/* Course shell + reading pages. Carbon tokens come from carbon.css. */
:root { --rail-w: 272px; --stepbar-h: 56px; --blue-10: #edf5ff; --blue-20: #d0e2ff; --yellow-bg: #fcf4d6; }

/* ---------- layout ---------- */
#course { display: flex; height: calc(100vh - var(--header-h)); min-width: 0; }
#stage { flex: 1; min-width: 0; display: flex; flex-direction: column; }
#stage-body { flex: 1; min-height: 0; position: relative; }
#page { position: absolute; inset: 0; overflow-y: auto; overflow-x: hidden; background: var(--light-canvas); color: var(--text-dark); display: none; outline: none; }
#stage-body > #main { position: absolute; inset: 0; height: auto; display: none; }
body[data-mode="lesson"] #page, body[data-mode="quiz"] #page { display: block; }
body[data-mode="lab"] #stage-body > #main { display: flex; }

/* header: four unit tabs */
.tab { position: relative; min-width: 0; }
.tab .tab-prog { position: absolute; left: 0; right: 0; bottom: 0; height: 3px; background: transparent; }
.tab .tab-prog b { display: block; height: 100%; background: var(--valid); }
.brand span { overflow: hidden; text-overflow: ellipsis; }
@media (max-width: 1599px) { .brand span { display: none; } .hdr-btn { padding: 0 12px; } .tab { padding: 0 12px; } }

/* ---------- rail ---------- */
#rail { width: var(--rail-w); flex: none; background: var(--dark-canvas); color: var(--text-light); border-right: 1px solid var(--hair-dark); display: flex; flex-direction: column; min-height: 0; overflow: hidden; }
.rail-head { height: 40px; flex: none; display: flex; align-items: center; justify-content: space-between; padding-left: 16px; border-bottom: 1px solid var(--hair-dark); font: 500 12px var(--sans); letter-spacing: 0.08em; color: var(--text-muted-dark); }
.rail-toggle { width: 40px; height: 40px; background: none; border: 0; border-left: 1px solid var(--hair-dark); color: var(--text-light); cursor: pointer; font-size: 16px; }
.rail-toggle:hover { background: var(--dark-surface); }
.rail-scroll { flex: 1; overflow-y: auto; min-height: 0; }
.rail-unit { border-bottom: 1px solid var(--hair-dark); }
.rail-unit-h { width: 100%; display: flex; align-items: center; gap: 8px; padding: 10px 16px; background: var(--dark-surface); border: 0; border-left: 3px solid transparent; color: #fff; cursor: pointer; text-align: left; font: 600 13px/1.3 var(--sans); }
.rail-unit.current .rail-unit-h { border-left-color: var(--primary); }
.rail-unit-h:hover { background: #333; }
.ru-n { font: 500 12px var(--mono); color: var(--secondary); }
.ru-t { flex: 1; min-width: 0; }
.ru-c { font: 500 12px var(--mono); color: var(--text-muted-dark); }
.rail-steps { display: none; padding: 4px 0 8px; }
.rail-unit.open .rail-steps { display: block; }
.rail-step { width: 100%; display: flex; align-items: flex-start; gap: 10px; padding: 7px 16px 7px 19px; background: none; border: 0; border-left: 3px solid transparent; color: #c6c6c6; cursor: pointer; text-align: left; font: 400 13px/1.35 var(--sans); }
.rail-step:hover { background: var(--dark-surface); color: #fff; }
.rail-step.current { background: #393939; color: #fff; border-left-color: var(--primary); }
.rs-i { flex: none; width: 14px; text-align: center; font-size: 13px; line-height: 1.35; color: #8d8d8d; }
.rs-i[data-s="done"] { color: #42be65; }
.rs-i[data-s="skipped"] { color: var(--warn); }
.rs-i[data-s="current"] { color: var(--secondary); }
.rs-t { flex: 1; min-width: 0; }
.rs-k { display: block; font: 500 10px var(--mono); letter-spacing: 0.08em; color: #8d8d8d; }
.rs-m { flex: none; font: 500 11px var(--mono); color: var(--text-muted-dark); padding-top: 14px; }
.rail-foot { flex: none; border-top: 1px solid var(--hair-dark); }
.rail-reset { width: 100%; height: 40px; background: none; border: 0; color: var(--text-muted-dark); cursor: pointer; font-size: 13px; text-align: left; padding: 0 16px; }
.rail-reset:hover { background: var(--dark-surface); color: #fff; }
#rail.collapsed { width: 40px; }
#rail.collapsed .rail-title, #rail.collapsed .rail-scroll, #rail.collapsed .rail-foot { display: none; }
#rail.collapsed .rail-head { padding: 0; }
#rail.collapsed .rail-toggle { border-left: 0; }

