:root {
  color-scheme: light;
  --paper: #fff8e7;
  --paper-deep: #f3e7c9;
  --ink: #17324d;
  --ink-soft: #52677a;
  --coral: #c84833;
  --coral-soft: #f9d6cb;
  --teal: #087f7b;
  --teal-soft: #ccebe7;
  --leaf: #447f42;
  --leaf-soft: #dcebd1;
  --sun: #f2c84b;
  --white: #fffdf8;
  --line: rgba(23, 50, 77, 0.16);
  --shadow: rgba(23, 50, 77, 0.14);
  --display-font: "ZCOOL KuaiLe", "FZKaTong-M19S", cursive;
  --body-font: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  min-width: 320px;
  margin: 0;
  overflow-x: hidden;
  color: var(--ink);
  background:
    linear-gradient(rgba(23, 50, 77, 0.035) 1px, transparent 1px),
    linear-gradient(90deg, rgba(23, 50, 77, 0.035) 1px, transparent 1px),
    var(--paper);
  background-size: 28px 28px;
  font-family: var(--body-font);
  font-size: 16px;
  line-height: 1.75;
}

button,
input,
summary {
  font: inherit;
}

button,
input[type="range"],
summary {
  touch-action: manipulation;
}

button:focus-visible,
input:focus-visible,
summary:focus-visible,
a:focus-visible {
  outline: 3px solid var(--sun);
  outline-offset: 3px;
}

.skip-link {
  position: fixed;
  top: 12px;
  left: 12px;
  z-index: 20;
  padding: 8px 14px;
  color: var(--white);
  background: var(--ink);
  border-radius: 6px;
  transform: translateY(-160%);
  transition: transform 160ms ease;
}

.skip-link:focus {
  transform: translateY(0);
}

.paper-noise {
  position: fixed;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  opacity: 0.24;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 120 120' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.82' numOctaves='2' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)' opacity='.13'/%3E%3C/svg%3E");
}

.page-shell {
  width: min(1180px, calc(100% - 40px));
  margin: 0 auto;
  padding: 20px 0 28px;
}

.course-nav {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px;
  width: min(610px, calc(100% - 3.5%));
  margin-left: 3.5%;
}

.course-nav a {
  display: grid;
  grid-template-columns: 34px minmax(0, 1fr) 18px;
  gap: 10px;
  align-items: center;
  min-height: 54px;
  padding: 7px 11px;
  color: var(--ink);
  background: rgba(255, 253, 248, 0.82);
  border: 2px solid var(--ink);
  border-radius: 6px;
  box-shadow: 3px 3px 0 rgba(23, 50, 77, 0.2);
  text-decoration: none;
  transition: color 140ms ease, background 140ms ease, transform 140ms ease, box-shadow 140ms ease;
}

.course-nav a:hover,
.course-nav a:focus-visible {
  color: var(--ink);
  background: var(--sun);
  transform: translateY(-2px);
  box-shadow: 4px 5px 0 var(--ink);
}

.course-nav a[aria-current="page"] {
  color: var(--white);
  background: var(--teal);
  border-color: var(--teal);
  box-shadow: 4px 4px 0 var(--ink);
}

.course-nav__number {
  display: grid;
  width: 34px;
  height: 34px;
  place-items: center;
  color: var(--white);
  background: var(--ink);
  border-radius: 50%;
  font-size: 0.75rem;
  font-weight: 800;
}

.course-nav a[aria-current="page"] .course-nav__number {
  color: var(--ink);
  background: var(--sun);
}

.course-nav__copy {
  display: flex;
  flex-direction: column;
  font-size: 0.83rem;
  font-weight: 800;
  line-height: 1.22;
}

.course-nav__copy small {
  margin-top: 2px;
  color: var(--ink-soft);
  font-size: 0.65rem;
  font-weight: 600;
}

.course-nav a[aria-current="page"] .course-nav__copy small {
  color: rgba(255, 253, 248, 0.78);
}

.course-nav svg {
  width: 18px;
  height: 18px;
}

.intro-band {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 252px;
  gap: 28px;
  align-items: center;
  margin-bottom: 22px;
}

