:root {
  --font:16px;
  --bg:#f4f8f8;
  --paper:#fff;
  --ink:#12333a;
  --muted:#627c82;
  --line:#d4e4e7;
  --teal:#078b98;
  --teal2:#13aaa8;
  --orange:#ed6a2f;
  --soft:#eaf4f5;
  --code:#0d1d21;
  --shadow:0 22px 65px rgba(17,52,58,.13)
}
html[data-theme=dark] {
  --bg:#061012;
  --paper:#0d1b1f;
  --ink:#e8f6f5;
  --muted:#91aaae;
  --line:#20383d;
  --teal:#32bec8;
  --teal2:#50d3cc;
  --orange:#ff8750;
  --soft:#13272b;
  --code:#071113;
  --shadow:0 22px 65px rgba(0,0,0,.42)
}
* {
  box-sizing:border-box
}
html {
  scroll-behavior:smooth
}
body {
  margin:0;
  background:var(--bg);
  color:var(--ink);
  font:var(--font)/1.63 Inter,Segoe UI,Arial,sans-serif
}
.reading-bar {
  position:fixed;
  z-index:100;
  top:0;
  left:0;
  width:0;
  height:3px;
  background:linear-gradient(90deg,var(--orange),var(--teal))
}
.topbar {
  height:72px;
  display:flex;
  justify-content:space-between;
  align-items:center;
  padding:0 22px;
  border-bottom:1px solid var(--line);
  background:color-mix(in srgb,var(--paper) 92%,transparent);
  backdrop-filter:blur(16px);
  position:sticky;
  top:0;
  z-index:50
}
.brand {
  display:flex;
  gap:12px;
  align-items:center;
  color:var(--ink);
  text-decoration:none;
  letter-spacing:.08em
}
.brand-wave {
  display:grid;
  place-items:center;
  width:42px;
  height:42px;
  border-radius:13px;
  background:linear-gradient(135deg,var(--orange),var(--teal));
  color:#fff;
  font-size:27px
}
.brand span:last-child {
  display:flex;
  flex-direction:column
}
.brand small {
  font-size:.72rem;
  color:var(--muted);
  letter-spacing:0
}
.top-actions {
  display:flex;
  align-items:center;
  gap:7px
}
.top-btn,.font-box,.menu-btn {
  border:1px solid var(--line);
  background:var(--paper);
  color:var(--ink);
  border-radius:10px;
  padding:8px 11px;
  text-decoration:none;
  font:inherit;
  cursor:pointer;
  white-space:nowrap
}
.font-box {
  display:flex;
  padding:0;
  overflow:hidden
}
.font-box button {
  border:0;
  background:none;
  color:inherit;
  padding:8px;
  cursor:pointer
}
.font-box span {
  min-width:28px;
  text-align:center;
  padding:8px 0;
  color:var(--muted)
}
.menu-btn {
  display:none
}
.page-shell {
  display:grid;
  grid-template-columns:300px minmax(0,1fr);
  max-width:1720px;
  margin:auto
}
.side-nav {
  position:sticky;
  top:72px;
  height:calc(100vh - 72px);
  border-right:1px solid var(--line);
  padding:34px 24px;
  overflow:auto
}
.nav-head {
  font-size:.7rem;
  font-weight:900;
  letter-spacing:.18em;
  color:var(--muted);
  margin:0 12px 14px
}
.side-nav nav {
  display:flex;
  flex-direction:column
}
.side-nav nav a {
  color:var(--muted);
  text-decoration:none;
  border-left:3px solid transparent;
  padding:7px 12px;
  border-radius:0 10px 10px 0;
  font-size:.86rem
}
.side-nav nav a:hover,.side-nav nav a.active {
  color:var(--ink);
  background:var(--soft);
  border-left-color:var(--teal)
}
.nav-note {
  margin:22px 12px;
  padding:12px;
  background:var(--soft);
  border-radius:10px;
  color:var(--muted);
  font-size:.76rem
}
main {
  min-width:0
}
.lesson-section {
  max-width:1280px;
  margin:auto;
  padding:85px 5vw;
  border-bottom:1px solid var(--line);
  scroll-margin-top:82px
}
.hero {
  max-width:none;
  min-height:660px;
  display:grid;
  grid-template-columns:minmax(0,1fr) minmax(420px,.8fr);
  align-items:center;
  gap:70px
}
.kicker {
  font-size:.75rem;
  font-weight:900;
  letter-spacing:.19em;
  color:var(--teal);
  margin-bottom:15px
}
.hero h1 {
  font-size:clamp(3.2rem,6vw,6.5rem);
  line-height:.92;
  letter-spacing:-.06em;
  margin:0;
  max-width:800px
}
.lead {
