/* Course UI: orient, choose a path, read, practice, continue. */
[hidden] { display: none !important; }
.brand-image, .brand-image img { display: block; flex: none; width: 36px; height: 36px; }
.site-header { max-width: 1320px; padding-top: 17px; padding-bottom: 17px; }
.site-header nav a { display: flex; align-items: center; min-height: 44px; font-size: 14px; }
.site-header .header-github { min-height: 44px; font-size: 13px; }
.brand { font-size: 18px; }
.brand small { font-size: 10px; letter-spacing: 0; }
.course-home { max-width: 1240px; }
.course-intro { display: grid; grid-template-columns: 1.15fr 1fr; gap: 65px; align-items: center; padding: 42px 0 30px; }
.course-intro h1 { font-size: clamp(37px,4vw,51px); letter-spacing: -2.3px; margin-bottom: 16px; }
.course-intro .hero-kicker { font-size: 12px; margin-bottom: 15px; }
.course-intro .lead { font-size: 16px; max-width: 540px; margin-bottom: 23px; }
.path-picker { padding: 0; margin: 0; border: 0; }
.path-picker legend { font-size: 14px; font-weight: 750; margin-bottom: 12px; }
.path-picker > div { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); gap: 9px; }
.path-picker button { min-height: 77px; padding: 12px; text-align: left; color: var(--ink); border: 1px solid #cbd5e4; border-radius: 8px; background: white; }
.path-picker button strong, .path-picker button span { display: block; }
.path-picker button strong { font-size: 13px; font-weight: 750; }
.path-picker button span { font-size: 11px; margin-top: 5px; color: var(--muted); line-height: 1.5; }
.path-picker button[aria-pressed=true] { border-color: var(--accent); background: #edf1ff; box-shadow: inset 0 0 0 1px var(--accent); }
.path-picker button[aria-pressed=true] strong { color: #2546c4; }
.path-picker > p { margin: 10px 0 0; min-height: 36px; color: var(--muted); font-size: 11px; }
.resume-panel { padding: 27px; background: white; border: 1px solid var(--line); border-top: 3px solid var(--accent); border-radius: 11px; }
.resume-panel .eyebrow { display: block; margin-bottom: 14px; font-size: 10px; }
.resume-position { color: var(--muted); font-size: 12px; margin-bottom: 8px; }
.resume-panel h2 { font-size: 26px; letter-spacing: -.8px; line-height: 1.3; }
.resume-panel > p[data-resume-summary] { margin: 12px 0 19px; font-size: 14px; color: var(--muted); line-height: 1.7; }
.resume-panel .button { width: 100%; justify-content: space-between; min-height: 48px; font-size: 14px; }
.resume-progress { display: flex; align-items: center; gap: 16px; padding-top: 20px; }
.resume-progress > span { white-space: nowrap; color: var(--muted); font-size: 12px; }
.resume-progress progress { width: 100%; }
.resume-storage { display: block; font-size: 11px; color: var(--muted); margin-top: 8px; }
progress { display: block; height: 6px; overflow: hidden; border: 0; border-radius: 9px; appearance: none; background: #e0e7f1; accent-color: var(--accent); }
progress::-webkit-progress-bar { background: #e0e7f1; border-radius: 9px; }
progress::-webkit-progress-value { background: var(--accent); border-radius: 9px; }
progress::-moz-progress-bar { background: var(--accent); border-radius: 9px; }
.course-boundary { margin-bottom: 0; padding: 14px 18px; border-radius: 7px; background: #eaf0ff; color: var(--muted); font-size: 13px; }
.course-boundary strong { color: var(--ink); }
.curriculum-overview { padding-top: 34px; scroll-margin-top: 12px; }
