:root {
  --ownership: #e63946;
  --borrow-shared: #457b9d;
  --borrow-exclusive: #f4a261;
  --lifetime: #8338ec;
  --stack: #2d6a4f;
  --heap: #e76f51;
  --compiler: #023e8a;
  --error: #d62828;
  --valid: #52b788;
  --move: #fb8500;
  --copy: #74c69d;
  --drop: #6d6875;
  --trait: #219ebc;
  --unsafe: #ff006e;
  --async: #3a86ff;
  --perf: #ffbe0b;
  --ink: #1a1a2e;
  --paper: #fffdf8;
  --paper-strong: #fff6eb;
  --grid: rgba(2, 62, 138, 0.08);
  --card-border: rgba(2, 62, 138, 0.16);
  --page-width: 72rem;
  --gutter: 1.5rem;
  --font-display: "JetBrains Mono", "Space Mono", "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  --font-body: "IBM Plex Sans", "Source Sans Pro", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen-Sans, Ubuntu, Cantarell, "Helvetica Neue", sans-serif;
  --font-code: "JetBrains Mono", "Fira Code", "Cascadia Code", ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
}

html {
  scroll-behavior: smooth;
}

body {
  color: var(--ink);
  font-family: var(--font-body);
}

#mdbook-content main {
  max-width: var(--page-width);
}

#mdbook-content main p,
#mdbook-content main li {
  font-size: 1.1rem;
  line-height: 1.8;
  text-wrap: pretty;
  margin-bottom: 1.25rem;
}

#mdbook-content main > p,
#mdbook-content main > ul,
#mdbook-content main > ol,
#mdbook-content main > blockquote {
  max-width: 68ch; /* Optimal tracking width for reading */
}

#mdbook-content main li {
  margin-bottom: 0.5rem;
}

#mdbook-content main h1,
#mdbook-content main h2,
#mdbook-content main h3,
#mdbook-content main h4 {
  color: var(--compiler);
  font-family: var(--font-display);
  letter-spacing: 0.01em;
}

#mdbook-content main h1 {
  font-size: clamp(2.5rem, 4vw, 3.8rem);
  line-height: 1.1;
  margin-bottom: 2rem;
  max-width: 25ch;
  text-wrap: balance;
}

#mdbook-content main h2 {
  font-size: clamp(1.6rem, 2.5vw, 2.2rem);
  line-height: 1.2;
  border-left: 0.4rem solid var(--chapter-accent, var(--compiler));
  padding-left: 1rem;
  margin-top: 3.5rem;
  margin-bottom: 1.5rem;
}

#mdbook-content main h3 {
  font-size: clamp(1.2rem, 1.8vw, 1.5rem);
  line-height: 1.3;
  margin-top: 2.5rem;
  margin-bottom: 1rem;
}

#mdbook-content main a {
  text-decoration-thickness: 0.08em;
  text-underline-offset: 0.15em;
  transition: color 0.15s ease, text-decoration-color 0.15s ease;
}

#mdbook-content main a:hover {
  text-decoration-thickness: 0.12em;
  color: var(--chapter-accent, var(--compiler));
}

#mdbook-content main pre,
#mdbook-content main code {
  font-family: var(--font-code);
}

#mdbook-content main p code,
#mdbook-content main li code,
#mdbook-content main td code,
#mdbook-content main th code {
  padding: 0.15rem 0.4rem;
  border: 1px solid color-mix(in srgb, var(--chapter-accent, var(--compiler)) 30%, white 70%);
  border-radius: 0.3rem;
  background: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 8%, white 92%);
  color: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 80%, black 20%);
  font-weight: 500;
  font-size: 0.9em;
  word-break: break-word;
}

html.navy #mdbook-content main p code,
html.mocha #mdbook-content main p code,
html.ayu #mdbook-content main p code,
html.navy #mdbook-content main li code,
html.mocha #mdbook-content main li code,
html.ayu #mdbook-content main li code,
html.navy #mdbook-content main td code,
html.mocha #mdbook-content main td code,
html.ayu #mdbook-content main td code,
html.navy #mdbook-content main th code,
html.mocha #mdbook-content main th code,
html.ayu #mdbook-content main th code {
  border-color: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 30%, #334155 70%);
  background: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 15%, #0f172a 85%);
  color: #e2e8f0;
}

#mdbook-content main :target {
  scroll-margin-top: 5.5rem;
}

#mdbook-content main a:focus-visible,
#mdbook-content main button:focus-visible {
  outline: 3px solid var(--chapter-accent, var(--compiler));
  outline-offset: 3px;
  border-radius: 0.2rem;
  text-decoration: none;
}

.skip-to-content {
  position: fixed;
  top: 0.6rem;
  left: 0.8rem;
  z-index: 9999;
  transform: translateY(-180%);
  transition: transform 0.18s ease;
  border-radius: 0.65rem;
  border: 1px solid rgba(2, 62, 138, 0.35);
  background: color-mix(in srgb, var(--compiler) 14%, white 86%);
  color: var(--ink);
  padding: 0.55rem 0.8rem;
  font-family: var(--font-display);
  font-size: 0.76rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  text-decoration: none;
}

.skip-to-content:focus-visible {
  transform: translateY(0);
  outline: 3px solid var(--chapter-accent, var(--compiler));
  outline-offset: 2px;
}

#mdbook-sidebar a {
  min-height: 2rem;
  padding-block: 0.25rem;
}

/* ─── Code blocks: readable, scrollable, not overflowing ─────────────────── */

#mdbook-content main pre {
  background: #1a1b26;
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 0.75rem;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.12);
  overflow-x: auto;
  max-width: 100%;
  padding: 1.25rem;
  font-size: 0.95em;
  line-height: 1.6;
}

#mdbook-content main pre,
.visual-table-wrapper,
.visual-figure__body {
  scrollbar-width: thin;
  scrollbar-color: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 55%, #64748b 45%) transparent;
}

#mdbook-content main pre::-webkit-scrollbar,
.visual-table-wrapper::-webkit-scrollbar,
.visual-figure__body::-webkit-scrollbar {
  height: 0.62rem;
  width: 0.62rem;
}

