/*
 * LearnBySlides lesson player + code-drawn scenes. Loaded only on pages with a player.
 * Works without JavaScript (slides stack as a readable page). public/assets/lesson.js adds .is-live to .lp.
 * Motion: transforms and opacity only; off under prefers-reduced-motion; the pause button stops looping motion.
 */

/* ───────── scene palette ───────── */
.lp,
.scene-host {
  --sc-leaf: #6cb35d;
  --sc-leaf-line: #2f7a35;
  --sc-leaf-pale: #e5f3df;
  --sc-cell: #eef8ea;
  --sc-cp: #3f9a3c;
  --sc-light: #e0a21b;
  --sc-light-text: #8a5d00;
  --sc-water: #2f7fd0;
  --sc-water-text: #1f5fa3;
  --sc-co2: #6b7590;
  --sc-co2-text: #4c5570;
  --sc-o2: #17998b;
  --sc-o2-text: #0f6f64;
  --sc-sugar: #d98a1c;
  --sc-sugar-text: #8f5600;
  --sc-energy: #b8509a;
  --sc-energy-text: #8e3474;
  --sc-sun: #f7b955;
  --sc-glass: #e4f1f7;
}
:root[data-theme='dark'] .lp,
:root[data-theme='dark'] .scene-host {
  --sc-leaf-pale: #1f3a2c;
  --sc-cell: #203c2e;
  --sc-glass: #1b3550;
  --sc-light-text: #f7c86f;
  --sc-water-text: #8cc0f5;
  --sc-co2-text: #b8c0d6;
  --sc-o2-text: #79d9cc;
  --sc-sugar-text: #f3b45c;
  --sc-energy-text: #e79ccf;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme='light']) .lp,
  :root:not([data-theme='light']) .scene-host {
    --sc-leaf-pale: #1f3a2c;
    --sc-cell: #203c2e;
    --sc-glass: #1b3550;
    --sc-light-text: #f7c86f;
    --sc-water-text: #8cc0f5;
    --sc-co2-text: #b8c0d6;
    --sc-o2-text: #79d9cc;
    --sc-sugar-text: #f3b45c;
    --sc-energy-text: #e79ccf;
  }
}

/* ───────── player shell ───────── */
.lp {
  position: relative;
}
.lp-bar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.75rem 1.25rem;
  margin-bottom: 1rem;
}
.lp-modes {
  display: inline-flex;
  padding: 4px;
  gap: 2px;
  border: 2px solid var(--ink);
  border-radius: 999px;
  background: var(--card);
}
.lp-modes button {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  min-height: 42px;
  padding: 0.4rem 1.05rem;
  border: 0;
  border-radius: 999px;
  background: transparent;
  color: var(--ink);
  font: inherit;
  font-weight: 750;
  cursor: pointer;
}
/* Narrow phones: tighter tabs without icons; if a very wide font still does not fit, the strip scrolls, not the page. */
.lp-modes {
  max-width: 100%;
  overflow-x: auto;
}
.lp-modes button {
  flex: none;
  white-space: nowrap;
}
@media (max-width: 379.98px) {
  .lp-modes button {
    padding: 0.4rem 0.8rem;
  }
  .lp-modes button svg {
    display: none;
  }
}
.lp-modes button:hover {
  background: var(--paper-2);
}
.lp-modes button[aria-selected='true'] {
  background: var(--ink);
  color: var(--paper);
}
.lp-mode-hint {
  color: var(--ink-2);
  font-size: var(--fs-small);
  max-width: 52ch;
}

.lp-body {
  display: grid;
  gap: 1.5rem;
  align-items: start;
}
@media (min-width: 1120px) {
  .lp-body {
    grid-template-columns: minmax(0, 1fr) 270px;
  }
  .lp--preview .lp-body {
    grid-template-columns: 1fr;
  }
}
.lp-main {
  min-width: 0;
}
.lp-stage {
  overflow: hidden;
}

/* Outline */
.lp-outline {
  background: var(--card);
  border: 1.5px solid var(--rule);
  border-radius: var(--radius-m);
  padding: 0.9rem 0.6rem 0.9rem 0.9rem;
}
.lp-outline-h {
  font-size: 1rem;
  font-weight: 750;
  margin: 0 0 0.5rem 0.25rem;
}
.lp-outline ol {
  display: grid;
  gap: 2px;
  max-height: min(70vh, 640px);
  overflow: auto;
  padding-right: 0.3rem;
}
.lp-outline a {
  display: grid;
  grid-template-columns: 1.9rem 1fr auto;
  align-items: center;
  gap: 0.35rem;
  padding: 0.45rem 0.4rem;
  border-radius: 8px;
  color: var(--ink);
  text-decoration: none;
  font-size: 0.9375rem;
  line-height: 1.3;
}
.lp-outline a:hover {
  background: var(--paper-2);
}
.lp-outline a[aria-current='step'] {
  background: var(--accent-soft);
  font-weight: 750;
}
.lp-o-n {
  font-variant-numeric: tabular-nums;
  color: var(--ink-2);
  font-size: 0.8125rem;
  text-align: right;
  padding-right: 0.25rem;
}
.lp-o-dot {
  width: 8px;
  height: 8px;
  border-radius: 99px;
  background: var(--accent);
}
@media (min-width: 1120px) {
  .lp-outline {
    position: sticky;
    top: 86px;
  }
}
@media (max-width: 1119.98px) {
  .lp.is-live .lp-outline {
    display: none;
  }
  .lp.is-live.outline-open .lp-outline {
    display: block;
  }
}
@media (min-width: 1120px) {
  .lp-outline-btn {
    display: none !important;
  }
}

/* Controls */
.lp-controls {
  display: grid;
  grid-template-columns: auto 1fr auto;
  grid-template-areas: 'prev track next' 'tools tools tools';
  align-items: center;
  gap: 0.6rem 0.75rem;
  margin-top: 1rem;
}
.lp-nav {
  grid-area: prev;
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
  min-height: 50px;
  padding: 0 1rem 0 0.6rem;
  border-radius: 999px;
  border: 2px solid var(--ink);
  background: var(--card);
  color: var(--ink);
  font: inherit;
  font-weight: 750;
  cursor: pointer;
}
.lp-nav--next {
  grid-area: next;
  padding: 0 0.6rem 0 1.1rem;
  background: var(--ink);
  color: var(--paper);
}
.lp-nav:disabled {
  opacity: 0.35;
  cursor: default;
}
.lp-nav:not(:disabled):hover {
  transform: translateY(-1px);
}
.lp-track {
  grid-area: track;
  min-width: 0;
}
.lp-count {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.6rem;
  font-size: var(--fs-meta);
  font-weight: 700;
  color: var(--ink);
  font-variant-numeric: tabular-nums;
}
.lp-steps {
  display: inline-flex;
  gap: 4px;
}
.lp-steps i {
  width: 8px;
  height: 8px;
  border-radius: 99px;
  background: var(--rule);
}
.lp-steps i.on {
  background: var(--accent-ink);
}
.lp-progress {
  margin-top: 0.4rem;
  height: 6px;
  border-radius: 99px;
  background: var(--paper-3);
  overflow: hidden;
}
.lp-progress span {
  display: block;
  height: 100%;
  width: 0;
  background: var(--accent);
  border-radius: 99px;
  transition: width 300ms var(--ease-out);
}
.lp-tools {
  grid-area: tools;
  display: flex;
  justify-content: center;
  gap: 0.25rem;
}
.lp-tools .icon-btn[aria-pressed='true'] {
  background: var(--paper-2);
}
.lp-tools .i-play {
  display: none;
}
.lp.is-paused .lp-tools .i-play {
  display: block;
}
.lp.is-paused .lp-tools .i-pause {
  display: none;
}
.lp-only-teach {
  display: none !important;
}
.lp[data-mode='teach'] .lp-only-teach {
  display: inline-flex !important;
}
@media (min-width: 720px) {
  .lp-controls {
    grid-template-columns: auto 1fr auto auto;
    grid-template-areas: 'prev track next tools';
  }
  .lp-tools {
    justify-content: flex-end;
  }
}
@media (max-width: 719.98px) {
  .lp.is-live:not([data-mode='revise']) .lp-controls {
    position: sticky;
    bottom: 0;
    z-index: 6;
    margin-inline: calc(var(--gutter) * -1);
    padding: 0.6rem var(--gutter) calc(0.6rem + env(safe-area-inset-bottom));
    background: var(--paper);
    border-top: 1px solid var(--rule);
  }
  .lp-nav-t {
    display: none;
  }
  .lp-nav,
  .lp-nav--next {
    padding: 0 0.75rem;
    min-width: 56px;
    justify-content: center;
  }
}
.lp-preview-more {
  margin-top: 1rem;
}