.curriculum-overview .section-heading { margin-bottom: 18px; }
.curriculum-overview .section-heading h2 { font-size: 30px; letter-spacing: -1px; }
.curriculum-overview .section-heading p:last-child { font-size: 14px; margin-top: 10px; }
.course-module { margin: 22px 0; border: 1px solid var(--line); border-radius: 10px; background: white; overflow: hidden; }
.module-heading { display: flex; justify-content: space-between; align-items: center; gap: 20px; padding: 20px 25px; border-bottom: 1px solid var(--line); background: #f9fafc; }
.module-heading .eyebrow { margin: 0 0 6px; font-size: 10px; }
.module-heading h2 { font-size: 22px; letter-spacing: -.7px; }
.module-heading > span { font-size: 12px; color: var(--muted); }
.lesson-card { display: flex; align-items: center; gap: 18px; padding: 20px 25px; border-bottom: 1px solid var(--line); text-decoration: none; }
.lesson-card:last-child { border-bottom: 0; }
.lesson-card:hover { background: #f3f6ff; }
.lesson-card:focus-visible { outline-offset: -3px; }
.lesson-number { display: grid; place-items: center; flex: none; width: 30px; height: 30px; background: #e9eef9; color: var(--muted); border-radius: 7px; font-size: 11px; font-weight: 750; }
.lesson-card > div { min-width: 0; flex: 1; }
.lesson-track { display: block; margin-bottom: 4px; color: var(--muted); font-size: 11px; }
.lesson-card h3 { margin: 0 0 5px; font-size: 17px; line-height: 1.45; letter-spacing: -.3px; }
.lesson-card p { margin: 0; color: var(--muted); font-size: 14px; line-height: 1.7; max-width: 700px; }
.lesson-state { flex: none; color: var(--muted); font-size: 12px; padding-left: 8px; }
.lesson-card > span[aria-hidden] { color: var(--accent); }
.is-complete .lesson-number { background: #e3f1c7; color: #345518; }
.is-complete .lesson-state { color: #365c1a; }
.course-resources { padding: 23px 0 30px; }
.course-resources h2 { font-size: 26px; letter-spacing: -.8px; }
.course-resources p { font-size: 15px; color: var(--muted); margin: 12px 0 16px; }
.course-resources .text-link { display: inline-block; font-size: 14px; padding: 8px 0; margin-right: 22px; }
.course-footer { border-top: 1px solid var(--line); font-size: 11px; line-height: 1.8; }
.progress-settings { margin: 0 0 22px; padding-top: 15px; border-top: 1px solid var(--line); }
.progress-settings summary { min-height: 44px; display: flex; align-items: center; color: var(--muted); cursor: pointer; font-size: 12px; list-style: none; }
.progress-settings summary::after { content: '+'; margin-left: 12px; }
.progress-settings[open] summary::after { content: '−'; }
.progress-settings p { color: var(--muted); font-size: 12px; margin: 0 0 7px; }
.reset-progress, .show-all-lessons { border: 0; background: none; color: var(--muted); font-size: 12px; text-decoration: underline; text-underline-offset: 4px; min-height: 44px; padding: 8px 0; }
.show-all-lessons { color: var(--accent); font-weight: 650; }
.undo-notice { position: fixed; z-index: 20; bottom: 24px; left: 50%; transform: translateX(-50%); display: flex; align-items: center; gap: 16px; width: max-content; max-width: calc(100% - 32px); padding: 12px 14px 12px 20px; border-radius: 10px; background: var(--ink); color: white; box-shadow: 0 6px 25px #14243b30; }
.undo-notice p { font-size: 13px; line-height: 1.5; margin: 0; }
.undo-notice button { background: none; color: white; border: 1px solid #75849b; border-radius: 5px; min-height: 44px; white-space: nowrap; padding: 7px 12px; font-size: 12px; }
