.module-page {
  background:
    radial-gradient(circle at 72% -10%, color-mix(in srgb, var(--accent) 16%, transparent), transparent 34%),
    radial-gradient(circle at 10% 10%, color-mix(in srgb, var(--accent-3) 13%, transparent), transparent 30%),
    var(--body-gradient);
}

.back-link {
  color: var(--accent);
  font-weight: 900;
  white-space: nowrap;
}

.pilot-badge,
.module-badge {
  padding: 0.35rem 0.65rem;
  border: 1px solid color-mix(in srgb, var(--accent-2) 38%, var(--line));
  border-radius: 999px;
  color: var(--accent-2);
  font-size: 0.84rem;
  white-space: nowrap;
}

.lesson-rail {
  position: sticky;
  top: 73px;
  z-index: 60;
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--bg) 84%, transparent);
  backdrop-filter: blur(14px);
}

.lesson-rail-inner {
  display: flex;
  gap: 0.55rem;
  padding: 0.55rem 0;
  overflow-x: auto;
  scrollbar-width: thin;
}

.lesson-rail a {
  flex: 0 0 auto;
  padding: 0.45rem 0.72rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--soft);
  font-size: 0.88rem;
  white-space: nowrap;
}

.lesson-rail a:hover {
  border-color: var(--accent);
}

.lesson-rail span {
  margin-right: 0.25rem;
  color: var(--accent);
  font-weight: 900;
}

.lesson-hero {
  position: relative;
  overflow: hidden;
  padding: 72px 0;
  border-bottom: 1px solid var(--line);
}

.lesson-hero::after {
  position: absolute;
  right: -10%;
  bottom: -55%;
  width: 55vw;
  height: 55vw;
  border: 1px solid color-mix(in srgb, var(--accent-3) 17%, transparent);
  border-radius: 50%;
  content: "";
  pointer-events: none;
}

.lesson-hero-grid {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(320px, 420px);
  align-items: center;
  gap: 3rem;
}

.lesson-hero-copy {
  min-width: 0;
}

.lesson-kicker {
  position: static;
  max-width: 100%;
  margin-bottom: 1.15rem;
}

.lesson-hero h1 {
  max-width: 100%;
  margin: 0 0 1rem;
  font-size: clamp(2.85rem, 6vw, 5.8rem);
  line-height: 0.98;
  overflow-wrap: anywhere;
}

.lesson-hero h1 em {
  color: var(--accent);
  font-style: normal;
}

.lesson-hero .lesson-lede {
  max-width: 760px;
}

.lesson-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem;
}

.lesson-meta span {
  padding: 0.65rem 0.8rem;
  border: 1px solid var(--line);
  border-radius: var(--radius-small);
  background: var(--glass);
  color: var(--muted);
}

.lesson-meta b {
  display: block;
  color: var(--text);
}

.hero-topic-art {
  position: relative;
  display: grid;
  min-height: 410px;
  place-items: center;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 34px;
  background:
    linear-gradient(color-mix(in srgb, var(--text) 4%, transparent) 1px, transparent 1px),
    linear-gradient(90deg, color-mix(in srgb, var(--text) 4%, transparent) 1px, transparent 1px),
    linear-gradient(145deg, var(--glass-strong), color-mix(in srgb, var(--panel) 35%, transparent));
  background-size: 28px 28px, 28px 28px, auto;
  box-shadow: var(--shadow);
}

.hero-topic-art::before,
.hero-topic-art::after {
  position: absolute;
  border: 1px solid var(--line);
  border-radius: 50%;
  content: "";
}

.hero-topic-art::before {
  width: 300px;
  height: 300px;
}

.hero-topic-art::after {
  width: 220px;
  height: 220px;
  transform: rotate(32deg);
}

