/*  Learning to Fly from the Beginning — design system
    ---------------------------------------------------
    Warm paper, Fraunces display, Source Serif body and JetBrains Mono for
    numbers, as in the other Curionode courses; this course adds the
    simulator — a view out of the window, an instrument panel, a lesson card
    and a debrief — so its furniture is styled here once.

    Colours are tokens. The dark values are written twice: once for a reader
    whose system asks for dark (no script, so no flash of light page) and once
    for an explicit choice; tools/build.py fails if the two copies drift.
*/
@import url('../vendor/fonts/fonts.css');

:root {
    --paper: #fbf8f3;  --paper-deep: #f4ede0;  --paper-rule: #e3dac6;
    --ink: #1c1c1f;  --ink-soft: #3a3a3f;  --ink-mute: #6e6e74;  --ink-faint: #9a958b;
    --red: #b8312f;  --red-tint: #f5e7e3;
    --blue: #1d4ed8;  --blue-tint: #e6ecf6;
    --teal: #0f6e6a;  --teal-tint: #e1eeec;
    --plum: #5a3a7a;  --plum-tint: #ece2f0;
    --ochre: #b3791f;  --ochre-tint: #f4e6c8;
    --green: #2d6a4f;  --green-tint: #e0ede4;
    --sienna: #a8530c;
    --input: #fffefb;
    --fig-paper: #fffdf7;  --fig-grid: #cfc6b0;  --fig-rule: #e3dac6;
    --fig-ink: #1c1c1f;  --fig-muted: #6e6e74;  --fig-faint: #9a958b;
    --fig-blue: #1d4ed8;  --fig-red: #b8312f;  --fig-green: #2d6a4f;  --fig-teal: #0f6e6a;
    --fig-plum: #5a3a7a;  --fig-ochre: #b3791f;  --fig-sienna: #a8530c;
    --fig-dial: #1d1d21;  --fig-dialink: #f3efe4;  --fig-panel: #34343a;  --fig-sky: #4a86c5;  --fig-earth: #8a5a2e;
    --shadow: 0 2px 6px rgba(28, 28, 31, 0.06);
    --font-display: 'Fraunces', 'Iowan Old Style', Georgia, serif;
    --font-body: 'Source Serif 4', 'Iowan Old Style', Georgia, serif;
    --font-mono: 'JetBrains Mono', ui-monospace, Menlo, Consolas, monospace;
    --font-zh: 'PingFang SC', 'Hiragino Sans GB', 'Noto Serif CJK SC', 'Source Han Serif SC', 'Microsoft YaHei', serif;
}

@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
    --paper: #17150f;  --paper-deep: #1e1b14;  --paper-rule: #3a3427;
    --ink: #ece5d6;  --ink-soft: #c8c0ae;  --ink-mute: #9b9384;  --ink-faint: #756e60;
    --red: #e2706a;  --red-tint: #3b211f;
    --blue: #82a8f4;  --blue-tint: #1d2740;
    --teal: #4fb5ae;  --teal-tint: #16302e;
    --plum: #b492d8;  --plum-tint: #2c2339;
    --ochre: #e2b257;  --ochre-tint: #3b3017;
    --green: #6cba8e;  --green-tint: #1a3026;
    --sienna: #e28c48;
    --input: #1c1a13;
    --fig-paper: #1a1710;  --fig-grid: #3a3427;  --fig-rule: #3a3427;
    --fig-ink: #ece5d6;  --fig-muted: #9b9384;  --fig-faint: #756e60;
    --fig-blue: #82a8f4;  --fig-red: #e2706a;  --fig-green: #6cba8e;  --fig-teal: #4fb5ae;
    --fig-plum: #b492d8;  --fig-ochre: #e2b257;  --fig-sienna: #e28c48;
    --fig-dial: #111114;  --fig-dialink: #ece5d6;  --fig-panel: #26262b;  --fig-sky: #2f5f93;  --fig-earth: #6b4524;
    --shadow: 0 2px 6px rgba(0, 0, 0, 0.38);
    }
}
:root[data-theme="dark"] {
    --paper: #17150f;  --paper-deep: #1e1b14;  --paper-rule: #3a3427;
    --ink: #ece5d6;  --ink-soft: #c8c0ae;  --ink-mute: #9b9384;  --ink-faint: #756e60;
    --red: #e2706a;  --red-tint: #3b211f;
    --blue: #82a8f4;  --blue-tint: #1d2740;
    --teal: #4fb5ae;  --teal-tint: #16302e;
    --plum: #b492d8;  --plum-tint: #2c2339;
    --ochre: #e2b257;  --ochre-tint: #3b3017;
    --green: #6cba8e;  --green-tint: #1a3026;
    --sienna: #e28c48;
    --input: #1c1a13;
    --fig-paper: #1a1710;  --fig-grid: #3a3427;  --fig-rule: #3a3427;
    --fig-ink: #ece5d6;  --fig-muted: #9b9384;  --fig-faint: #756e60;
    --fig-blue: #82a8f4;  --fig-red: #e2706a;  --fig-green: #6cba8e;  --fig-teal: #4fb5ae;
    --fig-plum: #b492d8;  --fig-ochre: #e2b257;  --fig-sienna: #e28c48;
    --fig-dial: #111114;  --fig-dialink: #ece5d6;  --fig-panel: #26262b;  --fig-sky: #2f5f93;  --fig-earth: #6b4524;
    --shadow: 0 2px 6px rgba(0, 0, 0, 0.38);
}

