/* ==========================================================================
   Eurorack Buffered Multiple — SKiDL Interactive Course Stylesheet
   Dark-mode Tufte-inspired layout with @media print light override
   ========================================================================== */

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

:root {
  color-scheme: dark;

  --bg-canvas: #0b0f17;
  --bg-surface: #121826;
  --bg-elevated: #1a2234;
  --bg-code: #0e1420;
  --border-subtle: #28334aff;
  --border-strong: #3b4c6b;

  --text-primary: #eef2f8;
  --text-secondary: #b2bfd4;
  --text-muted: #8494ae;

  --accent: #38bdf8;
  --accent-strong: #7dd3fc;
  --accent-bg: rgba(56, 189, 248, 0.12);

  --success: #34d399;
  --success-bg: rgba(52, 211, 153, 0.13);
  --warning: #fbbf24;
  --warning-bg: rgba(251, 191, 36, 0.13);
  --danger: #f87171;
  --danger-bg: rgba(248, 113, 113, 0.14);

  --scrollbar-thumb: #475878;
  --scrollbar-track: #121826;

  --font-sans: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-serif: "Newsreader", "Charter", "Iowan Old Style", "Palatino Linotype", Georgia, serif;
  --font-mono: "JetBrains Mono", "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;

  scrollbar-color: var(--scrollbar-thumb) var(--scrollbar-track);
  scrollbar-width: thin;
  accent-color: var(--accent);
}

pre,
code,
.scroller {
  color-scheme: dark;
  accent-color: var(--accent);
  scrollbar-color: var(--scrollbar-thumb) var(--scrollbar-track);
  scrollbar-width: thin;
}

@supports not (scrollbar-color: auto) {
  :root::-webkit-scrollbar,
  pre::-webkit-scrollbar,
  .scroller::-webkit-scrollbar {
    width: 10px;
    height: 10px;
  }

  :root::-webkit-scrollbar-thumb,
  pre::-webkit-scrollbar-thumb,
  .scroller::-webkit-scrollbar-thumb {
    background: var(--scrollbar-thumb);
    border-radius: 5px;
  }

  :root::-webkit-scrollbar-track,
  pre::-webkit-scrollbar-track,
  .scroller::-webkit-scrollbar-track {
    background: var(--scrollbar-track);
  }
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  font-size: 100%;
  scroll-behavior: smooth;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

body {
  margin: 0;
  background-color: var(--bg-canvas);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 1.03rem;
  line-height: 1.68;
  text-align: start;
  accent-color: var(--accent);
}

/* Accessibility Utilities */
.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;
}

.skip-link:where(:focus-within, :active) {
  position: fixed;
  top: 0.75rem;
  left: 0.75rem;
  z-index: 1000;
  padding: 0.55rem 1rem;
  background: var(--accent);
  color: #06101e;
  font-weight: 700;
  border-radius: 6px;
  text-decoration: none;
}

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

/* Typography & Legibility */
h1,
h2,
h3,
h4,
th {
  text-wrap: balance;
  color: var(--text-primary);
  line-height: 1.25;
  letter-spacing: -0.015em;
}

p,
li,
blockquote {
  text-wrap: pretty;
  max-width: 76ch;
}

h1 {
  font-family: var(--font-serif);
  font-size: clamp(1.9rem, 3vw, 2.55rem);
  font-weight: 600;
  margin: 0.4rem 0 0.75rem;
}

h2 {
  font-size: 1.45rem;
  margin-top: 2.6rem;
  margin-bottom: 0.85rem;
  padding-bottom: 0.4rem;
  border-bottom: 1px solid var(--border-subtle);
}

h3 {
  font-size: 1.16rem;
  margin-top: 1.8rem;
  margin-bottom: 0.55rem;
  color: var(--accent-strong);
}

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

a:any-link:hover {
  color: var(--accent-strong);
}

code {
  font-family: var(--font-mono);
  font-size: 0.9em;
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  padding: 0.12rem 0.36rem;
  border-radius: 4px;
}

pre code {
  background: transparent;
  border: 0;
  padding: 0;
  font-size: 0.88rem;
}

/* Layout Shell */
.site-header {
  border-bottom: 1px solid var(--border-subtle);
  background: rgba(18, 24, 38, 0.9);
  backdrop-filter: blur(8px);
  position: sticky;
  top: 0;
  z-index: 50;
}

.header-inner {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0.75rem 1.5rem;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.85rem;
}

.brand-title {
  font-weight: 700;
  font-size: 0.96rem;
  color: var(--text-primary);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

.brand-badge {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  padding: 0.15rem 0.45rem;
  border-radius: 4px;
  background: var(--accent-bg);
  color: var(--accent-strong);
  border: 1px solid rgba(56, 189, 248, 0.35);
}