.hero-topic-symbol {
  position: relative;
  z-index: 2;
  display: grid;
  width: 180px;
  height: 180px;
  place-items: center;
  border: 1px solid color-mix(in srgb, var(--accent) 48%, var(--line));
  border-radius: 32px;
  background: linear-gradient(135deg, color-mix(in srgb, var(--accent) 22%, transparent), color-mix(in srgb, var(--accent-3) 12%, transparent));
  color: var(--accent);
  box-shadow: 0 24px 70px color-mix(in srgb, var(--accent) 18%, transparent);
  font-family: var(--display-font);
  font-size: clamp(3.5rem, 8vw, 6.6rem);
  font-weight: 800;
  transform: rotate(-4deg);
}

.hero-topic-art .art-caption {
  position: absolute;
  right: 20px;
  bottom: 18px;
  left: 20px;
  z-index: 3;
  margin: 0;
  color: var(--muted);
  font-size: 0.9rem;
  text-align: center;
}

.lesson-section {
  padding: 70px 0;
  border-bottom: 1px solid color-mix(in srgb, var(--text) 7%, transparent);
}

.lesson-two-column,
.theorem-layout,
.challenge-layout,
.application-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(280px, 0.85fr);
  align-items: start;
  gap: 2rem;
}

.lesson-copy p,
.content-copy p,
.application-copy p {
  color: var(--muted);
  font-size: 1.07rem;
}

.lesson-copy strong,
.content-copy strong,
.application-copy strong {
  color: var(--text);
}

.think-prompt,
.lab-note,
.proof-note {
  padding: 1rem;
  border-left: 4px solid var(--accent);
  border-radius: 0 var(--radius-small) var(--radius-small) 0;
  background: color-mix(in srgb, var(--accent) 9%, transparent);
}

.think-prompt span,
.lab-eyebrow,
.result-kicker,
.definition-label,
.application-label,
.assessment-label {
  color: var(--accent-2);
  font-size: 0.75rem;
  font-weight: 900;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.concept-card,
.mystery-visual {
  padding: 1.25rem;
}

.mystery-visual-stage {
  position: relative;
  display: grid;
  min-height: 240px;
  place-items: center;
  overflow: hidden;
  margin-bottom: 1rem;
  border: 1px solid var(--line);
  border-radius: 22px;
  background: color-mix(in srgb, var(--panel) 72%, transparent);
}

.mystery-symbol {
  color: var(--accent);
  font-family: var(--display-font);
  font-size: clamp(3.5rem, 9vw, 7rem);
  font-weight: 800;
}

.mystery-orbit {
  position: absolute;
  width: 190px;
  height: 190px;
  border: 1px solid var(--line);
  border-radius: 50%;
}

.mystery-orbit:nth-child(2) {
  width: 130px;
  height: 230px;
  transform: rotate(38deg);
}

.lesson-heading {
  margin-bottom: 1.35rem;
}

.narrow-heading {
  max-width: 840px;
  margin-inline: auto;
  text-align: center;
}

.lab-shell {
  padding: 1.2rem;
}

.lab-layout {
  display: grid;
  grid-template-columns: minmax(0, 1.25fr) minmax(260px, 0.75fr);
  gap: 1.2rem;
}

.lab-visual,
.lab-controls,
.lab-output {
  min-width: 0;
}

.lab-canvas-wrap,
.svg-stage,
.visual-stage {
  position: relative;
  min-height: 390px;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 24px;
  background:
    linear-gradient(color-mix(in srgb, var(--text) 3.8%, transparent) 1px, transparent 1px),
    linear-gradient(90deg, color-mix(in srgb, var(--text) 3.8%, transparent) 1px, transparent 1px),
    color-mix(in srgb, var(--panel) 76%, transparent);
  background-size: 28px 28px, 28px 28px, auto;
}

.lab-canvas-wrap canvas {
  width: 100%;
  min-height: 390px;
}

.control-group {
  padding: 1rem;
  margin-bottom: 1rem;
  border: 1px solid var(--line);
  border-radius: 22px;
  background: var(--glass);
}

.control-heading {
  display: flex;
  align-items: start;
  justify-content: space-between;
  gap: 1rem;
}

.control-heading strong,
.control-heading span {
  color: var(--accent);
}

.control-heading small {
  display: block;
  color: var(--muted);
}

.control-row {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.75rem;
  margin-top: 0.8rem;
}

