/* Lesson 3.4 ratio table lab. Light classroom theme; tokens on :root. */
:root {
  color-scheme: light;
  --ink: #182844;
  --muted: #526079;
  --blue: #315cde;
  --blue-dark: #2349bc;
  --blue-light: #edf2ff;
  --green: #11684e;
  --green-light: #e7f5ee;
  --orange: #a64020;
  --orange-light: #fff0e6;
  --gold: #8a5a00;
  --gold-light: #fff4d6;
  --purple: #6a3fb5;
  --line: #d7deeb;
  --canvas: #f5f7fb;
  --panel: #fff;
  --error: #982d30;
  --error-light: #fff0ed;
  --radius: 14px;
}
* {
  box-sizing: border-box;
}
body {
  margin: 0;
  background: var(--canvas);
  color: var(--ink);
  font-family: "Avenir Next", "Trebuchet MS", Arial, sans-serif;
  font-size: 18px;
  line-height: 1.5;
}
button,
input,
select {
  font: inherit;
}
button {
  cursor: pointer;
  color: inherit;
  min-height: 46px;
  border-radius: 10px;
}
button,
input {
  touch-action: manipulation;
}
input {
  border-radius: 10px;
}
button:disabled {
  cursor: default;
  opacity: 0.55;
}
button:focus-visible,
input:focus-visible,
a:focus-visible,
summary:focus-visible,
.plot-board:focus-visible {
  outline: 3px solid var(--blue);
  outline-offset: 4px;
}
h1,
h2,
h3,
p,
dl,
dd {
  margin: 0;
}
h1 {
  font-size: clamp(2rem, 4vw, 2.8rem);
  letter-spacing: -0.04em;
  line-height: 1.15;
}
h2 {
  font-size: clamp(1.6rem, 3vw, 2rem);
  letter-spacing: -0.025em;
  line-height: 1.2;
}
h3 {
  font-size: 1.1rem;
  line-height: 1.35;
}
p {
  max-width: 64ch;
}
.small {
  font-size: 0.88rem;
}
.muted {
  color: var(--muted);
}
.green {
  color: var(--green);
}
.orange {
  color: var(--orange);
}
[hidden] {
  display: none !important;
}
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}
.skip {
  position: fixed;
  z-index: 20;
  top: 1rem;
  left: 1rem;
  background: #fff;
  padding: 0.7rem;
  color: var(--blue);
}
.skip:not(:focus) {
  clip-path: inset(50%);
  width: 1px;
  height: 1px;
  overflow: hidden;
}

/* Chrome */
.topbar {
  background: #fff;
  border-bottom: 1px solid var(--line);
}
.topbar-inner {
  max-width: 1240px;
  margin: auto;
  padding: 0.85rem 1.5rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
}
.brand {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-weight: 800;
  font-size: 1rem;
}
.brand svg {
  width: 28px;
  height: 28px;
}
.meta {
  font-size: 0.83rem;
  color: var(--muted);
}
.quiet {
  border: 0;
  background: transparent;
  color: var(--muted);
  padding: 0.4rem 0.7rem;
  font-size: 0.85rem;
  text-decoration: underline;
  text-underline-offset: 4px;
  min-height: 40px;
}
.shell {
  max-width: 1240px;
  margin: auto;
  padding: 1.7rem 1.5rem 1rem;
}
.intro {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1.5rem;
  margin-bottom: 1.2rem;
}
.intro p {
  margin-top: 0.45rem;
  color: var(--muted);
  font-size: 1rem;
}
.goals {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-top: 0.7rem;
  padding: 0;
  list-style: none;
}
.goals li {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--blue-dark);
  background: var(--blue-light);
  border-radius: 100px;
  padding: 0.2rem 0.7rem;
}
.constant {
  display: flex;
  gap: 0.75rem;
  align-items: center;
  border: 1px solid var(--line);
  background: #fff;
  border-radius: var(--radius);
  padding: 0.65rem 1rem;
  flex-shrink: 0;
}
.constant .ball-icon {
  width: 32px;
  height: 32px;
}
.constant strong {
  display: block;
  font-size: 1rem;
}
.constant span {
  font-size: 0.8rem;
  color: var(--muted);
}