/* ---------- step bar ---------- */
#stepbar { height: var(--stepbar-h); flex: none; display: flex; align-items: center; gap: 16px; padding: 0 16px; background: var(--dark-canvas); border-top: 1px solid var(--hair-dark); }
#stepbar .btn { white-space: nowrap; text-align: center; }
.sb-label { flex: 1; min-width: 0; text-align: center; font: 500 13px var(--sans); color: var(--text-light); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.sb-right { display: flex; gap: 8px; }
#stepbar .btn-secondary { background: var(--dark-surface); border-color: var(--hair-dark); }
#stepbar .btn-secondary:hover:not([disabled]) { background: var(--dark-raised); }
#stepbar .btn[disabled] { background: transparent; color: #6f6f6f; border: 1px solid var(--hair-dark); }
#stepbar .btn.is-skip { background: transparent; border-color: var(--primary); color: #78a9ff; }
#stepbar .btn.is-skip:hover { background: var(--primary); color: #fff; }

/* ---------- lab: viewport bar and HUD adapt to a narrower stage ---------- */
#vbar .coords, .track-dots { display: none; }
#vbar .step-label { flex: 1; max-width: none; }
#vbar .spacer { display: none; }
.hud-legend { top: auto; right: auto; left: var(--s15); bottom: calc(var(--vbar-h) + var(--s15)); flex-wrap: wrap; gap: 6px 14px; max-width: calc(100% - 24px); }
.hud-now { bottom: calc(var(--vbar-h) + 52px); }
.hud-tl { max-width: calc(100% - 24px); }
.hud-tl .hud-title { font-size: 18px; }

/* lab tasks card (sticky at the top of the dock) */
.lab-tasks { position: sticky; top: 0; z-index: 4; background: #fff; border-bottom: 1px solid #c6c6c6; border-top: 3px solid var(--primary); box-shadow: 0 2px 6px rgba(0,0,0,0.12); max-height: 50vh; overflow-y: auto; }
.lt-head { display: flex; align-items: center; gap: 10px; padding: 0 0 0 16px; height: 40px; position: sticky; top: 0; background: #fff; }
.lt-title { font: 600 12px var(--sans); letter-spacing: 0.08em; color: var(--text-muted); }
.lt-count { flex: 1; font-size: 12px; color: var(--primary); }
.lt-toggle { width: 40px; height: 40px; background: none; border: 0; cursor: pointer; font-size: 13px; color: var(--text-muted); }
.lt-toggle:hover { background: #e8e8e8; }
.lt-body-wrap { padding: 0 16px 12px; }
.lab-tasks.collapsed .lt-body-wrap { display: none; }
.lt-intro { margin: 0 0 8px; font-size: 14px; line-height: 1.45; }
.lt-list { list-style: none; margin: 0; padding: 0; }
.lt-item { display: flex; gap: 10px; padding: 6px 0; border-top: 1px solid var(--hair-light); font-size: 14px; line-height: 1.4; }
.lt-box { flex: none; width: 18px; height: 18px; margin-top: 1px; border: 1px solid #8d8d8d; display: grid; place-items: center; font-size: 13px; line-height: 1; color: #fff; }
.lt-item[data-done="true"] .lt-box { background: var(--valid); border-color: var(--valid); }
.lt-item[data-done="true"] .lt-text { color: var(--text-muted); text-decoration: line-through; }
.lt-item.next .lt-box { border-color: var(--primary); border-width: 2px; }
.lt-item.next .lt-text { font-weight: 600; }
.lt-hint { display: none; margin-top: 2px; font-size: 13px; color: var(--text-muted); }
.lt-item.next .lt-hint { display: block; }
.lt-all { margin: 8px 0 0; padding: 8px 12px; background: #defbe6; border-left: 3px solid var(--valid); font-size: 14px; }
.lt-all[hidden] { display: none; }