/* ───────── slides ───────── */
.ls {
  position: relative;
}
.lp:not(.is-live) .ls + .ls {
  border-top: 2px dashed var(--rule);
}
.lp.is-live .ls {
  display: none;
}
/* Before lesson.js starts, show only the first slide (an inline script sets .lp-js early), so the browser does not
   lay out every slide only to hide them. If the script never starts, the inline fallback removes .lp-js again. */
.lp-js .lp:not(.is-live) .ls:not(:first-of-type) {
  display: none;
}
.lp.is-live .ls.is-current {
  display: block;
}
.ls-canvas {
  position: relative;
  container-type: inline-size;
  background: var(--card);
}
.ls-num {
  position: absolute;
  right: 0.9rem;
  bottom: 0.6rem;
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--ink-2);
  font-variant-numeric: tabular-nums;
}
.lp--preview .ls-num {
  display: none;
}
.ls-in {
  padding: 1.25rem 1.1rem 1.75rem;
}
.ls-h {
  font-family: var(--font-display);
  font-weight: 780;
  letter-spacing: -0.02em;
  line-height: 1.08;
  font-size: 1.5rem;
  margin: 0 0 0.75rem;
  color: var(--ink);
}
.ls-h--title {
  /* Scales down with the slide on narrow phones so one long word (Photosynthesis) still fits. */
  font-size: min(2.6rem, 12cqi);
  line-height: 0.98;
  letter-spacing: -0.035em;
  margin: 0;
}
.ls-h {
  overflow-wrap: break-word;
}
.ls-h--q {
  font-family: var(--font-body);
  font-weight: 750;
  letter-spacing: 0;
  font-size: 1.2rem;
  line-height: 1.35;
}
.ls-kicker {
  font-weight: 700;
  color: var(--accent-ink);
  margin: 0 0 0.5rem;
}
.ls-lead {
  font-size: 1.1rem;
  margin-bottom: 0.75rem;
}
.ls-tag {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.8125rem;
  font-weight: 750;
  color: var(--accent-ink);
  background: var(--accent-soft);
  border-radius: 999px;
  padding: 0.2rem 0.65rem;
  margin-bottom: 0.6rem;
}
.ls-points {
  display: grid;
  gap: 0.55rem;
  font-size: 1.0625rem;
  line-height: 1.45;
}
.ls-points li {
  position: relative;
  padding-left: 1.25rem;
}
.ls-points li::before {
  content: '';
  position: absolute;
  left: 0.1rem;
  top: 0.55em;
  width: 0.5rem;
  height: 0.5rem;
  border-radius: 2px;
  background: var(--accent);
  transform: rotate(45deg);
}
.ls-points--row li {
  font-size: 0.95rem;
}
.ls-points--small {
  font-size: 0.95rem;
  color: var(--ink-2);
}
.ls-points--case li {
  padding: 0.55rem 0.8rem 0.55rem 1.1rem;
  background: var(--paper-2);
  border-radius: 10px;
}
.ls-points--case li::before {
  left: 0.45rem;
  top: 1.05em;
  width: 0.35rem;
  height: 0.35rem;
}
.ls-goals {
  display: grid;
  gap: 0.6rem;
  font-size: 1.0625rem;
}
.ls-goals li {
  display: grid;
  grid-template-columns: 1.6rem 1fr;
  gap: 0.5rem;
  align-items: start;
}
.ls-goals svg {
  color: var(--accent-ink);
  margin-top: 0.1rem;
}
.ls-takeaways {
  display: grid;
  gap: 0.6rem;
  counter-reset: tk;
}
.ls-takeaways li {
  counter-increment: tk;
  display: grid;
  grid-template-columns: 2rem 1fr;
  gap: 0.6rem;
  align-items: start;
  font-size: 1.05rem;
  padding: 0.6rem 0.75rem;
  border-radius: 12px;
  background: var(--accent-soft);
}
.ls-takeaways li::before {
  content: counter(tk);
  display: grid;
  place-items: center;
  width: 1.8rem;
  height: 1.8rem;
  border-radius: 99px;
  background: var(--card);
  border: 2px solid var(--ink);
  font-weight: 800;
  font-size: 0.9rem;
}
.ls-stat {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
  margin: 0.5rem 0 1rem;
}
.ls-stat-v {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 5rem;
  line-height: 0.9;
  letter-spacing: -0.05em;
  color: var(--accent-ink);
  font-variant-numeric: tabular-nums;
}
.ls-stat-l {
  font-size: 1.15rem;
  font-weight: 650;
  max-width: 30ch;
}
.ls-cols {
  display: grid;
  gap: 1rem;
}
.ls-cols h4 {
  font-weight: 800;
  margin-bottom: 0.4rem;
}
.ls-cols > div {
  background: var(--paper-2);
  border-radius: 12px;
  padding: 0.8rem 1rem;
}
.ls--image img {
  display: block;
  width: 100%;
  height: auto;
}
.ls--image {
  padding: 0 !important;
}
.ls-options--static {
  list-style: upper-alpha;
  padding-left: 1.5rem;
  display: grid;
  gap: 0.4rem;
}
.ls-visual {
  min-width: 0;
}
.ls-visual .sc-svg {
  display: block;
  width: 100%;
  height: auto;
  max-height: 62vh;
  margin-inline: auto;
}
.ls--split,
.ls--title.has-visual {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 1rem;
}
.ls--title {
  padding-block: 1.75rem 2rem;
}
.ls-cover .lcover {
  border-radius: 12px;
  border: 2px solid var(--ink);
}

/* Learn text and teacher notes */
.ls-learn {
  display: flex;
  gap: 0.6rem;
  align-items: flex-start;
  margin: 0;
  padding: 0.95rem 1.1rem;
  background: var(--accent-soft);
  border-top: 2px solid var(--ink);
  font-size: 1.0625rem;
  line-height: 1.55;
}
.ls-learn svg {
  flex: none;
  margin-top: 0.15rem;
  color: var(--accent-ink);
}
.ls-notes {
  display: none;
}
.lp:not(.is-live) .ls-notes {
  display: none;
}
.lp[data-mode='teach'] .ls-learn {
  display: none;
}

