/* ==========================================================================
   Taller de Estudio — cuaderno de campo para Ingeniería Agrícola
   Shared design system. Palette and type mirror the Motores atlas.
   ========================================================================== */

@font-face {
  font-family: 'Cormorant Garamond';
  src: url('../fonts/cormorant-var.woff2') format('woff2');
  font-weight: 300 700;
  font-style: normal;
  font-display: swap;
}

@font-face {
  font-family: 'Cormorant Garamond';
  src: url('../fonts/cormorant-italic-500.woff2') format('woff2');
  font-weight: 500;
  font-style: italic;
  font-display: swap;
}

@font-face {
  font-family: 'DM Sans';
  src: url('../fonts/dmsans-var.woff2') format('woff2');
  font-weight: 100 900;
  font-style: normal;
  font-display: swap;
}

@font-face {
  font-family: 'Comic Neue';
  src: url('../fonts/comicneue-400.woff2') format('woff2');
  font-weight: 400;
  font-style: normal;
  font-display: swap;
}

@font-face {
  font-family: 'Comic Neue';
  src: url('../fonts/comicneue-700.woff2') format('woff2');
  font-weight: 700;
  font-style: normal;
  font-display: swap;
}

@font-face {
  font-family: 'Comic Neue';
  src: url('../fonts/comicneue-italic-400.woff2') format('woff2');
  font-weight: 400;
  font-style: italic;
  font-display: swap;
}

/* ---------------------------------------------------------------- tokens */

:root {
  --ink: #2e2823;
  --ink-soft: #453d36;
  --muted: #5d544c;
  --faint: #6e645b;

  --canvas: #f6efe5;
  --paper: #fffdf8;
  --paper-2: #fbf5ea;
  --paper-3: #f4ebdd;

  --line: rgba(94, 72, 52, 0.16);
  --line-strong: rgba(94, 72, 52, 0.3);

  --accent: #4e7f5f;
  --accent-ink: #2f5a41;
  --accent-soft: rgba(78, 127, 95, 0.1);
  --accent-line: rgba(78, 127, 95, 0.32);

  --coral: #c25a41;
  --amber: #a9772a;
  --blue: #3f7391;
  --plum: #7a5a9e;

  --serif: 'Cormorant Garamond', 'Iowan Old Style', Georgia, serif;
  --sans: 'DM Sans', system-ui, -apple-system, 'Segoe UI', sans-serif;
  --hand: 'Comic Neue', 'Comic Sans MS', 'Bradley Hand', cursive;

  --shadow-sm: 0 1px 2px rgba(74, 53, 35, 0.04), 0 10px 24px -16px rgba(74, 53, 35, 0.35);
  --shadow-md: 0 2px 4px rgba(74, 53, 35, 0.05), 0 22px 48px -26px rgba(74, 53, 35, 0.45);

  --radius: 14px;
  --radius-sm: 10px;
  --shell: 1200px;
  --bar-h: 62px;
}

/* ---------------------------------------------------------------- reset */

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

/* author display rules must not resurrect elements the engine hides */
[hidden] {
  display: none !important;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--bar-h) + 24px);
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  min-width: 320px;
  color: var(--ink);
  font-family: var(--sans);
  font-size: 15.5px;
  line-height: 1.62;
  background:
    radial-gradient(1100px 560px at 12% -8%, #fffdf9 0%, rgba(255, 253, 249, 0) 62%),
    radial-gradient(900px 480px at 98% 2%, #fbf2e3 0%, rgba(251, 242, 227, 0) 58%),
    var(--canvas);
  background-attachment: fixed;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

body::before {
  content: '';
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  opacity: 0.16;
  mix-blend-mode: multiply;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='140' height='140'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.82' numOctaves='3' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='140' height='140' filter='url(%23n)' opacity='0.5'/%3E%3C/svg%3E");
}

img,
svg {
  max-width: 100%;
}

a {
  color: inherit;
}

button,
input,
textarea,
select {
  font: inherit;
  color: inherit;
}

button {
  cursor: pointer;
}

::selection {
  background: rgba(194, 90, 65, 0.2);
}

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: 3px;
}

.skip {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 100;
  background: var(--paper);
  color: var(--ink);
  padding: 12px 18px;
  border-radius: 0 0 10px 0;
  font-weight: 600;
}

.skip:focus {
  left: 0;
}

/* ---------------------------------------------------------------- bar */

.bar {
  position: sticky;
  top: 0;
  z-index: 40;
  height: var(--bar-h);
  display: flex;
  align-items: center;
  gap: 20px;
  padding: 0 clamp(16px, 3vw, 32px);
  background: rgba(250, 244, 235, 0.86);
  backdrop-filter: blur(14px) saturate(1.1);
  -webkit-backdrop-filter: blur(14px) saturate(1.1);
  border-bottom: 1px solid var(--line);
}

.bar__brand {
  display: flex;
  align-items: center;
  gap: 11px;
  text-decoration: none;
  flex-shrink: 0;
}

.bar__mark {
  width: 34px;
  height: 34px;
  display: grid;
  place-items: center;
  border-radius: 9px;
  background: var(--accent);
  color: #fffdf8;
  font-family: var(--serif);
  font-size: 17px;
  font-weight: 700;
  letter-spacing: 0.02em;
  box-shadow: inset 0 -1px 0 rgba(0, 0, 0, 0.15);
}

.bar__name {
  display: flex;
  flex-direction: column;
  font-family: var(--serif);
  font-size: 17px;
  font-weight: 600;
  line-height: 1.05;
  letter-spacing: 0.01em;
}

.bar__name em {
  font-family: var(--sans);
  font-style: normal;
  font-size: 9.5px;
  font-weight: 600;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--faint);
  margin-top: 3px;
}

.bar__nav {
  display: flex;
  align-items: center;
  gap: 2px;
  margin-left: auto;
  overflow-x: auto;
  scrollbar-width: none;
}

.bar__nav::-webkit-scrollbar {
  display: none;
}

.bar__nav a {
  position: relative;
  padding: 7px 11px;
  border-radius: 8px;
  font-size: 12.5px;
  font-weight: 500;
  color: var(--muted);
  text-decoration: none;
  white-space: nowrap;
  transition: color 0.2s ease, background 0.2s ease;
}

