:root {
  --slide-bg: #f8fafc;
  --ink: #10253f;
  --muted: #526579;
  --navy: #163a5f;
  --blue: #075ea8;
  --teal: #087f8c;
  --green: #147d46;
  --orange: #c45a0a;
  --red: #b42318;
  --purple: #6d3bb5;
  --line: #cbd5e1;
  --soft-blue: #eaf3fb;
  --soft-green: #eaf7ef;
  --soft-orange: #fff3e8;
  --soft-red: #fcedeb;
  --soft-purple: #f2ecfa;
}

* { box-sizing: border-box; }
html, body { background: #081a2d; }
body { margin: 0; }

.skip-link {
  background: #fff;
  color: #10253f;
  left: 12px;
  padding: 10px 14px;
  position: fixed;
  top: -80px;
  z-index: 100;
}
.skip-link:focus { top: 12px; }

.reveal {
  color: var(--ink);
  font-family: Arial, Helvetica, sans-serif;
  font-size: 34px;
}

.reveal .slides section {
  background: var(--slide-bg);
  border-top: 10px solid var(--blue);
  border-radius: 12px;
  height: 100%;
  padding: 58px 72px 52px;
  text-align: left;
}

.reveal .slides section.title-slide,
.reveal .slides section.section-slide,
.reveal .slides section.chapter-slide {
  align-content: center;
  background: linear-gradient(135deg, #0c2b48, #174e78);
  border-top: 0;
  color: #fff;
  text-align: center;
}
.chapter-slide p:not(.slide-meta) {
  font-size: 1.08em;
  margin-left: auto;
  margin-right: auto;
  max-width: 900px;
}

.reveal h1, .reveal h2, .reveal h3 {
  color: var(--navy);
  font-family: Georgia, "Times New Roman", serif;
  letter-spacing: -0.02em;
  margin: 0 0 0.45em;
  text-transform: none;
}

.reveal h1 { font-size: 2.35em; }
.reveal h2 { font-size: 1.58em; }
.reveal h3 { font-size: 1.12em; }
.title-slide h1, .title-slide h2, .title-slide h3,
.section-slide h1, .section-slide h2, .section-slide h3 { color: #fff; }

.reveal p, .reveal li { line-height: 1.35; }
.reveal ul, .reveal ol { margin: 0.35em 0 0.35em 1.15em; }
.reveal li + li { margin-top: 0.24em; }
.reveal strong { color: #092f55; }
.title-slide strong, .section-slide strong { color: #fff; }

.eyebrow {
  color: #9fdbf5;
  font-size: 0.62em;
  font-weight: 700;
  letter-spacing: 0.15em;
  text-transform: uppercase;
}

.subtitle { color: inherit; font-size: 0.82em; opacity: 0.9; }
.source-note {
  bottom: 20px;
  color: var(--muted);
  font-size: 0.42em;
  left: 72px;
  position: absolute;
}

.slide-meta {
  bottom: 18px;
  color: var(--muted);
  display: flex;
  font-size: 0.38em;
  justify-content: space-between;
  left: 72px;
  margin: 0;
  position: absolute;
  right: 72px;
}
.title-slide .slide-meta, .chapter-slide .slide-meta { color: #d8ecf8; }
.optional-badge {
  background: #475569;
  border-radius: 999px;
  color: #fff;
  font-size: 0.42em;
  font-weight: 800;
  padding: 0.45em 0.8em;
  position: absolute;
  right: 72px;
  top: 34px;
  text-transform: uppercase;
}

.pacing-badge {
  background: #fff4cc;
  border: 2px solid #9a6b00;
  border-radius: 999px;
  color: #3c2b00;
  float: right;
  font-size: 0.38em;
  font-weight: 800;
  letter-spacing: 0.04em;
  margin-top: 0.25em;
  padding: 0.4em 0.75em;
  text-transform: uppercase;
}

.grid-2, .grid-3 {
  display: grid;
  gap: 28px;
}
.grid-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }

.card, .concept, .example, .practice, .warning, .solution, .optional {
  background: #fff;
  border: 2px solid var(--line);
  border-left-width: 10px;
  border-radius: 10px;
  box-shadow: 0 5px 14px rgb(15 35 55 / 8%);
  margin: 0.45em 0;
  padding: 0.65em 0.8em;
}