#mdbook-content main pre::-webkit-scrollbar-thumb,
.visual-table-wrapper::-webkit-scrollbar-thumb,
.visual-figure__body::-webkit-scrollbar-thumb {
  background: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 52%, #64748b 48%);
  border-radius: 999px;
  border: 2px solid transparent;
  background-clip: content-box;
}

#mdbook-content main pre::-webkit-scrollbar-track,
.visual-table-wrapper::-webkit-scrollbar-track,
.visual-figure__body::-webkit-scrollbar-track {
  background: transparent;
}

.scrollable-x {
  position: relative;
}

.scrollable-x:focus-visible {
  outline: 3px solid var(--chapter-accent, var(--compiler));
  outline-offset: 2px;
}

.scrollable-x.is-scrollable-x:not(.is-scrolled-end)::after {
  content: attr(data-scroll-hint);
  position: absolute;
  top: 0.5rem;
  right: 0.5rem;
  z-index: 2;
  padding: 0.22rem 0.52rem;
  border-radius: 999px;
  font-family: var(--font-display);
  font-size: 0.64rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  white-space: nowrap;
  color: #f8fafc;
  background: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 55%, #0f172a 45%);
  pointer-events: none;
  opacity: 0.95;
}

.scrollable-x.is-scrollable-x:not(.is-scrolled-end)::before {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  width: clamp(1.75rem, 5vw, 2.35rem);
  height: 100%;
  background: linear-gradient(to left, color-mix(in srgb, var(--paper, #fff) 92%, transparent 8%), transparent);
  pointer-events: none;
}

.visual-edition-page {
  --chapter-accent: var(--compiler);
}

.visual-edition-page[data-concept="ownership"] {
  --chapter-accent: var(--ownership);
}

.visual-edition-page[data-concept="borrowing"] {
  --chapter-accent: var(--borrow-shared);
}

.visual-edition-page[data-concept="mutability"] {
  --chapter-accent: var(--borrow-exclusive);
}

.visual-edition-page[data-concept="lifetimes"] {
  --chapter-accent: var(--lifetime);
}

.visual-edition-page[data-concept="memory"] {
  --chapter-accent: var(--stack);
}

.visual-edition-page[data-concept="compiler"] {
  --chapter-accent: var(--compiler);
}

.visual-edition-page[data-concept="async"] {
  --chapter-accent: var(--async);
}

.visual-edition-page[data-concept="traits"] {
  --chapter-accent: var(--trait);
}

.visual-edition-page[data-concept="unsafe"] {
  --chapter-accent: var(--unsafe);
}

.visual-edition-page[data-concept="performance"] {
  --chapter-accent: var(--perf);
}

.chapter-hero,
.part-spread {
  position: relative;
  overflow: hidden;
  margin: 0 0 2.5rem;
  border-radius: 1.75rem;
  padding: clamp(1.4rem, 2vw, 2rem);
  color: #fff;
  background:
    radial-gradient(circle at top right, rgba(255, 255, 255, 0.18), transparent 28%),
    linear-gradient(135deg, color-mix(in srgb, var(--chapter-accent, var(--compiler)) 88%, #09111d 12%), #09111d);
  box-shadow: 0 28px 60px rgba(15, 23, 42, 0.22);
}

.chapter-hero::before,
.part-spread::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(255, 255, 255, 0.08) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255, 255, 255, 0.08) 1px, transparent 1px);
  background-size: 28px 28px;
  opacity: 0.35;
  pointer-events: none;
}

.chapter-hero__grid,
.part-spread__grid {
  position: relative;
  z-index: 1;
  display: grid;
  gap: 1.5rem;
  grid-template-columns: minmax(0, 1.15fr) minmax(320px, 0.85fr);
  align-items: center;
}

.chapter-hero__eyebrow,
.part-spread__eyebrow {
  margin: 0 0 0.6rem;
  color: rgba(255, 255, 255, 0.78);
  font-family: var(--font-display);
  font-size: 0.85rem;
  letter-spacing: 0.2em;
  text-transform: uppercase;
}

.chapter-hero__title,
.part-spread__title {
  margin: 0;
  color: #fff;
  font-family: var(--font-display);
  font-size: clamp(2.2rem, 4vw, 4.5rem);
  line-height: 0.96;
  text-transform: uppercase;
}

.chapter-hero__hook,
.part-spread__hook {
  max-width: 40rem;
  margin: 1rem 0 0;
  color: rgba(255, 255, 255, 0.92);
  font-size: 1.06rem;
  line-height: 1.7;
}

.chapter-hero__meta,
.part-spread__meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem;
  margin-top: 1rem;
}

.chapter-hero__pill,
.part-spread__pill {
  border: 1px solid rgba(255, 255, 255, 0.26);
  border-radius: 999px;
  padding: 0.45rem 0.8rem;
  color: rgba(255, 255, 255, 0.95);
  font-family: var(--font-display);
  font-size: 0.76rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  backdrop-filter: blur(6px);
}

.visual-figure {
  margin: 2.5rem 0;
  border: 1px solid var(--card-border);
  border-radius: 1rem;
  background: #ffffff;
  box-shadow: 0 12px 32px rgba(15, 23, 42, 0.06), 0 2px 6px rgba(15, 23, 42, 0.04);
  overflow: hidden;
}

.visual-figure--dark {
  background: #0f172a;
  border-color: rgba(255, 255, 255, 0.1);
  box-shadow: 0 12px 32px rgba(0, 0, 0, 0.3);
}

.visual-figure__header {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.5rem 1rem;
  padding: 1rem 1.15rem 0.35rem;
}

.visual-figure__eyebrow {
  color: var(--chapter-accent, var(--compiler));
  font-family: var(--font-display);
  font-size: 0.76rem;
  font-weight: 700;
  letter-spacing: 0.18em;
  text-transform: uppercase;
}

.visual-figure__title {
  margin: 0;
  color: var(--ink);
  font-family: var(--font-display);
  font-size: 1.15rem;
  line-height: 1.2;
}