.control-stack {
  display: grid;
  gap: 0.75rem;
}

.control-field {
  display: grid;
  gap: 0.32rem;
}

.control-field > span,
.control-field label,
.range-label {
  color: var(--soft);
  font-size: 0.86rem;
  font-weight: 800;
}

.control-field input[type="number"],
.control-field input[type="text"],
.control-field select,
.control-field textarea,
.lab-controls select,
.lab-controls input[type="number"],
.lab-controls input[type="text"] {
  width: 100%;
  min-height: 44px;
  padding: 0.68rem 0.75rem;
  border: 1px solid var(--line);
  border-radius: 13px;
  outline: none;
  background: color-mix(in srgb, var(--bg-2) 82%, transparent);
  color: var(--text);
}

input[type="range"] {
  width: 100%;
  accent-color: var(--accent);
}

.range-value {
  color: var(--accent);
  font-weight: 900;
}

.preset-buttons,
.segmented-control {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
  margin-top: 0.75rem;
}

.preset-buttons button,
.segmented-control button,
.lab-action {
  min-height: 42px;
  padding: 0.58rem 0.72rem;
  border: 1px solid var(--line);
  border-radius: 13px;
  background: var(--glass);
  color: var(--text);
  cursor: pointer;
}

.preset-buttons button:hover,
.segmented-control button:hover,
.lab-action:hover,
.preset-buttons button.active,
.segmented-control button.active {
  border-color: var(--accent);
}

.lab-stat-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.65rem;
  margin-top: 0.8rem;
}

.lab-stat {
  padding: 0.75rem;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: color-mix(in srgb, var(--panel) 64%, transparent);
}

.lab-stat span,
.lab-stat small {
  display: block;
  color: var(--muted);
  font-size: 0.78rem;
}

.lab-stat strong {
  display: block;
  margin-top: 0.18rem;
  color: var(--accent);
  font-size: 1.18rem;
}

.lab-explanation {
  margin-top: 0.9rem;
  padding: 0.9rem;
  border: 1px solid var(--line);
  border-radius: 17px;
  background: color-mix(in srgb, var(--panel) 64%, transparent);
  color: var(--muted);
}

.definition-card {
  max-width: 920px;
  margin: 0 auto 1rem;
  padding: 1.45rem;
  text-align: center;
}

.definition-card p {
  font-size: 1.1rem;
}

.definition-expression {
  margin-top: 0.6rem;
  color: var(--accent);
  font-family: var(--display-font);
  font-size: clamp(1.65rem, 4vw, 2.55rem);
  font-weight: 850;
  overflow-wrap: anywhere;
}

.concept-grid,
.application-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
  margin-top: 1rem;
}

.concept-grid article,
.application-grid article {
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 21px;
  background: var(--glass);
}

.concept-grid .concept-symbol,
.application-grid .concept-symbol {
  display: inline-grid;
  width: 42px;
  height: 42px;
  place-items: center;
  margin-bottom: 0.65rem;
  border-radius: 13px;
  background: color-mix(in srgb, var(--accent-3) 14%, transparent);
  color: var(--accent-3);
  font-weight: 900;
}

.theorem-card {
  padding: 1.25rem;
}

.theorem-card > span {
  color: var(--accent-2);
  font-size: 0.77rem;
  font-weight: 900;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.theorem-card > p {
  margin-top: 0.5rem;
  color: var(--text);
  font-size: 1.24rem;
}

.theorem-card small {
  color: var(--muted);
}

.proof-steps {
  padding: 0;
  margin: 1rem 0;
  list-style: none;
}

.proof-steps li {
  display: flex;
  gap: 1rem;
  margin: 0.85rem 0;
}

.proof-steps li > span {
  display: grid;
  width: 36px;
  height: 36px;
  flex: 0 0 auto;
  place-items: center;
  border-radius: 50%;
  background: var(--accent);
  color: #161006;
  font-weight: 900;
}