/* ─── Base ─────────────────────────────────────────────────── */

*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--paper); color: var(--ink); font: 17px/1.62 var(--font-body); font-optical-sizing: auto; }
::selection { background: var(--ochre-tint); }
a { color: var(--blue); text-underline-offset: 2px; }
code, kbd, .mono { font-family: var(--font-mono); font-size: 0.86em; }
p code, li code, dd code, .prose code, .info-box code, .marginalia code, .key-concept code, .quiz-q code, .challenge code, .lesson code {
    background: var(--paper-deep); border: 1px solid var(--paper-rule); border-radius: 3px; padding: 0 0.28em;
}
kbd { border: 1px solid var(--paper-rule); border-bottom-width: 2px; border-radius: 3px; padding: 0 0.35em; background: var(--paper); }
button { font: inherit; color: inherit; }
:focus-visible { outline: 2px solid var(--blue); outline-offset: 2px; }

/* ─── Topbar ───────────────────────────────────────────────── */

.topbar {
    position: sticky; top: 0; z-index: 20; display: flex; align-items: center; justify-content: space-between; gap: 12px;
    padding: 12px 32px; background: color-mix(in srgb, var(--paper) 92%, transparent); backdrop-filter: blur(6px); border-bottom: 1px solid var(--paper-rule);
}
.topbar-left { display: flex; align-items: baseline; gap: 20px; min-width: 0; }
.topbar-back { font: 500 11px/1 var(--font-mono); letter-spacing: 0.12em; text-transform: uppercase; color: var(--ink-mute); text-decoration: none; white-space: nowrap; }
.topbar-back:hover { color: var(--red); }
.topbar-title { font: 400 19px/1.2 var(--font-display); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.topbar-title .icon { font: 600 12px/1 var(--font-mono); letter-spacing: 0.14em; text-transform: uppercase; color: var(--red); margin-right: 10px; }
.lang-btn { border: 1px solid var(--paper-rule); background: var(--paper); font: 500 12px/1 var(--font-mono); padding: 6px 12px; border-radius: 3px; cursor: pointer; }
.lang-btn:hover { border-color: var(--ink-mute); }