.component-card, .practice-panel, .formula-focus, .warning-panel,
.check-panel, .poll-panel, .exit-card, .example-prompt {
  background: #fff;
  border: 2px solid var(--line);
  border-radius: 12px;
  box-shadow: 0 5px 14px rgb(15 35 55 / 8%);
  padding: 0.72em 0.9em;
}
.component-concept .component-card { border-left: 10px solid var(--blue); }
.formula-focus { background: var(--soft-blue); border-left: 10px solid var(--teal); }
.practice-panel { background: var(--soft-green); border-left: 10px solid var(--green); }
.warning-panel { background: var(--soft-red); border-left: 10px solid var(--red); }
.poll-panel { background: #fffbea; border-left: 10px solid #a66b00; }
.exit-card { background: var(--soft-purple); border-left: 10px solid var(--purple); }

.objective-roadmap {
  display: grid;
  gap: 22px;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  list-style: none;
  margin: 0;
  padding: 0;
}
.objective-roadmap li {
  align-items: center;
  background: #fff;
  border: 2px solid var(--line);
  border-radius: 12px;
  display: grid;
  gap: 18px;
  grid-template-columns: auto 1fr;
  margin: 0;
  padding: 0.65em 0.8em;
}
.objective-roadmap span, .decision-guide span, .derivation-step span {
  align-items: center;
  background: var(--blue);
  border-radius: 50%;
  color: #fff;
  display: inline-flex;
  font-size: 0.7em;
  font-weight: 800;
  height: 2.2em;
  justify-content: center;
  width: 2.2em;
}
.objective-roadmap p { margin: 0; }

.diagram-layout {
  align-items: center;
  display: grid;
  gap: 30px;
  grid-template-columns: 1.15fr 0.85fr;
}
.asset-grid { display: grid; gap: 18px; }
.asset-grid.asset-count-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.asset-grid figure { margin: 0; text-align: center; }
.asset-grid figcaption {
  color: var(--muted);
  font-size: 0.42em;
  line-height: 1.3;
  margin-top: 0.4em;
}

.derivation-flow { display: grid; gap: 16px; }
.derivation-step {
  align-items: center;
  background: #fff;
  border: 2px solid var(--line);
  border-radius: 10px;
  display: grid;
  gap: 18px;
  grid-template-columns: auto 1fr;
  padding: 0.45em 0.7em;
}
.derivation-step p { margin: 0; }

.comparison-grid, .misconception-grid, .summary-grid {
  display: grid;
  gap: 26px;
  grid-template-columns: repeat(2, minmax(0, 1fr));
}
.decision-guide {
  display: grid;
  gap: 14px;
  grid-template-columns: repeat(2, minmax(0, 1fr));
}
.decision-guide > div {
  align-items: center;
  background: #fff;
  border: 2px solid var(--line);
  border-radius: 10px;
  display: grid;
  gap: 16px;
  grid-template-columns: auto 1fr;
  padding: 0.55em 0.7em;
}
.decision-guide p { margin: 0; }

.worked-example {
  display: grid;
  gap: 24px;
  grid-template-columns: 0.8fr 1.2fr;
}
.worked-steps {
  background: var(--soft-orange);
  border: 2px solid #f3c49d;
  border-left: 10px solid var(--orange);
  border-radius: 12px;
  margin: 0;
  padding: 0.7em 0.9em 0.7em 1.8em;
}
.worked-example .asset-grid { grid-column: 1 / -1; }
.poll-instruction {
  color: #765000;
  font-size: 0.72em;
  font-weight: 800;
}
.solution-panel {
  background: var(--soft-purple);
  border: 2px solid #c9b4e8;
  border-left: 10px solid var(--purple);
  border-radius: 10px;
  margin-top: 0.55em;
  padding: 0.6em 0.8em;
}
.concept { background: var(--soft-blue); border-left-color: var(--blue); }
.example { background: var(--soft-orange); border-left-color: var(--orange); }
.practice { background: var(--soft-green); border-left-color: var(--green); }
.warning { background: var(--soft-red); border-left-color: var(--red); }
.solution { background: var(--soft-purple); border-left-color: var(--purple); }
.optional { border-left-color: var(--muted); opacity: 0.9; }