  font-size:1.18rem;
  color:var(--muted);
  max-width:770px
}
.hero-actions,.finish-card>div {
  display:flex;
  gap:10px;
  flex-wrap:wrap;
  margin-top:25px
}
.primary-link,.secondary-link {
  display:inline-flex;
  align-items:center;
  padding:12px 17px;
  border-radius:11px;
  text-decoration:none;
  font-weight:750
}
.primary-link {
  background:var(--teal);
  color:#fff
}
.secondary-link {
  border:1px solid var(--line);
  color:var(--ink);
  background:var(--paper)
}
.hero-array {
  height:500px;
  position:relative;
  border:1px solid var(--line);
  border-radius:30px;
  background:radial-gradient(circle at 75% 18%,rgba(41,205,204,.28),transparent 38%),linear-gradient(145deg,var(--paper),var(--soft));
  box-shadow:var(--shadow);
  overflow:hidden
}
.array-chip {
  position:absolute;
  padding:15px 17px;
  border:1px solid var(--line);
  border-radius:14px;
  background:var(--paper);
  box-shadow:0 15px 35px rgba(22,59,64,.14)
}
.array-chip b {
  display:block;
  color:var(--orange);
  font-size:.72rem
}
.array-chip span {
  font:700 1rem/1.6 ui-monospace,monospace
}
.array-chip.scalar {
  left:9%;
  top:13%;
  transform:rotate(-4deg)
}
.array-chip.vector {
  right:7%;
  top:10%;
  transform:rotate(3deg)
}
.array-chip.matrix {
  left:30%;
  top:32%;
  transform:rotate(-1deg)
}
.hero-array svg {
  position:absolute;
  left:4%;
  right:4%;
  bottom:5%;
  width:92%;
  height:43%
}
.hero-array svg path {
  fill:none;
  stroke:var(--teal2);
  stroke-width:7;
  stroke-linecap:round
}
.hero-array svg circle {
  fill:var(--orange);
  stroke:var(--paper);
  stroke-width:4
}
.section-head {
  display:grid;
  grid-template-columns:60px minmax(0,1fr) auto;
  gap:18px;
  align-items:start;
  margin-bottom:38px
}
.section-head>span {
  font:900 .78rem ui-monospace,monospace;
  color:var(--teal);
  border-top:3px solid var(--teal);
  padding-top:8px
}
.section-head h2 {
  font-size:clamp(2.1rem,4vw,4rem);
  line-height:1.02;
  letter-spacing:-.045em;
  margin:0
}
.section-head p {
  color:var(--muted);
  margin:9px 0 0;
  max-width:760px
}
.source-slide-btn {
  border:1px solid var(--line);
  background:var(--paper);
  color:var(--ink);
  border-radius:12px;
  padding:9px 11px;
  display:grid;
  grid-template-columns:auto auto;
  gap:0 7px;
  align-items:center;
  cursor:pointer
}
.source-slide-btn span:first-child {
  grid-row:1/3;
  color:var(--teal)
}
.source-slide-btn small {
  color:var(--muted);
  text-align:left
}
.split-story {
  display:grid;
  grid-template-columns:1fr 1fr;
  gap:22px
}
.named-box-demo,.shape-stage,.vector-builder,.spacing-demo,.matrix-index-demo,.diary-demo,.precedence-demo,.operation-demo,.broadcast-demo,.assembly-demo,.special-builder,.slice-demo,.flip-demo {
  border:1px solid var(--line);
  border-radius:22px;
  background:var(--paper);
  padding:25px;
  box-shadow:0 12px 35px rgba(21,56,61,.05)
}
.named-box-demo {
  display:flex;
  flex-direction:column;
  gap:13px
}
.named-box-demo input,.builder-controls input {
  border:2px solid var(--line);
  background:var(--bg);
  color:var(--ink);
  border-radius:10px;
  padding:13px;
  font:700 1.1rem ui-monospace,monospace
}
.name-rules {
  display:flex;
  flex-direction:column;
  gap:8px
}
.name-rules span {
  color:var(--muted);
  padding:7px 10px;
  border-radius:8px;
  background:var(--soft)
}
.name-rules span.ok {
  color:#14885d;
  background:rgba(26,179,117,.11)
}
.name-rules span.bad {
  color:#ce4c38;
  background:rgba(223,77,54,.11)
}
#nameVerdict {
  font-weight:800;
  font-size:1.1rem
}
.explain-stack {
  display:grid;
  gap:12px
}
.explain-stack article,.concept-grid article,.three-way article {