.undo-notice .dismiss-notice { border: 0; font-size: 23px; padding: 7px; }

/* A focused reading column and path-aware curriculum. */
.course-layout { display: grid; grid-template-columns: 230px minmax(0,1fr); gap: 55px; max-width: 1280px; margin: 0 auto; padding: 0 40px; }
.curriculum { position: sticky; top: 87px; max-height: calc(100vh - 105px); overflow-y: auto; align-self: start; padding: 25px 12px 20px 0; }
.back-course { display: inline-flex; align-items: center; min-height: 44px; font-size: 13px; font-weight: 650; color: var(--muted); text-decoration: none; }
.sidebar-path { margin: 15px 0 20px; }
.path-select-label { display: block; font-size: 11px; color: var(--muted); margin-bottom: 7px; }
[data-path-select] { width: 100%; min-height: 44px; background: white; border: 1px solid #c4cfdf; border-radius: 6px; color: var(--ink); padding: 8px 30px 8px 11px; font: 13px var(--sans); }
[data-path-select]:focus-visible { outline: 3px solid var(--accent); outline-offset: 3px; }
.course-progress { margin-bottom: 25px; }
.course-progress > div { display: flex; justify-content: space-between; gap: 10px; font-size: 12px; }
.course-progress > div strong { font-weight: 650; }
.course-progress > div span { color: var(--muted); }
.course-progress progress { width: 100%; height: 5px; margin-top: 12px; }
.curriculum nav { display: block; margin: 0; }
.curriculum-group { margin-bottom: 23px; }
.curriculum-group h2 { display: flex; align-items: center; gap: 9px; margin-bottom: 10px; font-size: 11px; font-weight: 750; letter-spacing: 0; }
.curriculum-group h2 > span { color: var(--accent); font-size: 9px; }
.curriculum-group a { display: flex; align-items: center; gap: 10px; padding: 10px; min-height: 44px; margin-left: -10px; border-radius: 6px; font-size: 12px; color: var(--muted); }
.curriculum-group a[aria-current=page] { background: #e7edfc; color: #254acb; font-weight: 750; }
.curriculum-group a:hover { background: #eaf0fd; }
.curriculum-group .lesson-number { width: 25px; height: 25px; font-size: 9px; }
.curriculum .progress-settings { margin-top: 15px; }
.lesson-main { width: 100%; max-width: 850px; margin: 0; padding: 30px 0 0; }
.lesson-breadcrumb { display: flex; align-items: center; gap: 10px; color: var(--muted); font-size: 12px; margin-bottom: 22px; }
.lesson-breadcrumb a { padding: 5px 0; text-decoration: none; }
.lesson-heading { margin-bottom: 20px; }
.lesson-heading h1 { font-size: clamp(30px,3vw,39px); line-height: 1.2; letter-spacing: -1.6px; margin-bottom: 17px; }
.lesson-heading .lead { max-width: 720px; font-size: 16px; margin-bottom: 20px; }
.learning-goals { padding: 0 0 0 17px; border-left: 3px solid #c6d4f7; }
.learning-goals > span { font-size: 12px; font-weight: 750; color: var(--muted); }
.learning-goals ul { margin: 7px 0 0; padding-left: 17px; font-size: 14px; line-height: 1.8; }
.lesson-jumps { display: flex; flex-wrap: wrap; gap: 8px; margin: 20px 0 0; }
.lesson-jumps a { display: inline-flex; align-items: center; min-height: 44px; padding: 8px 13px; border: 1px solid var(--line); border-radius: 6px; background: white; color: var(--ink); text-decoration: none; font-size: 12px; font-weight: 650; }
.lesson-jumps a:hover { border-color: var(--accent); }
.mobile-curriculum { display: none; }
.outside-path { padding: 15px 18px; background: #f2f0e6; border: 1px solid #e5dfc5; border-radius: 8px; font-size: 14px; color: #61572e; }
