:root {
  --ink: #172033;
  --muted: #586174;
  --paper: #fff;
  --canvas: #eef1f5;
  --line: #d6dce7;
  --accent: #1f5fbf;
  --accent-dark: #16488f;
  --soft: #edf4ff;
  --warning: #fff7df;
  --danger: #fff0ef;
  --code: #111827;
  --code-text: #e5edf8;
  --radius: .5rem;
  --measure: 74rem;
  color-scheme: light;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: var(--canvas); color: var(--ink); line-height: 1.62; }
a { color: var(--accent-dark); text-underline-offset: .18em; }
button, select { min-height: 2.75rem; font: inherit; }
:focus-visible { outline: 3px solid #f4a024; outline-offset: 3px; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; border: 0; }
.skip-link { position: fixed; top: -5rem; left: 1rem; z-index: 30; padding: .7rem 1rem; background: var(--ink); color: #fff; }
.skip-link:focus { top: 1rem; }

.toolbar { position: sticky; top: 0; z-index: 10; display: flex; align-items: center; justify-content: space-between; gap: 1rem; min-height: 4.25rem; padding: .65rem max(1rem, calc((100vw - var(--measure)) / 2)); border-bottom: 1px solid var(--line); background: rgb(255 255 255 / .96); backdrop-filter: blur(10px); }
.breadcrumb { display: flex; align-items: center; min-width: 0; gap: .45rem; color: var(--muted); font-size: .88rem; white-space: nowrap; }
.breadcrumb a { color: var(--accent-dark); font-weight: 750; text-decoration: none; }
.breadcrumb [aria-current="page"] { overflow: hidden; color: var(--ink); font-weight: 800; text-overflow: ellipsis; }
.toolbar-actions { display: flex; align-items: center; gap: .75rem; }
.section-navigation { max-width: 20rem; }
select { padding: 0 2.25rem 0 .7rem; border: 1px solid #9ca8bb; border-radius: var(--radius); background: #fff; color: var(--ink); }
.button { display: inline-flex; align-items: center; justify-content: center; min-height: 2.75rem; padding: .65rem 1rem; border: 1px solid #9ca8bb; border-radius: var(--radius); background: #fff; color: var(--ink); font-weight: 750; line-height: 1.2; text-decoration: none; cursor: pointer; }
.button:hover { border-color: var(--accent); }
.button-primary { border-color: var(--accent); background: var(--accent); color: #fff; }
.button-primary:hover { border-color: var(--accent-dark); background: var(--accent-dark); }

main { width: min(100% - 2rem, var(--measure)); margin: 2rem auto 5rem; }
.toc-page, .course-document { border: 1px solid var(--line); background: var(--paper); box-shadow: 0 1rem 3rem rgb(26 39 65 / .08); }
.toc-page { min-height: 54rem; padding: clamp(2rem, 6vw, 5rem); }
.document-mark { padding-bottom: 1.25rem; border-bottom: 3px solid var(--accent); color: var(--muted); font-size: .82rem; font-weight: 800; letter-spacing: .09em; text-transform: uppercase; }
.eyebrow { margin: 2rem 0 .45rem; color: var(--accent); font-size: .78rem; font-weight: 850; letter-spacing: .12em; text-transform: uppercase; }
h1, h2, h3 { line-height: 1.18; letter-spacing: -.025em; }
h1 { max-width: 18ch; margin: 0; font-size: clamp(2.4rem, 7vw, 4.8rem); }
h2 { margin: 0 0 1rem; font-size: clamp(1.8rem, 4vw, 2.7rem); }
h3 { margin: 0 0 .55rem; font-size: 1.15rem; }
p { margin: 0 0 1rem; }
.toc-intro, .lead { max-width: 52rem; color: var(--muted); font-size: 1.12rem; }
.toc-intro { margin-top: 1rem; }

.prerequisite-panel { margin: 2rem 0; padding: 1.2rem; border: 1px solid var(--line); border-left: 4px solid var(--accent); border-radius: var(--radius); background: #fbfcfe; }
.prerequisite-panel h2 { font-size: 1.4rem; }
.prerequisite-paths { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1rem; }
.prerequisite-paths > div { display: flex; align-items: flex-start; flex-direction: column; padding: 1rem; border: 1px solid var(--line); border-radius: var(--radius); background: #fff; }
.prerequisite-paths .button { margin-top: auto; }

