/* ══════════════════════════════════════════════════════════════════
   SLIDE VIEWER — swipeable browser-friendly slides
   ══════════════════════════════════════════════════════════════════ */

.deck-body {
  background: var(--paper);
  overflow-x: hidden;
  overscroll-behavior: none;
}

/* ─── SKIP LINK — hidden until keyboard-focused, jumps past the header/
   breadcrumb/chapter-nav straight to the lesson content ────────────── */
.skip-link {
  position: absolute;
  top: -100px;
  left: 8px;
  z-index: 1000;
  background: var(--ink);
  color: var(--paper);
  padding: 10px 18px;
  border-radius: 6px;
  font-family: var(--font-sans);
  font-size: .8rem;
  font-weight: 700;
  text-decoration: none;
  transition: top .15s ease;
}
.skip-link:focus {
  top: 8px;
}

/* ─── SLIDE ENTRY ANIMATION ─────────────────────────────────────── */
@keyframes deckSlideIn {
  from { opacity: 0; transform: translateX(22px); }
  to   { opacity: 1; transform: translateX(0); }
}
.slide-anim { animation: deckSlideIn .28s ease-out; }

/* ─── DECK NAV BAR — fixed at bottom, prev / counter / next ─────── */
.deck-nav {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 20px;
  background: var(--paper);
  border-top: 1px solid var(--hairline);
  z-index: 100;
  transform: translateZ(0);
  -webkit-transform: translateZ(0);
}
/* Promote fixed elements to GPU layers so card swipe doesn't jitter them */
body.deck-body .site-header {
  transform: translateZ(0);
  -webkit-transform: translateZ(0);
}
body.deck-body .deck-progress {
  transform: translateZ(0);
  -webkit-transform: translateZ(0);
}
.deck-btn {
  padding: 9px 20px;
  font-family: var(--font-sans);
  font-size: .75rem;
  font-weight: 700;
  letter-spacing: 1px;
  text-transform: uppercase;
  border: 1.5px solid var(--hairline);
  border-radius: 4px;
  background: transparent;
  color: var(--ink);
  cursor: pointer;
  transition: border-color .15s, color .15s;
}
.deck-btn:hover:not(:disabled) { border-color: var(--amber); color: var(--amber); }
.deck-btn:disabled { opacity: .3; cursor: default; }
.deck-btn.primary { background: var(--amber); color: #1A1A1A; border-color: var(--amber); }
.counter, .deck-counter {
  font-family: var(--font-sans);
  font-size: .82rem;
  font-weight: 600;
  color: var(--muted);
}

/* Progress bar at top of screen */
.deck-progress {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--hairline);
  z-index: 50;
}
.deck-progress-fill {
  height: 100%;
  background: var(--accent);
  width: 0%;
  transition: width 0.3s ease-out;
}

/* ─── SLIDE CONTAINER — block layout (all sections visible) ─────── */
.deck-viewport {
  max-width: 840px;
  margin: 0 auto;
  padding: 8px 20px 100px;
}
.slide {
  display: none;           /* deck.js shows the active slide */
  width: 100%;
  max-width: 780px;
  margin: 0 auto;
  padding: 0 16px;
}

/* ─── SLIDE CARD ───────────────────────────────────────────────── */
.slide-card {
  background: var(--paper);
  border-radius: 10px;
  padding: 32px 28px;
  box-shadow: 0 2px 12px rgba(0,0,0,.08);
  border: 1.5px solid var(--border-soft);
  transition: transform .15s ease-out, opacity .15s ease-out;
  will-change: transform;
  user-select: none;
  -webkit-user-select: none;
}

/* ─── TITLE SLIDE (dark) ───────────────────────────────────────── */
.slide.title-slide .slide-card {
  background: var(--navy-deep);
  color: white;
  border: none;
  text-align: left;
  padding: 56px 32px;
}
.slide.title-slide .chapter-num {
  font-family: var(--font-sans);
  font-size: 0.8rem;
  letter-spacing: 3px;
  text-transform: uppercase;
  color: var(--muted);
  font-weight: 700;
  margin-bottom: 20px;
}
.slide.title-slide h1 {
  color: white;
  font-size: 3.2rem;
  line-height: 1;
  margin-bottom: 20px;
}
.slide.title-slide .deck-sub {
  color: var(--accent);
  font-size: 1.2rem;
  margin-bottom: 32px;
}
.slide.title-slide .deck-level {
  display: inline-block;
  padding: 6px 14px;
  background: var(--accent);
  color: white;
  font-family: var(--font-sans);
  font-size: 0.75rem;
  letter-spacing: 2px;
  text-transform: uppercase;
  font-weight: 700;
  border-radius: 3px;
}