/* ---------- reading pages (lesson + quiz) ---------- */
.lesson, .quiz { max-width: 760px; margin: 0 auto; padding: 48px 24px 96px; font: 400 16px/1.6 var(--sans); color: var(--text-dark); }
.ls-eyebrow { display: flex; justify-content: space-between; gap: 16px; font: 500 12px var(--sans); letter-spacing: 0.08em; text-transform: uppercase; color: var(--primary); }
.ls-min { color: var(--text-muted); letter-spacing: 0.02em; text-transform: none; white-space: nowrap; }
.ls-title { font: 700 32px/1.2 var(--sans); margin: 8px 0 24px; }
.ls-h { font: 600 24px/1.3 var(--sans); margin: 40px 0 8px; padding-top: 16px; border-top: 1px solid #c6c6c6; }
.ls-title + .ls-h { border-top: 0; margin-top: 0; padding-top: 0; }
.ls-p { margin: 0 0 16px; max-width: 70ch; }
.lesson code, .quiz code { font: 500 0.9em var(--mono); background: #e0e0e0; padding: 1px 5px; border-radius: 2px; }
.lesson math, .quiz math { font-size: 1.1em; }
.ls-tag { display: inline-block; font: 600 11px var(--mono); letter-spacing: 0.08em; padding: 2px 8px; background: #393939; color: #fff; margin-bottom: 8px; }
.ls-list { margin: 0 0 16px; padding-left: 24px; }
.ls-list li { margin: 4px 0; }

.ls-def { background: #fff; border: 1px solid var(--hair-light); border-left: 3px solid var(--primary); padding: 10px 16px; margin: 8px 0 12px; }
.ls-def + .ls-def { margin-top: -4px; }
.ls-def .ls-tag { display: none; }
.ls-def-term { display: inline; font: 600 16px/1.6 var(--sans); color: #001d6c; }
.ls-def-term::after { content: ' — '; font-weight: 400; color: var(--text-muted); }
.ls-def-text { display: inline; font-size: 16px; line-height: 1.6; }

.ls-note { background: #e8e8e8; border-left: 4px solid #6f6f6f; padding: 12px 20px; margin: 16px 0; }
.ls-note .ls-tag { background: #6f6f6f; margin-bottom: 4px; }
.ls-warn { background: var(--yellow-bg); border-left: 4px solid var(--warn); border-top: 1px solid #f0dd9a; border-right: 1px solid #f0dd9a; border-bottom: 1px solid #f0dd9a; padding: 12px 20px; margin: 20px 0; }
.ls-warn .ls-tag { background: var(--warn); color: #000; margin-bottom: 4px; }

.ls-exam { background: var(--blue-20); border-left: 4px solid var(--primary); padding: 16px 20px; margin: 32px 0 0; }
.ls-exam-head { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; margin-bottom: 8px; }
.ls-exam .ls-tag { background: var(--primary); margin: 0; }
.ls-exam-sub { font-size: 14px; color: #161616; }
.ls-ref { display: inline-block; font: 500 12px var(--mono); background: #fff; color: #001d6c; border: 1px solid #a6c8ff; padding: 1px 8px; }
.ls-exam .ls-list { margin: 4px 0 0; }