.days-overview { margin: 2rem 0; }
.day-overview { overflow: hidden; border: 1px solid var(--line); border-radius: var(--radius); background: #fbfcfe; }
.day-overview summary { display: grid; grid-template-columns: 5rem minmax(0, 1fr) auto; align-items: center; gap: .35rem 1rem; padding: 1rem 1.15rem; cursor: pointer; list-style: none; }
.day-overview summary::-webkit-details-marker { display: none; }
.day-overview summary::after { grid-column: 3; grid-row: 1 / 3; content: "+"; color: var(--accent); font-size: 1.6rem; }
.day-overview[open] summary::after { content: "−"; }
.day-overview summary:hover { background: var(--soft); }
.day-label { grid-column: 1; grid-row: 1 / 3; color: var(--accent); font-size: .78rem; font-weight: 850; letter-spacing: .1em; text-transform: uppercase; }
.day-overview summary strong { grid-column: 2; }
.day-duration { grid-column: 2; color: var(--muted); font-size: .82rem; }
.day-sections { padding: .8rem 1.15rem 1.15rem; border-top: 1px solid var(--line); }
.toc-list { display: grid; margin: .8rem 0 0; padding: 0; list-style: none; border-top: 1px solid var(--line); }
.toc-list a { display: grid; grid-template-columns: 3rem 1fr; gap: .75rem; padding: .72rem 0; border-bottom: 1px solid var(--line); color: var(--ink); text-decoration: none; }
.toc-list span { color: var(--accent); font-variant-numeric: tabular-nums; }
.toc-meta { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1rem; margin-top: 2rem; }
.toc-meta div { padding-top: .75rem; border-top: 3px solid var(--ink); }
.toc-meta dt { color: var(--muted); font-size: .8rem; font-weight: 750; text-transform: uppercase; }
.toc-meta dd { margin: .2rem 0 0; font-weight: 700; }

.course-document { margin-top: 2rem; }
.lesson-section { padding: clamp(2rem, 6vw, 5rem); border-top: 1px solid var(--line); scroll-margin-top: 5rem; }
.lesson-section:first-child { border-top: 0; }
.section-heading-number { display: inline-block; margin-right: 4px; color: var(--accent); font-size: .46em; font-weight: 850; letter-spacing: .1em; vertical-align: .25em; }
.section-heading-number::after { content: "."; }
.lesson-actions { display: flex; flex-wrap: wrap; gap: .75rem; margin-top: 1.5rem; }
.resource-list, .steps { display: grid; gap: .65rem; padding-left: 1.4rem; }
.resource-list { grid-template-columns: repeat(2, minmax(0, 1fr)); margin: 1.5rem 0; padding: 0; list-style: none; }
.resource-list a { display: block; height: 100%; padding: .8rem 1rem; border: 1px solid var(--line); border-radius: var(--radius); background: #fbfcfe; font-weight: 750; }
.section-metadata { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1rem; margin: 1.5rem 0; }
.note, .checkpoint { margin: 1.5rem 0; padding: 1rem 1.15rem; border-left: 4px solid var(--accent); background: var(--soft); }
.section-metadata .note { margin: 0; }
.note p, .checkpoint p { margin-bottom: 0; }
.warning { border-color: #b7791f; background: var(--warning); }
.checkpoint strong { display: block; margin-bottom: .35rem; color: var(--accent-dark); }