/* ─── The plate ────────────────────────────────────────────── */

.main-content { max-width: 980px; margin: 0 auto; padding: 34px 32px 80px; }
.plate-meta { display: flex; justify-content: space-between; gap: 16px; flex-wrap: wrap; padding-bottom: 10px; border-bottom: 1px solid var(--paper-rule);
    font: 500 11px/1.6 var(--font-mono); letter-spacing: 0.12em; text-transform: uppercase; color: var(--ink-mute); }
.plate-meta b { color: var(--red); font-weight: 600; margin-right: 8px; }
.thread { display: inline-block; margin-left: 6px; padding: 0 5px; border: 1px solid var(--blue); color: var(--blue); border-radius: 2px; font-size: 10px; }
h1.plate-title { font: 400 clamp(36px, 6vw, 56px)/1.05 var(--font-display); font-variation-settings: 'opsz' 144, 'SOFT' 30; letter-spacing: -0.02em; margin: 32px 0 14px; }
h1.plate-title em { color: var(--red); }
.plate-deck { font: italic 20px/1.45 var(--font-body); color: var(--ink-soft); margin: 0 0 32px; max-width: 720px; }
.info-box.lede { border-left: 3px solid var(--ink); padding: 2px 0 2px 18px; margin: 0 0 30px; max-width: 720px; }
.info-box.lede p { margin: 0 0 12px; }
.info-box.lede > p:first-child::first-letter { float: left; font: 400 66px/0.84 var(--font-display); color: var(--red); margin: 6px 10px 0 0; }
.info-box.lede > em { display: block; padding-top: 12px; border-top: 1px solid var(--paper-rule); font-size: 15px; color: var(--ink-soft); }
.formula-group { display: flex; flex-wrap: wrap; gap: 18px 40px; align-items: center; background: var(--paper-deep); border-top: 1px solid var(--paper-rule);
    border-bottom: 1px solid var(--paper-rule); padding: 20px 26px; margin: 0 0 30px; max-width: 720px; }
.formula { font-size: 17px; overflow-x: auto; max-width: 100%; }
.formula[data-eq]::after { content: '(' attr(data-eq) ')'; margin-left: 16px; font: italic 13px var(--font-body); color: var(--ink-faint); }
.learning-objectives { border-top: 1px solid var(--ink); padding-top: 14px; margin: 0 0 34px; max-width: 720px; }
.learning-objectives-title, .section-title { font: 600 11px/1.4 var(--font-mono); letter-spacing: 0.14em; text-transform: uppercase; color: var(--ink-mute); }
.learning-objectives-title::before { content: '§ '; color: var(--red); }
.learning-objectives ul { list-style: none; padding: 0; margin: 12px 0 0; counter-reset: obj; }
.learning-objectives li { counter-increment: obj; position: relative; padding: 6px 0 6px 36px; border-bottom: 1px solid var(--paper-rule); }
.learning-objectives li::before { content: counter(obj, decimal-leading-zero); position: absolute; left: 0; top: 7px; font: italic 14px var(--font-display); color: var(--red); }
.section-title { margin: 20px 0 16px; display: flex; align-items: center; gap: 12px; }
.section-title::before { content: ''; width: 26px; border-top: 1px solid var(--ink-mute); }
h2 { font: 400 30px/1.2 var(--font-display); letter-spacing: -0.01em; margin: 44px 0 14px; }
.prose { max-width: 720px; }
.prose p { margin: 0; }
.prose p + p { text-indent: 1.4em; margin-top: 12px; }
.marginalia { margin: 28px 0; padding: 12px 16px; max-width: 760px; border-left: 2px solid var(--red); background: var(--red-tint); font: italic 15px/1.55 var(--font-body); color: var(--ink-soft); }
dl.terms { max-width: 720px; margin: 0; }
dl.terms dt { font: italic 18px var(--font-display); margin-top: 14px; }
dl.terms dd { margin: 4px 0 0; padding-bottom: 12px; border-bottom: 1px solid var(--paper-rule); color: var(--ink-soft); }
.key-concept { margin: 40px 0; padding: 4px 0 4px 22px; max-width: 720px; border-left: 3px solid var(--red); font: italic 21px/1.45 var(--font-body); }
.key-concept::before { content: 'In short'; display: block; margin-bottom: 6px; font: 600 11px/1 var(--font-mono); font-style: normal; letter-spacing: 0.14em; text-transform: uppercase; color: var(--red); }
html[lang="zh"] .key-concept::before { content: '要点'; }
.key-concept strong { font-weight: 600; }
.disclaimer { margin: 30px 0 0; max-width: 760px; font: 13px/1.5 var(--font-mono); color: var(--ink-faint); border-top: 1px dashed var(--paper-rule); padding-top: 10px; }
.section-break { text-align: center; margin: 46px 0 20px; color: var(--ink-faint); }
.section-break::before { content: '⁂'; font-size: 22px; }
.nav-footer { display: flex; justify-content: space-between; gap: 12px; flex-wrap: wrap; border-top: 1px solid var(--paper-rule); padding-top: 16px;
    font: 500 12px var(--font-mono); letter-spacing: 0.08em; text-transform: uppercase; }
.nav-footer a { color: var(--ink-soft); text-decoration: none; }
.nav-footer a:hover { color: var(--red); }
.nav-footer a.nav-report { color: var(--ink-faint); }