.outside-path button { border: 0; background: none; color: #61572e; font: inherit; text-decoration: underline; min-height: 44px; padding: 0; }
.lesson-content { min-width: 0; }
.lesson-content h2 { font-size: 25px; letter-spacing: -.8px; line-height: 1.35; margin: 29px 0 15px; }
.lesson-content h3 { font-size: 18px; }
.lesson-content .lesson-lead, .lesson-prose p, .lesson-prose ol, .lesson-prose ul { font-size: 16px; line-height: 1.85; color: #45556b; }
.lesson-prose p { max-width: 72ch; }
.lesson-prose strong { color: var(--ink); }
.lesson-prose ol, .lesson-prose ul { padding-left: 24px; }
.lesson-prose li { margin-bottom: 10px; }
.lesson-content .glossary { grid-template-columns: 1fr 1fr; }
.lesson-content .glossary article { margin: 0; padding: 22px 20px 22px 0; }
.lesson-content .glossary article + article { padding-left: 20px; }
.lesson-content .glossary article:nth-child(3) { border-left: 0; padding-left: 0; }
.lesson-content .glossary article:nth-child(n+3) { border-top: 1px solid var(--line); }
.lesson-content .glossary h3 { margin: 0 0 12px; }
.lesson-content .glossary p { font-size: 15px; line-height: 1.8; }
.lesson-content .glossary .number { margin-bottom: 12px; }
.lesson-content .concept-tag { font-size: 12px; }
.lesson-part { margin: 24px 0; }
.lesson-visual { margin: 22px 0 26px; border: 1px solid var(--line); border-radius: 8px; background: white; overflow: hidden; }
.lesson-visual > summary { display: flex; align-items: center; justify-content: space-between; min-height: 58px; padding: 15px 18px; gap: 15px; cursor: pointer; font-size: 14px; font-weight: 700; list-style: none; }
.lesson-visual > summary::-webkit-details-marker { display: none; }
.visual-disclosure { font-size: 12px; color: var(--accent); font-weight: 550; }
.visual-collapse, .lesson-visual[open] .visual-expand { display: none; }
.lesson-visual[open] .visual-collapse { display: inline; }
.lesson-visual[open] .visual-disclosure { color: var(--muted); }
.lesson-visual[open] .visual-disclosure > span[aria-hidden] { display: inline-block; transform: rotate(45deg); }
.lesson-figure { margin: 0; border-top: 1px solid var(--line); background: #f3f6fa; }
.lesson-figure a, .lesson-figure img { display: block; width: 100%; height: auto; }
.lesson-figure img { max-height: 420px; object-fit: contain; }
.lesson-figure figcaption { font-size: 12px; }
.lesson-content .path-header { align-items: start; }
.lesson-content .path-header h3 { font-size: 22px; }
.lesson-content .path-badge { font-size: 9px; }
.lesson-content .path-panel { padding: 24px; }
.lesson-content .path-panel p, .lesson-content .path-panel ol { font-size: 14px; line-height: 1.85; }
.lesson-content .plain-note, .lesson-content .source-note { font-size: 12px; }
.lesson-content .explain-grid { gap: 25px; }
.lesson-content .explain-grid h3 { font-size: 17px; }
.lesson-content .explain-grid dt, .lesson-content .explain-grid dd { font-size: 14px; }
.lesson-content .recipe-browser { grid-template-columns: 190px minmax(0,1fr); }
.lesson-content .recipe-detail { padding: 22px; }
.lesson-content .recipe-detail h3 { font-size: 22px; }
.lesson-content .recipe-detail p { font-size: 14px; }
.lesson-content .recipe-list button { min-height: 54px; padding: 12px 10px; font-size: 12px; }
.lesson-content .recipe-list button small { font-size: 9px; }
.lesson-content .recipe-detail pre { font-size: 12px; }
