/* ==========================================================================
   Learn egui — Tufte-Inspired Dark-Mode Course & Reference Stylesheet
   Shared across all ./lessons/*.html and ./reference/*.html
   Includes Prism.js token theme & Mermaid.js diagram container styling
   ========================================================================== */

:root {
  /* MANDATORY: Apply color-scheme to :root so viewport scrollbars, form controls,
     and initial canvas background adopt dark mode */
  color-scheme: dark;

  --bg-paper: #121518;
  --bg-elevated: #1a1f24;
  --bg-surface: #222830;
  --bg-code: #0c0e11;
  --text-main: #e8e6df;
  --text-muted: #9da6b0;
  --text-sidenote: #adb6c0;
  --accent-pcb: #3dd68c;       /* Luminous solder-mask green accent */
  --accent-pcb-btn: #1f7a4c;   /* Button fill green */
  --accent-copper: #ff8b6b;    /* Luminous top-copper rust/terracotta accent */
  --accent-silk: #6cb6ff;      /* Blueprint / silkscreen sky blue */
  --border-subtle: #2d353f;
  --border-strong: #465260;
  --ok-bg: #132a20;
  --ok-border: #3dd68c;
  --ok-text: #b4f4d3;
  --err-bg: #2d1614;
  --err-border: #ff6b5b;
  --err-text: #ffbab3;
  --font-serif: "ETBook", "Palatino Linotype", Palatino, "Book Antiqua", Georgia, serif;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-mono: "JetBrains Mono", "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;

  --scrollbar-thumb: #465260;
  --scrollbar-track: #1a1f24;
  scrollbar-width: thin;
  scrollbar-color: var(--scrollbar-thumb) var(--scrollbar-track);
  accent-color: var(--accent-pcb);
}

@supports not (scrollbar-color: auto) {
  ::-webkit-scrollbar {
    width: 10px;
    height: 10px;
  }
  ::-webkit-scrollbar-thumb {
    background: var(--scrollbar-thumb);
  }
  ::-webkit-scrollbar-track {
    background: var(--scrollbar-track);
  }
}

@supports not (accent-color: var(--accent-pcb)) {
  input[type="range"] {
    -webkit-appearance: none;
    appearance: none;
    background: transparent;
  }
  input[type="range"]::-webkit-slider-runnable-track {
    width: 100%;
    height: 8px;
    background: var(--border-strong);
    border-radius: 4px;
  }
  input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    height: 16px;
    width: 16px;
    border-radius: 50%;
    background: var(--accent-pcb);
    cursor: pointer;
    margin-top: -4px;
  }
}

* {
  box-sizing: border-box;
}

html {
  font-size: 17px;
  background-color: var(--bg-paper);
  color: var(--text-main);
  -webkit-font-smoothing: antialiased;
}

@media (prefers-reduced-motion: no-preference) {
  @view-transition {
    navigation: auto;
  }
}

:where(a, button, input, summary, [tabindex="0"]):focus-visible {
  outline: 2px solid var(--accent-silk);
  outline-offset: 2px;
}

body {
  font-family: var(--font-serif);
  line-height: 1.68;
  margin: 0;
  padding: 2.5rem 2rem 5rem 2rem;
  max-width: 1180px;
  margin-left: auto;
  margin-right: auto;
  counter-reset: sidenote-counter;
}

/* Top Navigation Bar (Minimal Tufte Breadcrumb + Pager) */
.course-nav {
  font-family: var(--font-sans);
  font-size: 0.82rem;
  letter-spacing: 0.03em;
  text-transform: uppercase;
  color: var(--text-muted);
  border-bottom: 1px solid var(--border-subtle);
  padding-bottom: 0.75rem;
  margin-bottom: 2.5rem;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  gap: 0.75rem 1.25rem;
}

.course-nav .nav-breadcrumbs,
.course-nav .nav-controls {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.55rem;
}

.course-nav .nav-controls {
  gap: 0.85rem;
}

.course-nav a {
  color: var(--text-muted);
  text-decoration: none;
  transition: color 0.15s ease;
}