/* Wider containers: real 16:9 slides with type that scales with the slide */
@container (min-width: 600px) {
  .ls-in {
    aspect-ratio: 16 / 9;
    padding: 4.2cqi 5cqi 4.6cqi;
    display: flex;
    flex-direction: column;
    justify-content: center;
  }
  .ls-h {
    font-size: 3.5cqi;
    margin-bottom: 1.6cqi;
  }
  .ls-h--title {
    font-size: 6.6cqi;
  }
  .ls-h--q {
    font-size: 2.6cqi;
  }
  .ls-kicker {
    font-size: 1.9cqi;
  }
  .ls-lead {
    font-size: 2.2cqi;
  }
  .ls-tag {
    font-size: 1.45cqi;
    padding: 0.35cqi 1.2cqi;
    margin-bottom: 1.2cqi;
    align-self: flex-start;
  }
  .ls-points {
    font-size: 2.15cqi;
    gap: 1.1cqi;
  }
  .ls-points--row {
    display: flex;
    flex-wrap: wrap;
    gap: 0.8cqi 2.4cqi;
    margin-top: 1.6cqi;
  }
  .ls-points--row li {
    font-size: 1.75cqi;
  }
  .ls-points--small {
    font-size: 1.8cqi;
  }
  .ls-goals,
  .ls-takeaways li {
    font-size: 2.15cqi;
  }
  .ls-takeaways {
    gap: 1cqi;
  }
  .ls-takeaways li {
    padding: 1cqi 1.4cqi;
    grid-template-columns: 3.4cqi 1fr;
    gap: 1.2cqi;
  }
  .ls-takeaways li::before {
    width: 3.2cqi;
    height: 3.2cqi;
    font-size: 1.5cqi;
  }
  .ls-stat-v {
    font-size: 14cqi;
  }
  .ls-stat-l {
    font-size: 2.4cqi;
  }
  .ls-cols {
    grid-template-columns: 1fr 1fr;
    gap: 2cqi;
  }
  .ls-cols h4 {
    font-size: 2.2cqi;
  }
  .ls--split {
    display: grid;
    grid-template-columns: minmax(0, 1.2fr) minmax(0, 1fr);
    align-items: center;
    gap: 3.5cqi;
  }
  .ls--split .ls-text {
    order: 2;
  }
  .ls--title.has-visual {
    display: grid;
    grid-template-columns: 1fr 1fr;
    align-items: center;
    gap: 3cqi;
  }
  .ls-visual .sc-svg {
    max-height: 36cqi;
  }
  .ls--split .ls-visual .sc-svg {
    max-height: 33cqi;
  }
  .ls--title .ls-visual .sc-svg {
    max-height: 44cqi;
  }
  .ls--wide .ls-visual,
  .ls--full .ls-visual {
    flex: 1;
    display: flex;
    flex-direction: column;
    justify-content: center;
    min-height: 0;
  }
  .ls-learn {
    font-size: 1.0625rem;
  }
}

/* Text-only slides get bigger type: they have the whole slide to themselves (projected, read from the back). */
@container (min-width: 600px) {
  .ls--concept .ls-h, .ls--cols .ls-h, .ls--example .ls-h, .ls--list .ls-h, .ls--summary .ls-h { font-size: 4.3cqi; margin-bottom: 2.4cqi; }
  .ls--concept .ls-points { font-size: 2.85cqi; gap: 1.7cqi; }
  .ls--concept .ls-lead { font-size: 2.6cqi; }
  .ls--cols .ls-points { font-size: 2.45cqi; gap: 1.3cqi; }
  .ls--cols h4 { font-size: 2.7cqi; }
  .ls--cols > .ls-cols > div { padding: 2cqi 2.4cqi; }
  .ls--example .ls-points--case { gap: 1cqi; }
  .ls--example .ls-points--case li { font-size: 2.3cqi; padding: 1cqi 1.6cqi 1cqi 2.4cqi; }
  .ls--list .ls-goals { font-size: 2.7cqi; gap: 1.5cqi; }
  .ls--summary .ls-takeaways { gap: 0.9cqi; }
  .ls--summary .ls-takeaways li { font-size: 2.3cqi; padding: 0.9cqi 1.4cqi; }
  /* Five or more points: step the type down so a full slide still fits 16:9. */
  .ls--concept .ls-points:has(> li:nth-child(5)) { font-size: 2.5cqi; gap: 1.3cqi; }
}

/* ───────── modes ───────── */
.lp[data-mode='teach'] .lp-outline {
  display: none !important;
}
.lp[data-mode='teach'] .lp-body {
  grid-template-columns: 1fr;
}
@media (min-width: 1000px) {
  .lp[data-mode='teach'] .ls.is-current {
    display: grid;
    grid-template-columns: minmax(0, 1fr) 300px;
  }
  .lp[data-mode='teach'].notes-off .ls.is-current {
    grid-template-columns: 1fr;
  }
}
.lp[data-mode='teach'] .ls.is-current .ls-notes {
  display: block;
}
.lp[data-mode='teach'].notes-off .ls-notes {
  display: none !important;
}
.ls-notes {
  background: var(--paper-2);
  border-left: 2px solid var(--ink);
  padding: 1.1rem 1.2rem;
  font-size: 0.975rem;
  line-height: 1.55;
  overflow: auto;
}
@media (max-width: 999.98px) {
  .ls-notes {
    border-left: 0;
    border-top: 2px solid var(--ink);
  }
}
.ls-notes h4 {
  font-weight: 800;
  margin-bottom: 0.4rem;
}
.ls-discuss {
  display: flex;
  gap: 0.5rem;
  margin-top: 0.85rem;
  padding: 0.7rem 0.8rem;
  background: var(--card);
  border-radius: 10px;
  font-weight: 650;
}
.ls-discuss svg {
  flex: none;
  margin-top: 0.2rem;
  color: var(--accent-ink);
}

/* Fullscreen presenting (real fullscreen or the .is-fs fallback) */
.lp.is-fs {
  position: fixed;
  inset: 0;
  z-index: 100;
  background: #0b1426;
  padding: 1rem;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}
.lp.is-fs .lp-bar,
.lp.is-fs .lp-outline,
.lp.is-fs .lp-revise {
  display: none !important;
}
.lp.is-fs .lp-body {
  flex: 1;
  min-height: 0;
  display: flex;
}
.lp.is-fs .lp-main {
  flex: 1;
  display: flex;
  flex-direction: column;
  min-height: 0;
}
.lp.is-fs .lp-stage {
  flex: 1;
  min-height: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: transparent;
  border: 0;
  box-shadow: none;
}
.lp.is-fs .ls.is-current {
  width: min(100%, calc((100dvh - 7rem) * 16 / 9));
}
.lp.is-fs .ls-canvas {
  border-radius: 12px;
  overflow: hidden;
}
.lp.is-fs .ls-in {
  overflow: hidden;
}
.lp.is-fs .ls-notes,
.lp.is-fs .ls-learn {
  display: none !important;
}
.lp.is-fs.show-notes .ls.is-current {
  width: min(100%, calc((100dvh - 7rem) * 16 / 9 + 320px));
  display: grid;
  grid-template-columns: minmax(0, 1fr) 320px;
}
.lp.is-fs.show-notes .ls-notes {
  display: block !important;
  color: var(--ink);
}
.lp.is-fs .lp-controls {
  position: static;
  margin: 0.75rem auto 0;
  width: min(100%, 980px);
  background: transparent;
  border: 0;
}
.lp.is-fs .lp-count,
.lp.is-fs .icon-btn {
  color: #e8edf8;
}
.lp.is-fs .icon-btn:hover {
  background: rgba(255, 255, 255, 0.1);
}
.lp.is-fs .lp-nav {
  background: transparent;
  color: #fff;
  border-color: rgba(255, 255, 255, 0.6);
}
.lp.is-fs .lp-nav--next {
  background: #fff;
  color: #0b1426;
  border-color: #fff;
}
.lp.is-fs .lp-progress {
  background: rgba(255, 255, 255, 0.15);
}

/* Revise */
.lp-revise {
  display: grid;
  gap: 2.25rem;
}
.lp-revise[hidden] {
  display: none;
}
.lp[data-mode='revise'] .lp-body {
  display: none;
}
.rv-h {
  font-size: 1.4rem;
  font-weight: 780;
  margin-bottom: 0.9rem;
}
.rv-ideas {
  display: grid;
  gap: 0.75rem;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 240px), 1fr));
}
.rv-ideas li {
  background: var(--card);
  border: 2px solid var(--ink);
  border-radius: var(--radius-m);
  padding: 1rem 1.1rem;
  font-size: 1.05rem;
  font-weight: 650;
  line-height: 1.4;
  box-shadow: 4px 4px 0 0 var(--accent);
}
.rv-diagrams {
  display: grid;
  gap: 1.75rem;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 380px), 1fr));
}
.rv-diagram {
  margin: 0;
  padding: 1rem;
}
.rv-diagram figcaption {
  margin-top: 0.75rem;
  font-size: var(--fs-small);
  color: var(--ink-2);
}
.rv-diagram .sc-captions {
  display: none;
}
.rv-next {
  margin-top: -0.5rem;
}