  border:1px solid var(--line);
  border-radius:15px;
  padding:17px;
  background:var(--paper)
}
.explain-stack h3,.three-way h3 {
  margin:0 0 7px
}
.explain-stack p,.concept-grid p,.three-way p {
  margin:0;
  color:var(--muted)
}
.concept-grid {
  display:grid;
  grid-template-columns:repeat(4,1fr);
  gap:12px;
  margin-top:18px
}
.concept-grid b {
  font-size:1.1rem
}
.shape-controls,.spacing-toolbar,.op-toolbar,.broadcast-controls,.assembly-controls,.special-controls,.slice-controls,.flip-controls {
  display:flex;
  gap:8px;
  flex-wrap:wrap
}
.shape-controls button,.spacing-toolbar button,.op-toolbar button,.broadcast-controls button,.assembly-controls button,.special-controls button,.slice-controls button,.flip-controls button,.diary-console button {
  border:1px solid var(--line);
  background:var(--soft);
  color:var(--ink);
  border-radius:9px;
  padding:8px 11px;
  cursor:pointer
}
.shape-controls button.active,.spacing-toolbar button.active,.op-toolbar button.active,.broadcast-controls button.active,.assembly-controls button.active,.special-controls button.active,.slice-controls button.active,.flip-controls button.active {
  background:var(--teal);
  color:#fff;
  border-color:var(--teal)
}
.shape-canvas {
  min-height:210px;
  display:grid;
  place-items:center;
  margin:20px 0
}
.shape-array {
  display:grid;
  gap:6px
}
.shape-array i,.vector-tiles i,.mini-matrix i,.matrix-grid button,.special-matrix i {
  display:grid;
  place-items:center;
  min-width:48px;
  min-height:48px;
  border:1px solid var(--line);
  background:var(--soft);
  border-radius:8px;
  font-style:normal;
  font-family:ui-monospace,monospace;
  font-weight:800
}
.shape-array.scalar {
  grid-template-columns:48px
}
.shape-array.row {
  grid-template-columns:repeat(4,48px)
}
.shape-array.column {
  grid-template-columns:48px
}
.shape-array.matrix {
  grid-template-columns:repeat(4,48px)
}
#shapeExplanation {
  text-align:center;
  color:var(--muted)
}
.builder-controls {
  display:grid;
  grid-template-columns:repeat(3,1fr);
  gap:13px
}
.builder-controls label {
  display:flex;
  flex-direction:column;
  gap:5px;
  color:var(--muted)
}
.colon-expression {
  display:flex;
  align-items:center;
  gap:20px;
  margin:25px 0
}
.colon-expression span {
  font:900 1.6rem ui-monospace,monospace;
  color:var(--orange)
}
.colon-expression small {
  color:var(--muted)
}
.vector-tiles {
  display:flex;
  gap:7px;
  flex-wrap:wrap
}
.vector-tiles i {
  animation:pop .25s both
}
@keyframes pop {
  from {
    transform:translateY(8px);
    opacity:0
  }
}
.three-way {
  display:grid;
  grid-template-columns:repeat(3,1fr);
  gap:12px;
  margin:18px 0
}
.three-way code,.precedence-demo code,.operation-demo>code {
  display:block;
  font:800 1rem ui-monospace,monospace;
  color:var(--orange);
  margin:9px 0
}
.spacing-toolbar {
  align-items:center
}
.spacing-toolbar label {
  display:flex;
  align-items:center;
  gap:8px;
  margin-right:auto
}
.number-line {
  height:125px;
  position:relative;
  margin:25px 0 5px;
  border-bottom:3px solid var(--line)
}
.number-line i {
  position:absolute;
  bottom:-8px;
  width:16px;
  height:16px;
  border-radius:50%;
  background:var(--teal);
  transform:translateX(-50%)
}
.number-line i b {
  position:absolute;
  bottom:22px;
  left:50%;
  transform:translateX(-50%);
  font-size:.65rem;
  color:var(--muted)
}
.gap-bars {
  height:110px;
  display:flex;
  align-items:end;
  gap:8px
}
.gap-bars i {
  flex:1;
  background:linear-gradient(var(--teal2),var(--teal));
  border-radius:6px 6px 0 0;
  min-height:5px
}