.visual-figure--dark .visual-figure__title {
  color: #f8fafc;
}

.visual-figure__body {
  padding: 0.75rem 1rem 1rem;
  overflow-x: auto;
}

.visual-figure__caption {
  padding: 0 1.15rem 1rem;
  color: #4b5563;
  font-size: 0.92rem;
  line-height: 1.65;
}

.visual-figure--dark .visual-figure__caption {
  color: rgba(248, 250, 252, 0.82);
}

.diagram-grid {
  display: grid;
  gap: 1rem;
}

.diagram-grid--two {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.diagram-grid--three {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.concept-card-row {
  display: grid;
  gap: 1rem;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  margin: 1.6rem 0 2rem;
}

.concept-card {
  border: 1px solid color-mix(in srgb, var(--chapter-accent, var(--compiler)) 34%, white 66%);
  border-radius: 1rem;
  padding: 1.25rem;
  background: #ffffff;
  box-shadow: 0 4px 12px rgba(15, 23, 42, 0.04);
}

html.navy .concept-card,
html.mocha .concept-card,
html.ayu .concept-card {
  background: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 15%, #0f172a 85%);
  border-color: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 40%, #0f172a 60%);
  color: #f8fafc;
}

.concept-card__num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.2rem;
  height: 2.2rem;
  border-radius: 999px;
  margin-bottom: 0.75rem;
  background: var(--chapter-accent, var(--compiler));
  color: #fff;
  font-family: var(--font-display);
  font-size: 1rem;
}

.concept-card__text {
  margin: 0;
  color: var(--ink);
  font-weight: 700;
  line-height: 1.5;
}

html.navy .concept-card__text,
html.mocha .concept-card__text,
html.ayu .concept-card__text {
  color: #f8fafc;
}

.memory-hook-panel {
  display: grid;
  grid-template-columns: minmax(180px, 0.6fr) minmax(0, 1fr);
  gap: 1.5rem;
  margin: 2.5rem 0;
  padding: 1.5rem;
  border: 2px dashed color-mix(in srgb, var(--chapter-accent, var(--compiler)) 40%, white 60%);
  border-radius: 1rem;
  background: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 4%, white 96%);
}

html.navy .memory-hook-panel,
html.mocha .memory-hook-panel,
html.ayu .memory-hook-panel {
  background: linear-gradient(180deg, #1e293b, color-mix(in srgb, var(--chapter-accent, var(--compiler)) 10%, #0f172a 90%));
  border-color: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 40%, #334155 60%);
}

.memory-hook-panel__art {
  align-self: center;
}

.memory-hook-panel__body {
  margin: 0;
  color: var(--ink);
  line-height: 1.7;
}

html.navy .memory-hook-panel__body,
html.mocha .memory-hook-panel__body,
html.ayu .memory-hook-panel__body {
  color: #e2e8f0;
}

.flashcard-grid {
  display: grid;
  gap: 1rem;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin: 1.6rem 0 2rem;
}

.flashcard {
  border: 1px solid color-mix(in srgb, var(--chapter-accent, var(--compiler)) 24%, white 76%);
  border-radius: 1.15rem;
  overflow: hidden;
  background: #fff;
  box-shadow: 0 16px 34px rgba(15, 23, 42, 0.08);
}

html.navy .flashcard,
html.mocha .flashcard,
html.ayu .flashcard {
  background: #1e293b;
  border-color: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 20%, #475569 80%);
}

.flashcard__front {
  padding: 1rem 1rem 0.9rem;
  background: linear-gradient(135deg, color-mix(in srgb, var(--chapter-accent, var(--compiler)) 86%, #09111d 14%), #09111d);
  color: #fff;
}

.flashcard__index {
  margin-bottom: 0.55rem;
  color: rgba(255, 255, 255, 0.94);
  font-family: var(--font-display);
  font-size: 0.74rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.flashcard__question,
.flashcard__answer {
  margin: 0;
  line-height: 1.55;
}

.flashcard__question {
  font-weight: 700;
}

.flashcard__back {
  padding: 0.95rem 1rem 1rem;
  background: #fff;
}

html.navy .flashcard__back,
html.mocha .flashcard__back,
html.ayu .flashcard__back {
  background: #1e293b;
}

html.navy .flashcard__answer,
html.mocha .flashcard__answer,
html.ayu .flashcard__answer {
  color: #e2e8f0;
}

.flashcard__answer-label {
  margin-bottom: 0.45rem;
  color: var(--chapter-accent, var(--compiler));
  font-family: var(--font-display);
  font-size: 0.76rem;
  font-weight: 800;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.cheat-sheet-panel {
  margin: 2.5rem 0;
  padding: 1rem;
  border: 1px solid var(--card-border);
  border-radius: 1rem;
  background: #ffffff;
  box-shadow: 0 8px 24px rgba(15, 23, 42, 0.06);
}

html.navy .cheat-sheet-panel,
html.mocha .cheat-sheet-panel,
html.ayu .cheat-sheet-panel {
  background: linear-gradient(180deg, #1e293b, color-mix(in srgb, var(--chapter-accent, var(--compiler)) 6%, #0f172a 94%));
  border-color: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 40%, #475569 60%);
}

.cheat-sheet-table th {
  background: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 9%, white 91%);
}

html.navy .cheat-sheet-table th,
html.mocha .cheat-sheet-table th,
html.ayu .cheat-sheet-table th {
  background: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 15%, #0f172a 85%);
}

.annotated-code {
  display: grid;
  grid-template-columns: minmax(0, 1.35fr) minmax(220px, 0.65fr);
  gap: 0;
  border: 1px solid var(--card-border);
  border-radius: 12px;
  overflow: hidden;
  margin: 1.5rem 0;
  font-size: 13px;
}

.annotated-code pre {
  margin: 0 !important;
  border-radius: 0 !important;
  border: none !important;
}

.ann-col {
  background: var(--quote-bg, rgba(0,0,0,0.03));
  border-left: 1px solid var(--card-border);
  padding: 12px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.ann-item {
  font-size: 11.5px;
  line-height: 1.45;
  padding: 6px 8px;
  border-radius: 5px;
  border-left: 3px solid transparent;
}