.bar__nav a:hover {
  color: var(--ink);
  background: rgba(94, 72, 52, 0.06);
}

.bar__nav a[aria-current='page'] {
  color: var(--accent-ink);
  background: var(--accent-soft);
  font-weight: 600;
}

.bar__nav a[aria-current='page']::after {
  content: '';
  position: absolute;
  left: 11px;
  right: 11px;
  bottom: 2px;
  height: 2px;
  border-radius: 2px;
  background: var(--accent);
}

.bar__actions {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
}

.bar__link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 7px 12px;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  background: transparent;
  font-size: 12px;
  font-weight: 600;
  color: var(--ink-soft);
  text-decoration: none;
  transition: background 0.2s ease, border-color 0.2s ease, color 0.2s ease;
}

.bar__link:hover {
  background: var(--paper);
  border-color: var(--accent-line);
  color: var(--accent-ink);
}

.bar__link svg {
  width: 13px;
  height: 13px;
}

.progress {
  position: fixed;
  top: var(--bar-h);
  left: 0;
  height: 2px;
  width: 0;
  z-index: 41;
  background: linear-gradient(90deg, var(--accent), var(--coral));
  transition: width 0.1s linear;
}

/* ---------------------------------------------------------------- hero */

.hero {
  position: relative;
  z-index: 1;
  overflow: hidden;
  border-bottom: 1px solid var(--line);
}

.hero__inner {
  max-width: var(--shell);
  margin: 0 auto;
  padding: clamp(44px, 7vw, 84px) clamp(20px, 4vw, 40px) clamp(38px, 5vw, 60px);
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 0.42fr);
  gap: clamp(24px, 4vw, 56px);
  align-items: center;
}

.hero__kicker {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  margin: 0 0 18px;
  font-size: 10.5px;
  font-weight: 700;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--accent-ink);
}

.hero__kicker::before {
  content: '';
  width: 26px;
  height: 1px;
  background: var(--accent);
}

.hero h1 {
  margin: 0;
  font-family: var(--serif);
  font-weight: 600;
  font-size: clamp(2.5rem, 6.2vw, 4.15rem);
  line-height: 0.98;
  letter-spacing: -0.012em;
  text-wrap: balance;
}

.hero h1 em {
  font-style: italic;
  font-weight: 500;
  color: var(--accent-ink);
}

.hero__lead {
  margin: 20px 0 0;
  max-width: 54ch;
  font-size: clamp(15px, 1.5vw, 17px);
  line-height: 1.6;
  color: var(--ink-soft);
  text-wrap: pretty;
}

.hero__meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 26px 0 0;
  padding: 0;
  list-style: none;
}

.hero__meta li {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 11px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: rgba(255, 253, 248, 0.6);
  font-size: 11.5px;
  font-weight: 500;
  color: var(--muted);
}

.hero__meta b {
  font-weight: 700;
  color: var(--ink);
}

.hero__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 28px;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 11px 20px;
  border-radius: 999px;
  border: 1px solid transparent;
  font-size: 13px;
  font-weight: 600;
  text-decoration: none;
  transition: transform 0.2s ease, box-shadow 0.2s ease, background 0.2s ease, color 0.2s ease;
}

.btn svg {
  width: 14px;
  height: 14px;
}

.btn--primary {
  background: var(--accent);
  color: #fffdf8;
  box-shadow: 0 8px 20px -10px rgba(47, 90, 65, 0.7);
}

.btn--primary:hover {
  background: var(--accent-ink);
  transform: translateY(-1px);
  box-shadow: 0 12px 26px -12px rgba(47, 90, 65, 0.8);
}

.btn--ghost {
  border-color: var(--line-strong);
  color: var(--ink-soft);
  background: rgba(255, 253, 248, 0.5);
}

.btn--ghost:hover {
  border-color: var(--accent-line);
  color: var(--accent-ink);
  background: var(--paper);
}

.hero__art {
  position: relative;
  display: grid;
  place-items: center;
  aspect-ratio: 1 / 1;
  max-height: 340px;
  justify-self: center;
  width: 100%;
}

.hero__art svg {
  width: 100%;
  height: 100%;
  max-width: 330px;
  overflow: visible;
}

.hero__art .art-line {
  fill: none;
  stroke: var(--accent);
  stroke-width: 1.1;
  stroke-linecap: round;
  stroke-linejoin: round;
  opacity: 0.85;
}

.hero__art .art-fill {
  fill: var(--accent-soft);
}

.hero__art .art-dash {
  fill: none;
  stroke: var(--accent);
  stroke-width: 0.9;
  stroke-dasharray: 3 5;
  opacity: 0.55;
}

.hero__art .art-hand {
  font-family: var(--hand);
  font-size: 11px;
  fill: var(--coral);
}

.hero__art .art-label {
  font-family: var(--sans);
  font-size: 7.5px;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  fill: var(--faint);
}

/* ---------------------------------------------------------------- layout */

.shell {
  position: relative;
  z-index: 1;
  max-width: var(--shell);
  margin: 0 auto;
  padding: 0 clamp(20px, 4vw, 40px) 96px;
  display: grid;
  grid-template-columns: 218px minmax(0, 1fr);
  gap: clamp(28px, 4vw, 64px);
  align-items: start;
}

.toc {
  position: sticky;
  top: calc(var(--bar-h) + 26px);
  padding-top: 46px;
  max-height: calc(100vh - var(--bar-h) - 60px);
  overflow-y: auto;
  overscroll-behavior: contain;
  scrollbar-width: thin;
}

.toc__label {
  margin: 0 0 14px;
  font-size: 9.5px;
  font-weight: 700;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--faint);
}

.toc ol {
  list-style: none;
  margin: 0;
  padding: 0;
  border-left: 1px solid var(--line);
}

.toc li {
  margin: 0;
}

.toc a {
  position: relative;
  display: flex;
  align-items: baseline;
  gap: 8px;
  padding: 6px 0 6px 14px;
  font-size: 12.5px;
  line-height: 1.35;
  color: var(--muted);
  text-decoration: none;
  transition: color 0.18s ease;
}

.toc a span {
  font-family: var(--serif);
  font-style: italic;
  font-size: 12px;
  color: var(--faint);
  flex-shrink: 0;
  min-width: 12px;
}

.toc a:hover {
  color: var(--ink);
}

.toc a[aria-current='true'] {
  color: var(--accent-ink);
  font-weight: 600;
}

.toc a[aria-current='true']::before {
  content: '';
  position: absolute;
  left: -1px;
  top: 4px;
  bottom: 4px;
  width: 2px;
  border-radius: 2px;
  background: var(--accent);
}