.spacing-demo>p,.operation-demo>p,.broadcast-demo>p,.assembly-demo>p,.special-builder>p,.slice-demo>p,.flip-demo>p {
  color:var(--muted)
}
.matrix-index-demo {
  display:grid;
  grid-template-columns:auto 1fr;
  gap:35px;
  align-items:center
}
.matrix-labels.top {
  display:grid;
  grid-template-columns:repeat(3,58px);
  margin-left:32px
}
.matrix-labels.side {
  display:grid;
  grid-template-rows:repeat(4,58px);
  width:28px
}
.matrix-labels i {
  display:grid;
  place-items:center;
  color:var(--muted);
  font-style:normal
}
.matrix-with-rows {
  display:flex
}
.matrix-grid {
  display:grid;
  grid-template-columns:repeat(3,58px);
  gap:4px
}
.matrix-grid button {
  min-width:58px;
  min-height:58px;
  color:var(--ink);
  cursor:pointer
}
.matrix-grid button.active {
  background:var(--orange);
  color:#fff;
  border-color:var(--orange)
}
.index-readout code {
  font:900 1.5rem ui-monospace,monospace;
  color:var(--teal)
}
.index-readout strong {
  display:block;
  font-size:4rem;
  color:var(--orange);
  line-height:1
}
.index-readout p {
  color:var(--muted)
}
.diary-demo {
  display:grid;
  grid-template-columns:1fr 1fr;
  gap:15px
}
.diary-console,.diary-file {
  border:1px solid var(--line);
  border-radius:13px;
  overflow:hidden
}
.diary-console {
  padding:14px;
  background:var(--code);
  color:#d7f1ef
}
.diary-console pre,.diary-file pre {
  min-height:130px;
  white-space:pre-wrap;
  font:600 .9rem/1.6 ui-monospace,monospace
}
.diary-file>div {
  padding:9px 13px;
  background:var(--soft);
  font-weight:800
}
.diary-file pre {
  margin:0;
  padding:14px
}
.operator-strip {
  display:grid;
  grid-template-columns:repeat(6,1fr);
  gap:9px;
  margin-bottom:18px
}
.operator-strip span {
  border:1px solid var(--line);
  background:var(--paper);
  border-radius:13px;
  padding:12px;
  text-align:center;
  color:var(--muted)
}
.operator-strip b {
  display:block;
  font-size:1.7rem;
  color:var(--teal)
}
.precedence-demo code {
  font-size:1.3rem
}
.precedence-demo>div {
  display:flex;
  gap:8px;
  flex-wrap:wrap
}
.precedence-demo button {
  border:1px solid var(--line);
  background:var(--soft);
  color:var(--ink);
  border-radius:8px;
  padding:8px;
  cursor:pointer
}
.precedence-demo button.active {
  background:var(--teal);
  color:#fff
}
.precedence-demo strong {
  display:block;
  margin-top:18px;
  font:900 1.8rem ui-monospace,monospace;
  color:var(--orange)
}
.op-toolbar {
  align-items:center
}
.op-toolbar input {
  margin-left:auto
}
.op-matrices,.broadcast-stage,.slice-stage {
  display:flex;
  align-items:center;
  justify-content:center;
  gap:20px;
  margin:28px 0;
  flex-wrap:wrap
}
.op-matrices>div {
  text-align:center
}
.mini-matrix {
  display:grid;
  grid-template-columns:repeat(2,54px);
  gap:4px
}
.mini-matrix.three {
  grid-template-columns:repeat(3,48px)
}
.mini-matrix i.hi {
  background:var(--orange);
  color:#fff;
  border-color:var(--orange)
}
.op-symbol {
  font-size:2rem
}
.transpose-demo {
  display:flex;
  align-items:center;
  justify-content:center;
  gap:28px;
  margin:25px 0
}
.transpose-card {
  border:1px solid var(--line);
  border-radius:16px;
  padding:20px;
  background:var(--paper);
  min-width:210px
}
.transpose-card>span {
  font-family:ui-monospace,monospace;
  color:var(--muted)
}
.row-vector,.column-vector {
  display:flex;
  gap:5px;
  margin-top:12px
}
.column-vector {
  flex-direction:column;
  align-items:start;
  transition:.5s
}
.row-vector i,.column-vector i {
  width:47px;
  height:47px;
  display:grid;
  place-items:center;
  background:var(--soft);
  border:1px solid var(--line);
  border-radius:7px;