.ann-item strong {
  display: block;
  font-size: 10px;
  font-family: monospace;
  letter-spacing: 0.5px;
  margin-bottom: 2px;
  text-transform: uppercase;
}

/* Concept-colored annotation variants */
.ann-own   { border-left-color: var(--ownership, #E63946); background: rgba(230,57,70,0.08); }
.ann-borrow{ border-left-color: var(--borrow-shared, #457B9D); background: rgba(69,123,157,0.08); }
.ann-mut   { border-left-color: var(--borrow-mut, #F4A261); background: rgba(244,162,97,0.08); }
.ann-valid { border-left-color: var(--valid, #52B788); background: rgba(82,183,136,0.08); }
.ann-error { border-left-color: var(--error, #D62828); background: rgba(214,40,40,0.08); }
.ann-move  { border-left-color: var(--move, #FB8500); background: rgba(251,133,0,0.08); }
.ann-life  { border-left-color: var(--lifetime, #8338EC); background: rgba(131,56,236,0.08); }
.ann-async { border-left-color: var(--async, #00B4D8); background: rgba(0,180,216,0.08); }

.ann-own   strong { color: var(--ownership, #E63946); }
.ann-borrow strong { color: var(--borrow-shared, #457B9D); }
.ann-mut   strong { color: var(--borrow-mut, #F4A261); }
.ann-valid strong { color: var(--valid, #52B788); }
.ann-error strong { color: var(--error, #D62828); }
.ann-move  strong { color: var(--move, #FB8500); }
.ann-life  strong { color: var(--lifetime, #8338EC); }
.ann-async strong { color: var(--async, #00B4D8); }


blockquote.callout {
  position: relative;
  margin: 2rem 0;
  border: 1px solid transparent;
  border-left-width: 0.5rem;
  border-radius: 0.75rem;
  padding: 1.25rem 1.5rem;
  box-shadow: 0 4px 12px rgba(15, 23, 42, 0.04);
}

blockquote.callout p:last-child {
  margin-bottom: 0;
}

blockquote.callout .callout__label {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.55rem;
  font-family: var(--font-display);
  font-size: 0.8rem;
  font-weight: 800;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

blockquote.callout--design-insight {
  border-color: var(--compiler);
  background: #eef2ff;
}

html.navy blockquote.callout--design-insight,
html.mocha blockquote.callout--design-insight,
html.ayu blockquote.callout--design-insight {
  background: color-mix(in srgb, var(--compiler) 15%, #0f172a 85%);
  color: #e2e8f0;
}

blockquote.callout--design-insight .callout__label {
  color: var(--compiler);
}

html.navy blockquote.callout--design-insight .callout__label,
html.mocha blockquote.callout--design-insight .callout__label,
html.ayu blockquote.callout--design-insight .callout__label {
  color: #9bd1ea;
}

blockquote.callout--expert-tip {
  border-color: var(--perf);
  background: #fff8df;
}

html.navy blockquote.callout--expert-tip,
html.mocha blockquote.callout--expert-tip,
html.ayu blockquote.callout--expert-tip {
  background: color-mix(in srgb, var(--perf) 15%, #0f172a 85%);
  color: #e2e8f0;
}

blockquote.callout--expert-tip .callout__label {
  color: #8a5d00;
}

html.navy blockquote.callout--expert-tip .callout__label,
html.mocha blockquote.callout--expert-tip .callout__label,
html.ayu blockquote.callout--expert-tip .callout__label {
  color: #ffd34d;
}

blockquote.callout--common-mistake {
  border-color: var(--error);
  background: #fff5f5;
}

html.navy blockquote.callout--common-mistake,
html.mocha blockquote.callout--common-mistake,
html.ayu blockquote.callout--common-mistake {
  background: color-mix(in srgb, var(--error) 15%, #0f172a 85%);
  color: #e2e8f0;
}

blockquote.callout--common-mistake .callout__label {
  color: var(--error);
}

html.navy blockquote.callout--common-mistake .callout__label,
html.mocha blockquote.callout--common-mistake .callout__label,
html.ayu blockquote.callout--common-mistake .callout__label {
  color: #fca5a5;
}

blockquote.callout--compiler-says {
  border-color: var(--lifetime);
  background: #f5f1ff;
}

html.navy blockquote.callout--compiler-says,
html.mocha blockquote.callout--compiler-says,
html.ayu blockquote.callout--compiler-says {
  background: color-mix(in srgb, var(--lifetime) 15%, #0f172a 85%);
  color: #e2e8f0;
}

blockquote.callout--compiler-says .callout__label {
  color: var(--lifetime);
}

html.navy blockquote.callout--compiler-says .callout__label,
html.mocha blockquote.callout--compiler-says .callout__label,
html.ayu blockquote.callout--compiler-says .callout__label {
  color: #c4b5fd;
}

blockquote.callout--memory-model {
  border-color: var(--borrow-shared);
  background: #0f172a;
  color: #f8fafc;
}

blockquote.callout--memory-model .callout__label {
  color: #9bd1ea;
}

blockquote.callout--zero-cost {
  border-color: var(--perf);
  background: #141b2d;
  color: #f8fafc;
}

blockquote.callout--zero-cost .callout__label {
  color: #ffd34d;
}

.visual-table {
  width: 100%;
  border-collapse: collapse;
  overflow: hidden;
  border-radius: 1rem;
}

/* Scrollable table wrapper for narrow viewports */
.visual-table-wrapper {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin: 1.6rem 0;
  border-radius: 1rem;
  border: 1px solid rgba(2, 62, 138, 0.12);
}

.visual-table-wrapper:focus-visible {
  outline: 3px solid var(--chapter-accent, var(--compiler));
  outline-offset: 2px;
}

.visual-table th,
.visual-table td {
  padding: 0.75rem 0.85rem;
  border-bottom: 1px solid rgba(2, 62, 138, 0.12);
  vertical-align: top;
}

html.navy .visual-table th,
html.navy .visual-table td,
html.mocha .visual-table th,
html.mocha .visual-table td,
html.ayu .visual-table th,
html.ayu .visual-table td {
  border-bottom-color: rgba(255, 255, 255, 0.08);
  color: #e2e8f0;
}