.toc a[aria-current='true'] span {
  color: var(--accent);
}

.toc__foot {
  margin-top: 22px;
  padding-top: 16px;
  border-top: 1px solid var(--line);
}

.toc__foot p {
  margin: 0 0 8px;
  font-family: var(--hand);
  font-size: 12.5px;
  line-height: 1.4;
  color: var(--coral);
  transform: rotate(-1.4deg);
}

.toc__foot a {
  font-size: 11.5px;
  font-weight: 600;
  color: var(--muted);
  text-decoration: none;
  border-bottom: 1px solid var(--line-strong);
}

.toc__foot a:hover {
  color: var(--accent-ink);
}

.content {
  min-width: 0;
  padding-top: 46px;
}

/* ---------------------------------------------------------------- sections */

.topic {
  padding: 34px 0 8px;
  border-top: 1px solid var(--line);
}

.topic:first-child {
  border-top: 0;
  padding-top: 0;
}

.topic__head {
  display: flex;
  align-items: baseline;
  gap: 12px;
  margin-bottom: 6px;
}

.topic__num {
  font-family: var(--serif);
  font-style: italic;
  font-size: 15px;
  color: var(--accent);
  min-width: 18px;
}

.topic h2 {
  margin: 0;
  font-family: var(--serif);
  font-weight: 600;
  font-size: clamp(1.65rem, 3vw, 2.1rem);
  line-height: 1.1;
  letter-spacing: -0.008em;
}

.topic__sub {
  margin: 0 0 22px 30px;
  font-size: 13px;
  color: var(--muted);
  max-width: 62ch;
}

.topic h3 {
  margin: 30px 0 10px;
  font-family: var(--sans);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--ink);
}

.topic p {
  margin: 0 0 14px;
  max-width: 68ch;
  text-wrap: pretty;
}

.topic p strong {
  font-weight: 600;
  color: var(--ink);
}

.topic ul,
.topic ol {
  margin: 0 0 16px;
  padding-left: 20px;
  max-width: 66ch;
}

.topic li {
  margin-bottom: 7px;
}

.topic li::marker {
  color: var(--accent);
}

.lede {
  font-size: 16.5px;
  line-height: 1.6;
  color: var(--ink-soft);
}

.hand {
  font-family: var(--hand);
  color: var(--coral);
}

/* ---------------------------------------------------------------- cards */

.grid {
  display: grid;
  gap: 14px;
  margin: 18px 0 22px;
}

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

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

.card {
  position: relative;
  padding: 18px 20px;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
}

.card h4 {
  margin: 0 0 6px;
  font-family: var(--serif);
  font-size: 19px;
  font-weight: 600;
  line-height: 1.15;
}

.card p {
  margin: 0;
  font-size: 13.5px;
  line-height: 1.55;
  color: var(--muted);
  max-width: none;
}

.card p + p {
  margin-top: 8px;
}

.card__tag {
  display: inline-block;
  margin-bottom: 8px;
  font-size: 9.5px;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
}

.card--tint {
  background: linear-gradient(180deg, rgba(255, 253, 248, 0.9), var(--paper-2));
}

.card--flat {
  box-shadow: none;
  background: var(--paper-2);
}

/* callouts */

.callout {
  position: relative;
  margin: 20px 0;
  padding: 16px 18px 16px 46px;
  border: 1px solid var(--line);
  border-left: 3px solid var(--accent);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  background: var(--paper);
  font-size: 14px;
  line-height: 1.55;
}

.callout p {
  margin: 0 0 8px;
  max-width: none;
  font-size: 14px;
}

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

.callout__icon {
  position: absolute;
  left: 15px;
  top: 15px;
  width: 19px;
  height: 19px;
  display: grid;
  place-items: center;
  border-radius: 50%;
  background: var(--accent-soft);
  color: var(--accent-ink);
  font-size: 11px;
  font-weight: 700;
  font-family: var(--sans);
}

.callout--warn {
  border-left-color: var(--amber);
  background: linear-gradient(180deg, rgba(255, 253, 248, 0.95), rgba(169, 119, 42, 0.05));
}

.callout--warn .callout__icon {
  background: rgba(169, 119, 42, 0.14);
  color: #7d5715;
}

.callout--danger {
  border-left-color: var(--coral);
  background: linear-gradient(180deg, rgba(255, 253, 248, 0.95), rgba(194, 90, 65, 0.05));
}

.callout--danger .callout__icon {
  background: rgba(194, 90, 65, 0.14);
  color: #9a3f2b;
}

.callout--tip {
  border-left-color: var(--blue);
  background: linear-gradient(180deg, rgba(255, 253, 248, 0.95), rgba(63, 115, 145, 0.05));
}

.callout--tip .callout__icon {
  background: rgba(63, 115, 145, 0.14);
  color: #2f5b73;
}

.callout__title {
  display: block;
  margin-bottom: 4px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-soft);
}

/* handwritten margin note */

.note {
  position: relative;
  margin: 22px 0;
  padding: 14px 18px;
  background: #fdf6e4;
  border: 1px solid rgba(169, 119, 42, 0.22);
  border-radius: 4px 12px 12px 12px;
  font-family: var(--hand);
  font-size: 14.5px;
  line-height: 1.45;
  color: #6d4f22;
  transform: rotate(-0.5deg);
  box-shadow: var(--shadow-sm);
}

.note p {
  margin: 0;
  max-width: none;
  font-family: inherit;
  font-size: inherit;
  color: inherit;
}

/* ---------------------------------------------------------------- formulas */

.formulas {
  display: grid;
  gap: 12px;
  margin: 18px 0 24px;
}

.formula {
  position: relative;
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1.05fr);
  gap: 20px;
  padding: 18px 20px;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
}

.formula__main {
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 6px;
}

.formula__name {
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 0.13em;
  text-transform: uppercase;
  color: var(--accent);
}

.formula__expr {
  font-family: var(--serif);
  font-size: clamp(19px, 2.2vw, 23px);
  font-weight: 500;
  line-height: 1.3;
  color: var(--ink);
  letter-spacing: 0.005em;
}