  font-style:normal;
  font-weight:800
}
.transpose-demo button {
  width:85px;
  height:85px;
  border-radius:50%;
  border:1px solid var(--line);
  background:var(--teal);
  color:#fff;
  cursor:pointer
}
.broadcast-stage>span,.slice-stage>span {
  font-size:2rem
}
.broadcast-addend {
  display:grid;
  gap:4px
}
.assembly-stage {
  min-height:240px;
  display:grid;
  place-items:center
}
.array-block {
  display:grid;
  gap:4px;
  position:relative
}
.array-block i {
  display:grid;
  place-items:center;
  min-width:45px;
  height:45px;
  border-radius:7px;
  background:var(--soft);
  border:1px solid var(--line);
  font-style:normal;
  font-family:ui-monospace,monospace
}
.assembly-group {
  display:flex;
  align-items:center;
  gap:22px
}
.assembly-group.vertical {
  flex-direction:column
}
.assembly-arrow {
  font-size:2rem;
  color:var(--teal)
}
.special-builder {
  margin-top:18px
}
.special-matrix {
  display:grid;
  gap:4px;
  justify-content:center;
  margin:25px
}
.slice-result-vector {
  display:flex;
  gap:4px
}
.slice-result-vector i {
  display:grid;
  place-items:center;
  width:48px;
  height:48px;
  background:var(--soft);
  border:1px solid var(--line);
  border-radius:7px;
  font-style:normal
}
.slice-result-matrix {
  display:grid;
  grid-template-columns:repeat(2,48px);
  gap:4px
}
.slice-result-matrix i {
  display:grid;
  place-items:center;
  height:48px;
  background:var(--soft);
  border:1px solid var(--line);
  border-radius:7px;
  font-style:normal
}
.flip-demo .mini-matrix {
  margin:25px auto
}
.summary-flow {
  display:flex;
  align-items:center;
  justify-content:center;
  gap:10px;
  flex-wrap:wrap
}
.summary-flow div {
  width:165px;
  min-height:120px;
  border:1px solid var(--line);
  border-radius:15px;
  background:var(--paper);
  padding:16px;
  text-align:center
}
.summary-flow b {
  width:34px;
  height:34px;
  margin:auto auto 10px;
  display:grid;
  place-items:center;
  border-radius:50%;
  background:var(--teal);
  color:#fff
}
.summary-flow i {
  font-style:normal;
  color:var(--teal);
  font-size:1.6rem
}
.finish-card {
  margin-top:35px;
  padding:35px;
  border-radius:22px;
  background:linear-gradient(135deg,var(--paper),var(--soft));
  border:1px solid var(--line)
}
.finish-card h3 {
  font-size:1.8rem;
  margin:0
}
.finish-card p {
  color:var(--muted)
}
/* Labs */
.matlab-lab {
  margin:25px 0;
  border-radius:22px;
  overflow:hidden;
  border:1px solid color-mix(in srgb,var(--teal) 45%,var(--line));
  background:var(--paper);
  box-shadow:var(--shadow)
}
.lab-header {
  display:flex;
  justify-content:space-between;
  gap:15px;
  align-items:center;
  padding:15px 17px;
  background:linear-gradient(90deg,#087b8b,#07969d);
  color:#fff
}
.lab-header h3 {
  margin:0
}
.lab-header small {
  opacity:.82
}
.lab-actions {
  display:flex;
  gap:7px;
  flex-wrap:wrap
}
.lab-actions button,.lab-collapse {
  border:1px solid rgba(255,255,255,.34);
  background:rgba(255,255,255,.12);
  color:#fff;
  border-radius:8px;
  padding:7px 10px;
  cursor:pointer
}
.lab-actions button:disabled {
  opacity:.45
}
.lab-body {
  display:flex;
  height:380px
}
.lab-pane {
  min-width:0;
  flex:1;
  display:flex;
  flex-direction:column
}
.lab-code-pane {
  flex-basis:50%;
  background:var(--code);
  color:#e0f4f2
}
.lab-result-pane {
  background:var(--paper)
}
.lab-pane-title {
  height:43px;
  border-bottom:1px solid var(--line);
  display:flex;
  align-items:center;
  justify-content:space-between;
  padding:0 14px;
  font-size:.76rem;
  letter-spacing:.08em
}
.lab-code-pane .lab-pane-title {
  border-color:#294046
}