/* Stepper */
.steps {
  display: grid;
  grid-template-columns: repeat(8, minmax(0, 1fr));
  gap: 0.45rem;
  padding: 0;
  margin: 0 0 0.6rem;
  list-style: none;
}
.step-link {
  border: 1px solid var(--line);
  background: #fff;
  width: 100%;
  display: flex;
  gap: 0.5rem;
  align-items: center;
  padding: 0.55rem 0.6rem;
  text-align: left;
  font-size: 0.92rem;
  font-weight: 700;
}
.step-link:hover {
  border-color: var(--blue);
}
.step-link[aria-current="step"] {
  color: var(--blue);
  border: 2px solid var(--blue);
  padding: calc(0.55rem - 1px) calc(0.6rem - 1px);
  background: var(--blue-light);
}
.step-no {
  display: grid;
  place-items: center;
  width: 26px;
  height: 26px;
  border-radius: 50%;
  background: var(--canvas);
  font-size: 0.78rem;
  flex-shrink: 0;
  border: 1px solid #b9c4d8;
}
.step-link[aria-current="step"] .step-no {
  background: var(--blue);
  color: #fff;
  border-color: var(--blue);
}
.step-link.done .step-no {
  background: var(--green);
  color: #fff;
  border-color: var(--green);
}
.progress-track {
  height: 6px;
  background: #e3e8f2;
  border-radius: 100px;
  overflow: hidden;
  margin-bottom: 1.2rem;
}
.progress-track span {
  display: block;
  height: 100%;
  background: var(--green);
  transition: width 0.3s ease;
}

/* Lesson frame */
.lesson {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 20px;
  overflow: hidden;
}
.lesson:focus {
  outline: none;
}
.stage-heading {
  padding: 1.45rem 1.65rem 1.2rem;
  border-bottom: 1px solid var(--line);
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 1rem;
}
.stage-heading p {
  font-size: 1rem;
  color: var(--muted);
  margin-top: 0.45rem;
}
.stage-heading h2:focus {
  outline: none;
}
.stage-tools {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 0.3rem;
  flex-shrink: 0;
}
.no-speech .speak {
  display: none;
}
.counter {
  font-size: 0.85rem;
  background: var(--canvas);
  color: var(--muted);
  border-radius: 100px;
  padding: 0.45rem 0.8rem;
  white-space: nowrap;
}
.workbench {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 300px;
  min-height: 410px;
}
.board {
  min-width: 0;
  padding: 1.65rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}
.coach {
  background: #f8faff;
  padding: 1.6rem;
  border-left: 1px solid var(--line);
  display: flex;
  flex-direction: column;
  gap: 1rem;
  align-items: stretch;
}
.coach p {
  font-size: 1rem;
}
.coach .btn {
  width: 100%;
}
.feedback {
  max-width: none;
  padding: 0.9rem 1.65rem;
  background: var(--blue-light);
  border-top: 1px solid var(--line);
  font-size: 1rem;
  min-height: 54px;
}
.feedback.error {
  background: var(--error-light);
  color: var(--error);
}
.feedback.success {
  background: var(--green-light);
  color: var(--green);
}
.feedback:empty {
  display: none;
}

/* Buttons */
.btn {
  border: 1px solid var(--blue);
  background: #fff;
  color: var(--blue);
  padding: 0.65rem 1rem;
  font-weight: 700;
  font-size: 1rem;
}
.btn:hover:not(:disabled) {
  background: var(--blue-light);
}
.btn.primary {
  background: var(--blue);
  color: #fff;
}
.btn.primary:hover:not(:disabled) {
  background: var(--blue-dark);
}
.btn.secondary {
  border-color: #a4b0c6;
  color: var(--muted);
  background: #fff;
}
.btn.success {
  color: #fff;
  border-color: var(--green);
  background: var(--green);
}
.btn.success:hover:not(:disabled) {
  background: #0c5540;
}