.hero {
  position: relative;
  width: 100%;
  padding: 25px 0 12px 3.5%;
}

.hero::before {
  position: absolute;
  top: 10px;
  left: 0;
  width: 72px;
  height: 6px;
  content: "";
  background: var(--coral);
  transform: rotate(-4deg);
}

.hero::after {
  display: none;
}

.lesson-tag {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 8px;
  color: var(--teal);
  font-weight: 800;
  font-size: 0.82rem;
  letter-spacing: 0.08em;
}

.lesson-tag__line {
  display: block;
  width: 34px;
  height: 2px;
  background: currentColor;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1 {
  max-width: 860px;
  margin-bottom: 8px;
  font-family: var(--display-font);
  font-size: clamp(2.4rem, 4.2vw, 3.4rem);
  font-weight: 400;
  line-height: 1.02;
  letter-spacing: -0.035em;
}

h1 mark {
  position: relative;
  display: inline;
  color: inherit;
  background: linear-gradient(transparent 68%, rgba(242, 200, 75, 0.74) 68%);
}

.hero__lead {
  max-width: 670px;
  margin-bottom: 5px;
  color: var(--ink-soft);
  font-size: clamp(0.9rem, 1.35vw, 1.02rem);
  font-weight: 500;
}

.hero__question {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  padding: 4px 0;
  color: var(--ink);
  border-bottom: 2px solid var(--teal);
  font-size: 0.82rem;
  font-weight: 800;
}

.hero__question svg {
  width: 18px;
  height: 18px;
}

.guess-note {
  position: relative;
  z-index: 2;
  width: 100%;
  padding: 17px 17px 14px;
  background: var(--sun);
  box-shadow: 6px 7px 0 var(--ink);
  transform: rotate(1.4deg);
}

.guess-note::after {
  position: absolute;
  right: -7px;
  bottom: -8px;
  width: 27px;
  height: 27px;
  content: "";
  background: linear-gradient(135deg, #d9a91e 50%, transparent 50%);
}

.tape {
  position: absolute;
  top: -11px;
  left: 78px;
  width: 78px;
  height: 20px;
  background: rgba(255, 253, 248, 0.72);
  transform: rotate(-5deg);
}

.guess-note__title {
  margin-bottom: 3px;
  font-family: var(--display-font);
  font-size: 1.3rem;
}

.guess-note p {
  margin-bottom: 5px;
  font-size: 0.82rem;
  line-height: 1.42;
}

.guess-note__hint {
  font-size: 0.72rem !important;
  font-weight: 700;
}

.experiment {
  position: relative;
  padding: clamp(26px, 4vw, 48px);
  background: var(--white);
  border: 3px solid var(--ink);
  box-shadow: 12px 14px 0 var(--ink);
}

.experiment::before {
  position: absolute;
  top: 25%;
  left: -13px;
  width: 22px;
  height: 72px;
  content: "";
  background: var(--coral);
}

.experiment__topline {
  display: block;
  padding-bottom: 20px;
  border-bottom: 2px dashed var(--line);
}

.section-index {
  margin-bottom: 4px;
  color: var(--coral);
  font-size: 0.8rem;
  font-weight: 800;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}

h2 {
  margin-bottom: 10px;
  font-family: var(--display-font);
  font-size: clamp(1.9rem, 4vw, 3.4rem);
  font-weight: 400;
  line-height: 1.16;
}

.section-intro {
  margin-bottom: 0;
  color: var(--ink-soft);
}

.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: center;
  justify-content: flex-end;
}

.control-button {
  display: inline-flex;
  min-height: 46px;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 9px 16px;
  color: var(--ink);
  background: transparent;
  border: 2px solid var(--ink);
  border-radius: 7px;
  box-shadow: 3px 3px 0 var(--ink);
  cursor: pointer;
  font-weight: 800;
  transition: transform 140ms ease, box-shadow 140ms ease;
}

.control-button svg {
  width: 18px;
  height: 18px;
}

.control-button:hover {
  transform: translate(-1px, -1px);
  box-shadow: 5px 5px 0 var(--ink);
}

