: var(--legend-stretch); color: var(--muted); }
.lesson-nav .next { text-align: right; }

/* ---------- quiz ---------- */
.quiz { display: grid; gap: 20px; margin: 18px 0; }
.quiz-item { border: var(--bw) solid var(--rule-strong); border-radius: var(--r-ctl); padding: 18px 20px; background: var(--card); min-width: 0; margin: 0; }
/* Floating the legend keeps it inside the box instead of on the fieldset's border line. */
.quiz-item legend { float: left; width: 100%; font-weight: 700; padding: 0; margin: 0 0 12px; }
.quiz-item legend + * { clear: both; }
.quiz-item > .figure { margin-top: 4px; }
.quiz-prompt { font-weight: 700; margin-bottom: 10px; }
.quiz-type { font: 620 var(--fs-xs) var(--display); font-stretch: var(--legend-stretch); color: var(--accent); display: block; margin-bottom: 4px; }
.quiz-options { display: grid; grid-template-columns: minmax(0, 1fr); gap: 8px; }
.quiz-option { display: flex; min-width: 0; gap: 12px; align-items: flex-start; padding: 10px 12px; border: var(--bw) solid var(--rule); border-radius: var(--r-ctl); cursor: pointer; background: var(--paper); }
.quiz-option:hover { border-color: var(--rule-strong); }
.quiz-option input { margin-top: 4px; accent-color: var(--accent); width: 18px; height: 18px; flex: none; }
.quiz-option > span { min-width: 0; }
/* Options often differ only at the end of a line: wrap rather than hide it behind a scroll. */
.quiz-option pre.code { flex: 1; min-width: 0; font-size: 13px; padding: 10px 12px; white-space: pre-wrap; overflow-wrap: break-word; }
.quiz-option.correct { border-color: var(--good); background: var(--good-soft); box-shadow: inset 4px 0 0 var(--good); }
.quiz-option.wrong { border-color: var(--bad); background: var(--bad-soft); box-shadow: inset 4px 0 0 var(--bad); }
.quiz-predict { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; }
.quiz-predict input { flex: 1 1 260px; min-height: 44px; font: 15px var(--mono); padding: 0 12px; border: var(--bw) solid var(--rule-strong); border-radius: var(--r-ctl); background: var(--paper); color: var(--ink); }
.quiz-feedback { margin: 12px 0 0; padding: 10px 12px; border-radius: var(--r-ctl); font-size: 15.5px; }
.quiz-feedback.right { background: var(--good-soft); border-left: 4px solid var(--good); }
.quiz-feedback.wrong { background: var(--bad-soft); border-left: 4px solid var(--bad); }
.quiz-actions { display: flex; align-items: center; gap: 14px; }
.quiz-score { font: 600 14px var(--mono); color: var(--muted); }

/* ---------- labels ---------- */
.badge { font: 600 11.5px/1.2 var(--sans); padding: 2px 7px; border-radius: var(--r-chip); border: var(--bw) solid var(--rule-strong); color: var(--muted); margin-left: 6px; white-space: nowrap; }