/* ───────── shared scene styles ───────── */
.sc-label {
  fill: var(--ink);
  font-family: var(--font-lbs-body), system-ui, sans-serif;
  paint-order: stroke;
  stroke: var(--card);
  stroke-width: 6px;
  stroke-linejoin: round;
}
.tx-muted {
  fill: var(--ink-2);
}
.tx-light {
  fill: var(--sc-light-text);
}
.tx-water {
  fill: var(--sc-water-text);
}
.tx-co2 {
  fill: var(--sc-co2-text);
}
.tx-o2 {
  fill: var(--sc-o2-text);
}
.tx-sugar {
  fill: var(--sc-sugar-text);
}
.tx-leaf {
  fill: var(--sc-leaf-line);
}
.tx-energy {
  fill: var(--sc-energy-text);
}
.tx-on-sugar {
  fill: #3d2600;
  stroke: none;
}
.sc-arrow {
  stroke-linecap: round;
  stroke-linejoin: round;
}
.st-ink {
  stroke: var(--ink);
}
.st-light {
  stroke: var(--sc-light);
}
.st-water {
  stroke: var(--sc-water);
}
.st-co2 {
  stroke: var(--sc-co2);
}
.st-o2 {
  stroke: var(--sc-o2);
}
.st-sugar {
  stroke: var(--sc-sugar);
}
.st-leaf {
  stroke: var(--sc-leaf);
}
.st-energy {
  stroke: var(--sc-energy);
}
.mk-ink {
  fill: var(--ink);
}
.mk-light {
  fill: var(--sc-light);
}
.mk-water {
  fill: var(--sc-water);
}
.mk-co2 {
  fill: var(--sc-co2);
}
.mk-o2 {
  fill: var(--sc-o2);
}
.mk-sugar {
  fill: var(--sc-sugar);
}
.mk-leaf {
  fill: var(--sc-leaf);
}
.mk-energy {
  fill: var(--sc-energy);
}
.sc-flow {
  stroke-dasharray: 11 9;
}
.sc-sun {
  fill: var(--sc-sun);
  stroke: #c98a12;
  stroke-width: 3;
}
.sc-ray {
  stroke: var(--sc-sun);
}
.sc-leaf {
  fill: var(--sc-leaf);
  stroke: var(--sc-leaf-line);
  stroke-width: 3;
}
.sc-leaf-vein {
  stroke: var(--sc-leaf-line);
  opacity: 0.75;
}
.sc-stem {
  stroke: var(--sc-leaf-line);
}
.sc-ground {
  stroke: var(--rule);
}
.sc-animal {
  fill: #c9b79c;
  stroke: #6b5a40;
  stroke-width: 3;
}
.sc-eye {
  fill: #2b2b2b;
}
.sc-leaf-body {
  fill: var(--sc-leaf-pale);
  stroke: var(--sc-leaf);
  stroke-width: 4;
}
.sc-chloro {
  fill: #8fcf7e;
  stroke: var(--sc-leaf-line);
  stroke-width: 4;
}
.sc-chloro-outer {
  fill: none;
  stroke: var(--sc-leaf-line);
  stroke-width: 3;
}
.sc-granum {
  fill: var(--sc-leaf-line);
}
.sc-lamella {
  stroke: var(--sc-leaf-line);
}
.sc-mito {
  fill: #f6c7a8;
  stroke: #b4572a;
  stroke-width: 4;
}
.sc-cristae {
  stroke: #b4572a;
}
.sc-vein {
  fill: #f3ecd6;
  stroke: #a08a52;
  stroke-width: 3;
}
.sc-xylem {
  fill: #d3e6f8;
  stroke: var(--sc-water);
  stroke-width: 3;
}
.sc-phloem {
  fill: #f9e3c0;
  stroke: var(--sc-sugar);
  stroke-width: 3;
}
.sc-guard {
  fill: #9fd38d;
  stroke: var(--sc-leaf-line);
  stroke-width: 3;
}
.sc-cell {
  fill: var(--sc-cell);
  stroke: var(--sc-leaf);
  stroke-width: 2.5;
}
.sc-cp {
  fill: var(--sc-cp);
}
.sc-epi {
  fill: var(--card);
  stroke: #9cc58f;
  stroke-width: 2.5;
}
.sc-cuticle {
  fill: #efdc8a;
}
.sc-leader {
  stroke: var(--ink-2);
  stroke-width: 2;
  fill: none;
}
.sc-white-beam {
  stroke: #fff8de;
  filter: drop-shadow(0 0 0.5px #c9b25d);
}
.sc-curve {
  stroke: var(--sc-leaf-line);
}
.sc-band-hi {
  fill: none;
  stroke: var(--ink);
  stroke-width: 4;
  stroke-dasharray: 8 6;
  opacity: 0;
}
.sc-glucose {
  fill: var(--sc-sun);
  stroke: #c98a12;
  stroke-width: 4;
}
.sc-node {
  fill: var(--card);
  stroke: var(--ink);
  stroke-width: 3;
}
.sc-glass {
  fill: var(--sc-glass);
  stroke: var(--ink);
  stroke-width: 4;
}
.sc-glass-roof {
  stroke: var(--ink);
  fill: var(--sc-glass);
}
.sc-glass-bar {
  stroke: var(--ink);
  opacity: 0.5;
}
.sc-vent {
  fill: var(--paper-3);
  stroke: var(--ink);
  stroke-width: 3;
}
.sc-thermo {
  fill: var(--card);
  stroke: var(--ink);
  stroke-width: 3;
}
.sc-thermo-fill {
  fill: var(--sc-water);
}
.sc-cycle {
  stroke: var(--rule);
}
[data-part] {
  transition: opacity 250ms var(--ease-out);
}
[data-part].is-dim {
  opacity: 0.22;
}

/* Captions that follow a build */
.sc-captions {
  display: grid;
  gap: 0.35rem;
  margin-top: 0.75rem;
  font-size: 0.95rem;
  counter-reset: none;
}
.sc-captions li {
  display: grid;
  grid-template-columns: 1.6rem 1fr;
  gap: 0.5rem;
  align-items: start;
  line-height: 1.35;
  color: var(--ink-2);
}
.sc-captions li.is-now {
  color: var(--ink);
  font-weight: 700;
}
.sc-cap-n {
  display: grid;
  place-items: center;
  width: 1.45rem;
  height: 1.45rem;
  border-radius: 99px;
  border: 2px solid currentColor;
  font-size: 0.75rem;
  font-weight: 800;
}
.sc-captions li.is-now .sc-cap-n {
  background: var(--ink);
  color: var(--paper);
  border-color: var(--ink);
}

/* Choosers (explore buttons) */
.sc-explore {
  margin-top: 0.75rem;
}
.sc-choose {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}
.sc-choose-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  min-height: 40px;
  padding: 0.35rem 0.85rem;
  border-radius: 999px;
  border: 2px solid var(--ink);
  background: var(--card);
  color: var(--ink);
  font: inherit;
  font-size: 0.9375rem;
  font-weight: 700;
  cursor: pointer;
}
.sc-choose-btn:hover {
  background: var(--paper-2);
}
.sc-choose-btn[aria-pressed='true'] {
  background: var(--ink);
  color: var(--paper);
}
.sc-swatch {
  width: 0.85rem;
  height: 0.85rem;
  border-radius: 99px;
  border: 1.5px solid rgba(0, 0, 0, 0.25);
}
.sc-when {
  margin-top: 0.6rem;
  font-size: 0.975rem;
  line-height: 1.5;
}
.js-lesson .sc-when {
  display: none;
}
.js-lesson [data-scene][data-active] .sc-when.is-on {
  display: block;
}
.sc-hint {
  margin-top: 0.6rem;
  color: var(--ink-2);
  font-size: 0.9375rem;
}
[data-scene][data-active] .sc-hint {
  display: none;
}
[data-scene] .sc-band-hi.is-on {
  opacity: 1;
}