.course-nav a:hover,
.course-nav a.active,
.course-nav .nav-current {
  color: var(--accent-copper);
  font-weight: 600;
}

.course-nav .nav-sep,
.course-nav .nav-dot,
.course-nav .nav-divider {
  color: var(--border-strong);
  user-select: none;
}

.course-nav .nav-pager-group {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  font-family: var(--font-mono);
  font-size: 0.78rem;
}

.course-nav .nav-pager {
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  padding: 0.18rem 0.5rem;
  border-radius: 3px;
  color: var(--text-main);
}

.course-nav .nav-pager:hover {
  border-color: var(--accent-copper);
  color: var(--accent-copper);
}

.course-nav .mission-badge {
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  padding: 0.25rem 0.65rem;
  border-radius: 3px;
  font-weight: 500;
  color: var(--accent-pcb);
  text-transform: none;
  letter-spacing: 0;
}

/* Tufte Two-Column Layout: Main Prose (63%) + Right Sidenote Margin (44% offset) */
article.tufte-article {
  position: relative;
}

.prose-col {
  width: 63%;
}

/* Typography */
h1, h2, h3, th {
  text-wrap: balance;
}

h1 {
  font-weight: 400;
  font-size: 2.35rem;
  line-height: 1.18;
  margin-top: 0.5rem;
  margin-bottom: 0.5rem;
  color: var(--text-main);
}

.subtitle {
  font-style: italic;
  font-size: 1.2rem;
  color: var(--text-muted);
  margin-top: 0;
  margin-bottom: 2rem;
  text-wrap: balance;
}

h2 {
  font-weight: 400;
  font-style: italic;
  font-size: 1.55rem;
  margin-top: 2.6rem;
  margin-bottom: 0.8rem;
  border-bottom: 1px solid var(--border-subtle);
  padding-bottom: 0.3rem;
  color: var(--text-main);
}

h3 {
  font-family: var(--font-sans);
  font-size: 1.02rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  margin-top: 1.8rem;
  margin-bottom: 0.5rem;
  color: var(--text-main);
}

p, ul, ol {
  margin-top: 0;
  margin-bottom: 1.2rem;
}

p, li, blockquote {
  text-wrap: pretty;
}

a {
  color: var(--accent-silk);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

a:hover {
  color: var(--accent-copper);
}

/* Sidenotes & Margin Notes */
.sidenote-number {
  counter-increment: sidenote-counter;
}

.sidenote-number::after,
.sidenote::before {
  font-family: var(--font-sans);
  position: relative;
  vertical-align: baseline;
}

.sidenote-number::after {
  content: counter(sidenote-counter);
  font-size: 0.7rem;
  top: -0.45rem;
  left: 0.1rem;
  color: var(--accent-copper);
  font-weight: 700;
}

.sidenote::before {
  content: counter(sidenote-counter) ". ";
  font-size: 0.75rem;
  color: var(--accent-copper);
  font-weight: 700;
}

.sidenote,
.marginnote {
  float: right;
  clear: right;
  margin-right: -52%;
  width: 44%;
  margin-top: 0.2rem;
  margin-bottom: 1.2rem;
  font-size: 0.84rem;
  line-height: 1.45;
  color: var(--text-sidenote);
  font-family: var(--font-sans);
  border-left: 2px solid var(--border-subtle);
  padding-left: 0.85rem;
}

/* Inline & Block Code + Prism.js Theme */
code {
  font-family: var(--font-mono);
  font-size: 0.84em;
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  color: #f0ede6;
  padding: 0.1rem 0.35rem;
  border-radius: 3px;
}

pre:has(> code),
pre[class*="language-"],
pre.code-block {
  background: var(--bg-code);
  color: #e8e6df;
  padding: 1.15rem 1.35rem;
  border-radius: 5px;
  overflow-x: auto;
  line-height: 1.52;
  margin: 1.25rem 0 1.5rem 0;
  border: 1px solid var(--border-subtle);
  border-left: 4px solid var(--accent-copper);
  tab-size: 4;
}