.formula__expr i {
  font-style: italic;
}

.formula__expr sub {
  font-size: 0.62em;
  vertical-align: -0.22em;
}

.formula__expr sup {
  font-size: 0.62em;
  vertical-align: 0.5em;
}

.formula__where {
  margin: 0;
  padding: 0;
  list-style: none;
  font-size: 12.5px;
  line-height: 1.5;
  color: var(--muted);
  border-left: 1px solid var(--line);
  padding-left: 18px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 3px;
}

.formula__where li {
  margin: 0;
}

.formula__where b {
  font-family: var(--serif);
  font-style: italic;
  font-size: 14px;
  font-weight: 600;
  color: var(--ink-soft);
  margin-right: 4px;
}

.formula__where em {
  font-style: normal;
  color: var(--faint);
}

/* ---------------------------------------------------------------- steps */

.steps {
  counter-reset: step;
  list-style: none;
  margin: 20px 0 24px;
  padding: 0;
  max-width: none;
}

.steps > li {
  counter-increment: step;
  position: relative;
  padding: 0 0 20px 46px;
  margin: 0;
  border-left: 1px solid var(--line);
  margin-left: 13px;
}

.steps > li:last-child {
  border-left-color: transparent;
  padding-bottom: 0;
}

.steps > li::before {
  content: counter(step);
  position: absolute;
  left: -13px;
  top: -2px;
  width: 26px;
  height: 26px;
  display: grid;
  place-items: center;
  border-radius: 50%;
  background: var(--paper);
  border: 1px solid var(--accent-line);
  color: var(--accent-ink);
  font-family: var(--serif);
  font-size: 14px;
  font-weight: 600;
}

.steps h4 {
  margin: 0 0 5px;
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--ink);
}

.steps p {
  margin: 0 0 8px;
  font-size: 14px;
  max-width: 62ch;
}

.steps .calc {
  display: block;
  margin: 8px 0;
  padding: 10px 14px;
  background: var(--paper-2);
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  font-family: var(--serif);
  font-size: 17px;
  line-height: 1.35;
  color: var(--ink);
}

.steps .calc b {
  color: var(--accent-ink);
  font-weight: 600;
}

/* ---------------------------------------------------------------- tables */

.table-wrap {
  margin: 18px 0 24px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--paper);
  overflow-x: auto;
  box-shadow: var(--shadow-sm);
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 13px;
  min-width: 480px;
}

caption {
  caption-side: top;
  padding: 14px 18px 0;
  text-align: left;
  font-size: 10.5px;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
}

th,
td {
  padding: 10px 16px;
  text-align: left;
  vertical-align: top;
  border-bottom: 1px solid var(--line);
}

thead th {
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--muted);
  background: var(--paper-2);
  white-space: nowrap;
}

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

tbody tr:hover {
  background: rgba(94, 72, 52, 0.025);
}

td.num,
th.num {
  text-align: right;
  font-variant-numeric: tabular-nums;
}

td code,
p code,
li code,
td strong {
  font-family: var(--sans);
  font-size: 0.94em;
  font-weight: 600;
  color: var(--ink);
  background: var(--paper-3);
  padding: 1px 5px;
  border-radius: 4px;
}

td code {
  white-space: nowrap;
}

/* ---------------------------------------------------------------- diagram */

.figure {
  margin: 20px 0 26px;
  padding: 22px;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
}

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

.figure figcaption {
  margin-top: 14px;
  padding-top: 12px;
  border-top: 1px solid var(--line);
  font-size: 12px;
  line-height: 1.5;
  color: var(--muted);
}

.figure figcaption b {
  color: var(--ink-soft);
}

.fig-read {
  margin: 16px 0 0;
  padding: 10px 12px;
  border-left: 2px solid var(--accent-line);
  background: var(--accent-soft);
  border-radius: 0 8px 8px 0;
  font-size: 12.5px;
  line-height: 1.5;
  color: var(--ink-soft);
}

.fig-read b {
  color: var(--accent-ink);
}

.dg-line {
  fill: none;
  stroke: var(--ink-soft);
  stroke-width: 1.4;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.dg-thin {
  fill: none;
  stroke: var(--line-strong);
  stroke-width: 1;
}

.dg-dash {
  fill: none;
  stroke: var(--accent);
  stroke-width: 1;
  stroke-dasharray: 4 4;
  opacity: 0.7;
}

.dg-accent {
  fill: none;
  stroke: var(--accent);
  stroke-width: 1.6;
  stroke-linecap: round;
}

.dg-fill {
  fill: var(--accent-soft);
  stroke: var(--accent);
  stroke-width: 1.2;
}

.dg-fill-2 {
  fill: rgba(194, 90, 65, 0.09);
  stroke: var(--coral);
  stroke-width: 1.2;
}

.dg-text {
  font-family: var(--sans);
  font-size: 8.5px;
  font-weight: 600;
  letter-spacing: 0.06em;
  fill: var(--ink-soft);
}

.dg-small {
  font-family: var(--sans);
  font-size: 7.5px;
  fill: var(--muted);
}

.dg-hand {
  font-family: var(--hand);
  font-size: 10px;
  fill: var(--coral);
}

.dg-math {
  font-family: var(--serif);
  font-style: italic;
  font-size: 10px;
  fill: var(--ink-soft);
}

.dg-coral {
  fill: none;
  stroke: var(--coral);
  stroke-width: 1.4;
  stroke-linecap: round;
}

.dg-ink {
  fill: none;
  stroke: var(--ink);
  stroke-width: 1.7;
  stroke-linecap: round;
}

.dg-fill-ink {
  fill: var(--ink);
  stroke: var(--bg);
  stroke-width: 1.4;
}

.dg-coral-dash {
  fill: none;
  stroke: var(--coral);
  stroke-width: 1;
  stroke-dasharray: 4 4;
  opacity: 0.85;
}

.dg-area {
  fill: var(--accent-soft);
  stroke: none;
}

.dg-grid {
  stroke: var(--line);
  stroke-width: 0.8;
  fill: none;
}

/* ---------------------------------------------------------------- flashcards */

.flash {
  margin: 20px 0 24px;
}

.flash__bar {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 12px;
  flex-wrap: wrap;
}

.flash__count {
  font-size: 11.5px;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  font-variant-numeric: tabular-nums;
}