.proof-steps p {
  margin: 0;
  color: var(--muted);
}

.formula-box {
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 20px;
  background: color-mix(in srgb, var(--panel) 70%, transparent);
  color: var(--accent);
  font-family: var(--display-font);
  font-size: clamp(1.25rem, 3vw, 2rem);
  text-align: center;
  overflow-wrap: anywhere;
}

.application-callout {
  padding: 1.2rem;
  border: 1px solid var(--line);
  border-radius: 24px;
  background: linear-gradient(145deg, color-mix(in srgb, var(--accent) 11%, transparent), color-mix(in srgb, var(--accent-3) 7%, transparent));
}

.application-callout h3 {
  color: var(--accent);
}

.connection-card-grid {
  grid-template-columns: repeat(4, 1fr);
}

.connection-card-grid a {
  display: block;
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 22px;
  background: var(--glass);
}

.connection-card-grid a:hover {
  border-color: var(--accent);
}

.connection-card-grid span {
  color: var(--accent-2);
  font-size: 0.75rem;
  font-weight: 900;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.connection-card-grid b {
  color: var(--accent);
}

.lesson-ending {
  margin-top: 3rem;
  padding: 2rem;
  border: 1px solid var(--line);
  border-radius: 32px;
  background: linear-gradient(145deg, color-mix(in srgb, var(--accent) 12%, transparent), color-mix(in srgb, var(--accent-3) 7%, transparent));
  text-align: center;
}

.lesson-ending > span {
  color: var(--accent-2);
  font-size: 0.8rem;
  font-weight: 900;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

/* Assessment */
.assessment-shell {
  display: grid;
  grid-template-columns: minmax(0, 0.75fr) minmax(0, 1.25fr);
  gap: 1.2rem;
  align-items: start;
}

.assessment-intro {
  position: sticky;
  top: 150px;
  padding: 1.25rem;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--glass);
}

.assessment-intro ul {
  padding-left: 1.15rem;
  color: var(--muted);
}

.assessment-privacy {
  padding: 0.8rem;
  border-left: 3px solid var(--accent-2);
  border-radius: 0 12px 12px 0;
  background: color-mix(in srgb, var(--accent-2) 8%, transparent);
  color: var(--muted);
  font-size: 0.9rem;
}

.assessment-card {
  min-height: 430px;
  padding: 1.25rem;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: linear-gradient(145deg, var(--glass-strong), color-mix(in srgb, var(--panel) 46%, transparent));
  box-shadow: var(--shadow-soft);
}

.assessment-progress-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 0.8rem;
  color: var(--muted);
  font-size: 0.88rem;
}

.assessment-progress {
  height: 8px;
  margin-bottom: 1.2rem;
  overflow: hidden;
  border-radius: 999px;
  background: color-mix(in srgb, var(--text) 10%, transparent);
}

.assessment-progress > span {
  display: block;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  transition: width 0.25s ease;
}

.assessment-question {
  font-size: clamp(1.22rem, 2.5vw, 1.65rem);
}

.assessment-options {
  display: grid;
  gap: 0.7rem;
  margin-top: 1rem;
}

.assessment-option {
  display: grid;
  grid-template-columns: 36px minmax(0, 1fr);
  align-items: center;
  gap: 0.75rem;
  min-height: 58px;
  padding: 0.72rem;
  border: 1px solid var(--line);
  border-radius: 17px;
  background: var(--glass);
  color: var(--text);
  text-align: left;
  cursor: pointer;
}

.assessment-option:hover:not(:disabled) {
  border-color: var(--accent);
}

.assessment-option .option-letter {
  display: grid;
  width: 34px;
  height: 34px;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: 50%;
  color: var(--accent);
  font-weight: 900;
}

.assessment-option.correct {
  border-color: var(--success);
  background: color-mix(in srgb, var(--success) 11%, transparent);
}

.assessment-option.incorrect {
  border-color: var(--danger);
  background: color-mix(in srgb, var(--danger) 10%, transparent);
}