/* Word equation */
.eq {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 0.75rem 0.6rem;
  padding: 0.5rem 0;
}
.eq-term {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 0.7rem 1rem 0.65rem;
  border-radius: 14px;
  background: var(--card);
  border: 2px solid var(--ink);
  border-top-width: 8px;
  min-width: 7.5rem;
}
.eq-name {
  font-family: var(--font-display);
  font-weight: 780;
  font-size: 1.3rem;
  line-height: 1.1;
}
.eq-note {
  font-size: 0.85rem;
  color: var(--ink-2);
  margin-top: 0.2rem;
}
.eq-op {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.8rem;
}
.eq-arrow {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.2rem;
  padding: 0 0.25rem;
}
.eq-arrow svg {
  width: 7.5rem;
  height: auto;
}
.eq-arrow-line {
  stroke: var(--ink);
}
.eq-arrow-head {
  fill: var(--ink);
}
.eq-over {
  font-weight: 800;
  color: var(--sc-light-text);
  font-size: 0.95rem;
}
.eq-under {
  font-size: 0.8125rem;
  color: var(--ink-2);
}
.tn-co2 {
  border-top-color: var(--sc-co2);
}
.tn-water {
  border-top-color: var(--sc-water);
}
.tn-sugar {
  border-top-color: var(--sc-sugar);
}
.tn-o2 {
  border-top-color: var(--sc-o2);
}
.tn-leaf {
  border-top-color: var(--sc-leaf);
}
.tn-energy {
  border-top-color: var(--sc-energy);
}

/* Atom counting */
.ac {
  display: grid;
  gap: 1rem;
  justify-items: center;
}
.ac-eq {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: baseline;
  gap: 0.35rem 0.6rem;
  font-family: var(--font-display);
  font-weight: 750;
  font-size: 1.9rem;
  letter-spacing: 0.01em;
}
.ac-k {
  font-weight: 800;
  color: var(--accent-ink);
  margin-right: 0.08em;
}
.ac-op,
.ac-arrow {
  color: var(--ink-2);
}
.ac-el {
  border-radius: 6px;
  padding: 0 0.06em;
  transition: background-color 200ms;
}
.ac-table {
  border-collapse: separate;
  border-spacing: 0;
  font-size: 0.975rem;
  min-width: min(100%, 26rem);
}
.ac-table th,
.ac-table td {
  padding: 0.45rem 0.8rem;
  text-align: left;
  border-bottom: 1px solid var(--rule);
}
.ac-table thead th {
  font-size: 0.8125rem;
  color: var(--ink-2);
}
.ac-table tbody th {
  font-weight: 750;
}
.ac-table tr {
  transition: background-color 200ms;
}
[data-scene][data-active='C'] .ac-el[data-el='C'],
[data-scene][data-active='H'] .ac-el[data-el='H'],
[data-scene][data-active='O'] .ac-el[data-el='O'] {
  background: color-mix(in srgb, var(--sun) 70%, transparent);
}
[data-scene][data-active='C'] tr[data-row='C'],
[data-scene][data-active='H'] tr[data-row='H'],
[data-scene][data-active='O'] tr[data-row='O'] {
  background: var(--sun-soft);
}

/* Comparison cards */
.cmp {
  display: grid;
  gap: 1rem;
  align-items: stretch;
}
.cmp-card {
  background: var(--card);
  border: 2px solid var(--ink);
  border-top-width: 8px;
  border-radius: 16px;
  padding: 0.9rem 1.1rem 1rem;
}
.cmp-card h4 {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.3rem;
  margin: 0.3rem 0 0.2rem;
}
.cmp-eq {
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--ink-2);
  margin-bottom: 0.5rem;
}
.cmp-card ul {
  display: grid;
  gap: 0.3rem;
  font-size: 0.975rem;
}
.cmp-card li {
  padding-left: 1rem;
  position: relative;
}
.cmp-card li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0.6em;
  width: 0.4rem;
  height: 0.4rem;
  border-radius: 99px;
  background: var(--ink-2);
}
.cmp-icon {
  width: 6rem;
  height: auto;
}
.cmp-link {
  display: none;
}
@container (min-width: 600px) {
  .cmp {
    grid-template-columns: 1fr 3.5cqi 1fr;
    gap: 1.5cqi;
  }
  .cmp-link {
    display: flex;
    align-items: center;
  }
  .cmp-link svg {
    width: 100%;
  }
  .cmp-card {
    padding: 1.4cqi 1.8cqi;
  }
  .cmp-card h4 {
    font-size: 2.6cqi;
  }
  .cmp-eq {
    font-size: 1.55cqi;
  }
  .cmp-card ul {
    font-size: 1.75cqi;
  }
  .cmp-icon {
    width: 9cqi;
  }
  .eq {
    flex-wrap: nowrap;
    gap: 1.2cqi;
  }
  .eq-name {
    font-size: 2.3cqi;
  }
  .eq-note {
    font-size: 1.35cqi;
  }
  .eq-term {
    min-width: 0;
    padding: 1.2cqi 1.5cqi;
    border-radius: 1.6cqi;
  }
  .eq-op {
    font-size: 3cqi;
  }
  .eq-arrow svg {
    width: 11cqi;
  }
  .eq-over {
    font-size: 1.55cqi;
  }
  .eq-under {
    font-size: 1.3cqi;
    white-space: nowrap;
  }
  .ac-eq {
    font-size: 4.4cqi;
  }
  .ac-table {
    font-size: 1.7cqi;
  }
  .ac {
    gap: 1.6cqi;
  }
  .sc-captions {
    font-size: 1.55cqi;
    gap: 0.5cqi;
    margin-top: 1cqi;
  }
  .sc-captions li {
    grid-template-columns: 2.6cqi 1fr;
  }
  .sc-cap-n {
    width: 2.3cqi;
    height: 2.3cqi;
    font-size: 1.2cqi;
  }
  .sc-choose-btn {
    font-size: 1.45cqi;
    min-height: 0;
    padding: 0.55cqi 1.3cqi;
  }
  .sc-when,
  .sc-hint {
    font-size: 1.55cqi;
  }
}

/* Flip cards (no 3D: the faces cross-fade) */
.flips {
  display: grid;
  gap: 0.8rem;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 220px), 1fr));
}
.flip {
  position: relative;
  display: grid;
  text-align: left;
  min-height: 8.5rem;
  padding: 0;
  border: 2px solid var(--ink);
  border-radius: 14px;
  background: var(--card);
  color: var(--ink);
  font: inherit;
  cursor: pointer;
  overflow: hidden;
}
.flip > span {
  grid-area: 1 / 1;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  padding: 0.9rem 1rem;
  transition:
    opacity 260ms var(--ease-out),
    transform 260ms var(--ease-out);
}
.flip-tag {
  font-size: 0.8125rem;
  font-weight: 750;
  color: var(--accent-ink);
}
.flip-text {
  font-size: 1.02rem;
  font-weight: 650;
  line-height: 1.4;
}
.flip-term {
  font-family: var(--font-display);
  font-size: 1.35rem;
  font-weight: 780;
}
.flip-hint {
  margin-top: auto;
  font-size: 0.8125rem;
  color: var(--ink-2);
  font-weight: 700;
}
.flip-back {
  background: var(--accent-soft);
}
.js-lesson .flip-back {
  opacity: 0;
  transform: translateY(6px);
  pointer-events: none;
}
.js-lesson .flip[aria-pressed='true'] .flip-front {
  opacity: 0;
  transform: translateY(-6px);
}
.js-lesson .flip[aria-pressed='true'] .flip-back {
  opacity: 1;
  transform: none;
}
.lp:not(.is-live) .flip > span,
html:not(.js-lesson) .flip > span {
  position: static;
}
html:not(.js-lesson) .flip {
  display: block;
  cursor: default;
}
@container (min-width: 600px) {
  .ls .flips {
    grid-template-columns: 1fr 1fr;
    gap: 1.4cqi;
  }
  .ls .flip {
    min-height: 11cqi;
  }
  .ls .flip > span {
    padding: 1.3cqi 1.7cqi;
    gap: 0.6cqi;
  }
  .ls .flip-text {
    font-size: 1.85cqi;
  }
  .ls .flip-tag,
  .ls .flip-hint {
    font-size: 1.35cqi;
  }
}