/* Ratio tables */
.table-scroll {
  overflow-x: auto;
  padding: 4px 4px 8px;
  margin: -4px -4px 0;
}
.ratio-table {
  border-collapse: separate;
  border-spacing: 0;
  width: 100%;
  table-layout: fixed;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  font-variant-numeric: tabular-nums;
}
.ratio-table caption {
  text-align: left;
  color: var(--muted);
  font-size: 0.9rem;
  font-weight: 700;
  padding-bottom: 0.7rem;
}
.ratio-table th,
.ratio-table td {
  height: 78px;
  border-right: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  text-align: center;
  padding: 0.4rem 0.25rem;
}
.ratio-table th {
  width: 120px;
  font-size: 0.95rem;
  font-weight: 700;
  text-align: left;
  padding: 0.6rem 0.85rem;
}
.ratio-table td {
  font-size: clamp(1.3rem, 2.7vw, 2.05rem);
  font-weight: 700;
}
.ratio-table tr:last-child > * {
  border-bottom: 0;
}
.ratio-table tr > *:last-child {
  border-right: 0;
}
.ratio-table .top-row th {
  background: var(--green-light);
  color: var(--green);
}
.ratio-table .bottom-row th {
  background: var(--orange-light);
  color: var(--orange);
}
.ratio-table .top-row .active {
  background: var(--green-light);
  box-shadow: inset 0 3px var(--green);
}
.ratio-table .bottom-row .active {
  background: var(--orange-light);
  box-shadow: inset 0 -3px var(--orange);
}
.ratio-table .marked {
  background: #f3f6fd;
  color: var(--blue-dark);
}
.ratio-table .empty {
  color: #a3adc0;
  font-weight: 400;
}
.ratio-table .answer-cell {
  padding: 0.3rem;
}
.mini-table th,
.mini-table td {
  height: 48px;
}
.mini-table td {
  font-size: 1.2rem;
}
.mini-table th {
  width: 78px;
  font-size: 0.8rem;
  padding: 0.35rem 0.5rem;
}
.mini-table caption {
  font-size: 0.8rem;
  padding-bottom: 0.4rem;
}
.number-input {
  width: 100%;
  max-width: 76px;
  min-width: 48px;
  height: 52px;
  text-align: center;
  border: 2px solid var(--blue);
  background: #fff;
  color: var(--ink);
  font-size: 1.5rem;
  font-weight: 700;
  padding: 0.25rem;
  appearance: textfield;
  -moz-appearance: textfield;
}
.number-input::-webkit-inner-spin-button,
.number-input::-webkit-outer-spin-button {
  -webkit-appearance: none;
  margin: 0;
}
.number-input[aria-invalid="true"] {
  border-color: var(--error);
  background: #fff6f5;
}
.table-note {
  display: flex;
  gap: 0.6rem;
  align-items: center;
  justify-content: center;
  text-align: center;
  color: var(--muted);
  font-size: 0.98rem;
  flex-wrap: wrap;
  max-width: none;
}
.pair-chip {
  display: inline-block;
  border-radius: 8px;
  background: var(--blue-light);
  color: #294db1;
  padding: 0.2rem 0.6rem;
  font-weight: 700;
  white-space: nowrap;
}
.check-cell {
  background: #fff;
  border: 1px solid #a4b0c6;
  font: inherit;
  min-width: 55px;
  padding: 0.3rem;
}
.check-cell:hover {
  background: var(--blue-light);
  border-color: var(--blue);
}

.ratio-table tr:first-child > :first-child { border-top-left-radius: calc(var(--radius) - 1px); }
.ratio-table tr:first-child > :last-child { border-top-right-radius: calc(var(--radius) - 1px); }
.ratio-table tr:last-child > :first-child { border-bottom-left-radius: calc(var(--radius) - 1px); }
.ratio-table tr:last-child > :last-child { border-bottom-right-radius: calc(var(--radius) - 1px); }
.verdict:disabled[aria-pressed="true"] { opacity: 1; }
.verdict:disabled { opacity: 0.45; }