.flash__bar .spacer {
  flex: 1;
}

.btn-mini {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 6px 11px;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  background: var(--paper);
  font-size: 11.5px;
  font-weight: 600;
  color: var(--ink-soft);
  transition: border-color 0.2s ease, color 0.2s ease, background 0.2s ease;
}

.btn-mini:hover {
  border-color: var(--accent-line);
  color: var(--accent-ink);
  background: var(--paper-2);
}

.btn-mini svg {
  width: 12px;
  height: 12px;
}

.flash__stage {
  perspective: 1400px;
}

.flashcard {
  position: relative;
  display: block;
  width: 100%;
  min-height: 210px;
  padding: 0;
  border: 0;
  background: transparent;
  text-align: left;
  transform-style: preserve-3d;
  transition: transform 0.55s cubic-bezier(0.2, 0.8, 0.2, 1);
}

.flashcard[aria-expanded='true'] {
  transform: rotateY(180deg);
}

.flashcard__face {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 10px;
  padding: 28px 30px;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: var(--paper);
  box-shadow: var(--shadow-md);
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  overflow: hidden;
}

.flashcard__face::after {
  content: '';
  position: absolute;
  left: 0;
  right: 0;
  top: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--accent), transparent 70%);
}

.flashcard__face--back {
  transform: rotateY(180deg);
  background: linear-gradient(180deg, var(--paper), var(--paper-2));
}

.flashcard__face--back::after {
  background: linear-gradient(90deg, var(--coral), transparent 70%);
}

.flashcard__tag {
  font-size: 9.5px;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--faint);
}

.flashcard__q {
  font-family: var(--serif);
  font-size: clamp(19px, 2.4vw, 24px);
  font-weight: 600;
  line-height: 1.25;
  color: var(--ink);
}

.flashcard__a {
  font-size: 14.5px;
  line-height: 1.55;
  color: var(--ink-soft);
}

.flashcard__a b {
  color: var(--accent-ink);
}

.flashcard__hint {
  position: absolute;
  right: 20px;
  bottom: 14px;
  font-family: var(--hand);
  font-size: 11.5px;
  color: var(--faint);
}

.flash__nav {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-top: 12px;
}

.flash__nav .spacer {
  flex: 1;
}

.flash__dots {
  display: flex;
  gap: 4px;
  flex-wrap: wrap;
}

.flash__dots button {
  width: 7px;
  height: 7px;
  padding: 0;
  border: 0;
  border-radius: 50%;
  background: var(--line-strong);
  transition: background 0.2s ease, transform 0.2s ease;
}

.flash__dots button[aria-current='true'] {
  background: var(--accent);
  transform: scale(1.35);
}

/* ---------------------------------------------------------------- quiz */

.quiz {
  margin: 20px 0 24px;
  padding: 22px;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
}

.quiz__top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}

.quiz__step {
  font-size: 10.5px;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  font-variant-numeric: tabular-nums;
}

.quiz__score {
  font-size: 11.5px;
  font-weight: 600;
  color: var(--muted);
  font-variant-numeric: tabular-nums;
}

.quiz__q {
  margin: 0 0 16px;
  font-family: var(--serif);
  font-size: clamp(19px, 2.3vw, 23px);
  font-weight: 600;
  line-height: 1.3;
  color: var(--ink);
}

.quiz__opts {
  display: grid;
  gap: 8px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.quiz__opt {
  display: flex;
  align-items: flex-start;
  gap: 11px;
  width: 100%;
  padding: 12px 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--paper-2);
  text-align: left;
  font-size: 14px;
  line-height: 1.45;
  color: var(--ink-soft);
  transition: border-color 0.18s ease, background 0.18s ease, color 0.18s ease;
}

.quiz__opt:hover:not(:disabled) {
  border-color: var(--accent-line);
  background: var(--paper);
}

.quiz__opt:disabled {
  cursor: default;
}

.quiz__key {
  flex-shrink: 0;
  width: 21px;
  height: 21px;
  display: grid;
  place-items: center;
  border-radius: 6px;
  border: 1px solid var(--line-strong);
  background: var(--paper);
  font-size: 10.5px;
  font-weight: 700;
  color: var(--muted);
}

.quiz__opt.is-correct {
  border-color: rgba(78, 127, 95, 0.5);
  background: rgba(78, 127, 95, 0.09);
  color: var(--accent-ink);
}

.quiz__opt.is-correct .quiz__key {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

.quiz__opt.is-wrong {
  border-color: rgba(194, 90, 65, 0.45);
  background: rgba(194, 90, 65, 0.08);
  color: #8f3a26;
}

.quiz__opt.is-wrong .quiz__key {
  background: var(--coral);
  border-color: var(--coral);
  color: #fff;
}

.quiz__opt.is-muted {
  opacity: 0.55;
}

.quiz__feedback {
  margin-top: 14px;
  padding: 12px 14px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--line);
  background: var(--paper-2);
  font-size: 13.5px;
  line-height: 1.5;
  color: var(--ink-soft);
}

.quiz__feedback[hidden] {
  display: none;
}

.quiz__feedback b {
  display: block;
  margin-bottom: 3px;
  font-size: 10.5px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.quiz__feedback.is-ok {
  border-color: rgba(78, 127, 95, 0.35);
  background: rgba(78, 127, 95, 0.07);
}

.quiz__feedback.is-ok b {
  color: var(--accent-ink);
}

.quiz__feedback.is-no {
  border-color: rgba(194, 90, 65, 0.32);
  background: rgba(194, 90, 65, 0.06);
}

.quiz__feedback.is-no b {
  color: #9a3f2b;
}

.quiz__foot {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-top: 16px;
  flex-wrap: wrap;
}

.quiz__foot .spacer {
  flex: 1;
}

.quiz__result {
  text-align: center;
  padding: 14px 6px 6px;
}

.quiz__result[hidden] {
  display: none;
}

.quiz__result .score {
  font-family: var(--serif);
  font-size: 46px;
  font-weight: 600;
  line-height: 1;
  color: var(--accent-ink);
}

.quiz__result .score span {
  font-size: 20px;
  color: var(--faint);
}

.quiz__result p {
  margin: 8px auto 16px;
  max-width: 44ch;
  font-size: 14px;
  color: var(--muted);
}

/* ---------------------------------------------------------------- checklist */

.checklist {
  margin: 18px 0 22px;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 2px;
}