.ls-steps { list-style: none; counter-reset: st; margin: 0 0 20px; padding: 0; }
.ls-steps li { counter-increment: st; position: relative; padding: 8px 0 8px 44px; min-height: 36px; }
.ls-steps li::before { content: counter(st); position: absolute; left: 0; top: 8px; width: 28px; height: 28px; display: grid; place-items: center; background: var(--primary); color: #fff; font: 600 13px var(--mono); border-radius: 50%; }
.ls-steps li:not(:last-child)::after { content: ''; position: absolute; left: 13px; top: 38px; bottom: -6px; width: 2px; background: #c6c6c6; }
.ls-step-text { padding-top: 2px; }

.ls-example { background: #fff; border: 1px solid var(--hair-light); padding: 20px 24px; margin: 20px 0; }
.ls-example .ls-tag { background: #198038; }
.ls-example-title { font: 600 18px/1.3 var(--sans); margin-bottom: 12px; }
.ls-example .ls-steps { margin-bottom: 12px; }
.ls-answer { display: flex; gap: 12px; align-items: baseline; background: #defbe6; border-left: 4px solid var(--valid); padding: 10px 16px; }
.ls-answer-k { font: 600 12px var(--mono); letter-spacing: 0.08em; text-transform: uppercase; color: #044317; }
.ls-answer-v { font-weight: 600; min-width: 0; }

.ls-table-wrap { overflow-x: auto; margin: 16px 0 20px; background: #fff; border: 1px solid var(--hair-light); }
.ls-table { width: 100%; border-collapse: collapse; font-size: 15px; }
.ls-table th { background: #e0e0e0; text-align: left; font-weight: 600; padding: 10px 14px; font-size: 14px; }
.ls-table td { padding: 10px 14px; border-top: 1px solid var(--hair-light); vertical-align: top; }
.ls-table tbody tr:nth-child(even) td { background: #fafafa; }

.ls-code { margin: 16px 0 20px; }
.ls-code .code-wrap { margin: 0; }
.ls-code .code { max-height: 460px; }
.ls-code .code code, .ls-code .code-head .mono { background: none; padding: 0; font-size: 13px; }
.ls-caption, .lesson figcaption { font-size: 14px; color: var(--text-muted); margin-top: 8px; }

.ls-math { margin: 16px 0 20px; background: #fff; border: 1px solid var(--hair-light); border-left: 4px solid var(--primary); padding: 16px 20px; overflow-x: auto; }
.ls-math-body { font-size: 1.1em; text-align: center; }
.ls-math figcaption { text-align: center; margin-top: 8px; }
.ls-figure { margin: 20px 0; background: #fff; border: 1px solid var(--hair-light); padding: 16px; }
.ls-figure-body svg { display: block; width: 100%; height: auto; max-width: 100%; }
.ls-figure figcaption { margin-top: 8px; }