/* Bag model */
.rack {
  display: flex;
  gap: 0.6rem;
  justify-content: center;
  flex-wrap: wrap;
  padding: 0.4rem 0.2rem;
}
.mini-bag {
  width: 72px;
  flex-shrink: 0;
  position: relative;
}
.bag-drawing {
  width: 100%;
  height: 86px;
  border: 2px solid #7d968a;
  border-radius: 11px 11px 20px 20px;
  background: #f5fbf7;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  align-content: center;
  gap: 4px;
  padding: 7px;
}
.bag-drawing::before {
  content: "";
  position: absolute;
  top: -5px;
  left: 22px;
  right: 22px;
  height: 5px;
  border: 2px solid #7d968a;
  border-radius: 5px;
  background: #fff;
}
.ball-icon {
  width: 100%;
  height: auto;
  display: block;
}
.mini-bag small {
  display: block;
  text-align: center;
  font-size: 0.72rem;
  color: var(--muted);
  margin-top: 0.3rem;
}
.math-strip {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 0.55rem 0.8rem;
  padding: 0.8rem;
  border-radius: 10px;
  background: var(--canvas);
  font-size: 1.1rem;
  flex-wrap: wrap;
  text-align: center;
}
.math-strip .green,
.math-strip .orange {
  font-weight: 700;
}
.math-strip .divider {
  width: 1px;
  align-self: stretch;
  background: var(--line);
}

/* Coach content */
.notice {
  border-radius: 10px;
  background: var(--green-light);
  padding: 0.85rem 1rem;
  color: var(--green);
  font-size: 0.95rem;
}
.hint {
  border-radius: 10px;
  background: var(--gold-light);
  padding: 0.85rem 1rem;
  color: #644700;
  font-size: 0.95rem;
}
.points-note {
  font-size: 0.9rem;
  color: var(--muted);
}
.frame {
  font-style: italic;
  background: #fff;
  border: 1px dashed #9eabc3;
  border-radius: 10px;
  padding: 0.7rem 0.9rem;
}
.factor-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.45rem;
  width: 100%;
}
.factor {
  font-weight: 700;
  color: var(--blue);
  background: #fff;
  border: 1px solid #879ac6;
  padding: 0.5rem 0.3rem;
  font-size: 1.05rem;
  line-height: 1.2;
}
.factor[aria-pressed="true"] {
  background: var(--blue);
  color: #fff;
  border-color: var(--blue);
}
.toolkit {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  gap: 0.3rem;
  font-size: 0.88rem;
  color: var(--muted);
}
.toolkit li {
  display: flex;
  gap: 0.5rem;
  align-items: center;
}
.toolkit li span[aria-hidden] {
  display: grid;
  place-items: center;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  border: 1px solid #b9c4d8;
  font-size: 0.72rem;
  background: #fff;
}
.toolkit li.now {
  color: var(--ink);
  font-weight: 700;
}
.toolkit li.got span[aria-hidden] {
  background: var(--green);
  border-color: var(--green);
  color: #fff;
}