.code-block-wrapper {
  position: relative;
  margin: 1.25rem 0 1.5rem 0;
}

.code-block-wrapper.is-compact {
  margin: 0;
}

.code-block-wrapper > pre:has(> code),
.code-block-wrapper > pre[class*="language-"],
.code-block-wrapper > pre.code-block {
  margin: 0;
  padding-right: 5.5rem;
}

.code-block-wrapper.is-compact > pre:has(> code),
.code-block-wrapper.is-compact > pre[class*="language-"] {
  padding-top: 2.1rem !important;
  padding-right: 0.85rem !important;
}

.copy-code-btn {
  position: absolute;
  top: 0.55rem;
  right: 0.55rem;
  z-index: 2;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-family: var(--font-sans);
  font-size: 0.74rem;
  font-weight: 600;
  line-height: 1;
  color: var(--text-main);
  background: var(--bg-surface);
  border: 1px solid var(--border-strong);
  border-radius: 4px;
  padding: 0.34rem 0.58rem;
  cursor: pointer;
  user-select: none;
  transition: background-color 0.14s ease, border-color 0.14s ease, color 0.14s ease;
}

.code-block-wrapper.is-compact > .copy-code-btn {
  top: 0.38rem;
  right: 0.38rem;
  padding: 0.24rem 0.48rem;
  font-size: 0.7rem;
}

.copy-code-btn:hover {
  background: #2c3540;
  border-color: var(--accent-silk);
  color: #ffffff;
}

.copy-code-btn.copied {
  background: var(--ok-bg);
  border-color: var(--ok-border);
  color: var(--ok-text);
}

.visually-hidden:where(:not(:focus-within, :active)) {
  position: absolute !important;
  clip-path: inset(50%) !important;
  overflow: hidden !important;
  width: 1px !important;
  height: 1px !important;
  margin: -1px !important;
  padding: 0 !important;
  border: 0 !important;
  white-space: nowrap !important;
}

pre code,
pre[class*="language-"] code {
  background: transparent;
  border: none;
  padding: 0;
  color: inherit;
  font-size: 0.84rem;
  font-family: var(--font-mono);
}

/* Prism.js Token Colors (PCB / Dark Blueprint Palette) */
.token.comment,
.token.prolog,
.token.doctype,
.token.cdata {
  color: #7f8994;
  font-style: italic;
}

.token.punctuation {
  color: #c5c8c6;
}

.token.keyword,
.token.operator,
.token.tag {
  color: #ff8b7b;
  font-weight: 600;
}

.token.class-name,
.token.type-definition,
.token.namespace {
  color: #7fd1b9;
}

.token.function,
.token.macro.property {
  color: #82b4ff;
}

.token.string,
.token.char,
.token.attr-value {
  color: #e5c07b;
}

.token.boolean,
.token.number,
.token.constant,
.token.symbol {
  color: #ffb86c;
  font-weight: 600;
}

.token.attribute,
.token.atrule,
.token.property,
.token.table {
  color: #c792ea;
}

.token.lifetime-annotation {
  color: #f78c6c;
}

/* Mermaid.js Diagram Containers */
.mermaid-figure {
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  border-left: 4px solid var(--accent-pcb);
  border-radius: 5px;
  padding: 1.25rem 1.5rem;
  margin: 1.5rem 0 1.8rem 0;
  overflow-x: auto;
}

.mermaid-figure figcaption {
  font-family: var(--font-sans);
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: 0.75rem;
  text-align: center;
}

pre.mermaid {
  background: transparent;
  border: none;
  padding: 0;
  margin: 0;
  text-align: center;
  color: var(--text-main);
  font-family: var(--font-sans);
}

/* Full-Bleed Figures & Interactive Widgets */
.full-width-panel {
  width: 100%;
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  border-radius: 6px;
  padding: 1.5rem;
  margin: 2rem 0;
}

.panel-header {
  font-family: var(--font-sans);
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid var(--border-subtle);
  padding-bottom: 0.75rem;
  margin-bottom: 1.25rem;
}

.panel-title {
  font-weight: 700;
  font-size: 0.95rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--accent-pcb);
}

.panel-badge {
  font-size: 0.78rem;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  padding: 0.2rem 0.6rem;
  border-radius: 3px;
  color: var(--text-muted);
}