/* Quick check and quiz */
.qc {
  border: 0;
  padding: 0;
  margin: 0;
}
.qc-opts {
  display: grid;
  gap: 0.5rem;
}
.qc-opt {
  display: grid;
  grid-template-columns: 2rem 1fr;
  gap: 0.6rem;
  align-items: center;
  padding: 0.6rem 0.8rem;
  border: 2px solid var(--rule);
  border-radius: 12px;
  background: var(--card);
  cursor: pointer;
  font-size: 1rem;
  line-height: 1.35;
}
.qc-opt:hover {
  border-color: var(--ink);
}
.qc-opt input {
  position: absolute;
  opacity: 0;
  width: 1px;
  height: 1px;
}
.qc-letter {
  display: grid;
  place-items: center;
  width: 1.9rem;
  height: 1.9rem;
  border-radius: 99px;
  border: 2px solid var(--ink);
  font-weight: 800;
  font-size: 0.9rem;
}
.qc-opt:has(input:checked) {
  border-color: var(--ink);
  background: var(--blue-soft);
}
.qc-opt:has(input:checked) .qc-letter {
  background: var(--ink);
  color: var(--paper);
}
.qc-opt:has(input:focus-visible) {
  outline: 3px solid var(--blue);
  outline-offset: 2px;
}
.qc-opt.is-right {
  border-color: #2e7d4f;
  background: #e3f4e9;
}
.qc-opt.is-wrong {
  border-color: #b23a3a;
  background: #fbe4e4;
}
:root[data-theme='dark'] .qc-opt.is-right {
  background: #173d2a;
}
:root[data-theme='dark'] .qc-opt.is-wrong {
  background: #4a1f25;
}
.qc-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 0.8rem;
}
.qc-fb {
  margin-top: 0.6rem;
  font-weight: 750;
}
.qc-fb:empty {
  display: none;
}
.qc-fb.is-right {
  color: #23683f;
}
.qc-fb.is-wrong {
  color: #a12f2f;
}
:root[data-theme='dark'] .qc-fb.is-right {
  color: #8fd9a8;
}
:root[data-theme='dark'] .qc-fb.is-wrong {
  color: #f2a3a3;
}
.qc-explain {
  margin-top: 0.3rem;
  font-size: 0.975rem;
  line-height: 1.5;
}
.qc-nojs {
  margin-top: 0.6rem;
}
.js-lesson [data-nojs-only] {
  display: none !important;
}
@container (min-width: 600px) {
  .ls .qc-opts {
    grid-template-columns: 1fr 1fr;
    gap: 1cqi;
  }
  .ls .qc-opt {
    font-size: 1.75cqi;
    padding: 1cqi 1.3cqi;
    grid-template-columns: 3.4cqi 1fr;
  }
  .ls .qc-letter {
    width: 3.2cqi;
    height: 3.2cqi;
    font-size: 1.45cqi;
  }
  .ls .qc-fb,
  .ls .qc-explain {
    font-size: 1.7cqi;
  }
}

/* Greenhouse gauges */
.gh {
  display: grid;
  gap: 0.6rem;
  margin-top: 0.75rem;
}
.gh-gauges {
  display: grid;
  gap: 0.35rem;
  font-size: 0.95rem;
}
.gh-gauges > div {
  display: grid;
  grid-template-columns: 8.5rem 1fr;
  align-items: center;
  gap: 0.6rem;
}
.gh-gauges dt {
  font-weight: 750;
}
.gh-gauges dd {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  color: var(--ink-2);
}
.gh-bar {
  flex: none;
  width: 5rem;
  height: 0.7rem;
  border-radius: 99px;
  background: linear-gradient(90deg, var(--sc-light) calc(var(--v) * 100%), var(--paper-3) 0);
  border: 1.5px solid var(--ink);
}
.gh-bar--cold {
  background: linear-gradient(90deg, var(--sc-water) calc(var(--v) * 100%), var(--paper-3) 0);
}
.gh-bar--co2 {
  background: linear-gradient(90deg, var(--sc-co2) calc(var(--v) * 100%), var(--paper-3) 0);
}
.gh-answer {
  padding: 0.6rem 0.8rem;
  border-radius: 12px;
  background: var(--sun-soft);
  font-size: 0.975rem;
  line-height: 1.45;
}
.gh-answer--later {
  background: var(--paper-2);
}
@container (min-width: 600px) {
  .gh-wrap {
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(0, 1.05fr);
    gap: 3cqi;
    align-items: center;
  }
  .gh-wrap .sc-svg {
    max-height: 27cqi;
  }
  .gh {
    gap: 0.9cqi;
    margin-top: 0;
  }
  .gh-gauges {
    font-size: 1.6cqi;
    gap: 0.5cqi;
  }
  .gh-gauges > div {
    grid-template-columns: 14cqi 1fr;
  }
  .gh-bar {
    width: 9cqi;
    height: 1.1cqi;
  }
  .gh-answer {
    font-size: 1.6cqi;
    padding: 1cqi 1.3cqi;
  }
}

/* Limiting factors simulator */
.lf {
  display: grid;
  gap: 1rem;
}
.lf-axis {
  stroke: var(--ink);
}
.lf-curve {
  stroke: var(--sc-leaf-line);
  stroke-linejoin: round;
  transition: none;
}
.lf-ref {
  stroke: var(--rule);
  stroke-dasharray: 6 6;
}
.lf-ref.is-current {
  opacity: 0;
}
.lf-ref-label {
  fill: var(--ink-2);
  font-family: var(--font-lbs-body), system-ui, sans-serif;
  font-weight: 600;
}
.lf-point {
  fill: var(--sc-sun);
  stroke: var(--ink);
  stroke-width: 3;
}
.lf-controls {
  display: grid;
  gap: 0.8rem;
}
.lf-controls label {
  display: grid;
  gap: 0.3rem;
  font-weight: 700;
  font-size: 0.975rem;
}
.lf-controls label > span {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
}
.lf-controls output {
  font-weight: 800;
  color: var(--accent-ink);
  font-variant-numeric: tabular-nums;
}
.lf-controls input[type='range'] {
  width: 100%;
  accent-color: var(--ink);
  min-height: 32px;
}
.lf-read {
  padding: 0.65rem 0.85rem;
  background: var(--accent-soft);
  border-radius: 12px;
  font-size: 0.975rem;
  line-height: 1.45;
}
.lf-note {
  font-size: 0.8125rem;
  color: var(--ink-2);
}
@container (min-width: 600px) {
  .lf {
    grid-template-columns: minmax(0, 1.35fr) minmax(0, 1fr);
    align-items: center;
    gap: 1.5cqi 3cqi;
  }
  .lf .sc-svg {
    max-height: 30cqi;
  }
  .ls--wide .lf .sc-svg {
    max-height: 25cqi;
  }
  .ls--wide .lf {
    gap: 1cqi 3cqi;
  }
  .lf-controls {
    gap: 1.1cqi;
  }
  .lf-controls label {
    font-size: 1.6cqi;
  }
  .lf-controls input[type='range'] {
    min-height: 0;
  }
  .lf-read {
    font-size: 1.55cqi;
    padding: 1cqi 1.3cqi;
  }
  .lf-note {
    grid-column: 1 / -1;
    font-size: 1.25cqi;
  }
}