/* ─── Figures and benches ──────────────────────────────────── */

main { counter-reset: fig; }
.figure { margin: 0 0 26px; counter-increment: fig; }
.figure-caption { margin-top: 10px; font: italic 14px/1.5 var(--font-body); color: var(--ink-soft); max-width: 780px; }
.figure-caption::before { content: 'Fig. ' counter(fig) '.'; margin-right: 8px; font: 600 11px var(--font-mono); font-style: normal; letter-spacing: 0.1em; text-transform: uppercase; color: var(--red); }
html[lang="zh"] .figure-caption::before { content: '图 ' counter(fig); }
.ws { border: 1px solid var(--paper-rule); background: var(--fig-paper); box-shadow: var(--shadow); }
.ws canvas { display: block; width: 100%; touch-action: none; }
.ws-bar { display: flex; flex-wrap: wrap; gap: 8px 14px; align-items: center; padding: 9px 12px; border-bottom: 1px solid var(--paper-rule); background: var(--paper); font: 12px var(--font-mono); }
.ws-bar label { color: var(--ink-mute); display: inline-flex; gap: 6px; align-items: center; }
.ws-bar input[type="range"] { width: 120px; }
.ws-bar b[data-pv] { color: var(--ink); font-weight: 500; min-width: 3.5em; }
.ws-body { display: grid; grid-template-columns: minmax(0, 1fr) 240px; }
.ws-body > .ws-canvas { border-right: 1px solid var(--paper-rule); min-width: 0; }
.ws-rail { padding: 10px 14px; font: 13px/1.5 var(--font-mono); background: var(--paper); min-width: 0; }
.ws-rail h4 { font: 600 10px/1 var(--font-mono); letter-spacing: 0.14em; text-transform: uppercase; color: var(--ink-faint); margin: 4px 0 8px; }
.rail-stats { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 3px 12px; }
.rail-stats span:nth-child(odd) { color: var(--ink-mute); }
.rail-stats span:nth-child(even) { color: var(--ink); text-align: right; white-space: nowrap; font-variant-numeric: tabular-nums; }
.rail-stats span.wide { grid-column: 1 / -1; }
.rail-stats span.wide:nth-child(even) { text-align: left; white-space: normal; padding-left: 10px; margin-bottom: 4px; }
.ws-note { padding: 9px 14px; border-top: 1px solid var(--paper-rule); background: var(--paper); font: 14px/1.5 var(--font-body); color: var(--ink-soft); min-height: 2.6em; }
.btn, .seg button { border: 1px solid var(--paper-rule); background: var(--paper); color: var(--ink-soft); font: 500 12px/1 var(--font-mono); padding: 7px 11px; border-radius: 3px; cursor: pointer; white-space: nowrap; }
.btn:hover, .seg button:hover { border-color: var(--ink-mute); color: var(--ink); }
.btn.primary { background: var(--ink); color: var(--paper); border-color: var(--ink); }
.btn[aria-pressed="true"] { background: var(--ochre-tint); border-color: var(--ochre); color: var(--ink); }
.seg { display: inline-flex; flex-wrap: wrap; }
.seg button { border-radius: 0; margin-left: -1px; }
.seg button:first-child { border-radius: 3px 0 0 3px; margin-left: 0; }
.seg button:last-child { border-radius: 0 3px 3px 0; }
.seg button[aria-pressed="true"] { background: var(--ink); color: var(--paper); border-color: var(--ink); position: relative; }
input[type="range"] { accent-color: var(--red); }
.ws-input, .ans-input { border: 1px solid var(--paper-rule); background: var(--input); color: var(--ink); font: 14px/1.4 var(--font-mono); padding: 5px 8px; border-radius: 3px; min-width: 0; }
.ws-input.bad { border-color: var(--red); }
.board { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 10px; padding: 12px; background: var(--paper); }
.board .card { border: 1px solid var(--paper-rule); background: var(--paper); padding: 12px 14px; cursor: pointer; text-align: left; font: 15px/1.45 var(--font-body); }
.board .card b { display: block; font: 400 18px/1.25 var(--font-display); margin-bottom: 4px; }
.board .card .tag { font: 600 10px var(--font-mono); letter-spacing: 0.12em; text-transform: uppercase; color: var(--red); }
.board .card .more { display: none; margin-top: 8px; padding-top: 8px; border-top: 1px solid var(--paper-rule); color: var(--ink-soft); font-size: 14px; }
.board .card.open .more { display: block; }
.board .card.open { border-color: var(--ink); }
.acs { padding: 12px 14px; background: var(--paper); overflow-x: auto; }
.acs h5 { font: 400 20px/1.25 var(--font-display); margin: 2px 0 10px; }
.acs-n { font: 600 11px var(--font-mono); letter-spacing: 0.12em; text-transform: uppercase; color: var(--red); margin-right: 6px; }
.acs-table { width: 100%; border-collapse: collapse; font: 14px/1.45 var(--font-body); }
.acs-table th { text-align: left; font: 600 10px var(--font-mono); letter-spacing: 0.12em; text-transform: uppercase; color: var(--ink-faint); border-bottom: 1px solid var(--ink-mute); padding: 4px 8px 6px 0; }
.acs-table td { border-bottom: 1px solid var(--paper-rule); padding: 6px 10px 6px 0; vertical-align: top; }
.acs-table td:nth-child(2) { font-family: var(--font-mono); font-size: 12.5px; }
.acs-k { color: var(--ink-faint); font-style: italic; font-family: var(--font-body); }
.acs-p { font: 12px var(--font-mono); color: var(--ink-mute); white-space: nowrap; }
.acs-sum { margin: 10px 0 0; font: italic 14px/1.5 var(--font-body); color: var(--ink-soft); }
.kt { margin: 0; padding: 8px 14px 4px 2.6em; background: var(--paper); }
.kt > li { padding: 8px 0 10px; border-bottom: 1px solid var(--paper-rule); }
.case-q { margin: 0 0 8px; font: 15px/1.5 var(--font-body); }
.case-opts { display: grid; gap: 6px; }
.case-why { margin: 8px 0 0; font: italic 14px/1.5 var(--font-body); color: var(--ink-soft); }
.kt-vol { font: 600 10px var(--font-mono); letter-spacing: 0.1em; color: var(--red); margin-right: 4px; }
.kt-end { margin: 0; padding: 10px 14px; font: italic 15px/1.5 var(--font-body); border-bottom: 1px solid var(--paper-rule); }
.kt-end.ok { background: var(--green-tint); }
.kt-end.bad { background: var(--red-tint); }