.visual-table th {
  color: var(--compiler);
  font-family: var(--font-display);
  font-size: 0.84rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  background: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 6%, white 94%);
}

.visual-table-wrapper .visual-table th {
  position: sticky;
  top: 0;
  z-index: 1;
}

.svg-frame {
  width: 100%;
  height: auto;
  display: block;
}

.svg-frame--wide {
  width: max(100%, var(--svg-min-width, 960px));
  max-width: none;
}

.inline-svg-icon {
  width: 1em;
  height: 1em;
  flex: 0 0 auto;
}

.svg-title {
  fill: currentColor;
  font-family: var(--font-display);
  font-size: 26px;
  font-weight: 800;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.svg-subtitle,
.svg-label,
.svg-note,
.svg-small {
  fill: currentColor;
  font-family: var(--font-body);
}

.svg-subtitle {
  font-size: 16px;
  font-weight: 700;
}

.svg-label {
  font-size: 14px;
  font-weight: 700;
}

.svg-note {
  font-size: 12px;
  font-weight: 600;
}

.svg-small {
  font-size: 11px;
}

.svg-chip {
  rx: 999px;
}

.caption-grid {
  display: grid;
  gap: 0.8rem;
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.chapter-break {
  margin: 2.8rem 0 1.5rem;
  border: 0;
  border-top: 1px solid rgba(2, 62, 138, 0.14);
}

/* ─── Interactive Flashcard Flip ──────────────────────────────────────────── */

.fc-counter {
  font-size: 0.78rem;
  color: var(--ink);
  opacity: 0.62;
  margin-bottom: 0.75rem;
  font-family: var(--font-display);
  letter-spacing: 0.5px;
}

.flashcard-grid .flashcard {
  perspective: 1200px;
  cursor: pointer;
  outline: none;
  min-height: 160px;
}

.flashcard-grid .flashcard:focus-visible .flashcard__inner {
  box-shadow: 0 0 0 3px var(--chapter-accent, var(--compiler));
}

.flashcard__inner {
  position: relative;
  width: 100%;
  height: 100%;
  min-height: 160px;
  transition: transform 0.5s cubic-bezier(0.4, 0, 0.2, 1);
  transform-style: preserve-3d;
}

.flashcard-grid .flashcard.flipped .flashcard__inner {
  transform: rotateY(180deg);
}

.flashcard-grid .flashcard .flashcard__front,
.flashcard-grid .flashcard .flashcard__back {
  position: absolute;
  width: 100%;
  min-height: 160px;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  border-radius: 1.15rem;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.flashcard-grid .flashcard .flashcard__back {
  transform: rotateY(180deg);
}

.flashcard-grid .flashcard .flashcard__front::after {
  content: "tap to flip →";
  display: block;
  font-size: 0.68rem;
  font-family: var(--font-display);
  opacity: 0.35;
  margin-top: 0.5rem;
  text-align: right;
}

.flashcard-grid .flashcard.seen .flashcard__front::before {
  content: "✓";
  position: absolute;
  top: 0.6rem;
  right: 0.75rem;
  font-size: 0.72rem;
  opacity: 0.45;
  color: var(--valid);
}

/* ─── Chapter Snapshot Card ───────────────────────────────────────────────── */

.chapter-snapshot {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 0.75rem;
  background: var(--paper-strong, #fff6eb);
  border: 1px solid var(--card-border);
  border-top: 4px solid var(--chapter-accent, var(--compiler));
  border-radius: 0 0 0.75rem 0.75rem;
  padding: 1rem 1.15rem;
  margin: 0 0 2rem;
  font-size: 0.85rem;
}

.snapshot-cell h4 {
  font-size: 0.62rem;
  letter-spacing: 1.5px;
  text-transform: uppercase;
  opacity: 0.55;
  font-family: var(--font-display);
  margin: 0 0 0.4rem;
  font-weight: 600;
}

.snapshot-cell ul {
  margin: 0;
  padding-left: 1rem;
  line-height: 1.7;
}

.snapshot-cell ul li {
  font-size: 0.82rem !important;
  margin-bottom: 0.2rem !important;
}

.snapshot-time {
  font-size: 2rem;
  font-weight: 700;
  color: var(--chapter-accent, var(--compiler));
  line-height: 1;
  margin-bottom: 0.15rem;
  font-family: var(--font-display);
}

.snapshot-time-unit {
  font-size: 0.72rem;
  opacity: 0.5;
}

.snapshot-prereq a {
  color: var(--chapter-accent, var(--compiler));
  font-size: 0.78rem;
  display: block;
  margin-bottom: 0.3rem;
}

body.navy .chapter-snapshot,
body.coal .chapter-snapshot,
body.ayu .chapter-snapshot {
  background: rgba(255, 255, 255, 0.04);
  border-color: rgba(255, 255, 255, 0.15);
}

/* ─── Cross-Chapter Link Callouts ─────────────────────────────────────────── */

.concept-link {
  display: flex;
  gap: 0.75rem;
  align-items: flex-start;
  padding: 0.85rem 1rem;
  border-radius: 0.5rem;
  margin: 1.2rem 0;
  font-size: 0.85rem;
  line-height: 1.55;
}

.concept-link-icon {
  font-size: 1.2rem;
  flex-shrink: 0;
  line-height: 1.2;
}

.concept-link-body strong {
  display: block;
  font-size: 0.68rem;
  font-family: var(--font-display);
  letter-spacing: 1px;
  text-transform: uppercase;
  margin-bottom: 0.2rem;
}

.concept-link-body a {
  font-size: 0.82rem;
  font-weight: 600;
}

.builds-on {
  background: color-mix(in srgb, var(--borrow-shared) 8%, white 92%);
  border-left: 3px solid var(--borrow-shared);
}

.builds-on .concept-link-body strong {
  color: var(--borrow-shared);
}

.needed-for {
  background: color-mix(in srgb, var(--ownership) 8%, white 92%);
  border-left: 3px solid var(--ownership);
}