/* Fractions */
.fr-shade {
  fill: var(--sun);
}
.fr-shade-2 {
  fill: #8fd1c8;
}
.fr-empty {
  fill: var(--card);
}
.fr-outline {
  fill: none;
  stroke: var(--ink);
  stroke-width: 4;
}
.fr-outline + * {
}
.fr-cut {
  stroke: var(--ink);
}
.fr-vinculum {
  stroke: var(--ink);
}
.fr-guide {
  stroke: var(--coral);
  stroke-dasharray: 8 6;
}
.fr-axis {
  stroke: var(--ink);
  fill: none;
}
.fr-dot {
  fill: var(--coral);
  stroke: var(--ink);
  stroke-width: 3;
}
.fr-mask {
  fill: var(--card);
}
.fr-group {
  fill: none;
  stroke: var(--ink);
  stroke-width: 3;
  stroke-dasharray: 9 7;
}
.fr-group-on {
  fill: var(--sun-soft);
  stroke: none;
}
.fr-counter {
  fill: var(--sun);
  stroke: var(--ink);
  stroke-width: 3;
}
g > rect.fr-shade,
g > rect.fr-empty {
  stroke: var(--ink);
  stroke-width: 2.5;
}
svg path.fr-shade,
svg path.fr-empty {
  stroke: var(--ink);
  stroke-width: 2.5;
}
.hfrac {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  vertical-align: middle;
  line-height: 1.05;
  font-weight: 800;
}
.hfrac > span:first-child {
  border-bottom: 2px solid currentColor;
  padding: 0 0.15em;
}
.fb {
  display: grid;
  gap: 1rem;
}
.fb-side {
  display: grid;
  gap: 0.8rem;
  align-content: center;
}
.fb-controls {
  display: grid;
  justify-items: center;
  gap: 0.35rem;
}
.fb-row {
  display: grid;
  grid-template-columns: 1fr auto auto auto;
  align-items: center;
  gap: 0.5rem;
  width: 100%;
  max-width: 20rem;
}
.fb-lab {
  font-weight: 700;
  font-size: 0.9375rem;
  color: var(--ink-2);
}
.fb-btn {
  width: 44px;
  height: 44px;
  border-radius: 999px;
  border: 2px solid var(--ink);
  background: var(--card);
  color: var(--ink);
  font: inherit;
  font-size: 1.4rem;
  font-weight: 800;
  line-height: 1;
  cursor: pointer;
}
.fb-btn:hover {
  background: var(--paper-2);
}
.fb-btn:disabled {
  opacity: 0.3;
  cursor: default;
}
.fb-num {
  min-width: 2.5ch;
  text-align: center;
  font-family: var(--font-display);
  font-size: 2.2rem;
  font-weight: 800;
  font-variant-numeric: tabular-nums;
}
.fb-line {
  width: 100%;
  max-width: 20rem;
  height: 0;
  border-top: 4px solid var(--ink);
}
.fb-read {
  padding: 0.65rem 0.85rem;
  background: var(--accent-soft);
  border-radius: 12px;
  font-size: 0.975rem;
  line-height: 1.45;
}
@container (min-width: 600px) {
  .fb {
    grid-template-columns: minmax(0, 1.3fr) minmax(0, 1fr);
    align-items: center;
    gap: 3cqi;
  }
  .fb .sc-svg {
    max-height: 30cqi;
  }
  .fb-lab {
    font-size: 1.5cqi;
  }
  .fb-btn {
    width: 4.6cqi;
    height: 4.6cqi;
    font-size: 2.4cqi;
  }
  .fb-num {
    font-size: 4.2cqi;
  }
  .fb-read {
    font-size: 1.6cqi;
    padding: 1cqi 1.3cqi;
  }
  .fb-row {
    max-width: none;
  }
  .fb-line {
    max-width: none;
  }
}

/* Sister-site posters on diagram slides: on slides, top and bottom halves side by side; on phones, the whole poster.
   --ratio (height / width) is set from the image by lesson.js (and by the export), 2.4 until then. */
.ls-poster { margin: 1rem 0 0; }
.ls-half { display: block; border: 2px solid var(--ink); border-radius: 10px; overflow: hidden; background: #fff; }
.ls-half img { display: block; width: 100%; height: auto; }
.ls-half--b { display: none; }
.ls-poster figcaption { margin-top: 0.4rem; font-size: 0.8125rem; color: var(--ink-2); }
@container (min-width: 600px) {
  .ls--poster { display: grid; grid-template-columns: minmax(0, 1fr) auto; align-items: center; gap: 3cqi; }
  .ls-poster { margin: 0; display: grid; grid-template-columns: auto auto; gap: 1.4cqi; align-items: start; }
  .ls-half, .ls-half--b { display: block; width: min(25cqi, calc(46cqi * 2 / var(--ratio, 2.4))); aspect-ratio: 2 / var(--ratio, 2.4); }
  .ls-half--b img { transform: translateY(-50%); }
  .ls-poster figcaption { grid-column: 1 / -1; font-size: 1.25cqi; margin-top: 0; }
}

/* Stacked scene wrappers */
.sc-split-cap {
  display: grid;
}

/* ───────── motion ───────── */
@media (prefers-reduced-motion: no-preference) {
  .lp.is-live [data-step] {
    transition:
      opacity 380ms var(--ease-out),
      transform 380ms var(--ease-out);
  }
  .lp.is-live .sc-flow {
    animation: sc-flow 1.15s linear infinite;
  }
  .lp.is-live .sc-pulse,
  .scene-host .sc-pulse {
    animation: sc-pulse 3.2s ease-in-out infinite;
    transform-box: fill-box;
    transform-origin: center;
  }
  .scene-host .sc-flow {
    animation: sc-flow 1.15s linear infinite;
  }
  .ls.is-current .ls-in {
    animation: ls-in 420ms var(--ease-out);
  }
}
@keyframes sc-flow {
  to {
    stroke-dashoffset: -20;
  }
}
@keyframes sc-pulse {
  0%,
  100% {
    opacity: 0.55;
  }
  50% {
    opacity: 1;
  }
}
@keyframes ls-in {
  from {
    opacity: 0;
    transform: translateX(14px);
  }
  to {
    opacity: 1;
    transform: none;
  }
}
.lp.is-live [data-step].is-pre {
  opacity: 0;
  transform: translateY(8px);
  pointer-events: none;
}
.lp.is-live svg [data-step].is-pre {
  transform: none;
}
/* Upcoming build captions stay in place, faded: no blank gap, and learners see where the build is going. */
.lp.is-live .sc-captions li.is-pre {
  opacity: 1;
  transform: none;
  pointer-events: auto;
}
.lp.is-live .sc-captions li.is-pre .sc-cap-n {
  border-style: dashed;
}
.lp.is-paused .sc-flow,
.lp.is-paused .sc-pulse,
.motion-off .sc-flow,
.motion-off .sc-pulse {
  animation-play-state: paused !important;
}
.ls-visual.is-final [data-step].is-pre {
  opacity: 1 !important;
  transform: none !important;
}
@media (prefers-reduced-motion: reduce) {
  .sc-flow {
    stroke-dasharray: none;
  }
}

/* Print: every slide, finished state, no controls */
@media print {
  .lp-bar,
  .lp-controls,
  .lp-outline,
  .lp-revise,
  .ls-notes {
    display: none !important;
  }
  .lp .ls {
    display: block !important;
    break-inside: avoid;
  }
  .lp [data-step] {
    opacity: 1 !important;
    transform: none !important;
  }
}

/* ───────── lesson page ───────── */
.lesson-top {
  display: grid;
  gap: 1.25rem;
  grid-template-areas: 'intro' 'player' 'goals';
}
.lesson-intro {
  grid-area: intro;
  min-width: 0;
}
.lesson-player {
  grid-area: player;
  min-width: 0;
}
.lesson-goals {
  grid-area: goals;
}
@media (min-width: 900px) {
  .lesson-top {
    grid-template-columns: minmax(0, 1fr) 340px;
    grid-template-areas: 'intro goals' 'player player';
    column-gap: 3rem;
    row-gap: 2rem;
    align-items: end;
  }
}
.lesson-title {
  margin-top: 0.75rem;
  max-width: 22ch;
}
.lesson-sum {
  margin-top: 0.75rem;
  font-size: 1.125rem;
  line-height: 1.55;
  color: var(--ink-2);
  max-width: 62ch;
}
@media (max-width: 639.98px) {
  .lesson-sum {
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
    font-size: 1.02rem;
  }
  .lesson-title {
    font-size: 2rem;
  }
}
.lesson-facts {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem 1rem;
  margin-top: 0.9rem;
}
.lesson-facts .lcard-facts {
  margin: 0;
  font-size: var(--fs-meta);
}
.lesson-goals {
  background: var(--card);
  border: 2px solid var(--ink);
  border-radius: var(--radius-m);
  padding: 1rem 1.15rem 1.1rem;
  box-shadow: var(--lift) var(--lift) 0 0 var(--accent);
}
.lesson-goals h2 {
  font-size: 1.1rem;
  font-weight: 780;
  margin-bottom: 0.5rem;
}
.lesson-goals ul {
  display: grid;
  gap: 0.4rem;
  font-size: 0.975rem;
  line-height: 1.4;
}
.lesson-goals li {
  padding-left: 1.4rem;
  position: relative;
}
.lesson-goals li::before {
  content: '';
  position: absolute;
  left: 0.15rem;
  top: 0.3em;
  width: 0.55rem;
  height: 0.85rem;
  border: solid var(--accent-ink);
  border-width: 0 3px 3px 0;
  transform: rotate(40deg);
}