.course-nav {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.35rem;
}

.course-nav a {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  padding: 0.3rem 0.58rem;
  border-radius: 5px;
  text-decoration: none;
  color: var(--text-secondary);
  border: 1px solid transparent;
}

.course-nav a:hover {
  background: var(--bg-elevated);
  color: var(--text-primary);
  border-color: var(--border-subtle);
}

.course-nav a[aria-current="page"] {
  background: var(--accent-bg);
  color: var(--accent-strong);
  border-color: rgba(56, 189, 248, 0.45);
  font-weight: 600;
}

.nav-sep {
  color: var(--border-strong);
  padding: 0 0.15rem;
  user-select: none;
}

.page-main {
  max-width: 1080px;
  margin: 0 auto;
  padding: 2.2rem 1.5rem 4rem;
}

/* Lesson Hero & Meta Badges */
.lesson-kicker {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
  margin-bottom: 0.25rem;
}

.lead {
  font-size: 1.14rem;
  color: var(--text-secondary);
  margin-top: 0.4rem;
  margin-bottom: 1.25rem;
}

.meta-bar {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
  margin: 1rem 0 1.8rem;
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  padding: 0.24rem 0.62rem;
  border-radius: 999px;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  color: var(--text-secondary);
}

.badge-success {
  background: var(--success-bg);
  border-color: rgba(52, 211, 153, 0.45);
  color: var(--success);
}

.badge-accent {
  background: var(--accent-bg);
  border-color: rgba(56, 189, 248, 0.4);
  color: var(--accent-strong);
}

.badge-warn {
  background: var(--warning-bg);
  border-color: rgba(251, 191, 36, 0.45);
  color: var(--warning);
}

/* Callouts / Side Notes */
.callout {
  margin: 1.4rem 0;
  padding: 1rem 1.2rem;
  border-radius: 8px;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-left: 4px solid var(--accent);
}

.callout-title {
  font-weight: 700;
  font-size: 0.94rem;
  margin-bottom: 0.35rem;
  color: var(--accent-strong);
  display: flex;
  align-items: center;
  gap: 0.45rem;
}

.callout-warn {
  border-left-color: var(--warning);
}

.callout-warn .callout-title {
  color: var(--warning);
}

.callout-success {
  border-left-color: var(--success);
}

.callout-success .callout-title {
  color: var(--success);
}

/* Code Blocks & Prism Integration */
.code-figure {
  margin: 1.35rem 0;
  border: 1px solid var(--border-subtle);
  border-radius: 8px;
  background: var(--bg-code);
  overflow: hidden;
}

.code-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.45rem 0.9rem;
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border-subtle);
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--text-secondary);
}

.copy-btn {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  padding: 0.2rem 0.55rem;
  border-radius: 4px;
  border: 1px solid var(--border-strong);
  background: var(--bg-elevated);
  color: var(--text-primary);
  cursor: pointer;
}

.copy-btn:hover {
  border-color: var(--accent);
  color: var(--accent-strong);
}

pre[class*="language-"],
pre.code-block {
  margin: 0;
  padding: 1rem 1.15rem;
  overflow-x: auto;
  background: var(--bg-code) !important;
  font-family: var(--font-mono);
  font-size: 0.88rem;
  line-height: 1.58;
}

/* Mermaid Diagrams */
.diagram-card {
  margin: 1.5rem 0;
  padding: 1.1rem 1.25rem;
  border-radius: 8px;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
}

.diagram-card figcaption {
  margin-top: 0.65rem;
  font-size: 0.86rem;
  color: var(--text-muted);
}

pre.mermaid {
  margin: 0;
  background: transparent;
  overflow-x: auto;
  text-align: center;
}

/* Tables */
.table-wrap {
  margin: 1.35rem 0;
  overflow-x: auto;
  border: 1px solid var(--border-subtle);
  border-radius: 8px;
  background: var(--bg-surface);
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92rem;
}

caption {
  text-align: start;
  padding: 0.75rem 1rem;
  font-weight: 600;
  color: var(--text-secondary);
  background: var(--bg-elevated);
  border-bottom: 1px solid var(--border-subtle);
}

th,
td {
  padding: 0.68rem 0.95rem;
  text-align: start;
  border-bottom: 1px solid var(--border-subtle);
  vertical-align: top;
}

th {
  background: rgba(26, 34, 52, 0.7);
  font-weight: 600;
  color: var(--text-primary);
}

tr:last-child td {
  border-bottom: 0;
}

/* Lesson Grid & Cards (Index + Navigation — 2-Wide Stack) */
.lesson-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1.25rem;
  margin: 1.25rem 0 2rem;
}

@media (max-width: 720px) {
  .lesson-grid {
    grid-template-columns: 1fr;
  }
}