/* ---------- quiz ---------- */
.quiz { padding-bottom: 120px; }
.qz-best { color: var(--text-muted); }
.qz-q { background: #fff; border: 1px solid var(--hair-light); border-left: 4px solid #c6c6c6; padding: 20px 24px; margin: 0 0 16px; }
.qz-q.is-right { border-left-color: var(--valid); }
.qz-q.is-bad { border-left-color: var(--error); }
.qz-qhead { display: flex; justify-content: space-between; margin-bottom: 8px; }
.qz-qn { font: 600 13px var(--mono); color: var(--primary); }
.qz-kind { font: 500 11px var(--mono); letter-spacing: 0.08em; color: var(--text-muted); }
.qz-prompt { font: 500 17px/1.5 var(--sans); margin-bottom: 12px; }
.qz-hint { font-size: 13px; color: var(--text-muted); margin-bottom: 8px; }
.qz-opts { display: flex; flex-direction: column; gap: 6px; }
.qz-opt { display: flex; gap: 12px; align-items: flex-start; padding: 10px 14px; background: var(--light-canvas); border: 1px solid transparent; cursor: pointer; }
.qz-opt:hover { background: #e8e8e8; }
.qz-opt:has(input:checked) { border-color: var(--primary); background: var(--blue-10); }
.qz-opt input { margin: 4px 0 0; width: 16px; height: 16px; accent-color: var(--primary); flex: none; }
.qz-opt.is-answer { background: #defbe6; border-color: var(--valid); }
.qz-opt.is-wrong { background: #fff1f1; border-color: var(--error); }
.qz-numrow { display: flex; align-items: center; gap: 12px; max-width: 360px; }
.qz-unit { color: var(--text-muted); font-family: var(--mono); font-size: 13px; }
.qz-order { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 6px; }
.qz-ord-item { display: flex; align-items: center; gap: 12px; padding: 6px 6px 6px 14px; background: var(--light-canvas); border: 1px solid transparent; }
.qz-ord-item.is-answer { background: #defbe6; border-color: var(--valid); }
.qz-ord-item.is-wrong { background: #fff1f1; border-color: var(--error); }
.qz-ord-n { flex: none; font: 600 12px var(--mono); color: var(--text-muted); width: 16px; }
.qz-ord-t { flex: 1; min-width: 0; }
.qz-mvs { display: flex; gap: 2px; }
.qz-mv { width: 32px; height: 32px; background: #fff; border: 1px solid #c6c6c6; cursor: pointer; font-size: 11px; color: var(--text-dark); }
.qz-mv:hover:not([disabled]) { background: var(--primary); color: #fff; border-color: var(--primary); }
.qz-mv[disabled] { color: #c6c6c6; cursor: default; }
.qz-fb { margin-top: 14px; padding: 12px 16px; border-left: 3px solid; font-size: 15px; }
.qz-fb.ok { background: #defbe6; border-color: var(--valid); }
.qz-fb.bad { background: #fff1f1; border-color: var(--error); }
.qz-verdict { font: 600 14px var(--sans); margin-bottom: 4px; }
.qz-fb-ans { margin-bottom: 4px; font-weight: 600; }
.qz-fb-foot { display: flex; flex-wrap: wrap; align-items: center; gap: 12px; margin-top: 8px; }
.qz-link { background: none; border: 0; padding: 0; color: var(--primary); cursor: pointer; font-size: 14px; text-decoration: underline; }
.qz-link:hover { color: var(--primary-hover); }
.qz-actions { margin-top: 24px; }
.qz-banner { position: sticky; top: 0; z-index: 3; display: flex; align-items: center; justify-content: space-between; gap: 16px; flex-wrap: wrap; padding: 16px 24px; margin: 0 0 24px; border-left: 6px solid; background: #fff; box-shadow: 0 2px 8px rgba(0,0,0,0.12); }
.qz-banner.ok { border-color: var(--valid); }
.qz-banner.bad { border-color: var(--error); }
.qz-score { font: 700 28px/1.2 var(--mono); }
.qz-passline { font-size: 14px; color: var(--text-muted); margin-top: 2px; }
.qz-banner .btn-row { margin: 0; }
.qz-banner .btn { text-align: center; }
.qz-actions .btn { text-align: center; }

/* ---------- narrow dock (labs at 1440 px): let long tokens wrap instead of widening the dock ---------- */
#dock .dt th, #dock .dt td { overflow-wrap: anywhere; }
#dock .dt { table-layout: auto; max-width: 100%; }
#dock .card, #dock .notice, #dock .trap { overflow-wrap: anywhere; }

/* In a lab, the lab card already says what the station is for: keep the station heading small. */
body[data-mode="lab"] .st-head .st-id,
body[data-mode="lab"] .st-head .expressive { display: none; }
body[data-mode="lab"] .st-head .st-title { font-size: 20px; line-height: 1.3; margin: 0 0 8px; }