.lesson-grid {
  display: grid;
  gap: 2.5rem;
  margin-top: clamp(3rem, 2rem + 3vw, 5rem);
}
@media (min-width: 1024px) {
  .lesson-grid {
    grid-template-columns: minmax(0, 1fr) 320px;
    gap: 4rem;
  }
  .lesson-side {
    position: sticky;
    top: 86px;
    align-self: start;
  }
}
.lesson-main {
  min-width: 0;
  max-width: 72ch;
}
.lesson-sec + .lesson-sec,
.lesson-sec {
  margin-top: 3.5rem;
}
.lesson-main > .lesson-sec:first-child {
  margin-top: 0;
}
.lesson-h2 {
  font-size: var(--fs-h2);
  font-weight: 780;
  line-height: 1.1;
  margin-bottom: 1rem;
}
.lesson-h3 {
  font-size: 1.3rem;
  font-weight: 750;
  margin: 2rem 0 1rem;
}
.lesson-note {
  color: var(--ink-2);
  margin-bottom: 1rem;
}
.lesson-prose h3 {
  margin-top: 1.75rem;
}
.lesson-main .lesson-prose:first-of-type h3 {
  margin-top: 0;
}

.terms {
  display: grid;
  gap: 0.75rem 1.5rem;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 260px), 1fr));
}
.terms > div {
  padding: 0.8rem 0 0.9rem;
  border-top: 2px solid var(--ink);
}
.terms dt {
  font-family: var(--font-display);
  font-weight: 780;
  font-size: 1.15rem;
}
.terms dd {
  margin-top: 0.3rem;
  color: var(--ink-2);
  line-height: 1.5;
}

.quiz-list {
  display: grid;
  gap: 1.25rem;
}
.quiz-list > li {
  background: var(--card);
  border: 1.5px solid var(--rule);
  border-radius: var(--radius-m);
  padding: 1rem 1.1rem 1.15rem;
}
.qc-q {
  display: flex;
  gap: 0.6rem;
  font-weight: 750;
  font-size: 1.08rem;
  line-height: 1.4;
  margin-bottom: 0.8rem;
  padding: 0;
}
.qc-num {
  flex: none;
  display: grid;
  place-items: center;
  width: 1.8rem;
  height: 1.8rem;
  border-radius: 99px;
  background: var(--accent-soft);
  color: var(--accent-ink);
  font-size: 0.9rem;
  font-weight: 800;
}
.quiz-foot {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.75rem 1.25rem;
  margin-top: 1rem;
}
.quiz-score {
  font-weight: 750;
}
.quiz-score:empty {
  display: none;
}

.teach-grid {
  display: grid;
  gap: 1rem;
}
@media (min-width: 760px) {
  .teach-grid {
    grid-template-columns: 1fr 1fr;
  }
}
.panel-h {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 1.1rem;
  font-weight: 780;
  margin-bottom: 0.6rem;
}
.panel-h svg {
  color: var(--accent-ink);
}
.panel p {
  line-height: 1.6;
}
.teach-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 1rem;
}
.discuss {
  display: grid;
  gap: 0.6rem;
}
.discuss li {
  display: grid;
  grid-template-columns: 2rem 1fr;
  gap: 0.6rem;
  align-items: start;
  line-height: 1.45;
}
.discuss-n {
  display: grid;
  place-items: center;
  width: 1.8rem;
  height: 1.8rem;
  border-radius: 8px;
  border: 2px solid var(--ink);
  font-size: 0.8125rem;
  font-weight: 800;
  color: var(--ink);
  text-decoration: none;
}
.discuss-n:hover {
  background: var(--paper-2);
}
.fit {
  margin-top: 1.5rem;
}
.notes-all,
.transcript {
  margin-top: 1.25rem;
  border: 1.5px solid var(--rule);
  border-radius: var(--radius-m);
  background: var(--card);
}
.notes-all > summary,
.transcript > summary,
.faqs summary {
  cursor: pointer;
  padding: 0.9rem 1.1rem;
  font-weight: 750;
  list-style-position: inside;
}
.notes-all ol,
.transcript ol {
  display: grid;
  gap: 1.1rem;
  padding: 0.25rem 1.1rem 1.2rem;
}
.notes-all p {
  margin-top: 0.25rem;
  color: var(--ink-2);
  line-height: 1.55;
}
.transcript h3 {
  font-size: 1.05rem;
  font-weight: 780;
  font-family: var(--font-body);
  letter-spacing: 0;
}
.transcript ul {
  list-style: disc;
  padding-left: 1.3rem;
  margin-top: 0.3rem;
}
.transcript p {
  margin-top: 0.3rem;
  line-height: 1.55;
}
.transcript-visual {
  color: var(--ink-2);
  font-style: italic;
}
.faqs {
  display: grid;
  gap: 0.6rem;
}
.faqs details {
  border: 1.5px solid var(--rule);
  border-radius: 12px;
  background: var(--card);
}
.faqs details p {
  padding: 0 1.1rem 1rem;
  line-height: 1.6;
  color: var(--ink-2);
}
.review {
  padding: 0.8rem 1rem;
  border-radius: 12px;
  background: var(--sun-soft);
  line-height: 1.5;
}
.review.is-reviewed {
  background: var(--teal-soft);
}
.review a,
.sources a,
.igh a,
.path a {
  color: var(--blue);
  text-decoration: underline;
  text-underline-offset: 3px;
}
.sources {
  display: grid;
  gap: 0.5rem;
  margin-top: 1rem;
  list-style: decimal;
  padding-left: 1.3rem;
}
.sources li span {
  display: block;
  font-size: var(--fs-meta);
  color: var(--ink-2);
}

.dl {
  padding: 1.1rem 1.1rem 1rem;
}
.dl h2 {
  font-size: 1.2rem;
  font-weight: 780;
  margin-bottom: 0.6rem;
}
.dl ul {
  display: grid;
  gap: 0.15rem;
}
.dl a {
  display: grid;
  grid-template-columns: 1.6rem 1fr;
  gap: 0.6rem;
  align-items: start;
  padding: 0.6rem 0.5rem;
  border-radius: 10px;
  color: var(--ink);
  text-decoration: none;
}
.dl a:hover {
  background: var(--paper-2);
}
.dl a svg {
  color: var(--accent-ink);
  margin-top: 0.1rem;
}
.dl a strong {
  display: block;
  font-weight: 750;
}
.dl a span span {
  display: block;
  font-size: var(--fs-caption);
  color: var(--ink-2);
  line-height: 1.35;
}
.dl-note {
  margin-top: 0.6rem;
  font-size: var(--fs-caption);
  color: var(--ink-2);
  line-height: 1.45;
}
.share {
  margin-top: 1.25rem;
}

.lesson-next .path {
  padding: 1.1rem 1.2rem;
  margin-bottom: 1rem;
}
.path-h {
  font-weight: 750;
  margin-bottom: 0.6rem;
}
.path-steps {
  display: grid;
  gap: 1rem;
}
@media (min-width: 700px) {
  .path-steps {
    grid-template-columns: 1fr 1fr;
  }
}
.path-steps .lrow {
  border-top: 0;
}
.igh {
  margin-top: 2rem;
  padding: 1.1rem 1.2rem;
  border: 2px dashed var(--rule);
  border-radius: var(--radius-m);
}
.igh h3 {
  margin-top: 0;
}
.igh p {
  line-height: 1.55;
}

/* Below-the-fold lesson sections are laid out only when they come near the screen (cuts first-load work). */
.lesson-sec, .lesson-next, .home > .sec:not(.showcase) { content-visibility: auto; contain-intrinsic-size: auto 900px; }