.assessment-option:disabled {
  cursor: default;
}

.assessment-feedback {
  min-height: 74px;
  margin-top: 1rem;
  padding: 0.9rem;
  border: 1px solid var(--line);
  border-radius: 17px;
  background: color-mix(in srgb, var(--panel) 68%, transparent);
  color: var(--muted);
}

.assessment-feedback strong {
  color: var(--text);
}

.assessment-actions {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.7rem;
  margin-top: 1rem;
}

.assessment-summary {
  display: grid;
  min-height: 380px;
  place-items: center;
  text-align: center;
}

.assessment-summary-icon {
  display: grid;
  width: 86px;
  height: 86px;
  place-items: center;
  margin: 0 auto 1rem;
  border-radius: 50%;
  background: color-mix(in srgb, var(--accent) 18%, transparent);
  color: var(--accent);
  font-size: 2.4rem;
}

/* Generic tables and data displays */
.data-table-wrap {
  overflow-x: auto;
  border: 1px solid var(--line);
  border-radius: 18px;
}

.data-table {
  width: 100%;
  border-collapse: collapse;
  min-width: 520px;
}

.data-table th,
.data-table td {
  padding: 0.62rem;
  border-bottom: 1px solid var(--line);
  text-align: center;
}

.data-table th {
  background: color-mix(in srgb, var(--accent) 9%, transparent);
  color: var(--accent);
}

.data-table td {
  color: var(--soft);
}

.data-table tr:last-child td {
  border-bottom: 0;
}

.matrix-display {
  display: inline-grid;
  grid-template-columns: repeat(2, minmax(56px, auto));
  gap: 0.25rem 0.75rem;
  padding: 0.7rem 1rem;
  border-left: 2px solid var(--accent);
  border-right: 2px solid var(--accent);
  color: var(--accent);
  font-variant-numeric: tabular-nums;
  font-weight: 900;
}

.sequence-strip,
.coefficient-strip {
  display: grid;
  grid-template-columns: repeat(8, minmax(34px, 1fr));
  gap: 0.4rem;
  margin-top: 0.8rem;
}

.sequence-strip span,
.coefficient-strip span {
  display: grid;
  min-height: 50px;
  place-items: center;
  padding: 0.3rem;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--glass);
  color: var(--soft);
  font-size: 0.82rem;
  font-variant-numeric: tabular-nums;
}

.coefficient-strip span.active {
  border-color: var(--accent);
  color: var(--accent);
}

/* Proof laboratory */
.proof-grid {
  display: grid;
  grid-template-columns: repeat(var(--proof-n, 5), minmax(12px, 1fr));
  width: min(100%, 420px);
  aspect-ratio: 1;
  gap: 3px;
  padding: 12px;
}

.proof-tile {
  border-radius: 4px;
  background: color-mix(in srgb, var(--accent) 76%, var(--accent-3));
}

.proof-counterexample {
  display: grid;
  min-height: 250px;
  place-items: center;
  padding: 1rem;
  text-align: center;
}

.proof-counterexample strong {
  color: var(--accent);
  font-size: clamp(2rem, 6vw, 4rem);
}

/* Euclidean algorithm */
.euclid-steps {
  display: grid;
  gap: 0.55rem;
  padding: 1rem;
}

.euclid-step {
  display: grid;
  grid-template-columns: 42px minmax(0, 1fr);
  align-items: center;
  gap: 0.75rem;
  padding: 0.65rem;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: var(--glass);
}

.euclid-step span {
  display: grid;
  width: 38px;
  height: 38px;
  place-items: center;
  border-radius: 50%;
  background: color-mix(in srgb, var(--accent) 14%, transparent);
  color: var(--accent);
  font-weight: 900;
}

/* Alignment table */
.alignment-table {
  border-collapse: collapse;
  margin: 0 auto;
  font-variant-numeric: tabular-nums;
}

.alignment-table th,
.alignment-table td {
  min-width: 44px;
  height: 44px;
  padding: 0.3rem;
  border: 1px solid var(--line);
  text-align: center;
}

.alignment-table th {
  color: var(--accent);
}

.alignment-table td.trace {
  background: color-mix(in srgb, var(--accent-2) 14%, transparent);
  color: var(--accent-2);
  font-weight: 900;
}