.needed-for .concept-link-body strong {
  color: var(--ownership);
}

body.navy .builds-on,
body.coal .builds-on,
body.ayu .builds-on {
  background: rgba(69, 123, 157, 0.12);
}

body.navy .needed-for,
body.coal .needed-for,
body.ayu .needed-for {
  background: rgba(230, 57, 70, 0.12);
}

/* ─── Error Decoder Cards ─────────────────────────────────────────────────── */

.error-card {
  background: var(--paper-strong, #fff6eb);
  border: 1px solid var(--error);
  border-left: 6px solid var(--error);
  border-radius: 0 0.75rem 0.75rem 0;
  padding: 1rem 1.15rem;
  margin: 1.5rem 0;
}

.error-code {
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--error);
  font-family: var(--font-display);
  line-height: 1;
  margin-bottom: 0.15rem;
}

.error-name {
  font-size: 0.85rem;
  opacity: 0.6;
  font-style: italic;
  margin-bottom: 0.75rem;
}

.error-invariant {
  font-size: 0.9rem;
  line-height: 1.65;
  margin-bottom: 0.75rem;
}

.error-fix {
  background: color-mix(in srgb, var(--valid) 10%, white 90%);
  border: 1px solid var(--valid);
  border-radius: 0.4rem;
  padding: 0.65rem 0.75rem;
  font-size: 0.85rem;
  line-height: 1.55;
}

.error-fix::before {
  content: "✓ Fix: ";
  font-weight: 700;
  font-family: var(--font-display);
  color: var(--valid);
}

body.navy .error-card,
body.coal .error-card,
body.ayu .error-card {
  background: rgba(214, 40, 40, 0.08);
  border-color: rgba(214, 40, 40, 0.5);
}

body.navy .error-fix,
body.coal .error-fix,
body.ayu .error-fix {
  background: rgba(82, 183, 136, 0.1);
  border-color: rgba(82, 183, 136, 0.4);
  color: #d9fbe9;
}

/* ─── Progress Tracker ────────────────────────────────────────────────────── */

.progress-cta {
  margin: 3rem 0 1rem;
  padding: 1rem;
  background: var(--paper-strong, #fff6eb);
  border-radius: 0.75rem;
  border: 1px solid var(--card-border);
  text-align: center;
}

body.navy .progress-cta,
body.coal .progress-cta,
body.ayu .progress-cta {
  background: rgba(255, 255, 255, 0.04);
  border-color: rgba(255, 255, 255, 0.15);
}

.progress-btn {
  padding: 0.6rem 1.5rem;
  font-size: 0.9rem;
  font-weight: 600;
  background: var(--valid);
  color: #fff;
  border: none;
  border-radius: 0.4rem;
  cursor: pointer;
  font-family: var(--font-body);
  transition: opacity 0.15s ease;
}

.progress-btn:hover {
  opacity: 0.88;
}

.progress-done {
  color: var(--valid);
  font-weight: 600;
  font-size: 0.9rem;
}

.progress-unmark {
  margin-left: 1rem;
  font-size: 0.75rem;
  opacity: 0.5;
  background: none;
  border: none;
  cursor: pointer;
  color: var(--ink);
  font-family: var(--font-body);
}

.sidebar-check {
  position: absolute;
  right: 0.5rem;
  top: 50%;
  transform: translateY(-50%);
  font-size: 0.65rem;
  color: var(--valid);
}

@media (max-width: 960px) {
  .annotated-code,
  .diagram-grid--two,
  .diagram-grid--three,
  .caption-grid,
  .memory-hook-panel,
  .annotated-code,
  .chapter-snapshot {
    grid-template-columns: 1fr;
  }

  .ann-col {
    border-left: none;
    border-top: 1px solid var(--card-border);
  }

  .chapter-hero,
  .part-spread {
    padding: 1.15rem;
  }
}

@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;
  }

  .flashcard__inner {
    transition: none !important;
    transform: none !important;
  }

  .flashcard-grid .flashcard.flipped .flashcard__inner {
    transform: none !important;
  }

  .flashcard-grid .flashcard .flashcard__front,
  .flashcard-grid .flashcard .flashcard__back {
    position: static;
    min-height: auto;
    backface-visibility: visible;
    -webkit-backface-visibility: visible;
  }

  .flashcard-grid .flashcard .flashcard__back {
    display: none;
    transform: none;
  }

  .flashcard-grid .flashcard.flipped .flashcard__front {
    display: none;
  }

  .flashcard-grid .flashcard.flipped .flashcard__back {
    display: flex;
  }
}

@media print {
  body,
  #mdbook-content main {
    background: #fff !important;
  }

  .chapter-hero,
  .part-spread,
  .visual-figure,
  .annotated-code,
  blockquote.callout {
    break-inside: avoid-page;
    page-break-inside: avoid;
    -webkit-print-color-adjust: exact;
    print-color-adjust: exact;
  }
}

/* ─── Dark mode — mdBook navy / coal / ayu themes ─────────────────────────── */

body.navy,
body.coal,
body.ayu {
  --ink: #d4d8e2;
  --paper: #1e2030;
  --paper-strong: #252840;
  --grid: rgba(100, 140, 220, 0.1);
  --card-border: rgba(100, 140, 220, 0.2);
}

body.navy #mdbook-content main p code,
body.navy #mdbook-content main li code,
body.navy #mdbook-content main td code,
body.navy #mdbook-content main th code,
body.coal #mdbook-content main p code,
body.coal #mdbook-content main li code,
body.coal #mdbook-content main td code,
body.coal #mdbook-content main th code,
body.ayu #mdbook-content main p code,
body.ayu #mdbook-content main li code,
body.ayu #mdbook-content main td code,
body.ayu #mdbook-content main th code {
  background: rgba(255, 255, 255, 0.08);
  border-color: rgba(255, 255, 255, 0.15);
  color: #e2e8f0;
}

body.navy .visual-table th,
body.coal .visual-table th,
body.ayu .visual-table th {
  background: rgba(255, 255, 255, 0.06);
  color: #93c5fd;
}

body.navy .visual-table th,
body.navy .visual-table td,
body.coal .visual-table th,
body.coal .visual-table td,
body.ayu .visual-table th,
body.ayu .visual-table td {
  border-bottom-color: rgba(255, 255, 255, 0.1);
}