.command-groups { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1rem; margin: 1.5rem 0; }
.command-groups > section { min-width: 0; padding: 1rem; border: 1px solid var(--line); border-radius: var(--radius); background: #fbfcfe; }
.command-groups pre { margin-bottom: 0; }
.command-strip { display: flex; flex-wrap: wrap; gap: .55rem; margin: 1.25rem 0; }
.command-strip code { padding: .45rem .7rem; border: 1px solid var(--line); border-radius: .35rem; background: #f4f6f9; }
.graph-comparison, .todo-comparison, .graph-cards, .danger-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1rem; margin: 1.5rem 0; }
.graph-cards { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.graph-comparison > div, .todo-comparison > div, .danger-grid > div { min-width: 0; padding: 1rem; border: 1px solid var(--line); border-radius: var(--radius); background: #fbfcfe; }
.danger-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.danger-grid .danger { border-color: #c94f46; background: var(--danger); }
.danger-grid h3 { font-size: .9rem; }
.deployment-flow { display: flex; align-items: stretch; justify-content: center; flex-wrap: wrap; gap: .55rem; margin: 1.5rem 0; }
.deployment-flow span { display: grid; place-items: center; min-height: 3rem; padding: .65rem .8rem; border: 1px solid var(--line); border-radius: var(--radius); background: #fbfcfe; text-align: center; font-weight: 750; }
.deployment-flow b { align-self: center; color: var(--accent); }

.table-scroll { margin: 1.5rem 0; overflow-x: auto; }
.reference-table { width: 100%; min-width: 48rem; border-collapse: collapse; font-size: .91rem; }
.reference-table caption { padding: .65rem; color: var(--muted); font-weight: 800; text-align: left; }
.reference-table th, .reference-table td { padding: .72rem .75rem; border: 1px solid var(--line); text-align: left; vertical-align: top; }
.reference-table thead th { background: #f0f3f8; color: var(--accent-dark); font-size: .78rem; text-transform: uppercase; }
.reference-table tbody th { background: #fbfcfe; }
.compact-matrix { min-width: 40rem; }

.api-list { margin: 1.5rem 0; }
.api-list div { display: grid; grid-template-columns: minmax(13rem, .7fr) 1.3fr; gap: 1rem; padding: .8rem 0; border-bottom: 1px solid var(--line); }
.api-list dt { font-weight: 750; }
.api-list dd { margin: 0; color: var(--muted); }
.extra-mile { margin: 1.5rem 0; overflow: hidden; border: 1px solid var(--line); border-left: 4px solid var(--accent); border-radius: var(--radius); background: #fbfcfe; }
.extra-mile summary { display: flex; justify-content: space-between; gap: 1rem; padding: .9rem 1rem; font-weight: 800; cursor: pointer; list-style: none; }
.extra-mile summary::-webkit-details-marker { display: none; }
.extra-mile summary::after { content: "+"; color: var(--accent); font-size: 1.25rem; }
.extra-mile[open] summary::after { content: "−"; }
.extra-mile > :not(summary) { margin: 0; padding: 1rem; color: var(--muted); }

pre { max-width: 100%; margin: 1.35rem 0; padding: 1.15rem; overflow-x: auto; border-radius: var(--radius); background: var(--code); color: var(--code-text); font: .88rem/1.55 ui-monospace, SFMono-Regular, Consolas, "Liberation Mono", monospace; tab-size: 2; }
code { font-family: ui-monospace, SFMono-Regular, Consolas, "Liberation Mono", monospace; }
:not(pre) > code { padding: .08em .32em; border-radius: .25rem; background: #edf0f5; font-size: .92em; }
.course-code-frame { position: relative; max-width: 100%; margin: 1.35rem 0; }
.course-code-frame > pre { margin: 0; padding-top: 3.5rem; }
.course-code-copy { position: absolute; top: .6rem; right: .6rem; z-index: 2; width: 2.25rem; min-height: 2.25rem; padding: 0; border: 1px solid #596579; border-radius: .35rem; background: #252b36; color: #e5edf8; font-weight: 800; cursor: pointer; }
.token-comment { color: #6a9955; }
.token-command { color: #569cd6; font-weight: 700; }
.token-option { color: #9cdcfe; }
.token-string { color: #ce9178; }
.token-key { color: #dcdcaa; }

.section-copyright { display: grid; grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr); align-items: center; gap: .5rem 1rem; margin-top: 2.5rem; padding-top: .75rem; border-top: 1px solid var(--line); color: var(--muted); font-size: .7rem; letter-spacing: .03em; }
.section-copyright-notice { text-align: center; }
.section-legal-links { display: flex; flex-wrap: wrap; justify-self: end; justify-content: flex-end; gap: .35rem .8rem; }
.section-legal-links a { color: inherit; }