.lesson-content pre, .lesson-prose code { font-size: 13px; }
.result-card { padding: 22px; background: white; border: 1px solid var(--line); border-radius: 8px; }
.result-card .mini-label { color: var(--accent); font-size: 11px; }
.result-card dl { margin-bottom: 0; }
.result-card dt { font-size: 14px; font-weight: 750; margin-top: 13px; }
.result-card dd { font-size: 14px; color: var(--muted); margin: 5px 0 0; }
.file-map { border: 1px solid var(--line); border-radius: 8px; padding: 5px 20px; background: white; }
.file-map p { display: flex; justify-content: space-between; align-items: center; gap: 15px; margin: 0; padding: 14px 0; border-bottom: 1px solid var(--line); }
.file-map p:last-child { border-bottom: 0; }
.file-map span { font-size: 13px; }
.proof-grid { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); gap: 12px; margin: 22px 0; }
.proof-grid article { padding: 18px; border: 1px solid var(--line); background: white; border-radius: 8px; }
.proof-grid h3 { font-size: 15px; line-height: 1.6; margin-bottom: 10px; }
.proof-grid p { font-size: 14px; margin: 0; }
.lesson-exercise { margin: 32px 0 25px; padding: 25px; border: 1px solid #d7e5bc; border-radius: 9px; background: #eef3e2; }
.lesson-exercise .eyebrow { color: #466622; }
.lesson-exercise h2 { font-size: 23px; letter-spacing: -.7px; }
.lesson-exercise ol { margin: 17px 0 0; padding-left: 20px; font-size: 15px; line-height: 1.9; color: #465a31; }
.lesson-exercise li { padding-left: 4px; margin: 9px 0; }
.checkpoint { padding: 26px; border: 1px solid var(--line); border-radius: 9px; background: white; }
.checkpoint > .eyebrow { display: block; }
.checkpoint h2 { font-size: 23px; letter-spacing: -.6px; line-height: 1.4; margin-bottom: 20px; }
.checkpoint fieldset { display: grid; gap: 10px; padding: 0; margin: 0 0 20px; border: 0; }
.checkpoint label { display: flex; align-items: start; gap: 13px; min-height: 50px; padding: 14px; border: 1px solid #cbd5e4; border-radius: 7px; font-size: 15px; cursor: pointer; }
.checkpoint label:has(input:checked) { border-color: var(--accent); background: #eff3ff; }
.checkpoint input { accent-color: var(--accent); width: 17px; height: 17px; margin-top: 4px; flex: none; }
.checkpoint .button { min-height: 44px; font-size: 13px; }
.checkpoint-feedback { margin: 16px 0 0; font-size: 14px; color: var(--muted); }
.checkpoint-feedback:empty { display: none; }
.checkpoint-feedback[data-result=correct] { color: #365c1a; }
.lesson-completion { display: flex; align-items: center; justify-content: space-between; gap: 22px; padding: 24px 0; }
.lesson-completion strong { font-size: 14px; }
.lesson-completion p { font-size: 12px; color: var(--muted); margin: 5px 0 0; }
.mark-complete { flex: none; border: 0; background: none; color: var(--accent); min-height: 44px; padding: 8px 0; font-size: 12px; text-decoration: underline; text-underline-offset: 4px; }
.mark-complete[aria-pressed=true] { color: #365c1a; }
.course-finish { padding: 26px; margin-bottom: 24px; border-radius: 9px; color: white; background: var(--ink); }
.course-finish h2 { font-size: 24px; letter-spacing: -.8px; }
.course-finish p { color: #c6d4e7; font-size: 15px; margin: 15px 0; }
.lesson-pagination { display: grid; grid-template-columns: minmax(0,1fr) minmax(0,1.15fr); gap: 20px; width: 100%; margin: 12px 0 30px; }
.lesson-pagination > a { padding: 17px 20px; border: 1px solid #ccd6e5; border-radius: 8px; text-decoration: none; }