body.navy .concept-card,
body.coal .concept-card,
body.ayu .concept-card {
  background: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 18%, #0b1220 82%);
  border-color: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 48%, #334155 52%);
}

body.navy .concept-card__text,
body.coal .concept-card__text,
body.ayu .concept-card__text {
  color: #f8fbff;
}

body.navy .flashcard,
body.coal .flashcard,
body.ayu .flashcard {
  background: #1e2030;
  border-color: rgba(255, 255, 255, 0.15);
}

body.navy .flashcard__back,
body.coal .flashcard__back,
body.ayu .flashcard__back {
  background: #252840;
}

body.navy .flashcard__answer,
body.coal .flashcard__answer,
body.ayu .flashcard__answer {
  color: #e2e8f0;
}

body.navy .flashcard__index,
body.coal .flashcard__index,
body.ayu .flashcard__index,
html.navy .flashcard__index,
html.mocha .flashcard__index,
html.ayu .flashcard__index {
  color: #f8fafc;
}

body.navy .flashcard__answer-label,
body.coal .flashcard__answer-label,
body.ayu .flashcard__answer-label,
html.navy .flashcard__answer-label,
html.mocha .flashcard__answer-label,
html.ayu .flashcard__answer-label {
  color: color-mix(in srgb, var(--chapter-accent, var(--compiler)) 70%, #f8fafc 30%);
}

body.navy blockquote.callout .callout__label,
body.coal blockquote.callout .callout__label,
body.ayu blockquote.callout .callout__label {
  color: #f8fafc;
}

body.navy blockquote.callout,
body.coal blockquote.callout,
body.ayu blockquote.callout {
  color: #f1f5f9;
}

body.navy .memory-hook-panel,
body.coal .memory-hook-panel,
body.ayu .memory-hook-panel {
  background: rgba(255, 255, 255, 0.04);
  border-color: rgba(255, 255, 255, 0.2);
}

body.navy .memory-hook-panel__body p,
body.coal .memory-hook-panel__body p,
body.ayu .memory-hook-panel__body p {
  color: #e2e8f0;
}

body.navy .cheat-sheet-panel,
body.coal .cheat-sheet-panel,
body.ayu .cheat-sheet-panel {
  background: rgba(255, 255, 255, 0.04);
  border-color: rgba(255, 255, 255, 0.2);
}

body.navy blockquote.callout--design-insight,
body.coal blockquote.callout--design-insight,
body.ayu blockquote.callout--design-insight {
  background: rgba(2, 62, 138, 0.2);
}

body.navy blockquote.callout--expert-tip,
body.coal blockquote.callout--expert-tip,
body.ayu blockquote.callout--expert-tip {
  background: rgba(138, 93, 0, 0.2);
}

body.navy blockquote.callout--common-mistake,
body.coal blockquote.callout--common-mistake,
body.ayu blockquote.callout--common-mistake {
  background: rgba(214, 40, 40, 0.15);
}

body.navy blockquote.callout--compiler-says,
body.coal blockquote.callout--compiler-says,
body.ayu blockquote.callout--compiler-says {
  background: rgba(131, 56, 236, 0.18);
}

body.navy .chapter-break,
body.coal .chapter-break,
body.ayu .chapter-break {
  border-top-color: rgba(255, 255, 255, 0.12);
}

blockquote.callout--learning-objective {
  border-color: var(--valid);
  background: color-mix(in srgb, var(--valid) 10%, #ffffff 90%);
}

html.navy blockquote.callout--learning-objective,
html.mocha blockquote.callout--learning-objective,
html.ayu blockquote.callout--learning-objective {
  background: color-mix(in srgb, var(--valid) 15%, #0f172a 85%);
  color: #e2e8f0;
}

blockquote.callout--learning-objective .callout__label {
  color: var(--valid);
}

html.navy blockquote.callout--learning-objective .callout__label,
html.mocha blockquote.callout--learning-objective .callout__label,
html.ayu blockquote.callout--learning-objective .callout__label {
  color: #86efac;
}

/* ═══ PLAYGROUND BUTTONS ═══════════════════════════════ */
.playground-btn {
  position: absolute;
  top: 6px;
  right: 6px;
  padding: 4px 10px;
  font-size: 11px;
  font-family: var(--font-mono, monospace);
  font-weight: 600;
  color: #fff;
  background: var(--ownership, #E63946);
  border: none;
  border-radius: 5px;
  cursor: pointer;
  text-decoration: none;
  opacity: 0.75;
  transition: opacity 0.2s;
  z-index: 2;
}

.playground-btn:hover {
  opacity: 1;
  text-decoration: none;
  color: #fff;
}

/* ═══ INTERACTIVE STEPPERS ═════════════════════════════ */
.stepper {
  background: var(--quote-bg, rgba(0,0,0,0.03));
  border: 1px solid var(--card-border, rgba(0,0,0,0.1));
  border-radius: 12px;
  padding: 1.25rem;
  margin: 1.5rem 0;
}

.stepper-step {
  min-height: 80px;
}

.stepper-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-top: 1rem;
  padding-top: 0.75rem;
  border-top: 1px solid var(--card-border, rgba(0,0,0,0.08));
}

.stepper-btn {
  padding: 6px 14px;
  font-size: 12px;
  font-weight: 600;
  border: 1px solid var(--card-border, rgba(0,0,0,0.15));
  border-radius: 6px;
  background: var(--sidebar-bg, #f8f9fa);
  color: var(--fg, #333);
  cursor: pointer;
  transition: background 0.15s;
}

.stepper-btn:hover:not(:disabled) {
  background: var(--links, #4183c4);
  color: #fff;
  border-color: transparent;
}

.stepper-btn:disabled {
  opacity: 0.3;
  cursor: default;
}

.stepper-counter {
  font-size: 12px;
  font-family: var(--font-mono, monospace);
  opacity: 0.5;
}