.lab-mode-badge,.lab-status {
  padding:3px 8px;
  border-radius:999px;
  background:rgba(255,255,255,.08)
}
.lab-status.ok {
  color:#18aa7a
}
.lab-status.error {
  color:#e45544
}
.lab-editor-wrap {
  position:relative;
  flex:1
}
.lab-prompt {
  position:absolute;
  left:14px;
  top:15px;
  color:#65ddd6;
  font:800 .9rem ui-monospace,monospace;
  z-index:2
}
.lab-editor {
  width:100%;
  height:100%;
  resize:none;
  border:0;
  outline:0;
  background:transparent;
  color:#e7f6f5;
  padding:16px 18px;
  font:650 .93rem/1.65 ui-monospace,Consolas,monospace;
  tab-size:4
}
.matlab-lab.is-command-mode .lab-editor {
  padding-left:47px
}
.lab-output {
  flex:1;
  overflow:auto;
  margin:0;
  padding:16px;
  white-space:pre-wrap;
  font:600 .9rem/1.6 ui-monospace,Consolas,monospace
}
.lab-workspace {
  min-height:43px;
  border-top:1px solid var(--line);
  padding:8px 12px;
  display:flex;
  gap:6px;
  flex-wrap:wrap
}
.lab-workspace span {
  background:var(--soft);
  border-radius:7px;
  padding:3px 7px;
  font:600 .72rem ui-monospace,monospace
}
.lab-splitter {
  width:10px;
  background:var(--soft);
  border-left:1px solid var(--line);
  border-right:1px solid var(--line);
  cursor:col-resize
}
.lab-extension {
  border-top:1px solid var(--line)
}
.lab-extension-head {
  display:flex;
  justify-content:space-between;
  padding:12px 16px;
  background:var(--soft)
}
.lab-extension-head div {
  display:flex;
  flex-direction:column
}
.lab-extension-subtitle {
  color:var(--muted)
}
.lab-collapse {
  background:var(--teal);
  border-color:var(--teal)
}
.lab-large-figures {
  min-height:0
}
.lab-extension.has-figure .lab-large-figures {
  min-height:500px;
  padding:15px
}
.lab-large-figures canvas,.lab-large-figures svg {
  max-width:100%
}
body.resizing {
  user-select:none;
  cursor:col-resize
}
/* Original slide viewer */
.source-slides-overlay {
  position:fixed;
  inset:0;
  z-index:200;
  background:rgba(1,10,12,.94);
  display:none;
  padding:2vh 3vw
}
.source-slides-overlay.open {
  display:block
}
.source-slides-dialog {
  height:96vh;
  display:flex;
  flex-direction:column;
  position:relative
}
.source-slides-close {
  position:absolute;
  right:0;
  top:0;
  width:46px;
  height:46px;
  border-radius:50%;
  border:1px solid #536063;
  background:#172125;
  color:#fff;
  font-size:1.8rem;
  cursor:pointer;
  z-index:5
}
.source-slides-header {
  display:flex;
  justify-content:space-between;
  align-items:center;
  color:#fff;
  padding:7px 70px 10px 0
}
.source-slides-kicker {
  font-size:.7rem;
  letter-spacing:.18em;
  color:#74ddd8
}
.source-slides-header h2 {
  margin:0
}
.source-slides-header p {
  margin:0;
  color:#a9bbbf
}
.source-slides-controls {
  display:flex;
  align-items:center;
  gap:8px
}
.source-slides-controls button,.source-stage-arrow {
  border:1px solid #4a595c;
  background:#182326;
  color:#fff;
  border-radius:9px;
  padding:8px 11px;
  cursor:pointer
}
.source-slides-stage {
  min-height:0;
  flex:1;
  display:grid;
  grid-template-columns:55px 1fr 55px;
  align-items:center
}
.source-stage-arrow {
  font-size:2rem
}
.source-slide-frame {
  height:100%;
  min-height:0;
  margin:0;
  display:flex;
  flex-direction:column;
  align-items:center;
  justify-content:center
}
.source-slide-frame img {
  max-width:100%;
  max-height:calc(100% - 35px);
  object-fit:contain;
  background:#fff;
  border-radius:8px;
  cursor:zoom-in
}
.source-slide-frame img.zoomed {
  max-width:none;
  max-height:none;
  width:auto;
  height:auto;
  cursor:zoom-out
}
.source-slide-frame figcaption {
  color:#d5e2e4;
  margin-top:7px
}