.previous-lesson { display: flex; align-items: start; justify-content: center; flex-direction: column; background: white; }
.previous-lesson span { display: block; font-size: 12px; color: var(--muted); margin-bottom: 4px; }
.previous-lesson strong { font-size: 14px; font-weight: 650; }
.lesson-pagination .complete-next { display: grid; grid-template-columns: minmax(0,1fr) 16px; gap: 4px 14px; text-align: left; border-color: var(--accent); font-size: 14px; }
.complete-next > span[aria-hidden] { grid-column: 2; grid-row: 1 / 3; }
.complete-next small { grid-column: 1; font-size: 11px; font-weight: 500; opacity: .85; }
@media(max-width:1100px) {
 .course-layout { grid-template-columns: 205px minmax(0,1fr); gap: 30px; padding: 0 30px; }
 .course-intro { gap: 30px; }
 .course-intro h1 { font-size: 42px; }
 .lesson-content .path-header { display: block; }
 .lesson-content .path-badge { display: inline-block; margin-top: 12px; }
 .lesson-content .explain-grid { grid-template-columns: 1fr; }
 .lesson-content .recipe-browser { grid-template-columns: 155px minmax(0,1fr); }
 .lesson-completion { display: block; }
 .mark-complete { margin-top: 8px; }
}
@media(max-width:820px) {
 .course-layout { display: block; padding: 0 24px; }
 .curriculum { display: none; }
 .lesson-main { max-width: 740px; margin: 0 auto; padding-top: 25px; }
 .mobile-curriculum { display: block; margin-bottom: 24px; padding: 0 16px; border: 1px solid var(--line); border-radius: 7px; background: white; }
 .mobile-curriculum summary { display: flex; align-items: center; justify-content: space-between; min-height: 52px; gap: 15px; cursor: pointer; font-size: 13px; font-weight: 650; list-style: none; }
 .mobile-curriculum summary span:last-child { font-size: 11px; font-weight: 500; color: var(--muted); }
 .mobile-path { margin: 0 0 10px; }
 .mobile-curriculum nav { display: grid; gap: 0; margin: 10px 0; }
 .mobile-curriculum nav a { display: flex; align-items: center; gap: 7px; min-height: 44px; font-size: 13px; padding: 8px 0; }
 .mobile-curriculum a[aria-current] { color: var(--accent); font-weight: 750; }
 .course-intro { grid-template-columns: 1fr; gap: 25px; max-width: 680px; padding-top: 30px; }
 .resume-panel { max-width: 680px; }
 .lesson-heading h1 { font-size: 34px; }
}
@media(max-width:560px) {
 html { scroll-padding-top: 88px; }
 .site-header { flex-wrap: nowrap; gap: 12px; padding: 14px 20px; }
 .site-header .brand { gap: 9px; font-size: 17px; }
 .site-header .brand small { font-size: 9px; }
 .site-header nav { order: 0; width: auto; gap: 0; padding-top: 0; margin-left: auto; }
 .site-header nav a { min-height: 44px; font-size: 12px; }
 .site-header nav a:first-child, .site-header .header-github { display: none; }
 .course-home { padding: 0 20px; }
 .course-intro { padding: 27px 0 23px; gap: 20px; }
 .course-intro h1 { font-size: 35px; letter-spacing: -1.7px; }
 .course-intro .hero-kicker { font-size: 11px; margin-bottom: 12px; }
 .course-intro .lead { font-size: 15px; line-height: 1.75; margin-bottom: 18px; }
 .path-picker legend { font-size: 13px; margin-bottom: 9px; }
 .path-picker > div { gap: 6px; }
 .path-picker button { min-height: 78px; padding: 10px; }
 .path-picker button strong { font-size: 12px; }
 .path-picker button span { font-size: 10px; }
 .path-picker > p { font-size: 11px; min-height: 0; }
 .resume-panel { padding: 21px; }