/* Learn */
.trio {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.8rem;
}
.view-card {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 0.9rem;
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
  background: #fff;
  min-width: 0;
}
.view-card h3 {
  font-size: 1rem;
  display: flex;
  gap: 0.45rem;
  align-items: center;
}
.view-card p {
  font-size: 0.95rem;
}
.view-card .rack {
  padding: 0;
  justify-content: flex-start;
}
.tag {
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  background: var(--canvas);
  border: 1px solid var(--line);
  border-radius: 100px;
  padding: 0.05rem 0.5rem;
  color: var(--muted);
}
.big-ratio {
  font-size: 2rem;
  font-weight: 800;
  letter-spacing: 0.02em;
}
.section-title {
  font-size: 1rem;
  margin-top: 0.4rem;
}
.vocab-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(210px, 1fr));
  gap: 0.6rem;
}
.vocab-card {
  border: 1px solid var(--line);
  border-left: 4px solid var(--blue);
  border-radius: 10px;
  padding: 0.65rem 0.8rem;
  background: #fbfcff;
}
.vocab-card dt {
  font-weight: 800;
}
.vocab-card dd {
  font-size: 0.9rem;
  color: var(--muted);
}
.vocab-ex {
  display: block;
  margin-top: 0.3rem;
  font-weight: 700;
  color: var(--blue-dark);
  font-size: 0.85rem;
}
.quick-check {
  border-top: 1px solid var(--line);
  padding-top: 1rem;
}

/* Choices */
fieldset {
  padding: 0;
  margin: 0;
  border: 0;
  min-width: 0;
}
legend {
  font-weight: 700;
  margin-bottom: 0.65rem;
}
.choice-list {
  display: grid;
  gap: 0.6rem;
}
.option {
  display: flex;
  gap: 0.6rem;
  padding: 0.7rem 0.8rem;
  border: 1px solid #9eabc3;
  border-radius: 9px;
  font-size: 0.98rem;
  background: #fff;
  align-items: flex-start;
  cursor: pointer;
}
.option:has(input:checked) {
  border-color: var(--blue);
  background: var(--blue-light);
}
input[type="radio"] {
  accent-color: var(--blue);
  width: 20px;
  height: 20px;
  margin: 0.12rem 0 0;
  flex-shrink: 0;
}
.pair-inputs {
  display: flex;
  gap: 0.6rem;
  align-items: end;
  justify-content: center;
  margin: 0.4rem 0;
}
.pair-inputs .paren {
  font-size: 2.5rem;
  line-height: 1.2;
}
.pair-inputs label {
  display: block;
  font-size: 0.85rem;
  margin-bottom: 0.3rem;
  color: var(--muted);
}
.pair-inputs .number-input {
  max-width: 90px;
  width: 90px;
}
.inline-form {
  display: flex;
  gap: 0.8rem;
  align-items: center;
  justify-content: center;
  flex-wrap: wrap;
  font-weight: 700;
}
.inline-form label {
  font-size: 1rem;
}

/* Graphs */
.graph-wrap {
  display: flex;
  justify-content: center;
}
.graph {
  width: 100%;
  max-width: 480px;
  height: auto;
  display: block;
  overflow: visible;
}
.graph text {
  font-family: Arial, sans-serif;
  font-size: 16px;
  fill: var(--ink);
}
.graph .axis-label {
  font-weight: 700;
  font-size: 15px;
}
.graph .grid {
  stroke: #d8e0ed;
  stroke-width: 1;
  fill: none;
}
.graph .axis {
  stroke: #5b6b84;
  stroke-width: 2;
  fill: none;
}
.graph .ratio-line {
  stroke: var(--green);
  stroke-width: 2.5;
  stroke-dasharray: 7 5;
  fill: none;
}
.graph .ratio-line.blue {
  stroke: var(--blue);
}
.graph .ratio-line.green {
  stroke: var(--green);
}
.graph .ratio-line.gold {
  stroke: var(--gold);
}
.graph .guide {
  stroke: var(--purple);
  stroke-width: 2.5;
  stroke-dasharray: 5 4;
  fill: none;
}
.graph .pt {
  fill: var(--blue);
  stroke: #fff;
  stroke-width: 2;
}
.graph .pt.plotted {
  fill: var(--blue);
}
.graph .pt.origin {
  fill: var(--ink);
}
.graph .pt.new {
  fill: var(--green);
}
.graph .pt.unit {
  fill: var(--orange);
}
.graph .pt.miss {
  fill: var(--error);
}
.graph .pt.blue {
  fill: var(--blue);
}
.graph .pt.green {
  fill: var(--green);
}
.graph .pt.gold {
  fill: var(--gold);
}
.graph .pt-label {
  font-weight: 700;
  font-size: 15px;
  paint-order: stroke;
  stroke: #fff;
  stroke-width: 4px;
}
.graph .hit {
  fill: transparent;
  cursor: crosshair;
}
.graph .hit:hover {
  fill: rgba(49, 92, 222, 0.18);
}
.graph .cursor {
  fill: none;
  stroke: var(--purple);
  stroke-width: 3;
  pointer-events: none;
}
.plot-board:not(:focus-visible) .cursor {
  stroke-opacity: 0.35;
}
.mini-graph {
  max-width: 300px;
}
.mini-graph text {
  font-size: 18px;
}