/* ─── CONTENT SLIDE HEADER ────────────────────────────────────── */
.slide-header {
  border-left: 4px solid var(--accent);
  padding: 6px 0 6px 16px;
  margin-bottom: 24px;
}
.slide-header h2 {
  font-size: 1.8rem;
  line-height: 1.1;
  margin-bottom: 4px;
}
.slide-header .slide-sub {
  color: var(--muted-deep);
  font-size: 0.95rem;
  font-style: italic;
}

/* ─── FORMULA BLOCKS ───────────────────────────────────────────── */
.formula-block {
  background: var(--cream-deep);
  border-left: 4px solid var(--accent);
  padding: 12px 16px;
  margin-bottom: 12px;
  border-radius: 0 4px 4px 0;
  font-weight: 700;
  font-size: 0.98rem;
}
.formula-block .arrow {
  color: var(--muted);
  margin: 0 8px;
}
.formula-block .result {
  color: var(--accent);
  font-weight: 700;
}

/* ─── EXPLANATION ─────────────────────────────────────────────── */
.slide-explanation {
  font-size: 1rem;
  line-height: 1.6;
  color: var(--navy);
  margin: 20px 0;
}
.slide-explanation strong { color: var(--accent); }

/* ─── EXAMPLE CARDS ──────────────────────────────────────────── */
.examples-row {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
  margin: 20px 0;
}
@media (min-width: 640px) {
  .examples-row { grid-template-columns: repeat(3, 1fr); }
}
.example-card {
  background: var(--paper);
  border: 1.5px solid var(--accent);
  border-radius: 4px;
  padding: 14px 16px;
}
.example-card .ex-text {
  font-style: italic;
  color: var(--navy);
  font-size: 0.95rem;
  margin-bottom: 8px;
  line-height: 1.4;
}
.example-card .ex-note {
  font-family: var(--font-sans);
  color: var(--muted);
  font-size: 0.78rem;
}

/* ─── WATCH OUT ──────────────────────────────────────────────── */
.watch-out {
  background: var(--cream-deep, #FFF4E8);
  border: 1px solid var(--amber);
  border-radius: 4px;
  padding: 10px 14px;
  margin-top: 16px;
  font-size: 0.88rem;
  line-height: 1.5;
}
.watch-out strong { color: var(--amber); }
.watch-out::before { content: 'Note — '; color: var(--amber); font-weight: 700; }

/* ─── EXAM STRATEGY CALLOUTS (B2+) ──────────────────────────── */
.exam-note {
  background: rgba(46, 125, 82, 0.08);
  border: 1px solid var(--green);
  border-radius: 4px;
  padding: 10px 14px;
  margin-top: 16px;
  font-size: 0.88rem;
  line-height: 1.5;
  color: var(--ink);
}
.exam-note strong { color: var(--green); }
.exam-note::before { content: 'FCE Strategy — '; color: var(--green); font-weight: 700; }

/* ─── OVERVIEW / SUMMARY ROWS ─────────────────────────────────── */
.overview-row, .summary-row {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 14px;
  border: 1px solid var(--border-soft);
  border-left: 4px solid var(--accent);
  border-radius: 0 4px 4px 0;
  margin-bottom: 8px;
  background: var(--paper);
}
.overview-row .num {
  font-family: var(--font-serif);
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--accent);
  width: 28px;
  text-align: center;
  flex-shrink: 0;
}
.overview-row .title {
  font-weight: 700;
  color: var(--navy);
  font-size: 0.95rem;
}
.overview-row .ex {
  color: var(--muted);
  font-style: italic;
  font-size: 0.85rem;
  margin-left: auto;
  text-align: right;
}
@media (max-width: 520px) {
  .overview-row { flex-direction: column; align-items: flex-start; gap: 4px; }
  .overview-row .ex { margin-left: 0; text-align: left; }
  .overview-row .num { width: auto; }
}

/* ─── COMPARISON PANELS ───────────────────────────────────────── */
.panel-pair {
  display: grid;
  grid-template-columns: 1fr;
  gap: 14px;
}
@media (min-width: 640px) {
  .panel-pair { grid-template-columns: 1fr 1fr; }
}
.panel {
  background: var(--paper);
  border: 1.5px solid var(--border);
  border-radius: 6px;
  overflow: hidden;
}
.panel-head {
  padding: 12px 16px;
  font-family: var(--font-sans);
  letter-spacing: 2px;
  font-weight: 700;
  font-size: 0.78rem;
  text-transform: uppercase;
  color: white;
}
.panel-head.green { background: var(--green); }
.panel-head.amber { background: var(--accent); }
.panel-head.red { background: var(--red); }
.panel-body { padding: 14px 16px; }
.panel-body .ex {
  padding: 10px 0;
  border-bottom: 1px solid var(--border-soft);
  font-size: 0.9rem;
}
.panel-body .ex:last-child { border-bottom: none; }
.panel-body .ex .sent { font-style: italic; color: var(--navy); margin-bottom: 4px; }
.panel-body .ex .note { color: var(--muted); font-size: 0.82rem; }