.control-button:active {
  transform: translate(2px, 2px);
  box-shadow: 1px 1px 0 var(--ink);
}

.control-button--primary {
  color: var(--white);
  background: var(--ink);
}

.speed-control {
  min-width: 142px;
  padding-left: 6px;
  font-size: 0.86rem;
  font-weight: 700;
}

.speed-control > span {
  display: flex;
  justify-content: space-between;
}

.speed-control output,
.timeline-control output {
  color: var(--teal);
  font-variant-numeric: tabular-nums;
}

input[type="range"] {
  width: 100%;
  height: 28px;
  margin: 0;
  accent-color: var(--teal);
  cursor: pointer;
}

.track-stack {
  padding: 12px 0 0;
}

.wheel-lane {
  --lane-color: var(--coral);
  position: relative;
  padding: 23px 0 17px;
  transition: background-color 140ms ease, box-shadow 140ms ease;
}

.wheel-lane.is-bunny-drop-target {
  background: rgba(8, 127, 123, 0.08);
  box-shadow: inset 0 0 0 2px var(--teal);
}

.wheel-lane.is-bunny-drop-target::after {
  position: absolute;
  top: 9px;
  right: 10px;
  z-index: 2;
  padding: 3px 9px;
  content: "放到这里";
  color: var(--white);
  background: var(--teal);
  border-radius: 4px;
  font-size: 0.7rem;
  font-weight: 800;
  line-height: 1.4;
  pointer-events: none;
}

.wheel-lane.is-waiting-for-bunny .height-readout::after {
  display: block;
  margin-top: 2px;
  content: "等待兔白白 · 车轮暂停";
  color: var(--coral);
  font-size: 0.67rem;
  font-weight: 800;
  line-height: 1.35;
  white-space: nowrap;
}

.wheel-lane + .wheel-lane {
  border-top: 2px dashed var(--line);
}

.wheel-lane--dodecagon {
  --lane-color: var(--teal);
}

.wheel-lane--circle {
  --lane-color: var(--leaf);
}

.wheel-lane__heading {
  display: grid;
  grid-template-columns: 48px minmax(0, 1fr) auto;
  gap: 14px;
  align-items: center;
  margin-bottom: 4px;
}

.shape-id {
  display: grid;
  width: 46px;
  height: 46px;
  place-items: center;
  color: var(--white);
  background: var(--lane-color);
  clip-path: polygon(50% 0, 100% 28%, 88% 100%, 12% 100%, 0 28%);
  font-size: 1.08rem;
  font-weight: 800;
}

.shape-id--circle {
  border-radius: 50%;
  clip-path: none;
}

.shape-id--circle::after {
  width: 12px;
  height: 12px;
  content: "";
  background: var(--white);
  border-radius: 50%;
}

.wheel-lane h3 {
  margin-bottom: 0;
  font-size: 1.15rem;
  line-height: 1.35;
}

.wheel-lane__heading p {
  margin-bottom: 0;
  color: var(--ink-soft);
  font-size: 0.9rem;
  line-height: 1.45;
}

.height-readout {
  min-width: 94px;
  color: var(--ink-soft);
  text-align: right;
}

.height-readout span,
.height-readout strong {
  display: block;
}

.height-readout span {
  font-size: 0.76rem;
}

.height-readout strong {
  color: var(--lane-color);
  font-size: 1rem;
  font-variant-numeric: tabular-nums;
}

.wheel-canvas {
  display: block;
  width: 100%;
  height: 154px;
}

.timeline-control {
  padding-top: 18px;
  border-top: 2px solid var(--ink);
}

.timeline-control label {
  display: flex;
  justify-content: space-between;
  font-size: 0.88rem;
  font-weight: 800;
}

.experiment-help {
  margin: 4px 0 0;
  color: var(--ink-soft);
  font-size: 0.83rem;
}

.finding {
  display: grid;
  grid-template-columns: 92px minmax(0, 1.2fr) minmax(250px, 0.8fr);
  gap: clamp(18px, 2.5vw, 32px);
  align-items: center;
  margin: 34px 2% 18px;
  padding: 20px 22px;
  background: rgba(255, 253, 248, 0.72);
  border-top: 2px solid var(--ink);
  border-bottom: 2px solid var(--ink);
}