/* ─── The simulator ────────────────────────────────────────── */

.sim { border: 1px solid var(--paper-rule); background: var(--fig-panel); box-shadow: var(--shadow); outline: none; }
.sim:focus-visible { outline: 2px solid var(--blue); }
.sim-bar { display: flex; flex-wrap: wrap; gap: 6px 10px; align-items: center; padding: 8px 10px; background: var(--paper); border-bottom: 1px solid var(--paper-rule); color: var(--ink); font: 12px var(--font-mono); }
.sim-bar .chk { display: inline-flex; gap: 4px; align-items: center; color: var(--ink-mute); }
.sim-stage { position: relative; height: clamp(240px, 46vw, 440px); touch-action: none; cursor: grab; }
.sim-stage canvas { position: absolute; inset: 0; width: 100%; height: 100%; display: block; }
.sim-hud { pointer-events: none; }
.sim-msg { position: absolute; left: 50%; bottom: 14%; transform: translateX(-50%); background: var(--fig-dial); color: var(--fig-dialink); opacity: 0.9; padding: 10px 16px;
    font: 15px/1.5 var(--font-body); max-width: 86%; text-align: center; pointer-events: none; border-radius: 3px; }
.sim-msg:empty { display: none; }
.sim-panel canvas { display: block; width: 100%; }
.sim-touch { display: flex; flex-wrap: wrap; gap: 6px 14px; align-items: center; padding: 6px 10px; background: var(--paper-deep); color: var(--ink); font: 12px var(--font-mono); border-top: 1px solid var(--paper-rule); }
.sim-touch label { display: inline-flex; gap: 6px; align-items: center; }
.sim-touch input[type=range] { width: 120px; }
.sim-lower { display: grid; grid-template-columns: minmax(0, 1fr) 300px; background: var(--paper); color: var(--ink); border-top: 1px solid var(--paper-rule); }
.lesson { padding: 10px 14px; font: 14px/1.5 var(--font-body); border-right: 1px solid var(--paper-rule); min-width: 0; }
.lesson h4, .debrief h4 { font: 600 10px/1 var(--font-mono); letter-spacing: 0.14em; text-transform: uppercase; color: var(--ink-faint); margin: 4px 0 8px; }
.lesson ol { margin: 0; padding-left: 1.3em; }
.lesson li { padding: 2px 0; color: var(--ink-mute); }
.lesson li.now { color: var(--ink); font-weight: 600; }
.lesson li.ok { color: var(--green); }
.lesson li.bad { color: var(--red); }
.debrief { margin-top: 10px; }
.debrief:empty { display: none; }
.debrief p { font: 400 18px var(--font-display); margin: 0 0 6px; }
.debrief .ok { color: var(--green); }
.debrief .bad { color: var(--red); }
.debrief ul { margin: 0; padding-left: 1.2em; font-size: 13px; }
.sim-side { padding: 10px 14px; font: 13px/1.5 var(--font-mono); min-width: 0; }
.sim-side .rail-stats { display: grid; grid-template-columns: 1fr auto; gap: 2px 10px; }
.sim-keys { margin: 10px 0 0; color: var(--ink-mute); font: 11px/1.6 var(--font-mono); }
.atc { margin-top: 8px; font: 13px/1.45 var(--font-body); }
.atc-line { padding: 3px 0; border-top: 1px dotted var(--paper-rule); }
.atc-line b { font: 600 11px var(--font-mono); color: var(--teal); margin-right: 6px; }