/* Graph modes + table studio */
.mode-tabs { display: inline-grid; grid-template-columns: 1fr 1fr; gap: 0.3rem; background: var(--canvas); border: 1px solid var(--line); border-radius: 12px; padding: 0.25rem; align-self: flex-start; }
.mode-tab { border: 0; background: transparent; font-weight: 700; font-size: 0.92rem; padding: 0.4rem 0.9rem; min-height: 40px; color: var(--muted); }
.mode-tab[aria-pressed="true"] { background: #fff; color: var(--blue); box-shadow: 0 1px 3px rgba(24, 40, 68, 0.15); }
.studio-names { display: flex; flex-wrap: wrap; gap: 0.8rem; }
.studio-names label { display: flex; flex-direction: column; gap: 0.25rem; font-size: 0.85rem; font-weight: 700; color: var(--muted); flex: 1 1 160px; }
.studio-names input { border: 2px solid #9eabc3; padding: 0.5rem 0.65rem; font-size: 1rem; color: var(--ink); background: #fff; }
.studio-names input:focus { border-color: var(--blue); }
.studio-table .number-input { max-width: 84px; }
.studio-row { display: flex; flex-wrap: wrap; gap: 0.45rem; }
.studio-row .btn { padding: 0.45rem 0.8rem; font-size: 0.9rem; min-height: 42px; }
.studio-verdict { max-width: none; border-radius: 10px; padding: 0.85rem 1rem; background: var(--blue-light); font-size: 1rem; }
.studio-verdict.success { background: var(--green-light); color: var(--green); }
.studio-verdict.error { background: var(--error-light); color: var(--error); }
.studio-verdict:empty { display: none; }
.ratio-seed { display: flex; flex-wrap: wrap; align-items: center; gap: 0.45rem; font-size: 1.5rem; font-weight: 800; }
.ratio-seed .number-input { width: 76px; }
.ratio-seed .btn { font-size: 1rem; flex-basis: 100%; }

/* Compare */
.team-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.8rem;
}
.team-card {
  border: 1px solid var(--line);
  border-top: 5px solid var(--blue);
  border-radius: var(--radius);
  padding: 0.85rem;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
  min-width: 0;
}
.team-card.gold {
  border-top-color: var(--gold);
}
.team-card.green {
  border-top-color: var(--green);
}
.team-card.solved {
  background: #fbfdfc;
}
.verdicts {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.4rem;
}
.verdict {
  border: 1px solid #879ac6;
  background: #fff;
  color: var(--blue);
  font-weight: 700;
  font-size: 0.92rem;
  padding: 0.45rem 0.4rem;
  line-height: 1.2;
}
.verdict[aria-pressed="true"] {
  background: var(--blue);
  color: #fff;
  border-color: var(--blue);
}
.final-compare {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: 1rem;
  align-items: center;
  border-top: 1px solid var(--line);
  padding-top: 1rem;
}