.checklist li {
  margin: 0;
}

.checklist label {
  display: flex;
  align-items: flex-start;
  gap: 11px;
  padding: 10px 12px;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  font-size: 14px;
  line-height: 1.45;
  color: var(--ink-soft);
  cursor: pointer;
  transition: background 0.18s ease, border-color 0.18s ease;
}

.checklist label:hover {
  background: var(--paper);
  border-color: var(--line);
}

.checklist input {
  position: absolute;
  opacity: 0;
  width: 0;
  height: 0;
}

.checklist .box {
  flex-shrink: 0;
  width: 18px;
  height: 18px;
  margin-top: 1px;
  border: 1.5px solid var(--line-strong);
  border-radius: 5px;
  background: var(--paper);
  display: grid;
  place-items: center;
  transition: background 0.18s ease, border-color 0.18s ease;
}

.checklist .box svg {
  width: 11px;
  height: 11px;
  opacity: 0;
  transform: scale(0.6);
  transition: opacity 0.18s ease, transform 0.18s ease;
  color: #fff;
}

.checklist input:checked + .box {
  background: var(--accent);
  border-color: var(--accent);
}

.checklist input:checked + .box svg {
  opacity: 1;
  transform: scale(1);
}

.checklist input:checked ~ .txt {
  color: var(--faint);
  text-decoration: line-through;
  text-decoration-color: var(--line-strong);
}

.checklist input:focus-visible + .box {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.checklist__foot {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-top: 12px;
  font-size: 12px;
  color: var(--muted);
  font-variant-numeric: tabular-nums;
}

.meter {
  flex: 1;
  height: 5px;
  border-radius: 999px;
  background: var(--paper-3);
  overflow: hidden;
}

.meter span {
  display: block;
  height: 100%;
  width: 0;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--accent), var(--coral));
  transition: width 0.3s ease;
}

/* ---------------------------------------------------------------- glossary */

.glossary {
  margin: 18px 0 24px;
  border-top: 1px solid var(--line);
}

.glossary div {
  display: grid;
  grid-template-columns: minmax(120px, 0.32fr) minmax(0, 1fr);
  gap: 18px;
  padding: 11px 0;
  border-bottom: 1px solid var(--line);
}

.glossary dt {
  font-family: var(--serif);
  font-size: 16.5px;
  font-weight: 600;
  line-height: 1.25;
  color: var(--ink);
}

.glossary dd {
  margin: 0;
  font-size: 13.5px;
  line-height: 1.55;
  color: var(--muted);
}

/* ---------------------------------------------------------------- footer */

.foot {
  position: relative;
  z-index: 1;
  border-top: 1px solid var(--line);
  background: linear-gradient(180deg, rgba(251, 245, 234, 0), var(--paper-2));
}

.foot__inner {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 40px clamp(20px, 4vw, 40px) 54px;
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1.1fr);
  gap: 32px;
}

.foot h2 {
  margin: 0 0 8px;
  font-family: var(--serif);
  font-size: 24px;
  font-weight: 600;
}

.foot p {
  margin: 0;
  font-size: 13px;
  color: var(--muted);
  max-width: 46ch;
}

.foot__links {
  display: grid;
  gap: 6px;
  align-content: start;
}

.foot__links a {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 9px 0;
  border-bottom: 1px solid var(--line);
  font-size: 13px;
  color: var(--ink-soft);
  text-decoration: none;
  transition: color 0.18s ease, padding 0.18s ease;
}

.foot__links a:hover {
  color: var(--accent-ink);
  padding-left: 4px;
}

.foot__links span {
  font-size: 10px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--faint);
}

.foot__base {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 0 clamp(20px, 4vw, 40px) 36px;
  display: flex;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
  font-size: 11.5px;
  color: var(--faint);
}

.foot__base a {
  color: var(--muted);
  text-decoration: none;
  border-bottom: 1px solid var(--line-strong);
}

/* ---------------------------------------------------------------- hub */

.hub-hero {
  max-width: var(--shell);
  margin: 0 auto;
  padding: clamp(48px, 7vw, 86px) clamp(20px, 4vw, 40px) 40px;
  position: relative;
  z-index: 1;
}

.hub-hero h1 {
  margin: 0;
  font-family: var(--serif);
  font-weight: 600;
  font-size: clamp(2.6rem, 6.5vw, 4.4rem);
  line-height: 0.98;
  letter-spacing: -0.012em;
  max-width: 18ch;
}

.hub-hero h1 em {
  font-style: italic;
  color: var(--accent-ink);
}

.hub-hero p {
  margin: 20px 0 0;
  max-width: 58ch;
  font-size: 16.5px;
  line-height: 1.6;
  color: var(--ink-soft);
}

.hub-grid {
  position: relative;
  z-index: 1;
  max-width: var(--shell);
  margin: 0 auto;
  padding: 0 clamp(20px, 4vw, 40px) 80px;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
}

.subject {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 10px;
  padding: 26px 26px 22px;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 18px;
  box-shadow: var(--shadow-sm);
  text-decoration: none;
  overflow: hidden;
  transition: transform 0.3s cubic-bezier(0.2, 0.8, 0.2, 1), box-shadow 0.3s ease, border-color 0.3s ease;
}

.subject::before {
  content: '';
  position: absolute;
  inset: 0 0 auto;
  height: 3px;
  background: linear-gradient(90deg, var(--subject, var(--accent)), transparent 65%);
}

.subject:hover {
  transform: translateY(-3px);
  border-color: var(--line-strong);
  box-shadow: var(--shadow-md);
}

.subject__num {
  font-family: var(--serif);
  font-style: italic;
  font-size: 13px;
  color: var(--subject, var(--accent));
}

.subject h2 {
  margin: 0;
  font-family: var(--serif);
  font-size: clamp(22px, 2.4vw, 27px);
  font-weight: 600;
  line-height: 1.12;
  letter-spacing: -0.005em;
  color: var(--ink);
}

.subject p {
  margin: 0;
  font-size: 13.5px;
  line-height: 1.55;
  color: var(--muted);
}

.subject__meta {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: auto;
  padding-top: 12px;
}

.subject__meta span {
  font-size: 10px;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--faint);
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 3px 8px;
}

.subject__go {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-top: 14px;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--subject, var(--accent));
}

.subject__go svg {
  width: 13px;
  height: 13px;
  transition: transform 0.25s ease;
}