/* ═══ 3-LEVEL TABS ═════════════════════════════════════ */
.level-tabs {
  margin: 1.5rem 0;
  border: 1px solid var(--card-border, rgba(0,0,0,0.1));
  border-radius: 12px;
  overflow: hidden;
}

.level-tab-bar {
  display: flex;
  background: var(--sidebar-bg, #f8f9fa);
  border-bottom: 1px solid var(--card-border, rgba(0,0,0,0.1));
}

.level-tab {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.42rem;
  flex: 1;
  padding: 10px 14px;
  font-size: 12px;
  font-weight: 600;
  border: none;
  background: transparent;
  color: var(--fg, #333);
  cursor: pointer;
  border-bottom: 3px solid transparent;
  transition: border-color 0.2s, background 0.2s;
}

.level-tab__icon {
  width: 0.95rem;
  height: 0.95rem;
}

.level-tab:hover {
  background: rgba(0,0,0,0.03);
}

.level-tab--active {
  border-bottom-color: var(--chapter-accent, var(--links, #4183c4));
  background: var(--bg, #fff);
}

.level-panel {
  padding: 1.25rem;
}

/* ═══ ANKI EXPORT ══════════════════════════════════════ */
.anki-export-btn {
  display: block;
  margin: 12px auto 0;
  padding: 6px 16px;
  font-size: 12px;
  font-weight: 500;
  border: 1px solid var(--card-border, rgba(0,0,0,0.12));
  border-radius: 6px;
  background: var(--sidebar-bg, #f8f9fa);
  color: var(--fg, #555);
  cursor: pointer;
  opacity: 0.65;
  transition: opacity 0.2s;
}

.anki-export-btn:hover {
  opacity: 1;
  border-color: var(--links, #4183c4);
  color: var(--links, #4183c4);
}

/* ═══ LANGUAGE COMPARISON BOXES ════════════════════════ */
.lang-compare {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  border: 1px solid var(--card-border, rgba(0,0,0,0.1));
  border-radius: 12px;
  overflow: hidden;
  margin: 1.5rem 0;
}

.lang-panel {
  padding: 0;
}

.lang-panel pre {
  margin: 0 !important;
  border-radius: 0 !important;
  border: none !important;
}

.lang-label {
  display: block;
  padding: 6px 12px;
  font-size: 10px;
  font-family: var(--font-mono, monospace);
  font-weight: 700;
  letter-spacing: 1px;
  text-transform: uppercase;
  border-bottom: 1px solid var(--card-border, rgba(0,0,0,0.08));
}

.lang-label--rust {
  background: rgba(230,57,70,0.08);
  color: var(--ownership, #E63946);
}

.lang-label--python {
  background: rgba(69,123,157,0.08);
  color: var(--borrow-shared, #457B9D);
}

.lang-label--go {
  background: rgba(0,180,216,0.08);
  color: var(--async, #00B4D8);
}

.lang-label--java {
  background: rgba(244,162,97,0.08);
  color: var(--borrow-mut, #F4A261);
}

.lang-panel + .lang-panel {
  border-left: 1px solid var(--card-border, rgba(0,0,0,0.1));
}

@media (max-width: 700px) {
  .lang-compare {
    grid-template-columns: 1fr;
  }
  .lang-panel + .lang-panel {
    border-left: none;
    border-top: 1px solid var(--card-border, rgba(0,0,0,0.1));
  }
}

@media (max-width: 900px) {
  #mdbook-content main {
    padding-inline: clamp(1rem, 4vw, 1.45rem);
  }

  #mdbook-sidebar a {
    padding-block: 0.32rem;
    line-height: 1.42;
  }

  .chapter-hero,
  .part-spread {
    padding: 1.1rem;
    border-radius: 1.35rem;
  }

  .chapter-hero__grid,
  .part-spread__grid {
    gap: 1rem;
    grid-template-columns: minmax(0, 1.08fr) minmax(240px, 0.92fr);
  }

  .chapter-hero__title,
  .part-spread__title {
    font-size: clamp(1.95rem, 5.2vw, 3.15rem);
  }
}

@media (max-width: 980px) {
  .concept-card-row {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 768px) {
  #mdbook-content main {
    padding-inline: 0.9rem;
  }

  #mdbook-sidebar a {
    min-height: 2.15rem;
    padding-block: 0.38rem;
  }

  .chapter-hero,
  .part-spread {
    margin-bottom: 1.9rem;
    padding: 1rem;
  }

  .chapter-hero__grid,
  .part-spread__grid,
  .memory-hook-panel {
    grid-template-columns: 1fr;
  }

  .chapter-hero__meta,
  .part-spread__meta {
    gap: 0.5rem;
  }

  .chapter-hero__hook,
  .part-spread__hook {
    margin-top: 0.7rem;
    line-height: 1.62;
  }

  .visual-table th,
  .visual-table td {
    padding: 0.82rem 0.9rem;
  }
}

@media (max-width: 700px) {
  .flashcard-grid,
  .concept-card-row {
    grid-template-columns: 1fr;
    gap: 0.9rem;
  }

  .flashcard-grid {
    margin: 1.25rem 0 1.6rem;
  }

  .flashcard-grid .flashcard,
  .flashcard__inner,
  .flashcard-grid .flashcard .flashcard__front,
  .flashcard-grid .flashcard .flashcard__back {
    min-height: 180px;
  }

  .concept-card {
    padding: 1rem;
  }
}

@media (max-width: 560px) {
  #mdbook-content main p,
  #mdbook-content main li {
    font-size: 0.97rem;
    line-height: 1.68;
  }

  .chapter-hero__title,
  .part-spread__title {
    font-size: clamp(1.35rem, 7.2vw, 2rem);
    line-height: 1.02;
  }

  .chapter-hero__hook,
  .part-spread__hook {
    font-size: 0.94rem;
    line-height: 1.56;
  }

  .chapter-hero__pill,
  .part-spread__pill {
    padding: 0.38rem 0.66rem;
    font-size: 0.7rem;
  }

  .scrollable-x.is-scrollable-x:not(.is-scrolled-end)::after {
    top: 0.4rem;
    right: 0.42rem;
    font-size: 0.6rem;
    padding: 0.2rem 0.42rem;
  }
}