/* Practice */
.problem-kicker {
  font-size: 0.8rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--muted);
}
.problem-prompt {
  font-size: 1.2rem;
  font-weight: 700;
  max-width: none;
}
.level-tabs {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.3rem;
}
.level {
  border: 1px solid #a4b0c6;
  background: #fff;
  font-size: 0.82rem;
  font-weight: 700;
  padding: 0.3rem;
  min-height: 42px;
}
.level[aria-pressed="true"] {
  background: var(--ink);
  color: #fff;
  border-color: var(--ink);
}
.meter-label {
  display: flex;
  justify-content: space-between;
  font-size: 0.9rem;
  margin-bottom: 0.3rem;
}
.meter-track {
  height: 12px;
  border-radius: 100px;
  background: #e3e8f2;
  overflow: hidden;
}
.meter-track span {
  display: block;
  height: 100%;
  background: var(--green);
  transition: width 0.3s ease;
}

/* Finish */
.finish {
  padding: 1.3rem;
  border-radius: var(--radius);
  background: var(--green-light);
  text-align: center;
  display: grid;
  justify-items: center;
  gap: 0.6rem;
}
.finish.compact {
  text-align: left;
  justify-items: start;
}
.finish-mark {
  width: 52px;
  height: 52px;
  border-radius: 50%;
  background: var(--green);
  color: #fff;
  display: grid;
  place-items: center;
  font-size: 1.7rem;
}
.finish h3 {
  font-size: 1.35rem;
}
.finish p {
  font-size: 1rem;
}
.checklist {
  margin: 0;
  padding-left: 1.2rem;
  display: grid;
  gap: 0.3rem;
  font-size: 1rem;
}

/* Footer */
.footer-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  margin-top: 1.15rem;
}
.footer-progress {
  font-size: 0.85rem;
  color: var(--muted);
  text-align: center;
}
.footer-nav .btn {
  min-width: 120px;
}
.save-line {
  max-width: none;
  text-align: center;
  font-size: 0.75rem;
  color: var(--muted);
  margin-top: 1rem;
}
.save-error {
  color: var(--error);
}
dialog {
  border: 1px solid var(--line);
  border-radius: 18px;
  padding: 1.8rem;
  max-width: 560px;
  width: calc(100% - 2rem);
  color: var(--ink);
}
dialog::backdrop {
  background: #17254470;
}
dialog p {
  margin: 0.8rem 0;
}
dialog h3 {
  margin-top: 1rem;
  font-size: 1rem;
}
dialog .actions {
  display: flex;
  gap: 0.7rem;
  margin-top: 1.2rem;
  flex-wrap: wrap;
}
dialog ul {
  padding-left: 1.2rem;
  font-size: 1rem;
  margin: 0.4rem 0;
}
.pulse {
  animation: arrive 0.3s ease-out;
}
@keyframes arrive {
  from {
    transform: translateY(5px);
  }
  to {
    transform: translateY(0);
  }
}
@media (prefers-reduced-motion: reduce) {
  .pulse {
    animation: none;
  }
  .progress-track span,
  .meter-track span {
    transition: none;
  }
}

/* Laptop */
@media (max-width: 1100px) {
  .workbench {
    grid-template-columns: minmax(0, 1fr) 260px;
  }
  .coach {
    padding: 1.2rem;
  }
  .board {
    padding: 1.3rem;
  }
  .steps {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
  .trio {
    grid-template-columns: 1fr 1fr;
  }
  .trio .view-card:last-child {
    grid-column: 1 / -1;
    align-items: center;
  }
  .team-grid {
    grid-template-columns: 1fr 1fr;
  }
}

/* Tablet */
@media (max-width: 820px) {
  .workbench {
    grid-template-columns: 1fr;
    min-height: 0;
  }
  .coach {
    border-left: 0;
    border-top: 1px solid var(--line);
  }
  .stage-heading {
    padding: 1.2rem;
  }
  .constant span {
    display: none;
  }
  .intro {
    gap: 1rem;
  }
  .intro p {
    font-size: 0.92rem;
  }
  .final-compare {
    grid-template-columns: 1fr;
  }
}