.lesson-card {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  padding: 1.2rem 1.3rem;
  border-radius: 10px;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  transition: border-color 0.16s ease, transform 0.16s ease;
}

.lesson-card:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
}

.lesson-card-Planned {
  opacity: 0.84;
  border-style: dashed;
}

.lesson-card h3 {
  margin: 0.45rem 0 0.5rem;
  font-size: 1.12rem;
}

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

.lesson-card h3 a:hover {
  color: var(--accent-strong);
}

.lesson-card p {
  font-size: 0.92rem;
  color: var(--text-secondary);
  margin: 0 0 0.9rem;
}

.lesson-meta-list {
  list-style: none;
  padding: 0;
  margin: 0 0 1rem;
  font-size: 0.82rem;
  color: var(--text-muted);
}

.lesson-meta-list li {
  margin-bottom: 0.28rem;
}

.card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  padding-top: 0.75rem;
  border-top: 1px solid var(--border-subtle);
  font-family: var(--font-mono);
  font-size: 0.78rem;
}

/* Interactive Fill-in-the-Blank Code Exercises */
.exercise-box {
  margin: 1.75rem 0;
  padding: 1.25rem 1.35rem;
  border-radius: 10px;
  background: var(--bg-surface);
  border: 1px solid var(--border-strong);
}

.exercise-box h3 {
  margin-top: 0;
}

input.code-blank {
  font-family: var(--font-mono);
  font-size: 0.88rem;
  padding: 0.12rem 0.4rem;
  margin: 0 0.15rem;
  border-radius: 4px;
  border: 1.5px solid var(--accent);
  background: #070b12;
  color: var(--accent-strong);
  min-width: 7ch;
}

input.code-blank.is-correct {
  border-color: var(--success);
  background: var(--success-bg);
  color: var(--success);
}

input.code-blank.is-incorrect {
  border-color: var(--danger);
  background: var(--danger-bg);
  color: var(--danger);
}

.exercise-actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.65rem;
  margin-top: 0.9rem;
}

.btn {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.88rem;
  padding: 0.48rem 0.95rem;
  border-radius: 6px;
  border: 1px solid var(--border-strong);
  background: var(--bg-elevated);
  color: var(--text-primary);
  cursor: pointer;
}

.btn-primary {
  background: var(--accent);
  border-color: var(--accent);
  color: #06101e;
}

.btn-primary:hover {
  background: var(--accent-strong);
  border-color: var(--accent-strong);
}

.btn:hover:not(.btn-primary) {
  border-color: var(--accent);
  color: var(--accent-strong);
}

.feedback-msg {
  font-size: 0.9rem;
  margin-top: 0.65rem;
  padding: 0.55rem 0.8rem;
  border-radius: 6px;
  display: none;
}

.feedback-msg.is-visible {
  display: block;
}

.feedback-msg.is-ok {
  background: var(--success-bg);
  border: 1px solid rgba(52, 211, 153, 0.45);
  color: var(--success);
}

.feedback-msg.is-err {
  background: var(--danger-bg);
  border: 1px solid rgba(248, 113, 113, 0.45);
  color: var(--danger);
}

/* Retrieval Quizzes */
.quiz-section {
  margin: 2rem 0;
  padding: 1.35rem 1.45rem;
  border-radius: 10px;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
}

.quiz-card {
  margin: 1.2rem 0;
  padding: 1.1rem 1.2rem;
  border-radius: 8px;
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
}

.quiz-question {
  font-weight: 600;
  margin-top: 0;
  margin-bottom: 0.8rem;
}

.quiz-options {
  display: grid;
  gap: 0.5rem;
}

.quiz-option {
  display: flex;
  align-items: flex-start;
  gap: 0.65rem;
  width: 100%;
  text-align: start;
  padding: 0.62rem 0.85rem;
  border-radius: 6px;
  border: 1px solid var(--border-strong);
  background: var(--bg-surface);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 0.93rem;
  cursor: pointer;
}

.quiz-option:hover {
  border-color: var(--accent);
}

.quiz-option.is-correct {
  border-color: var(--success);
  background: var(--success-bg);
}

.quiz-option.is-wrong {
  border-color: var(--danger);
  background: var(--danger-bg);
}

/* Interactive Component Explorer (Lesson 0002) */
.explorer-toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin-bottom: 1rem;
}

.explorer-input {
  flex: 1 1 240px;
  padding: 0.48rem 0.75rem;
  border-radius: 6px;
  border: 1px solid var(--border-strong);
  background: var(--bg-code);
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 0.88rem;
}

/* Interactive Cascaded Normalling Simulator (Lesson 0005 & Reference) */
.norm-sim-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1rem;
  margin: 1rem 0;
}