.finding__label {
  display: inline-block;
  padding: 7px 12px;
  color: var(--white);
  background: var(--coral);
  font-size: 0.83rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-align: center;
  transform: rotate(-6deg);
}

.finding__main h2 {
  margin-bottom: 7px;
  font-size: clamp(1.7rem, 3vw, 2.5rem);
}

.finding__main p {
  margin-bottom: 0;
  color: var(--ink-soft);
  font-size: 0.9rem;
  line-height: 1.55;
}

.comfort-meter {
  padding: 16px 18px;
  background: var(--paper-deep);
  border-left: 5px solid var(--sun);
  transform: rotate(0.6deg);
}

.comfort-row {
  display: grid;
  grid-template-columns: 84px 1fr 42px;
  gap: 9px;
  align-items: center;
  font-size: 0.8rem;
}

.comfort-row + .comfort-row {
  margin-top: 8px;
}

.comfort-row strong {
  text-align: right;
}

.comfort-track {
  height: 10px;
  overflow: hidden;
  background: rgba(23, 50, 77, 0.12);
  border-radius: 20px;
}

.comfort-track span {
  display: block;
  width: var(--level);
  height: 100%;
  background: var(--coral);
  border-radius: inherit;
}

.comfort-row:nth-child(2) .comfort-track span {
  background: var(--teal);
}

.comfort-row:nth-child(3) .comfort-track span {
  background: var(--leaf);
}

.learn-more {
  position: relative;
  margin: 28px 0 18px;
  padding: 22px 4% 24px;
  background: var(--ink);
  color: var(--white);
  transform: rotate(-0.25deg);
}

.learn-more::before,
.learn-more::after {
  position: absolute;
  width: 70px;
  height: 18px;
  content: "";
  background: var(--sun);
}

.learn-more::before {
  top: -9px;
  left: 16%;
  transform: rotate(5deg);
}

.learn-more::after {
  right: 12%;
  bottom: -9px;
  transform: rotate(-5deg);
}

.learn-more .section-index {
  color: var(--sun);
}

.learn-more > h2 {
  margin-bottom: 12px;
  font-size: clamp(1.7rem, 3vw, 2.45rem);
}

.learn-more__grid {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 28px;
  align-items: start;
}

.big-answer {
  margin-bottom: 0;
  font-size: clamp(0.95rem, 1.6vw, 1.08rem);
  font-weight: 600;
  line-height: 1.55;
}

details {
  color: var(--ink);
  background: var(--sun);
  box-shadow: 7px 7px 0 var(--coral);
  transform: rotate(1deg);
}

summary {
  display: flex;
  min-height: 52px;
  align-items: center;
  gap: 9px;
  padding: 12px 16px;
  cursor: pointer;
  font-weight: 800;
  list-style: none;
}

summary::-webkit-details-marker {
  display: none;
}

summary svg {
  width: 20px;
  height: 20px;
  flex: 0 0 auto;
}

.details-content {
  padding: 2px 18px 16px;
  font-size: 0.9rem;
}

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

footer {
  display: flex;
  justify-content: space-between;
  gap: 20px;
  padding: 9px 2%;
  color: var(--ink-soft);
  border-top: 2px solid var(--ink);
  font-size: 0.8rem;
  font-weight: 700;
}

.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;
}

@media (max-width: 900px) {
  .page-shell {
    width: min(100% - 28px, 760px);
    padding-top: 20px;
  }

  .intro-band {
    grid-template-columns: minmax(0, 1fr) 220px;
    gap: 16px;
    margin-bottom: 18px;
  }

  .hero {
    width: 100%;
    padding-left: 2%;
  }

  .course-nav {
    width: calc(100% - 2%);
    margin-left: 2%;
    padding: 0;
  }

  .guess-note {
    width: 100%;
    margin: 0;
  }

  .experiment__topline {
    grid-template-columns: 1fr;
  }

  .controls {
    justify-content: flex-start;
  }

  .finding {
    grid-template-columns: 90px 1fr;
    margin: 28px 1% 16px;
    padding: 18px;
  }