.card-label {
  color: var(--muted);
  display: block;
  font-size: 0.55em;
  font-weight: 800;
  letter-spacing: 0.08em;
  margin-bottom: 0.3em;
  text-transform: uppercase;
}
.concept .card-label { color: var(--blue); }
.example .card-label { color: var(--orange); }
.practice .card-label { color: var(--green); }
.warning .card-label { color: var(--red); }
.solution .card-label { color: var(--purple); }

.deck-image {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 10px;
  display: block;
  margin: 0.35em auto;
  max-height: 270px;
  max-width: 100%;
  object-fit: contain;
}
.image-grid .deck-image { max-height: 215px; }
.image-grid {
  display: grid;
  gap: 18px;
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.interactive-panel {
  align-items: center;
  display: grid;
  gap: 28px;
  grid-template-columns: 1.4fr 0.8fr;
}
.interactive-panel canvas {
  background: #fff;
  border: 2px solid var(--line);
  border-radius: 10px;
  height: auto;
  max-width: 100%;
}
.interactive-panel input[type="range"] { width: 100%; }
.generated-problem {
  font-size: 1.18em;
  font-weight: 700;
  min-height: 3.2em;
}

.dense { font-size: 0.82em; }

.reveal table {
  border-collapse: collapse;
  font-size: 0.78em;
  margin: 0.4em auto;
  width: 100%;
}
.reveal th, .reveal td { border: 1px solid var(--line); padding: 0.42em; }
.reveal th { background: var(--soft-blue); color: var(--navy); }

.answer-toggle, .deck-action {
  background: var(--blue);
  border: 0;
  border-radius: 7px;
  color: #fff;
  cursor: pointer;
  font: inherit;
  font-size: 0.62em;
  font-weight: 700;
  padding: 0.62em 1em;
}
.answer-toggle:hover, .answer-toggle:focus-visible,
.deck-action:hover, .deck-action:focus-visible { background: #03477f; outline: 4px solid #8ac4ed; }

[data-answer][hidden] { display: none !important; }
[data-answer] { margin-top: 0.5em; }

.lecture-meta {
  color: #d8ecf8;
  font-size: 0.55em;
  margin-top: 1.8em;
}

.slide-nav {
  font-family: Arial, Helvetica, sans-serif;
  left: 14px;
  position: fixed;
  top: 14px;
  z-index: 40;
}
.slide-nav > button {
  background: #0c3558;
  border: 1px solid #8db7d4;
  border-radius: 6px;
  color: #fff;
  cursor: pointer;
  font-size: 15px;
  padding: 9px 12px;
}
.slide-nav ol {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 8px;
  box-shadow: 0 8px 24px rgb(0 0 0 / 24%);
  display: none;
  list-style: decimal;
  margin: 6px 0 0;
  max-height: 78vh;
  min-width: 310px;
  overflow-y: auto;
  padding: 8px 8px 8px 38px;
}
.slide-nav.open ol { display: block; }
.slide-nav li { font-size: 14px; margin: 0; }
.slide-nav a {
  color: #173b5e;
  display: block;
  padding: 7px 5px;
  text-decoration: none;
}
.slide-nav a:hover, .slide-nav a:focus-visible { background: var(--soft-blue); }

.classroom-toolbar {
  bottom: 12px;
  display: flex;
  gap: 8px;
  position: fixed;
  right: 66px;
  z-index: 35;
}
.classroom-toolbar button {
  background: rgb(8 31 51 / 88%);
  border: 1px solid #8db7d4;
  border-radius: 5px;
  color: #fff;
  cursor: pointer;
  font-size: 13px;
  padding: 7px 9px;
}

.status-message {
  background: #fff4cc;
  border: 2px solid #9a6b00;
  color: #3c2b00;
  font-size: 16px;
  left: 50%;
  padding: 10px 16px;
  position: fixed;
  top: 12px;
  transform: translateX(-50%);
  z-index: 60;
}

@media (max-width: 800px) {
  .classroom-toolbar { display: none; }
}

@media print {
  .slide-nav, .classroom-toolbar, .reveal .controls, .reveal .progress { display: none !important; }
  [data-answer][hidden] { display: block !important; }
  .fragment { opacity: 1 !important; visibility: visible !important; }
}