/* Interactive Simulator Layout */
.sim-grid {
  display: grid;
  grid-template-columns: 270px 1fr 310px;
  gap: 1.25rem;
  align-items: stretch;
  font-family: var(--font-sans);
}

.sim-box {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: 5px;
  padding: 1rem;
}

.sim-box h4 {
  margin: 0 0 0.75rem 0;
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--text-muted);
  border-bottom: 1px solid var(--border-subtle);
  padding-bottom: 0.4rem;
}

/* Simulated egui Dark Window */
.egui-mock-window {
  background: #1b1b1b;
  color: #dcdcdc;
  border-radius: 6px;
  border: 1px solid #3c3c3c;
  display: grid;
  grid-template-columns: 185px 1fr;
  min-height: 250px;
  overflow: hidden;
  font-family: var(--font-sans);
  font-size: 0.85rem;
}

.egui-side-panel {
  background: #242424;
  border-right: 1px solid #383838;
  padding: 0.85rem;
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
}

.egui-side-panel .egui-heading {
  font-weight: 600;
  font-size: 0.9rem;
  color: #ffffff;
  padding-bottom: 0.35rem;
  border-bottom: 1px solid #3a3a3a;
  margin-bottom: 0.2rem;
}

.egui-checkbox {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  cursor: pointer;
  padding: 0.25rem 0.35rem;
  border-radius: 3px;
  user-select: none;
}

.egui-checkbox:hover {
  background: #323232;
}

.egui-checkbox input {
  accent-color: #4592e6;
  cursor: pointer;
}

.egui-btn {
  background: #363636;
  color: #e8e8e8;
  border: 1px solid #4d4d4d;
  border-radius: 3px;
  padding: 0.35rem 0.6rem;
  font-size: 0.8rem;
  cursor: pointer;
  margin-top: 0.3rem;
  text-align: left;
}

.egui-btn:hover {
  background: #444444;
  border-color: #666666;
}

.egui-central-canvas {
  background: #0f1412;
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0.5rem;
}

/* Interactive Code Exercise */
.code-challenge-input {
  font-family: var(--font-mono);
  font-size: 0.84rem;
  background: #1f262e;
  color: #ffb86c;
  border: 1px solid #58697a;
  border-radius: 3px;
  padding: 0.12rem 0.4rem;
  width: 220px;
}

.code-challenge-input:focus-visible {
  outline: 2px solid #82b4ff;
  outline-offset: 2px;
  border-color: transparent;
}

.btn-primary {
  font-family: var(--font-sans);
  background: var(--accent-pcb-btn);
  color: #ffffff;
  border: 1px solid var(--accent-pcb);
  border-radius: 4px;
  padding: 0.5rem 1rem;
  font-size: 0.86rem;
  font-weight: 600;
  cursor: pointer;
}

.btn-primary:hover {
  background: #28975f;
}

.btn-secondary {
  font-family: var(--font-sans);
  background: var(--bg-surface);
  color: var(--text-main);
  border: 1px solid var(--border-strong);
  border-radius: 4px;
  padding: 0.48rem 0.9rem;
  font-size: 0.84rem;
  cursor: pointer;
}

.btn-secondary:hover {
  background: #2c3540;
}

/* Feedback Banner */
.feedback-box {
  font-family: var(--font-sans);
  font-size: 0.88rem;
  padding: 0.75rem 1rem;
  border-radius: 4px;
  margin-top: 0.85rem;
  display: none;
}

.feedback-box.ok {
  display: block;
  background: var(--ok-bg);
  border-left: 4px solid var(--ok-border);
  color: var(--ok-text);
}

.feedback-box.err {
  display: block;
  background: var(--err-bg);
  border-left: 4px solid var(--err-border);
  color: var(--err-text);
}

/* Quiz Styles */
.quiz-question {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: 5px;
  padding: 1.15rem 1.25rem;
  margin-bottom: 1.1rem;
  font-family: var(--font-sans);
}

.quiz-prompt {
  font-weight: 600;
  font-size: 0.95rem;
  margin-bottom: 0.75rem;
  color: var(--text-main);
}