  .comfort-meter {
    grid-column: 2;
    transform: rotate(1deg);
  }
}

@media (max-width: 640px) {
  body {
    font-size: 15px;
  }

  .page-shell {
    width: calc(100% - 18px);
    padding-top: 14px;
  }

  .intro-band {
    grid-template-columns: 1fr;
    gap: 7px;
    margin-bottom: 14px;
  }

  .hero {
    width: 100%;
    padding: 21px 8px 9px;
  }

  .course-nav {
    gap: 6px;
    width: calc(100% - 16px);
    margin: 0 8px;
    padding: 0;
  }

  .course-nav a {
    grid-template-columns: 30px minmax(0, 1fr) 16px;
    gap: 7px;
    min-height: 52px;
    padding: 6px 8px;
  }

  .course-nav__number {
    width: 30px;
    height: 30px;
    font-size: 0.68rem;
  }

  .course-nav__copy {
    font-size: 0.75rem;
  }

  .course-nav__copy small {
    font-size: 0.58rem;
  }

  .course-nav svg {
    width: 16px;
    height: 16px;
  }

  h1 {
    margin-bottom: 6px;
    font-size: clamp(2.1rem, 11.2vw, 3rem);
  }

  .hero__lead {
    padding-right: 0;
    font-size: 0.86rem;
  }

  .hero__question {
    font-size: 0.76rem;
  }

  .guess-note {
    width: calc(100% - 16px);
    margin: 0 8px 5px;
    padding: 13px 14px 11px;
    transform: rotate(0.5deg);
  }

  .guess-note__title {
    font-size: 1.14rem;
  }

  .experiment {
    padding: 24px 15px 22px;
    box-shadow: 7px 8px 0 var(--ink);
  }

  .experiment::before {
    display: none;
  }

  .controls {
    display: grid;
    grid-template-columns: 1fr 1fr;
    align-items: end;
  }

  .control-button {
    padding-inline: 10px;
  }

  .speed-control {
    grid-column: 1 / -1;
    padding: 5px 2px 0;
  }

  .wheel-lane__heading {
    grid-template-columns: 42px minmax(0, 1fr);
    gap: 11px;
  }

  .shape-id {
    width: 40px;
    height: 40px;
  }

  .height-readout {
    grid-column: 2;
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    align-items: baseline;
    min-width: 0;
    text-align: left;
  }

  .wheel-lane.is-waiting-for-bunny .height-readout::after {
    width: 100%;
    margin-top: -4px;
  }

  .wheel-canvas {
    height: 138px;
  }

  .finding {
    grid-template-columns: 1fr;
    gap: 11px;
    margin: 28px 0 12px;
    padding: 16px 14px;
  }

  .finding__label {
    width: max-content;
  }

  .comfort-meter {
    grid-column: auto;
    margin: 0;
    padding: 14px 15px;
  }

  .learn-more {
    margin: 22px 0 12px;
    padding: 22px 16px 24px;
  }

  .learn-more__grid {
    grid-template-columns: 1fr;
    gap: 14px;
  }

  footer {
    flex-direction: column;
    gap: 0;
    padding: 8px 2%;
  }
}

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

  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    transition-duration: 0.01ms !important;
  }
}

/* The guide shares each canvas with its wheel, so both stay aligned on resize. */
.bunny-guide {
  display: flex;
  align-items: center;
  gap: 10px;
  margin: 16px 0 0;
  padding: 10px 16px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: #fff8e9;
  font-size: 0.82rem;
  color: var(--ink-soft);
}
.bunny-guide img { width: 26px; height: 44px; object-fit: contain; }
.bunny-guide strong { color: var(--ink); white-space: nowrap; }
.bunny-guide.is-sweating { background: #edf9fc; }
@media (max-width: 640px) {
  .bunny-guide { display: grid; grid-template-columns: 26px 1fr; gap: 2px 10px; padding: 10px 12px; }
  .bunny-guide img { grid-row: span 2; }
  .bunny-guide span { font-size: 0.75rem; }
}