/* ─── Challenges and the knowledge check ──────────────────── */

.try-block { margin: 28px 0 10px; }
.challenge { border: 1px solid var(--paper-rule); background: var(--paper); margin: 12px 0; padding: 14px 16px; }
.challenge-head { display: flex; justify-content: space-between; align-items: baseline; gap: 12px; }
.challenge-state { font: 600 11px var(--font-mono); letter-spacing: 0.1em; text-transform: uppercase; color: var(--ink-faint); white-space: nowrap; }
.challenge.solved { border-color: var(--green); background: var(--green-tint); }
.challenge.solved .challenge-state { color: var(--green); }
.challenge .given { font: 13px/1.5 var(--font-mono); background: var(--paper-deep); padding: 6px 10px; margin: 8px 0; white-space: pre-wrap; }
.challenge .row { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin-top: 8px; }
.challenge .opts { display: grid; gap: 5px; margin-top: 8px; }
.challenge .opts button { text-align: left; border: 1px solid var(--paper-rule); background: var(--paper); padding: 6px 10px; border-radius: 3px; cursor: pointer; font: 14px/1.4 var(--font-body); }
.challenge .opts button.right { border-color: var(--green); background: var(--green-tint); }
.challenge .opts button.wrong { border-color: var(--red); background: var(--red-tint); }
.challenge .msg { font: 13px/1.5 var(--font-body); margin-top: 8px; color: var(--ink-soft); }
.challenge .msg.bad { color: var(--red); }
.drill-score { font: 600 13px var(--font-mono); color: var(--ink-soft); margin: 8px 0; }
.quiz-container { margin: 46px 0 0; max-width: 780px; }
.quiz-title { font: 400 28px var(--font-display); margin: 0 0 4px; }
.quiz-sub { font: italic 15px var(--font-body); color: var(--ink-mute); margin: 0 0 16px; }
.quiz-q { border-top: 1px solid var(--paper-rule); padding: 16px 0; }
.quiz-q-text { margin: 0 0 10px; }
.quiz-q-text b { font: 600 12px var(--font-mono); color: var(--red); margin-right: 8px; }
.quiz-opts { display: grid; gap: 6px; }
.quiz-opt { text-align: left; border: 1px solid var(--paper-rule); background: var(--paper); cursor: pointer; padding: 8px 12px; border-radius: 3px; font: 15px/1.45 var(--font-body); }
.quiz-opt:hover:not([disabled]) { border-color: var(--ink-mute); }
.quiz-opt.right { border-color: var(--green); background: var(--green-tint); }
.quiz-opt.wrong { border-color: var(--red); background: var(--red-tint); }
.quiz-opt[disabled] { cursor: default; }
.quiz-expl { margin: 10px 0 0; font-size: 15px; color: var(--ink-soft); padding-left: 12px; border-left: 2px solid var(--paper-rule); }
.quiz-score { font: 600 13px var(--font-mono); margin-top: 14px; color: var(--ink-soft); }

/* ─── Chinese ──────────────────────────────────────────────── */

html[lang="zh"] body { font-family: var(--font-body), var(--font-zh); }
html[lang="zh"] h1.plate-title, html[lang="zh"] h2 { font-family: var(--font-display), var(--font-zh); letter-spacing: 0; }
html[lang="zh"] .info-box.lede > p:first-child::first-letter { float: none; font: inherit; color: inherit; margin: 0; }
html[lang="zh"] .prose p + p { text-indent: 2em; }

/* ─── Narrow viewports ─────────────────────────────────────── */

@media (max-width: 760px) {
    body { font-size: 16px; }
    .topbar { padding: 10px 16px; }
    .topbar-title .icon { display: none; }
    .main-content { padding: 22px 16px 60px; }
    .ws-body, .sim-lower { grid-template-columns: 1fr; }
    .ws-body > .ws-canvas, .lesson { border-right: 0; border-bottom: 1px solid var(--paper-rule); }
}