.subject:hover .subject__go svg {
  transform: translateX(4px);
}

.subject--atlas {
  grid-column: 1 / -1;
  background: linear-gradient(120deg, var(--paper), var(--paper-2));
}

.hub-note {
  position: relative;
  z-index: 1;
  max-width: var(--shell);
  margin: 0 auto;
  padding: 0 clamp(20px, 4vw, 40px) 70px;
}

.hub-note .note {
  max-width: 52ch;
}

/* ---------------------------------------------------------------- utils */

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

.mt-0 {
  margin-top: 0;
}

.mb-0 {
  margin-bottom: 0;
}

/* ---------------------------------------------------------------- responsive */

@media (max-width: 1080px) {
  .shell {
    grid-template-columns: 190px minmax(0, 1fr);
    gap: 32px;
  }

  .hero__inner {
    grid-template-columns: minmax(0, 1fr) minmax(0, 0.34fr);
  }
}

@media (max-width: 900px) {
  .bar__name em {
    display: none;
  }

  .shell {
    grid-template-columns: minmax(0, 1fr);
    gap: 0;
  }

  .toc {
    position: static;
    max-height: none;
    overflow: visible;
    padding: 22px 0 0;
    border-bottom: 1px solid var(--line);
    margin-bottom: 8px;
  }

  .toc__label {
    display: none;
  }

  .toc ol {
    display: flex;
    flex-wrap: wrap;
    gap: 4px;
    border-left: 0;
  }

  .toc a {
    padding: 5px 10px;
    border: 1px solid var(--line);
    border-radius: 999px;
    background: var(--paper);
    font-size: 11.5px;
  }

  .toc a span {
    display: none;
  }

  .toc a[aria-current='true'] {
    border-color: var(--accent-line);
    background: var(--accent-soft);
  }

  .toc a[aria-current='true']::before {
    display: none;
  }

  .toc__foot {
    display: none;
  }

  .content {
    padding-top: 26px;
  }

  .hero__inner {
    grid-template-columns: minmax(0, 1fr);
  }

  .hero__art {
    display: none;
  }

  .formula {
    grid-template-columns: minmax(0, 1fr);
    gap: 12px;
  }

  .formula__where {
    border-left: 0;
    border-top: 1px solid var(--line);
    padding-left: 0;
    padding-top: 10px;
    flex-direction: row;
    flex-wrap: wrap;
    gap: 4px 16px;
  }

  .grid--3 {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .foot__inner {
    grid-template-columns: minmax(0, 1fr);
    gap: 24px;
  }
}

@media (max-width: 640px) {
  :root {
    --bar-h: 92px;
  }

  body {
    font-size: 15px;
  }

  .bar {
    gap: 10px;
    padding: 0 14px;
    flex-wrap: wrap;
    align-content: center;
    row-gap: 4px;
  }

  .bar__name {
    display: none;
  }

  .bar__nav {
    order: 3;
    gap: 0;
    flex: 1 0 100%;
    margin-left: 0;
  }

  .bar__nav a {
    padding: 6px 9px;
    font-size: 12px;
  }

  .bar__actions {
    margin-left: auto;
  }

  .bar__link span {
    display: none;
  }

  .bar__link {
    padding: 7px 9px;
  }

  .grid--2,
  .grid--3 {
    grid-template-columns: minmax(0, 1fr);
  }

  .hub-grid {
    grid-template-columns: minmax(0, 1fr);
  }

  .flashcard {
    min-height: 240px;
  }

  .flashcard__face {
    padding: 22px 20px;
  }

  .quiz {
    padding: 18px 16px;
  }

  .glossary div {
    grid-template-columns: minmax(0, 1fr);
    gap: 3px;
  }

  .topic__sub {
    margin-left: 0;
  }

  .steps > li {
    padding-left: 38px;
  }

  .figure {
    padding: 14px;
  }
}

/* ---------------------------------------------------------------- motion */

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }
}

/* ---------------------------------------------------------------- print */

@media print {
  @page {
    margin: 16mm 14mm;
  }

  body {
    background: #fff;
    font-size: 10.5pt;
    color: #000;
  }

  body::before,
  .bar,
  .progress,
  .toc,
  .hero__art,
  .hero__actions,
  .flash__bar,
  .flash__nav,
  .quiz__foot,
  .foot__links,
  .skip {
    display: none !important;
  }

  .hero__inner,
  .shell,
  .foot__inner,
  .foot__base {
    display: block;
    max-width: none;
    padding: 0;
  }

  .hero {
    border-bottom: 1px solid #999;
    padding-bottom: 8mm;
  }

  .hero h1 {
    font-size: 26pt;
  }

  .content {
    padding-top: 0;
  }

  .topic {
    break-inside: avoid-page;
    padding-top: 5mm;
  }

  .card,
  .formula,
  .figure,
  .quiz,
  .table-wrap {
    box-shadow: none;
    break-inside: avoid;
    border-color: #bbb;
  }

  .flashcard {
    transform: none !important;
    min-height: 0;
  }

  .flashcard__face {
    position: static;
    transform: none !important;
    backface-visibility: visible;
    box-shadow: none;
    border: 1px solid #bbb;
    margin-bottom: 3mm;
    break-inside: avoid;
  }

  .flashcard__hint {
    display: none;
  }

  a {
    text-decoration: none;
    color: #000;
  }

  .foot {
    border-top: 1px solid #999;
  }
}

/* ==========================================================================
   Teaching tools: calculators, live figures, worked-example reveals
   ========================================================================== */

/* ---------------------------------------------------------------- calculator */

.calc {
  margin: 22px 0 26px;
  padding: 20px 22px 18px;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
}

.calc__head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 14px;
  flex-wrap: wrap;
  margin-bottom: 14px;
}

.calc__title {
  display: flex;
  align-items: baseline;
  gap: 10px;
  flex-wrap: wrap;
}

.calc__tag {
  font-size: 9px;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent-ink);
  background: var(--accent-soft);
  border: 1px solid var(--accent-line);
  border-radius: 999px;
  padding: 3px 8px;
}

.calc h4 {
  margin: 0;
  font-family: var(--serif);
  font-size: 21px;
  font-weight: 600;
  line-height: 1.2;
}

.calc__hint {
  margin: 0;
  font-size: 11.5px;
  color: var(--faint);
}

.calc__fields {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(148px, 1fr));
  gap: 12px;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 5px;
  min-width: 0;
}