.quiz-dialog { width: min(calc(100% - 2rem), 54rem); max-height: calc(100vh - 2rem); padding: 0; overflow: hidden; border: 1px solid var(--line); border-radius: .75rem; background: #fff; color: var(--ink); box-shadow: 0 1.5rem 5rem rgb(15 25 42 / .35); }
.quiz-dialog::backdrop { background: rgb(12 20 34 / .74); backdrop-filter: blur(4px); }
.quiz-dialog-header { display: flex; align-items: flex-start; justify-content: space-between; gap: 1rem; padding: 1.15rem 1.35rem; border-bottom: 1px solid var(--line); }
.quiz-dialog-kicker { margin: 0 0 .25rem; color: var(--accent-dark); font-size: .72rem; font-weight: 850; letter-spacing: .11em; text-transform: uppercase; }
.quiz-dialog-title { margin: 0; font-size: clamp(1.35rem, 3vw, 2rem); }
.quiz-close { flex: 0 0 auto; width: 2.5rem; height: 2.5rem; border: 1px solid var(--line); border-radius: var(--radius); background: #fff; color: var(--ink); font-size: 1.4rem; cursor: pointer; }
.quiz-dialog-body { max-height: calc(100vh - 8rem); padding: 1.35rem; overflow-y: auto; }
.quiz-intro { color: var(--muted); }
.quiz-progress-card { padding: 1rem 1.1rem; border-left: 4px solid var(--accent); background: var(--soft); }
.quiz-progress-card p { margin: 0; }
.quiz-score { color: var(--accent-dark); font-weight: 850; }
.quiz-setting { display: grid; grid-template-columns: auto 1fr; gap: .7rem; margin-top: 1rem; padding: .8rem 1rem; border: 1px solid var(--line); border-radius: var(--radius); cursor: pointer; }
.quiz-setting input, .quiz-option input { width: 1.05rem; height: 1.05rem; margin-top: .13rem; accent-color: var(--accent); }
.quiz-summary-actions, .quiz-question-actions { display: flex; flex-wrap: wrap; justify-content: flex-end; gap: .65rem; margin-top: 1.25rem; }
.quiz-question-meta { display: flex; justify-content: space-between; gap: 1rem; color: var(--muted); font-size: .82rem; font-weight: 750; }
.quiz-level { padding: .25rem .55rem; border-radius: 99rem; background: var(--soft); color: var(--accent-dark); }
.quiz-level-advanced { background: #fff2d6; color: #7b4d00; }
.quiz-question-prompt { margin: 1rem 0 .35rem; font-size: clamp(1.2rem, 3vw, 1.6rem); }
.quiz-question-hint { margin: 0 0 1rem; color: var(--muted); font-size: .9rem; }
.quiz-options { display: grid; gap: .65rem; margin: 0; padding: 0; border: 0; }
.quiz-option { display: grid; grid-template-columns: auto 1fr; gap: .75rem; padding: .85rem 1rem; border: 1px solid var(--line); border-radius: var(--radius); cursor: pointer; }
.quiz-option:hover, .quiz-option:has(input:checked) { border-color: var(--accent); background: var(--soft); }
.quiz-review-list { display: grid; gap: 1rem; }
.quiz-review-item, .quiz-immediate-review { padding: 1rem 1.1rem; border: 1px solid var(--line); border-left: 4px solid #8b97aa; border-radius: var(--radius); }
.quiz-review-item.is-correct { border-left-color: #26734d; }
.quiz-review-item.is-incorrect { border-left-color: #b7791f; }
.quiz-review-question { margin: 0 0 .45rem; font-size: 1rem; }
.quiz-review-status { margin: 0 0 .8rem; color: var(--muted); font-size: .8rem; font-weight: 850; text-transform: uppercase; }
.quiz-review-details { display: grid; grid-template-columns: minmax(8rem, .35fr) 1fr; gap: .35rem 1rem; margin: 0; }
.quiz-review-details dt { font-weight: 800; }
.quiz-review-details dd { margin: 0; color: var(--muted); }
.quiz-feedback-options { display: grid; gap: .6rem; }
.quiz-feedback-option { display: flex; justify-content: space-between; gap: 1rem; padding: .8rem 1rem; border: 1px solid var(--line); border-radius: var(--radius); }
.quiz-feedback-option.is-selected { border-color: #b7791f; background: #fff8e8; }
.quiz-feedback-option.is-correct { border-color: #26734d; background: #edf8f2; }
.quiz-feedback-badges { display: flex; flex-wrap: wrap; justify-content: flex-end; gap: .35rem; }
.quiz-feedback-badge { padding: .2rem .45rem; border-radius: 99rem; background: rgb(255 255 255 / .78); color: var(--muted); font-size: .68rem; font-weight: 800; }
.quiz-feedback-explanation { margin-top: .8rem; padding: 1rem 1.1rem; border-left: 4px solid var(--accent); background: var(--soft); }

