/* ===== Shared Tutorial Deck Styling ===== */
/* Used by ch19, ch20, ch21, exam2-solutions decks. */
/* Matches the aesthetic of faraday-lenz.html / kirchhoff-ohm.html / magnetism.html */

:root {
  --bg: #0a0a0a;
  --bg-2: #131313;
  --ink: #e8e6d9;
  --ink-dim: #a9a597;
  --gold: #d4af37;
  --gold-dim: #BA7517;
  --b-ext: #0F6E56;
  --b-ind: #1D9E75;
  --i-ind: #A32D2D;
  --v-vel: #185FA5;
  --loop: #7F77DD;
  --line: #2a2a2a;
}
* { box-sizing: border-box; }
html, body {
  margin: 0; padding: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}
.app {
  max-width: 920px;
  margin: 0 auto;
  padding: 24px 20px 130px;
}
header.deck-head {
  border-bottom: 1px solid var(--line);
  padding-bottom: 18px;
  margin-bottom: 24px;
}
header.deck-head .tag {
  color: var(--gold);
  text-transform: uppercase;
  letter-spacing: 2px;
  font-size: 11px;
  font-weight: 600;
}
header.deck-head h1 {
  font-size: 22px;
  margin: 6px 0 4px;
  font-weight: 600;
}
header.deck-head .sub { color: var(--ink-dim); font-size: 13px; }

.slide {
  display: none;
  animation: fade 0.25s ease-out;
}
.slide.active { display: block; }
@keyframes fade {
  from { opacity: 0; transform: translateY(6px); }
  to   { opacity: 1; transform: translateY(0); }
}
.slide h2 {
  color: var(--gold);
  font-size: 20px;
  margin: 0 0 4px;
  font-weight: 600;
  letter-spacing: 0.2px;
}
.slide h3 {
  color: var(--ink);
  font-size: 15px;
  margin: 16px 0 6px;
  font-weight: 600;
}
.slide .kicker {
  color: var(--ink-dim);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  margin-bottom: 18px;
}
.slide p { margin: 10px 0; font-size: 15px; }
.slide .quote {
  border-left: 2px solid var(--gold-dim);
  padding: 4px 14px;
  color: var(--ink);
  font-style: italic;
  margin: 12px 0;
  font-size: 14.5px;
  background: rgba(212, 175, 55, 0.04);
}
.slide ul { margin: 10px 0 10px 22px; padding: 0; }
.slide li { margin: 4px 0; font-size: 14.5px; }
.slide ol { margin: 10px 0 10px 22px; padding: 0; }
.eq {
  display: block;
  background: var(--bg-2);
  border: 1px solid var(--line);
  border-left: 3px solid var(--gold);
  padding: 12px 16px;
  margin: 14px 0;
  font-family: "Cambria Math", "STIX Two Math", Georgia, serif;
  font-size: 17px;
  color: var(--ink);
  border-radius: 2px;
}
.eq .note { color: var(--ink-dim); font-size: 13px; font-style: italic; font-family: inherit; }

.diagram {
  margin: 18px 0;
  padding: 18px;
  background: var(--bg-2);
  border: 1px solid var(--line);
  border-radius: 6px;
}
.diagram svg { display: block; width: 100%; height: auto; }
.diagram .caption {
  font-size: 12px;
  color: var(--ink-dim);
  text-align: center;
  margin-top: 10px;
  font-style: italic;
}

.given-box {
  background: rgba(15, 110, 86, 0.08);
  border: 1px solid rgba(29, 158, 117, 0.4);
  border-radius: 4px;
  padding: 12px 16px;
  margin: 12px 0;
  font-size: 13.5px;
}
.given-box h4 {
  margin: 0 0 6px;
  color: var(--b-ind);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 1.2px;
}

.lenz-box {
  background: rgba(163, 45, 45, 0.08);
  border: 1px solid rgba(163, 45, 45, 0.5);
  border-radius: 4px;
  padding: 12px 16px;
  margin: 12px 0;
  font-size: 13.5px;
}
.lenz-box h4 {
  margin: 0 0 6px;
  color: #d66a6a;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 1.2px;
}

.answer { color: var(--gold); font-weight: 600; }

.grid-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
}
@media (max-width: 640px) {
  .grid-2 { grid-template-columns: 1fr; }
  .slide h2 { font-size: 18px; }
}

/* Navigation bar (bottom) */
nav.deck-nav {
  position: fixed;
  bottom: 0; left: 0; right: 0;
  background: rgba(10, 10, 10, 0.94);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-top: 1px solid var(--line);
  padding: 12px 18px 14px;
  display: flex;
  flex-direction: column;
  gap: 10px;
  z-index: 100;
}
nav.deck-nav .dots {
  display: flex;
  flex-wrap: wrap;
  gap: 5px;
  justify-content: center;
}
nav.deck-nav .dots span {
  width: 8px; height: 8px;
  border-radius: 50%;
  background: var(--line);
  cursor: pointer;
  transition: all 0.15s;
  flex-shrink: 0;
}
nav.deck-nav .dots span.active { background: var(--gold); transform: scale(1.25); }
nav.deck-nav .dots span:hover { background: var(--gold-dim); }
nav.deck-nav .controls {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: 920px;
  margin: 0 auto;
  width: 100%;
  gap: 12px;
}
nav.deck-nav button {
  background: transparent;
  color: var(--ink);
  border: 1px solid var(--line);
  padding: 8px 16px;
  border-radius: 4px;
  font-size: 13px;
  cursor: pointer;
  font-family: inherit;
  transition: all 0.15s;
}
nav.deck-nav button:hover:not(:disabled) {
  border-color: var(--gold);
  color: var(--gold);
}
nav.deck-nav button:disabled { opacity: 0.3; cursor: not-allowed; }
nav.deck-nav .counter {
  color: var(--ink-dim);
  font-size: 12px;
  font-family: "SF Mono", Consolas, monospace;
  min-width: 60px;
  text-align: center;
}

@media (max-width: 640px) {
  .app { padding: 18px 16px 160px; }
  nav.deck-nav { padding: 10px 12px 12px; }
  nav.deck-nav button { padding: 7px 12px; font-size: 12px; }
  nav.deck-nav .dots span { width: 6px; height: 6px; }
}