.field > span:not(.field__input) {
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: var(--muted);
}

.field > span:not(.field__input) em {
  font-family: var(--serif);
  font-style: italic;
  font-size: 12px;
  letter-spacing: 0;
  text-transform: none;
  color: var(--accent-ink);
}

.field__input {
  display: flex;
  align-items: center;
  gap: 4px;
  border: 1px solid var(--line-strong);
  border-radius: 9px;
  background: var(--paper-2);
  padding: 0 10px;
  transition: border-color 0.18s ease, box-shadow 0.18s ease;
}

.field__input:focus-within {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.field input,
.field select {
  width: 100%;
  min-width: 0;
  border: 0;
  background: transparent;
  padding: 9px 0;
  font-size: 14px;
  font-weight: 500;
  font-variant-numeric: tabular-nums;
  color: var(--ink);
  appearance: none;
}

.field select {
  cursor: pointer;
}

.field .unit {
  font-size: 10.5px;
  font-weight: 600;
  color: var(--faint);
  white-space: nowrap;
}

.calc__out {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(132px, 1fr));
  gap: 10px;
  margin-top: 16px;
  padding-top: 15px;
  border-top: 1px dashed var(--line-strong);
}

.out {
  padding: 10px 12px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--paper-2);
  min-width: 0;
}

.out__label {
  display: block;
  font-size: 9.5px;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--faint);
  margin-bottom: 3px;
}

.out__value {
  display: block;
  font-family: var(--serif);
  font-size: 22px;
  font-weight: 600;
  line-height: 1.15;
  color: var(--accent-ink);
  font-variant-numeric: tabular-nums;
  overflow-wrap: anywhere;
}

.out__value small {
  font-family: var(--sans);
  font-size: 11px;
  font-weight: 500;
  color: var(--muted);
  margin-left: 3px;
}

.out--wide {
  grid-column: 1 / -1;
}

.out--verdict .out__value {
  font-family: var(--sans);
  font-size: 13px;
  font-weight: 600;
  line-height: 1.35;
}

.verdict {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 3px 9px;
  border-radius: 999px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.03em;
}

.verdict::before {
  content: '';
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: currentColor;
}

.verdict--ok {
  color: #2f5a41;
  background: rgba(78, 127, 95, 0.14);
}

.verdict--warn {
  color: #7d5715;
  background: rgba(169, 119, 42, 0.16);
}

.verdict--bad {
  color: #9a3f2b;
  background: rgba(194, 90, 65, 0.14);
}

.calc__note {
  margin: 12px 0 0;
  font-size: 11.5px;
  line-height: 1.5;
  color: var(--faint);
  max-width: none;
}

.calc__note b {
  color: var(--muted);
}

/* ---------------------------------------------------------------- live figure */

.fig-ctrl {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 14px 20px;
  margin-top: 16px;
  padding-top: 14px;
  border-top: 1px solid var(--line);
}

.fig-ctrl label {
  display: flex;
  flex-direction: column;
  gap: 6px;
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.01em;
  color: var(--muted);
}

.fig-ctrl label span {
  display: flex;
  justify-content: space-between;
  gap: 8px;
}

.fig-ctrl output {
  font-family: var(--serif);
  font-size: 15px;
  font-weight: 600;
  letter-spacing: 0;
  text-transform: none;
  color: var(--accent-ink);
  font-variant-numeric: tabular-nums;
}

input[type='range'] {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 4px;
  border-radius: 999px;
  background: var(--paper-3);
  accent-color: var(--accent);
  cursor: pointer;
}

input[type='range']::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 15px;
  height: 15px;
  border-radius: 50%;
  background: var(--accent);
  border: 2px solid var(--paper);
  box-shadow: 0 1px 4px rgba(47, 90, 65, 0.4);
}

input[type='range']::-moz-range-thumb {
  width: 13px;
  height: 13px;
  border-radius: 50%;
  background: var(--accent);
  border: 2px solid var(--paper);
}

/* ---------------------------------------------------------------- reveal */

.reveal {
  margin: 16px 0 22px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--paper);
  overflow: hidden;
}

.reveal > summary {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 13px 18px;
  cursor: pointer;
  list-style: none;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--accent-ink);
  background: var(--paper-2);
}

.reveal > summary::-webkit-details-marker {
  display: none;
}

.reveal > summary::after {
  content: '+';
  margin-left: auto;
  font-family: var(--serif);
  font-size: 18px;
  font-weight: 400;
  color: var(--accent);
}

.reveal[open] > summary::after {
  content: '\2212';
}

.reveal > summary:hover {
  background: var(--paper-3);
}

.reveal__body {
  padding: 4px 20px 16px;
}

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

/* ---------------------------------------------------------------- drill */

.drill {
  margin: 20px 0 24px;
  padding: 18px 20px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--paper-2);
}

.drill__q {
  margin: 0 0 12px;
  font-size: 14.5px;
  line-height: 1.55;
  color: var(--ink);
}

.drill__q b {
  color: var(--accent-ink);
}

.drill__row {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}

.drill__input {
  width: 130px;
  padding: 9px 12px;
  border: 1px solid var(--line-strong);
  border-radius: 9px;
  background: var(--paper);
  font-size: 14px;
  font-variant-numeric: tabular-nums;
}

.drill__input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.drill__unit {
  font-size: 11.5px;
  font-weight: 600;
  color: var(--faint);
}

.drill__fb {
  margin: 10px 0 0;
  font-size: 12.5px;
  line-height: 1.5;
  color: var(--muted);
}

.drill__fb.is-ok {
  color: var(--accent-ink);
  font-weight: 600;
}

.drill__fb.is-no {
  color: #9a3f2b;
  font-weight: 600;
}

/* ---------------------------------------------------------------- mobile */

@media (max-width: 640px) {
  .calc {
    padding: 16px 14px;
  }

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

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

  .reveal__body {
    padding: 4px 14px 14px;
  }
}

@media (max-width: 400px) {
  .calc__fields,
  .calc__out {
    grid-template-columns: minmax(0, 1fr);
  }
}

@media print {
  .calc,
  .fig-ctrl,
  .drill {
    display: none !important;
  }

  .reveal {
    border: 0;
  }

  .reveal > summary {
    display: none;
  }

  .reveal__body {
    display: block !important;
    padding: 0;
  }

  .reveal:not([open]) .reveal__body {
    display: block !important;
  }
}