.source-slide-loading {
  color:#fff
}
.source-slide-thumbs {
  height:74px;
  display:flex;
  gap:7px;
  overflow:auto;
  justify-content:center
}
.source-slide-thumbs button {
  border:2px solid transparent;
  background:#172125;
  color:#fff;
  border-radius:7px;
  padding:2px;
  display:flex;
  align-items:center;
  gap:5px;
  cursor:pointer
}
.source-slide-thumbs button.active {
  border-color:#52d1ca
}
.source-slide-thumbs img {
  height:58px
}
.source-slides-help {
  text-align:center;
  color:#9badaf;
  margin:7px 0 0;
  font-size:.76rem
}
.tooltip {
  position:fixed;
  display:none;
  z-index:300;
  pointer-events:none;
  max-width:370px;
  background:#0b2428;
  color:#efffff;
  border:1px solid #315057;
  border-radius:10px;
  padding:9px 12px;
  font-size:.82rem;
  box-shadow:0 12px 30px rgba(0,0,0,.28)
}
@media(max-width:1100px) {
  .page-shell {
    grid-template-columns:1fr
  }
  .side-nav {
    position:fixed;
    z-index:60;
    left:-320px;
    width:300px;
    background:var(--paper);
    transition:.25s
  }
  .side-nav.open {
    left:0
  }
  .menu-btn {
    display:block
  }
  .hero {
    grid-template-columns:1fr
  }
  .hero-array {
    height:420px
  }
  .concept-grid {
    grid-template-columns:repeat(2,1fr)
  }
}
@media(max-width:760px) {
  .topbar {
    padding:0 10px
  }
  .brand small,.top-actions>a:nth-child(2),#tipToggle,.font-box {
    display:none
  }
  .top-actions {
    gap:4px
  }
  .top-btn,.menu-btn {
    padding:7px
  }
  .lesson-section {
    padding:60px 18px
  }
  .section-head {
    grid-template-columns:42px 1fr
  }
  .section-head .source-slide-btn {
    grid-column:2
  }
  .split-story,.diary-demo {
    grid-template-columns:1fr
  }
  .concept-grid,.three-way {
    grid-template-columns:1fr
  }
  .builder-controls {
    grid-template-columns:1fr
  }
  .operator-strip {
    grid-template-columns:repeat(3,1fr)
  }
  .matrix-index-demo {
    grid-template-columns:1fr
  }
  .lab-body {
    height:600px;
    flex-direction:column
  }
  .lab-code-pane {
    flex-basis:50%!important
  }
  .lab-splitter {
    width:auto;
    height:10px;
    cursor:row-resize
  }
  .source-slides-header {
    display:block
  }
  .source-slides-controls {
    margin-top:8px
  }
  .source-slides-stage {
    grid-template-columns:35px 1fr 35px
  }
  .transpose-demo {
    flex-direction:column
  }
  .summary-flow i {
    transform:rotate(90deg)
  }
}
/* Performance and editor readability */
.lesson-section:not(.hero) {
  content-visibility:auto;
  contain-intrinsic-size:auto 900px;
  contain:layout paint style
}
.matlab-lab,.decision-gate,.if-simulator,.array-if-demo,.two-road,.grade-ladder,.switch-console,.logical-vector-builder,.mask-lab,.relation-playground,.roundoff-microscope,.logic-gates,.logical-index-demo {
  contain:layout paint
}
.lab-editor {
  white-space:pre!important;
  overflow:auto!important;
  overflow-wrap:normal!important;
  word-break:normal!important
}
.topbar {
  backdrop-filter:none!important;
  -webkit-backdrop-filter:none!important;
  background:var(--paper)!important
}
@media(prefers-reduced-motion:reduce) {
  html {
    scroll-behavior:auto!important
  }
  *,*::before,*::after {
    animation-duration:.001ms!important;
    animation-iteration-count:1!important;
    transition-duration:.001ms!important
  }
}
/* Input queue and theme-aware editor */
.lab-input-queue {
  border-bottom:1px solid var(--line);
  background:color-mix(in srgb,var(--teal) 5%,var(--paper));
  padding:14px 17px
}
.lab-input-head {
  display:flex;
  align-items:center;
  gap:12px;
  min-height:36px
}
.lab-input-head b {
  font-size:.95rem
}