/* ---------- problem catalog: a printed timetable ---------- */
.section { padding: var(--s6) var(--gutter) 0; }
.filters { display: grid; grid-template-columns: minmax(200px, 2fr) repeat(4, minmax(140px, 1fr)); gap: 12px; align-items: end; padding: 16px 0 18px; border-top: var(--bw-strong) solid var(--ink); position: sticky; top: 0; background: var(--paper); z-index: 2; }
/* Stuck to the top while scrolling, the bar's backdrop runs to both window edges with a hairline
   under it, so nothing scrolls past in the gutters beside it (catalog.mjs sets .is-stuck). The
   border-image and shadow are ink overflow: no horizontal scroll. */
.filters.is-stuck { border-image: conic-gradient(var(--paper) 0 0) fill 0 / 0 / 0 100vmax; box-shadow: 0 1px 0 100vmax var(--rule); clip-path: inset(0 -100vmax -1px); }
.filters label { min-width: 0; display: grid; gap: 4px; font: 600 var(--fs-xs) var(--display); font-stretch: var(--legend-stretch); color: var(--muted); }
.filters input, .filters select { width: 100%; min-width: 0; min-height: 44px; padding: 0 12px; border: var(--bw) solid var(--rule-strong); border-radius: var(--r-ctl); background: var(--card); color: var(--ink); font: 400 15px var(--sans); }
.filter-count { grid-column: 1 / -1; margin: 0; font: 600 13px var(--mono); color: var(--muted); }
.problem-group { margin: 30px 0 0; }
.problem-group h3 { display: flex; align-items: center; gap: 12px; font: 650 var(--fs-lg)/1.1 var(--display); font-stretch: var(--display-stretch); padding-bottom: 10px; border-bottom: var(--bw-strong) solid var(--ink); }
.problem-rows { list-style: none; margin: 0; padding: 0; }
.problem-row { display: grid; grid-template-columns: 70px minmax(0, 1fr) 84px 96px 84px 82px; gap: 8px 14px; align-items: center; padding: 9px 0; border-bottom: var(--bw) solid var(--rule); }
.problem-row:nth-child(3n) { border-bottom-color: var(--rule-strong); }
.problem-row a { color: var(--ink); text-decoration: none; font-weight: 600; }
.problem-row a:hover { color: var(--link); text-decoration: underline; }
.pid { font: 600 13px var(--mono); color: var(--muted); }
.chip { font: 600 12.5px/1.2 var(--sans); color: var(--ink-2); white-space: nowrap; }
.chip.engine { font-family: var(--mono); font-weight: 500; font-size: 12px; color: var(--muted); }
/* Difficulty: a four-step level meter beside the word. */
.chip.diff { --lvl: 0; display: inline-flex; align-items: center; gap: 7px; }
.chip.diff::before { content: ''; width: 27px; height: 8px; flex: none;
  background: linear-gradient(90deg, currentColor calc(var(--lvl) * 7px), color-mix(in srgb, currentColor 22%, transparent) 0);
  -webkit-mask: repeating-linear-gradient(90deg, #000 0 5px, transparent 5px 7px); mask: repeating-linear-gradient(90deg, #000 0 5px, transparent 5px 7px); }
.chip.diff.easy { --lvl: 1; color: var(--good); } .chip.diff.medium { --lvl: 2; color: var(--warn); }
.chip.diff.hard { --lvl: 3; color: var(--bad); } .chip.diff.expert { --lvl: 4; color: var(--ink); }
.chip.diff.unrated { color: var(--muted); }
.problem-row .badge { margin-left: 0; justify-self: start; }
.empty { color: var(--muted); padding: 20px 0; }

/* ---------- responsive and motion ---------- */
@media (max-width: 1180px) { .lesson-layout { grid-template-columns: 220px minmax(0, 1fr); } .lesson-toc { display: none; } }
@media (max-width: 900px) {
  .lesson-layout { grid-template-columns: 1fr; }
  /* Phones: the reading column first; the module's strip map follows the lesson. */
  .lesson-rail { position: static; order: 2; padding-top: var(--s5); border-top: var(--bw-strong) solid var(--ink); }
  .site-header { flex-wrap: wrap; gap: 10px; padding-block: 10px 0; }
  .site-nav { order: 3; width: calc(100% + 2 * var(--gutter)); margin: 0 calc(-1 * var(--gutter)); padding: 0 calc(var(--gutter) - 12px); overflow-x: auto; border-top: var(--bw) solid var(--rule); }
  .theme-picker { margin-left: auto; }
  .filters { grid-template-columns: 1fr 1fr; position: static; }
  /* Title on the first line, the labels together on one wrapped line under it. */
  .problem-row { position: relative; display: flex; flex-wrap: wrap; gap: 6px 16px; padding-left: 64px; }
  .problem-row .pid { position: absolute; left: 0; top: 11px; }
  .problem-row a { flex: 1 1 100%; min-width: 0; }
  .title-block { grid-template-columns: 1fr; }
  .title-block > * + * { border-left: 0; border-top: var(--bw) solid var(--ink); }
}
@media (max-width: 520px) {
  body { font-size: 16px; }
  .lesson-nav { grid-template-columns: 1fr; }
  .instrument { padding: 12px; }
  .theme-button-text { display: none; }
  .theme-button { padding: 0 10px; }
  .spec-block { grid-template-columns: 1fr 1fr; }
  .spec-block > div { border-bottom: var(--bw) solid var(--ink); margin-bottom: -1px; }
}
@media (prefers-reduced-motion: reduce) { * { transition: none !important; animation: none !important; scroll-behavior: auto !important; } }
@media (forced-colors: active) { .brand-mark, .theme-chip, .led { forced-color-adjust: none; } }