/* Phone */
@media (max-width: 560px) {
  body {
    font-size: 17px;
  }
  .topbar-inner {
    padding: 0.5rem 1rem;
  }
  .meta {
    display: none;
  }
  .shell {
    padding: 1.2rem 1rem 1rem;
  }
  .intro {
    align-items: flex-start;
    gap: 0.5rem;
    margin-bottom: 1rem;
  }
  .intro h1 {
    font-size: 2rem;
  }
  .goals {
    display: none;
  }
  .constant {
    padding: 0.4rem;
    border: 0;
    background: transparent;
  }
  .constant .ball-icon {
    width: 26px;
  }
  .constant .constant-copy {
    display: none;
  }
  .steps {
    gap: 0.25rem;
  }
  .step-link {
    flex-direction: column;
    justify-content: center;
    gap: 0.2rem;
    text-align: center;
    padding: 0.4rem 0.1rem;
    font-size: 0.72rem;
    min-height: 60px;
    border-radius: 9px;
  }
  .step-link[aria-current="step"] {
    padding: calc(0.4rem - 1px) 0;
  }
  .step-no {
    width: 22px;
    height: 22px;
    font-size: 0.7rem;
  }
  .stage-heading {
    padding: 1.1rem 1rem;
    gap: 0.6rem;
  }
  .stage-heading h2 {
    font-size: 1.5rem;
  }
  .stage-heading p {
    font-size: 0.95rem;
  }
  .counter {
    font-size: 0.72rem;
    padding: 0.3rem 0.5rem;
  }
  .board {
    padding: 1.1rem 0.7rem;
  }
  .coach {
    padding: 1rem;
    gap: 0.75rem;
  }
  .coach .btn {
    font-size: 0.92rem;
    padding: 0.6rem 0.65rem;
  }
  .ratio-table th {
    width: 74px;
    font-size: 0.78rem;
    padding: 0.4rem;
  }
  .ratio-table td {
    font-size: 1.35rem;
  }
  .ratio-table td,
  .ratio-table th {
    height: 66px;
  }
  .ratio-table .answer-cell {
    padding: 0.15rem;
  }
  .number-input {
    min-width: 0;
    padding: 0;
    height: 46px;
    font-size: 1.2rem;
  }
  .mini-table td,
  .mini-table th {
    height: 44px;
  }
  .mini-table td {
    font-size: 1.05rem;
  }
  .trio,
  .team-grid {
    grid-template-columns: 1fr;
  }
  .trio .view-card:last-child {
    grid-column: auto;
  }
  .mini-bag {
    width: 60px;
  }
  .bag-drawing {
    height: 74px;
    gap: 3px;
    padding: 6px;
  }
  .math-strip {
    font-size: 0.98rem;
    padding: 0.7rem;
  }
  .math-strip .divider {
    display: none;
  }
  .feedback {
    padding: 0.8rem 1rem;
    font-size: 0.92rem;
  }
  .graph text {
    font-size: 19px;
  }
  .graph .axis-label,
  .graph .pt-label {
    font-size: 17px;
  }
  .footer-nav {
    gap: 0.5rem;
  }
  .footer-nav .btn {
    min-width: 80px;
    font-size: 0.87rem;
    padding: 0.55rem 0.65rem;
  }
  .footer-progress {
    font-size: 0.75rem;
  }
  .finish {
    padding: 1rem;
  }
  .finish h3 {
    font-size: 1.2rem;
  }
  .lesson {
    border-radius: 15px;
  }
  .pair-inputs .number-input {
    width: 72px;
  }
}

@media (max-width: 560px) {
  .mode-tabs { display: grid; align-self: stretch; }
  .mode-tab { font-size: 0.82rem; padding: 0.35rem 0.4rem; }
  .studio-row .btn { flex: 1 1 45%; }
}

@media print {
  .topbar,
  .intro,
  .steps,
  .progress-track,
  .coach,
  .footer-nav,
  .save-line,
  button,
  .feedback {
    display: none !important;
  }
  .shell {
    padding: 0;
  }
  .lesson {
    border: 0;
  }
  .workbench {
    display: block;
  }
  .board {
    padding: 1rem;
  }
}
@page {
  margin: 15mm;
}