.lab-input-head small {
  color:var(--muted);
  margin-right:auto
}
.lab-input-actions {
  display:flex;
  align-items:center;
  gap:7px;
  flex:none
}
.lab-input-add,.lab-input-reset {
  height:34px;
  border:1px solid var(--line);
  border-radius:9px;
  background:var(--paper);
  color:var(--ink);
  padding:0 11px;
  font:700 .78rem/1 inherit;
  cursor:pointer
}
.lab-input-add:hover,.lab-input-reset:hover {
  border-color:color-mix(in srgb,var(--teal) 55%,var(--line));
  color:var(--teal);
  background:color-mix(in srgb,var(--teal) 7%,var(--paper))
}
.lab-input-list {
  display:flex;
  gap:9px;
  flex-wrap:wrap;
  margin-top:11px
}
.lab-input-list label {
  display:grid;
  grid-template-columns:auto minmax(78px,110px) auto 23px;
  gap:7px;
  align-items:center;
  border:1px solid var(--line);
  border-radius:11px;
  background:var(--paper);
  padding:7px 8px;
  min-height:42px;
  box-shadow:0 3px 12px rgba(18,55,61,.04)
}
.lab-input-list label>span {
  font-size:.76rem;
  color:var(--muted);
  white-space:nowrap
}
.lab-input-list input {
  min-width:0;
  width:100%;
  border:0;
  border-bottom:1px solid var(--line);
  background:transparent;
  color:var(--ink);
  font:700 .86rem ui-monospace,Consolas,monospace;
  outline:0;
  padding:3px 2px
}
.lab-input-list input:focus {
  border-color:var(--teal)
}
.lab-input-list i {
  font-style:normal;
  font-size:.69rem;
  color:var(--teal);
  white-space:nowrap
}
.lab-input-list label.consumed {
  opacity:.58
}
.lab-input-list label.consumed i {
  color:var(--orange)
}
.lab-input-remove {
  width:23px;
  height:23px;
  border:0;
  border-radius:7px;
  background:transparent;
  color:var(--muted);
  font-size:1rem;
  line-height:1;
  cursor:pointer;
  padding:0
}
.lab-input-remove:hover {
  background:color-mix(in srgb,var(--orange) 12%,transparent);
  color:var(--orange)
}
:root:not([data-theme="dark"]) .lab-code-pane {
  background:#fff!important;
  color:#18333a!important
}
:root:not([data-theme="dark"]) .lab-code-pane .lab-pane-title {
  border-color:var(--line)!important;
  color:#18333a
}
:root:not([data-theme="dark"]) .lab-editor {
  color:#18333a!important;
  caret-color:#087f8b!important
}
:root:not([data-theme="dark"]) .lab-prompt {
  color:#087f8b!important
}
:root:not([data-theme="dark"]) .lab-mode-badge {
  background:#edf4f5!important;
  color:#49646a!important
}
:root[data-theme="dark"] .lab-code-pane {
  background:#0a171b!important;
  color:#e7f6f5!important
}
:root[data-theme="dark"] .lab-editor {
  color:#e7f6f5!important;
  caret-color:#65ddd6!important
}
:root[data-theme="dark"] .lab-prompt {
  color:#65ddd6!important
}
@media(max-width:760px) {
  .lab-input-head {
    align-items:flex-start;
    flex-wrap:wrap
  }
  .lab-input-head small {
    width:100%;
    order:3
  }
  .lab-input-actions {
    margin-left:auto
  }
  .lab-input-list label {
    grid-template-columns:auto minmax(70px,1fr) auto 23px;
    flex:1 1 260px
  }
}


/* v1.3.1: shared content spacing for Lessons 03–08. */
.hero-badges{display:flex;gap:8px;flex-wrap:wrap;margin-top:22px}
.hero-badges span{padding:7px 11px;border:1px solid var(--line);border-radius:999px;background:var(--paper);color:var(--muted);font-size:.78rem;line-height:1.35}
.section-head p{line-height:1.72}
.concept-card h3,.plain-grid h3,.finish-card h3{line-height:1.35}
.concept-card p,.plain-grid p,.callout p{line-height:1.7}
@media(max-width:1450px) and (min-width:1101px){
  .hero{grid-template-columns:minmax(0,1.05fr) minmax(390px,.82fr);gap:44px}
  .hero-array,.hero-io,.hero-logic,.hero-function{height:470px;min-height:470px}
  .section-head{margin-bottom:34px}
}