.quiz-options {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.6rem;
}

.quiz-option-btn {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  text-align: left;
  background: var(--bg-paper);
  border: 1px solid var(--border-subtle);
  border-radius: 4px;
  padding: 0.65rem 0.8rem;
  cursor: pointer;
  transition: all 0.12s ease;
  color: var(--text-main);
}

.quiz-option-btn:hover {
  border-color: var(--accent-silk);
  background: #1a2430;
}

.quiz-option-btn.selected-correct {
  background: var(--ok-bg);
  border-color: var(--ok-border);
  color: var(--ok-text);
  font-weight: 600;
}

.quiz-option-btn.selected-wrong {
  background: var(--err-bg);
  border-color: var(--err-border);
  color: var(--err-text);
}

/* Step Checklist (for Hands-on Setup & Cargo Verification Steps) */
.step-checklist {
  list-style: none;
  padding-left: 0;
  font-family: var(--font-sans);
}

.step-checklist li {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: 5px;
  padding: 0.9rem 1.1rem;
  margin-bottom: 0.75rem;
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
}

.step-checklist input[type="checkbox"] {
  margin-top: 0.28rem;
  transform: scale(1.15);
  accent-color: var(--accent-pcb);
  cursor: pointer;
}

/* Cargo Verification & Mutation Coverage Scoreboard (shared across all lessons) */
.mutation-scoreboard {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 0.85rem;
  margin: 1rem 0 1.25rem 0;
  font-family: var(--font-sans);
}

.mutation-stat {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: 5px;
  padding: 0.75rem 1rem;
}

.mutation-stat .stat-label {
  font-size: 0.74rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--text-muted);
  margin-bottom: 0.25rem;
}

.mutation-stat .stat-value {
  font-family: var(--font-mono);
  font-size: 1.05rem;
  font-weight: 700;
}

.mutation-stat.caught {
  border-left: 3px solid var(--ok-border);
}

.mutation-stat.caught .stat-value {
  color: var(--ok-text);
}

.mutation-stat.missed {
  border-left: 3px solid var(--accent-copper);
}

.mutation-stat.missed .stat-value {
  color: var(--accent-copper);
}

.mutation-stat.tier {
  border-left: 3px solid var(--accent-silk);
}

.mutation-stat.tier .stat-value {
  color: var(--accent-silk);
}

/* Callouts & Footer */
.callout {
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  border-left: 3px solid var(--accent-silk);
  padding: 0.9rem 1.15rem;
  margin: 1.4rem 0;
  font-size: 0.94rem;
}

.teacher-prompt-box {
  background: #15221c;
  border: 1px solid #264637;
  border-left: 4px solid var(--accent-pcb);
  border-radius: 5px;
  padding: 1.15rem 1.35rem;
  margin-top: 2.5rem;
  font-family: var(--font-sans);
  font-size: 0.92rem;
}

/* Reference Table / Glossary Grid */
table.ref-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
  margin: 1.2rem 0 2rem 0;
}

table.ref-table th,
table.ref-table td {
  text-align: left;
  padding: 0.65rem 0.8rem;
  border-bottom: 1px solid var(--border-subtle);
  vertical-align: top;
}

table.ref-table th {
  font-family: var(--font-sans);
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--text-muted);
  border-bottom: 2px solid var(--border-strong);
}

/* Course Index Act Table of Contents */
.act-toc {
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  border-left: 4px solid var(--accent-copper);
  border-radius: 6px;
  padding: 1.15rem 1.4rem;
  margin: 1.5rem 0 2.25rem 0;
}

.act-toc-title {
  font-family: var(--font-sans);
  font-size: 0.95rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--accent-copper);
  margin-bottom: 0.75rem;
}

.act-toc ol {
  margin: 0;
  padding-left: 1.35rem;
}

.act-toc li {
  margin: 0.45rem 0;
  font-size: 0.93rem;
  line-height: 1.5;
  color: var(--text-muted);
}

.act-toc li a {
  font-weight: 600;
  color: var(--text-main);
  text-decoration: none;
}