.alignment-result {
  display: grid;
  gap: 0.25rem;
  margin-top: 0.8rem;
  padding: 0.8rem;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: var(--glass);
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  letter-spacing: 0.14em;
  overflow-x: auto;
}

/* Abstract algebra pilot styles */
.hero-symmetry-art {
  position: relative;
  display: grid;
  height: 420px;
  place-items: center;
}

.hero-ring {
  position: absolute;
  border: 1px solid var(--line);
  border-radius: 50%;
}

.ring-a { width: 360px; height: 360px; }
.ring-b { width: 250px; height: 250px; transform: rotate(25deg); }

.hero-square {
  position: absolute;
  width: 190px;
  height: 190px;
  border: 2px solid var(--line);
  border-radius: 22px;
  background: var(--glass);
}

.square-back { transform: rotate(45deg); border-color: color-mix(in srgb, var(--accent-3) 38%, transparent); }
.square-middle { transform: rotate(22deg); border-color: color-mix(in srgb, var(--accent-2) 38%, transparent); }
.square-front {
  border-color: color-mix(in srgb, var(--accent) 58%, transparent);
  background: linear-gradient(135deg, color-mix(in srgb, var(--accent) 22%, transparent), color-mix(in srgb, var(--accent-3) 10%, transparent));
  box-shadow: var(--shadow);
}

.square-front > span {
  position: absolute;
  display: grid;
  width: 34px;
  height: 34px;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: 50%;
  background: var(--panel);
  font-weight: 900;
}

.square-front span:nth-child(1) { top: -17px; left: -17px; }
.square-front span:nth-child(2) { top: -17px; right: -17px; }
.square-front span:nth-child(3) { right: -17px; bottom: -17px; }
.square-front span:nth-child(4) { bottom: -17px; left: -17px; }

.hero-motif {
  position: absolute;
  inset: 42px;
  border: 1px solid var(--line);
  border-radius: 50%;
}

.hero-symmetry-art > p {
  position: absolute;
  bottom: 10px;
  color: var(--accent);
  font-size: 2rem;
  font-weight: 900;
}

.mini-square-scene {
  position: relative;
  display: grid;
  height: 220px;
  place-items: center;
}

.mini-square {
  position: absolute;
  width: 130px;
  height: 130px;
  border: 2px solid var(--line);
  border-radius: 18px;
}

.mini-original { border-color: var(--line-strong); }
.mini-turned {
  border-color: var(--accent);
  background: color-mix(in srgb, var(--accent) 9%, transparent);
  transform: rotate(90deg);
}

.mini-square-scene > span {
  position: absolute;
  top: 20%;
  right: 18%;
  color: var(--accent);
  font-weight: 900;
}

.symmetry-lab {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(280px, 0.82fr);
  gap: 1.2rem;
}

.lab-toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 1rem;
}

.lab-toolbar code,
.result-symbol {
  display: grid;
  width: 54px;
  height: 54px;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: 17px;
  background: var(--panel);
  color: var(--accent);
  font-size: 1.2rem;
  font-weight: 900;
}

.square-stage {
  position: relative;
  display: grid;
  min-height: 430px;
  place-items: center;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 24px;
  background:
    linear-gradient(color-mix(in srgb, var(--text) 3.5%, transparent) 1px, transparent 1px),
    linear-gradient(90deg, color-mix(in srgb, var(--text) 3.5%, transparent) 1px, transparent 1px),
    color-mix(in srgb, var(--panel) 75%, transparent);
  background-size: 28px 28px;
}

.square-object {
  position: relative;
  width: 220px;
  height: 220px;
  border: 3px solid color-mix(in srgb, var(--accent) 66%, transparent);
  border-radius: 24px;
  background: linear-gradient(135deg, color-mix(in srgb, var(--accent) 12%, transparent), color-mix(in srgb, var(--accent-3) 10%, transparent));
  transition: transform 0.38s ease;
}