@media (max-width: 62rem) {
  .graph-cards, .danger-grid { grid-template-columns: 1fr; }
}
@media (max-width: 48rem) {
  .toolbar { position: static; align-items: flex-start; flex-direction: column; }
  .breadcrumb { max-width: 100%; white-space: normal; }
  .toolbar-actions { width: 100%; flex-wrap: wrap; }
  .section-navigation, .toolbar-actions select { flex: 1 1 10rem; max-width: none; }
  .toolbar-actions .button, .lesson-actions .button { flex: 1 1 100%; }
  main { width: min(100% - 1rem, var(--measure)); margin-top: .5rem; }
  .toc-page, .lesson-section { padding: 1.4rem; }
  .day-overview summary { grid-template-columns: 4rem minmax(0, 1fr) auto; }
  .toc-meta, .section-metadata, .resource-list, .prerequisite-paths, .command-groups, .graph-comparison, .todo-comparison { grid-template-columns: 1fr; }
  .api-list div { grid-template-columns: 1fr; gap: .3rem; }
  .section-copyright { grid-template-columns: 1fr; justify-items: center; text-align: center; }
  .section-legal-links { justify-self: center; justify-content: center; }
  .quiz-dialog { width: calc(100% - 1rem); max-height: calc(100vh - 1rem); }
  .quiz-dialog-body { max-height: calc(100vh - 7.5rem); padding: 1rem; }
  .quiz-review-details { grid-template-columns: 1fr; }
  .quiz-feedback-option { align-items: flex-start; flex-direction: column; }
}
@media print {
  @page { size: A4 portrait; margin: 16mm 16mm 18mm; }
  :root { font-size: 10.5pt; }
  html { scroll-behavior: auto; }
  body { background: #fff; color: #000; line-height: 1.45; }
  .screen-only, .no-print, .lesson-actions { display: none !important; }
  main { width: auto; margin: 0; }
  .toc-page, .course-document { border: 0; box-shadow: none; }
  .toc-page { min-height: 263mm; padding: 0; break-after: page; }
  .day-overview summary::after { display: none; }
  .day-overview > :not(summary), .extra-mile > :not(summary) { display: block !important; }
  .course-document { margin: 0; }
  .lesson-section { padding: 0; border: 0; }
  .lesson-section + .lesson-section { margin-top: 14mm; padding-top: 10mm; border-top: 1px solid #aaa; }
  h2, h3, .checkpoint strong { break-after: avoid-page; }
  pre, .note, .checkpoint, .extra-mile, .reference-table, .graph-comparison > div, .todo-comparison > div, .prerequisite-panel { break-inside: avoid; }
  pre { border: 1px solid #777; background: #f4f4f4; color: #000; white-space: pre-wrap; overflow-wrap: anywhere; }
  .course-code-copy { display: none; }
  .course-code-frame > pre { padding-top: 1.15rem; }
  .table-scroll { overflow: visible; }
  .reference-table { min-width: 0; font-size: 8pt; }
  .command-groups { grid-template-columns: repeat(2, 1fr); }
  a { color: #000; text-decoration: none; }
}