.act-toc li a:hover {
  color: var(--accent-silk);
  text-decoration: underline;
}

.act-toc-badge {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  color: var(--accent-copper);
  background: var(--bg-code);
  border: 1px solid var(--border-subtle);
  padding: 0.12rem 0.45rem;
  border-radius: 3px;
  margin-left: 0.4rem;
  white-space: nowrap;
}

/* Course Index Lesson Cards */
.lesson-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1.15rem;
  margin: 1.25rem 0 2rem 0;
  font-family: var(--font-sans);
}

.lesson-card {
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  border-left: 4px solid var(--accent-pcb);
  border-radius: 6px;
  padding: 1.2rem 1.35rem;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  gap: 0.75rem;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}

.lesson-card:hover {
  border-color: var(--border-strong);
  border-left-color: var(--accent-copper);
  background: var(--bg-surface);
}

.lesson-card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.5rem;
}

.lesson-card-num {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--accent-copper);
  background: var(--bg-code);
  border: 1px solid var(--border-subtle);
  padding: 0.15rem 0.5rem;
  border-radius: 3px;
}

.lesson-card-mutants {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--ok-text);
  background: var(--ok-bg);
  border: 1px solid var(--ok-border);
  padding: 0.12rem 0.5rem;
  border-radius: 3px;
}

.lesson-card h3 {
  margin: 0.2rem 0 0.25rem 0;
  font-size: 1.05rem;
  line-height: 1.35;
}

.lesson-card h3 a {
  text-decoration: none;
  color: var(--text-main);
}

.lesson-card h3 a:hover {
  color: var(--accent-silk);
  text-decoration: underline;
}

.lesson-card p {
  font-size: 0.88rem;
  color: var(--text-muted);
  margin: 0;
  line-height: 1.5;
}

.lesson-card-meta {
  font-size: 0.8rem;
  color: var(--text-sidenote);
  border-top: 1px solid var(--border-subtle);
  padding-top: 0.65rem;
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

/* Bottom-of-Lesson Pagination Cards */
.lesson-pager {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1.15rem;
  margin-top: 2.75rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border-subtle);
  font-family: var(--font-sans);
}

.lesson-pager-card {
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  border-radius: 6px;
  padding: 1rem 1.25rem;
  text-decoration: none;
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}

.lesson-pager-card.next {
  text-align: right;
  align-items: flex-end;
}

.lesson-pager-card:hover {
  border-color: var(--accent-copper);
  background: var(--bg-surface);
}

.lesson-pager-card .pager-direction {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--accent-copper);
  font-weight: 600;
}

.lesson-pager-card .pager-title {
  font-size: 0.96rem;
  font-weight: 600;
  color: var(--text-main);
  line-height: 1.35;
}

/* Responsive adjustments */
@media (max-width: 960px) {
  .prose-col {
    width: 100%;
  }
  .sidenote,
  .marginnote {
    float: none;
    margin-right: 0;
    width: 100%;
    margin: 0.75rem 0;
  }
  .sim-grid {
    grid-template-columns: 1fr;
  }
  .quiz-options {
    grid-template-columns: 1fr;
  }
  .lesson-grid,
  .lesson-pager {
    grid-template-columns: 1fr;
  }
  .lesson-pager-card.next {
    text-align: left;
    align-items: flex-start;
  }
}

/* Print-friendly styling for ./reference/*.html and ./lessons/*.html */
@media print {
  :root {
    color-scheme: light;
    --bg-paper: #ffffff;
    --bg-elevated: #f7f7f7;
    --bg-surface: #ffffff;
    --text-main: #111111;
    --text-muted: #444444;
    --text-sidenote: #333333;
    --border-subtle: #cccccc;
    --border-strong: #666666;
  }
  body {
    background: #fff;
    color: #000;
    padding: 0;
    font-size: 11pt;
  }
  .course-nav,
  .lesson-pager,
  .btn-primary,
  .btn-secondary,
  .copy-code-btn {
    display: none;
  }
  .full-width-panel,
  .quiz-question,
  .mermaid-figure,
  pre {
    break-inside: avoid;
  }
}