/* Picked-up mascot floats outside the track; its original position stays reserved. */
.bunny-pickup {
  position: fixed;
  z-index: 10000;
  pointer-events: none;
  user-select: none;
  filter: drop-shadow(0 8px 4px rgb(23 50 77 / 14%));
}
.bunny-pickup[hidden] { display: none; }
.bunny-pickup__struggle { position: relative; width: 100%; height: 100%; transform-origin: 50% 8%; animation: bunny-protest 320ms ease-in-out infinite; }
.bunny-pickup img { display: block; width: 100%; height: 100%; object-fit: contain; }
.bunny-pickup__speech {
  position: absolute;
  bottom: calc(100% + 9px);
  left: 50%;
  transform: translateX(-50%);
  padding: 5px 9px;
  border: 2px solid #c54835;
  border-radius: 12px 12px 12px 2px;
  background: #fff2e6;
  color: #a72d24;
  font-size: 12px;
  font-weight: 800;
  line-height: 1.3;
  white-space: nowrap;
}
.bunny-pickup__anger { position: absolute; top: 28%; right: -12px; width: 23px; height: 23px; fill: none; stroke: #db4938; stroke-width: 3; stroke-linecap: round; stroke-linejoin: round; }
body.is-bunny-dragging, body.is-bunny-dragging * { cursor: grabbing !important; user-select: none !important; }
@keyframes bunny-protest {
  0%, 100% { transform: rotate(-9deg) translateX(-2px); }
  25% { transform: rotate(3deg) scaleY(1.03); }
  50% { transform: rotate(9deg) translateX(2px); }
  75% { transform: rotate(-3deg) scaleY(0.98); }
}
@media (prefers-reduced-motion: reduce) {
  .bunny-pickup__struggle { animation: none; transform: rotate(-5deg); }
}

/* Keep the controls beside the three tracks while students compare their motion. */
.experiment__workspace {
  display: grid;
  grid-template-columns: 184px minmax(0, 1fr);
  align-items: start;
  gap: 28px;
  padding-top: 22px;
}
.control-panel {
  position: sticky;
  top: 20px;
  padding: 18px 15px;
  border: 2px solid var(--ink);
  border-radius: 12px;
  background: #fff8e9;
  box-shadow: 4px 4px 0 var(--ink);
}
.control-panel h3 { margin: 0 0 16px; color: var(--teal); font-size: 1rem; }
.control-panel .controls { display: grid; grid-template-columns: minmax(0, 1fr); gap: 13px; align-items: stretch; }
.control-panel .control-button { width: 100%; padding-inline: 9px; white-space: nowrap; }
.control-panel .speed-control { min-width: 0; padding: 7px 0 0; }
.control-panel .timeline-control { margin-top: 17px; padding-top: 15px; border-top: 1px dashed var(--line); }
.control-panel .timeline-control label { font-size: 0.78rem; gap: 6px; }
.experiment__display { min-width: 0; }
.experiment__display > .bunny-guide { margin-top: 0; }
@media (max-width: 900px) and (min-width: 701px) {
  .experiment__workspace { grid-template-columns: 165px minmax(0, 1fr); gap: 20px; }
  .control-panel { padding-inline: 12px; }
  .experiment__display .wheel-lane__heading { grid-template-columns: 42px minmax(0, 1fr); gap: 10px; }
  .experiment__display .height-readout { grid-column: 2; display: flex; gap: 8px; text-align: left; }
}
@media (max-width: 700px) {
  .experiment__workspace { grid-template-columns: minmax(0, 1fr); gap: 20px; padding-top: 18px; }
  .control-panel { position: static; padding: 14px; }
  .control-panel h3 { margin-bottom: 12px; font-size: 0.92rem; }
  .control-panel .controls { grid-template-columns: 1fr 1fr; gap: 12px; }
  .control-panel .speed-control { grid-column: 1 / -1; padding-top: 2px; }
  .control-panel .timeline-control { margin-top: 9px; padding-top: 9px; }
}


/* Three connected classroom experiments. */
.course-nav { grid-template-columns: repeat(3, minmax(0, 1fr)); width: min(920px, 100%); }
@media (max-width: 620px) { .course-nav { grid-template-columns: 1fr; margin-left: 0; } }