.vertex {
  position: absolute;
  display: grid;
  width: 42px;
  height: 42px;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: 50%;
  background: var(--panel);
  color: var(--text);
  font-weight: 900;
  transition: 0.38s ease;
}

.vertex-0 { top: -21px; left: -21px; }
.vertex-1 { top: -21px; right: -21px; }
.vertex-2 { right: -21px; bottom: -21px; }
.vertex-3 { bottom: -21px; left: -21px; }

.square-motif {
  position: absolute;
  inset: 55px;
  border: 1px solid var(--line);
  border-radius: 50%;
}

.square-motif span {
  position: absolute;
  top: 30px;
  left: 18px;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--accent-3);
}

.square-motif i {
  position: absolute;
  right: 18px;
  bottom: 34px;
  width: 45px;
  height: 8px;
  border-radius: 999px;
  background: var(--accent-4);
}

.axis-label {
  position: absolute;
  color: color-mix(in srgb, var(--muted) 45%, transparent);
  font-weight: 900;
  text-transform: uppercase;
}

.axis-top { top: 15px; }
.axis-right { right: 16px; writing-mode: vertical-rl; }

.lab-history {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  margin-top: 0.8rem;
  color: var(--muted);
}

.lab-history code {
  padding: 0.3rem 0.5rem;
  border-radius: 10px;
  background: var(--glass);
}

.transformation-buttons {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.65rem;
  margin-top: 0.8rem;
}

.transformation-buttons button,
.challenge-options button {
  padding: 0.8rem;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: var(--glass);
  color: var(--text);
  text-align: left;
  cursor: pointer;
}

.transformation-buttons button:hover,
.challenge-options button:hover {
  border-color: var(--accent);
}

.transformation-buttons span {
  color: var(--accent);
  font-size: 1.4rem;
}

.transformation-buttons strong,
.transformation-buttons small {
  display: block;
}

.transformation-buttons small {
  color: var(--muted);
}

.reset-lab {
  width: 100%;
  margin-top: 0.7rem;
}

.axiom-grid {
  grid-template-columns: repeat(4, 1fr);
}

.axiom-grid article {
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 22px;
  background: var(--glass);
}

.axiom-symbol {
  color: var(--accent);
  font-size: 1.5rem;
}

.axiom-grid code,
.order-comparison code {
  color: var(--accent-3);
  font-weight: 900;
}

.concept-note {
  margin-top: 1rem;
  padding: 1.1rem;
}

.concept-note > span {
  color: var(--accent-2);
  font-size: 0.75rem;
  font-weight: 900;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.composition-controls {
  display: flex;
  align-items: end;
  gap: 0.7rem;
}

.composition-controls label {
  flex: 1;
}

.composition-controls label > span {
  display: block;
  margin-bottom: 0.35rem;
  color: var(--accent-2);
  font-size: 0.76rem;
  font-weight: 900;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.composition-controls select {
  width: 100%;
  padding: 0.8rem;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: var(--bg-2);
  color: var(--text);
}

.swap-button {
  width: 48px;
  height: 48px;
  border: 1px solid var(--line);
  border-radius: 50%;
  background: var(--glass);
  color: var(--accent);
  font-size: 1.25rem;
  cursor: pointer;
}

.composition-result {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  margin-top: 1rem;
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 22px;
  background: color-mix(in srgb, var(--bg) 38%, transparent);
}

.composition-result strong {
  color: var(--accent);
  font-size: 1.5rem;
}

.notation-note {
  margin: 1rem 0;
  padding: 1rem;
}

.table-disclosure {
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 22px;
  background: var(--glass);
}

.table-disclosure summary {
  color: var(--accent);
  cursor: pointer;
  font-weight: 900;
}

.table-scroll {
  overflow: auto;
}

.composition-table {
  width: 100%;
  margin-top: 1rem;
  border-collapse: collapse;
}

.composition-table th,
.composition-table td {
  padding: 0.55rem;
  border: 1px solid var(--line);
  text-align: center;
}

.composition-table th {
  background: color-mix(in srgb, var(--accent) 8%, transparent);
  color: var(--accent);
}