.norm-ch-card {
  padding: 1rem 1.1rem;
  border-radius: 8px;
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
}

.norm-ch-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  margin-bottom: 0.7rem;
}

.norm-patch-label {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
  font-weight: 600;
  font-size: 0.92rem;
  cursor: pointer;
}

.norm-cv-row {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  margin: 0.65rem 0;
  font-family: var(--font-mono);
  font-size: 0.82rem;
}

.norm-cv-row input[type="range"] {
  flex: 1;
  accent-color: var(--accent);
}

.norm-outputs-list {
  list-style: none;
  padding: 0;
  margin: 0.65rem 0 0;
  font-family: var(--font-mono);
  font-size: 0.81rem;
}

.norm-outputs-list li {
  display: flex;
  justify-content: space-between;
  padding: 0.26rem 0.5rem;
  margin-bottom: 0.25rem;
  border-radius: 4px;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
}

@supports not (accent-color: var(--accent)) {
  .norm-patch-label input[type="checkbox"] {
    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;
  }

  .norm-patch-label {
    position: relative;
    padding-left: 1.75rem;
  }

  .norm-patch-label input[type="checkbox"] + span::before {
    content: "";
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 1.15rem;
    height: 1.15rem;
    border: 2px solid var(--border-strong);
    background: var(--bg-code);
    border-radius: 4px;
    box-sizing: border-box;
  }

  .norm-patch-label input[type="checkbox"]:focus-visible + span::before {
    outline: 2px solid var(--accent-strong);
    outline-offset: 2px;
  }

  .norm-patch-label input[type="checkbox"]:checked + span::before {
    background-color: var(--accent);
    border-color: var(--accent);
  }

  .norm-patch-label input[type="checkbox"]:checked + span::after {
    content: "✓";
    position: absolute;
    left: 0.22rem;
    top: 50%;
    transform: translateY(-50%);
    color: #06101e;
    font-weight: 700;
    font-size: 0.85rem;
  }

  .norm-cv-row input[type="range"] {
    -webkit-appearance: none;
    appearance: none;
    background: transparent;
  }

  .norm-cv-row input[type="range"]::-webkit-slider-runnable-track {
    width: 100%;
    height: 8px;
    background: linear-gradient(
      to right,
      var(--accent) var(--progress, 50%),
      var(--border-strong) var(--progress, 50%)
    );
    border-radius: 4px;
  }

  .norm-cv-row input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    height: 16px;
    width: 16px;
    border-radius: 50%;
    background: var(--accent);
    cursor: pointer;
    margin-top: -4px;
  }

  .norm-cv-row input[type="range"]::-moz-range-track {
    width: 100%;
    height: 8px;
    background: var(--border-strong);
    border-radius: 4px;
  }

  .norm-cv-row input[type="range"]::-moz-range-thumb {
    height: 16px;
    width: 16px;
    border-radius: 50%;
    background: var(--accent);
    cursor: pointer;
  }

  .norm-cv-row input[type="range"]::-moz-range-progress {
    background-color: var(--accent);
    height: 8px;
    border-radius: 4px;
  }
}

/* Adjacent Lesson Pagination & Footer */
.pager {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 1rem;
  margin-top: 2.8rem;
  padding-top: 1.4rem;
  border-top: 1px solid var(--border-subtle);
}

.pager a {
  display: inline-flex;
  flex-direction: column;
  padding: 0.75rem 1.05rem;
  border-radius: 8px;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  text-decoration: none;
  min-width: 220px;
}

.pager a:hover {
  border-color: var(--accent);
}

.pager-label {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  color: var(--text-muted);
  text-transform: uppercase;
}

.pager-title {
  font-weight: 600;
  color: var(--text-primary);
  margin-top: 0.2rem;
}

.site-footer {
  border-top: 1px solid var(--border-subtle);
  padding: 1.8rem 1.5rem 2.4rem;
  color: var(--text-muted);
  font-size: 0.86rem;
}

.footer-inner {
  max-width: 1080px;
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 1rem;
}

/* Clean Light-Mode Override for Print */
@media print {
  :root {
    color-scheme: light;
    --bg-canvas: #ffffff;
    --bg-surface: #f8fafc;
    --bg-elevated: #f1f5f9;
    --bg-code: #f8fafc;
    --border-subtle: #cbd5e1;
    --border-strong: #94a3b8;
    --text-primary: #0f172a;
    --text-secondary: #334155;
    --text-muted: #475569;
    --accent: #0369a1;
    --accent-strong: #075985;
  }

  .site-header,
  .copy-btn,
  .exercise-actions,
  .pager {
    display: none !important;
  }

  body {
    font-size: 10.5pt;
    color: #0f172a;
    background: #ffffff;
  }

  .page-main {
    max-width: 100%;
    padding: 0;
  }
}