 .resume-panel .eyebrow { margin-bottom: 10px; }
 .resume-panel h2 { font-size: 23px; }
 .resume-panel > p[data-resume-summary] { display: none; }
 .resume-panel .button { margin-top: 17px; }
 .resume-progress { padding-top: 15px; }
 .resume-position { font-size: 11px; }
 .course-boundary { padding: 15px 17px; font-size: 12px; }
 .curriculum-overview { padding-top: 30px; }
 .curriculum-overview .section-heading h2 { font-size: 26px; }
 .curriculum-overview .section-heading p:last-child { font-size: 13px; }
 .module-heading { padding: 18px; }
 .module-heading h2 { font-size: 21px; }
 .module-heading > span { font-size: 11px; }
 .lesson-card { flex-wrap: wrap; padding: 19px 18px; gap: 10px 13px; }
 .lesson-card > div { flex-basis: calc(100% - 50px); }
 .lesson-card h3 { font-size: 15px; }
 .lesson-card p { font-size: 13px; }
 .lesson-track { font-size: 11px; }
 .lesson-state { margin-left: 43px; padding-left: 0; font-size: 11px; }
 .lesson-card > span[aria-hidden] { margin-left: auto; }
 .course-layout { padding: 0 20px; }
 .lesson-breadcrumb { font-size: 11px; margin-bottom: 17px; }
 .lesson-heading h1 { font-size: 31px; letter-spacing: -1.2px; }
 .lesson-heading .eyebrow { font-size: 10px; }
 .lesson-heading .lead { font-size: 15px; }
 .learning-goals { padding-left: 13px; }
 .learning-goals ul { font-size: 13px; }
 .lesson-jumps { gap: 6px; margin-top: 16px; }
 .lesson-jumps a { padding: 8px 11px; font-size: 11px; }
 .lesson-content h2 { font-size: 23px; }
 .lesson-content .lesson-lead, .lesson-prose p, .lesson-prose ol, .lesson-prose ul { font-size: 15px; }
 .lesson-visual > summary { padding: 15px; font-size: 13px; }
 .visual-disclosure { font-size: 11px; }
 .lesson-content .path-panel { padding: 20px; }
 .lesson-content .glossary p { font-size: 14px; }
 .lesson-content .concept-tag { font-size: 11px; }
 .lesson-content .recipe-browser { display: block; }
 .lesson-content .recipe-detail { padding: 19px; }
 .lesson-content .recipe-list button { font-size: 11px; }
 .lesson-content .recipe-detail pre { font-size: 12px; }
 .file-map { padding: 2px 16px; }
 .file-map p { flex-direction: column; align-items: start; gap: 5px; }
 .proof-grid { grid-template-columns: 1fr; }
 .proof-grid article { padding: 16px; }
 .lesson-exercise, .checkpoint { padding: 20px; }
 .lesson-exercise h2, .checkpoint h2 { font-size: 22px; }
 .lesson-exercise ol, .checkpoint label { font-size: 14px; }
 .course-finish { padding: 22px; }
 .course-finish h2 { font-size: 22px; }
 body[data-lesson]:not([data-lesson=""]) { padding-bottom: calc(110px + env(safe-area-inset-bottom)); }
 .lesson-pagination { position: fixed; z-index: 8; bottom: 0; left: 0; right: 0; width: 100%; grid-template-columns: minmax(0,.75fr) minmax(0,1.65fr); gap: 10px; margin: 0; padding: 10px 16px calc(10px + env(safe-area-inset-bottom)); border-top: 1px solid #cdd7e6; background: var(--paper); box-shadow: 0 -3px 15px #17263d08; }
 .lesson-pagination > a { min-height: 66px; padding: 10px 12px; }
 .previous-lesson span { font-size: 11px; }
 .previous-lesson strong { font-size: 11px; overflow-wrap: anywhere; }
 .lesson-pagination .complete-next { font-size: 12px; gap: 4px 7px; }
 .complete-next small { font-size: 10px; }
 .undo-notice { bottom: 108px; gap: 9px; padding: 10px 10px 10px 15px; }
 body[data-lesson=""] .undo-notice { bottom: 16px; }
 .undo-notice p { font-size: 12px; }
 .undo-notice button { padding: 6px 9px; font-size: 11px; }
}