.composition-table td {
  color: var(--soft);
}

.counting-visual {
  padding: 1.2rem;
  border: 1px solid var(--line);
  border-radius: 28px;
  background: var(--glass);
  text-align: center;
}

.four-choice-grid {
  display: grid;
  grid-template-columns: repeat(2, 80px);
  justify-content: center;
  gap: 0.5rem;
}

.four-choice-grid i,
.two-choice-grid i {
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: var(--glass);
  color: var(--accent);
  font-weight: 900;
}

.two-choice-grid {
  display: flex;
  justify-content: center;
  gap: 0.6rem;
}

.counting-times,
.counting-equals {
  margin: 0.8rem;
  color: var(--accent);
  font-size: 2rem;
  font-weight: 900;
}

.order-comparison {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 1rem;
}

.order-comparison article {
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 24px;
  background: var(--glass);
  text-align: center;
}

.sequence-symbols {
  margin: 0.7rem 0;
  font-size: 1.4rem;
}

.not-equal {
  color: var(--accent-4);
  font-size: 2.4rem;
  font-weight: 900;
}

.challenge-options {
  display: grid;
  gap: 0.7rem;
}

.challenge-options button.correct {
  border-color: var(--success);
  background: color-mix(in srgb, var(--success) 12%, transparent);
}

.challenge-options button.incorrect {
  border-color: var(--danger);
  background: color-mix(in srgb, var(--danger) 10%, transparent);
}

.challenge-options code {
  color: var(--accent);
  font-size: 1.25rem;
}

.challenge-options span {
  display: block;
  color: var(--muted);
}

.challenge-feedback {
  margin-top: 1rem;
  padding: 1rem;
  border-radius: 18px;
  background: var(--glass);
  color: var(--muted);
}

.solution-disclosure {
  margin-top: 0.8rem;
}

@media (max-width: 1040px) {
  .lesson-hero-grid,
  .lesson-two-column,
  .theorem-layout,
  .challenge-layout,
  .application-layout,
  .lab-layout,
  .symmetry-lab,
  .assessment-shell {
    grid-template-columns: 1fr;
  }

  .concept-grid,
  .application-grid,
  .axiom-grid,
  .connection-card-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .hero-topic-art,
  .hero-symmetry-art {
    min-height: 330px;
    height: 330px;
  }

  .assessment-intro {
    position: static;
  }
}

@media (max-width: 700px) {
  .module-header-inner {
    flex-wrap: wrap;
    justify-content: center;
  }

  .module-header .brand {
    order: -1;
    width: 100%;
    justify-content: center;
  }

  .lesson-rail {
    top: 113px;
  }

  .lesson-hero {
    padding: 48px 0;
  }

  .lesson-hero h1 {
    font-size: clamp(2.55rem, 13vw, 4.2rem);
    line-height: 1.02;
  }

  .lesson-section {
    padding: 50px 0;
  }

  .concept-grid,
  .application-grid,
  .axiom-grid,
  .connection-card-grid,
  .control-row,
  .lab-stat-grid {
    grid-template-columns: 1fr;
  }

  .composition-controls {
    flex-direction: column;
    align-items: stretch;
  }

  .swap-button {
    align-self: center;
  }

  .order-comparison {
    grid-template-columns: 1fr;
  }

  .square-stage {
    min-height: 340px;
  }

  .square-object {
    width: 180px;
    height: 180px;
  }

  .transformation-buttons {
    grid-template-columns: 1fr;
  }

  .lab-canvas-wrap,
  .lab-canvas-wrap canvas,
  .svg-stage,
  .visual-stage {
    min-height: 330px;
  }

  .sequence-strip,
  .coefficient-strip {
    grid-template-columns: repeat(4, minmax(42px, 1fr));
  }

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

@media (max-width: 430px) {
  .lesson-rail {
    top: 148px;
  }

  .hero-topic-art,
  .hero-symmetry-art {
    min-height: 280px;
    height: 280px;
  }

  .hero-topic-symbol {
    width: 145px;
    height: 145px;
  }
}