/* ─── FCE TRAPS GRID (row format) ────────────────────────────── */
.trap-row {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 8px;
  align-items: center;
  margin-bottom: 10px;
  font-size: 0.88rem;
}
.trap-wrong {
  background: rgba(192,57,43,.08);
  border: 1px solid var(--red);
  padding: 8px 12px;
  border-radius: 4px;
  color: var(--red);
  text-decoration: line-through;
}
.trap-wrong::before { content: ''; }
.trap-arrow { color: var(--muted); font-size: 1rem; }
.trap-right {
  background: rgba(39,174,96,.08);
  border: 1px solid var(--green);
  padding: 8px 12px;
  border-radius: 4px;
  color: var(--green);
}
.trap-right::before { content: ''; }
.trap-note {
  grid-column: 1 / -1;
  font-size: 0.78rem;
  color: var(--muted);
  font-style: italic;
  padding: 2px 4px 6px;
}
@media (max-width: 520px) {
  .trap-row { grid-template-columns: 1fr; }
  .trap-arrow { display: none; }
}

/* ─── INLINE WRONG / RIGHT SPANS (overview-desc corrections) ──── */
/* Used when a wrong→correct pair appears inline in overview-desc  */
/* (replaces the stripped ✓ symbol — keeps right/wrong visually    */
/*  distinct without forbidden Unicode symbols)                     */
.ov-wrong { color: var(--red); text-decoration: line-through; font-style: italic; }
.ov-right { color: var(--green); font-weight: 600; }
body.dark .ov-wrong { color: #e57373; }
body.dark .ov-right { color: #5ecf85; }

/* ─── SUMMARY SLIDE (default = dark card, always) ───────────── */
.slide.summary-slide .slide-card {
  background: var(--navy-deep);
  color: white;
  border: none;
  padding: 40px 32px;
}
.slide.summary-slide h2 {
  color: white;
  font-size: 2rem;
  margin-bottom: 24px;
}
.summary-row {
  background: rgba(255,255,255,0.04);
  border-color: rgba(255,255,255,0.1);
  border-left-color: var(--accent);
  color: white;
  align-items: flex-start;
  flex-direction: column;
  gap: 6px;
  padding: 14px 16px;
}
.summary-row .label {
  color: var(--accent);
  font-weight: 700;
  font-size: 0.95rem;
  letter-spacing: 0.5px;
}
.summary-row .form {
  font-family: var(--font-serif);
  font-size: 0.88rem;
  color: #ECECEC;
}
.summary-row .ex {
  color: #B0B0B0;
  font-style: italic;
  font-size: 0.85rem;
  margin-left: 0;
}

/* ─── SUMMARY SLIDE — light mode override ───────────────────── */
body:not(.dark) .slide.summary-slide .slide-card {
  background: var(--cream-deep);
  color: var(--ink);
  border: 1.5px solid var(--hairline);
}
body:not(.dark) .slide.summary-slide h2 { color: var(--ink); }
body:not(.dark) .summary-row {
  background: var(--paper);
  border-color: var(--hairline);
  border-left-color: var(--amber);
  color: var(--ink);
}
body:not(.dark) .summary-row .label { color: var(--amber); }
body:not(.dark) .summary-row .form { color: var(--ink); }
body:not(.dark) .summary-row .ex { color: var(--muted); }

/* ─── TWO-UP EXAMPLE PAIRS ───────────────────────────────────── */
.compare-pair {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
  margin: 16px 0;
}
@media (min-width: 640px) {
  .compare-pair { grid-template-columns: 1fr 1fr; }
}
.compare-pair .side {
  background: var(--paper);
  border: 1.5px solid var(--border);
  border-radius: 4px;
  padding: 14px 16px;
}
.compare-pair .tag {
  font-family: var(--font-sans);
  font-size: 0.72rem;
  letter-spacing: 1.5px;
  text-transform: uppercase;
  font-weight: 700;
  margin-bottom: 6px;
}
.compare-pair .tag.green { color: var(--green); }
.compare-pair .tag.amber { color: var(--accent); }
.compare-pair .sent {
  font-style: italic;
  color: var(--navy);
  font-size: 0.95rem;
  margin-bottom: 4px;
}
.compare-pair .note {
  color: var(--muted);
  font-size: 0.82rem;
}

/* ─── MODIFIERS LIST (Ch2 slide 8) ───────────────────────────── */
.mod-list { display: flex; flex-direction: column; gap: 6px; }
.mod-row {
  display: grid;
  grid-template-columns: 100px 1fr;
  gap: 10px;
  padding: 10px 12px;
  background: var(--paper);
  border: 1px solid var(--border-soft);
  border-radius: 4px;
  font-size: 0.88rem;
}
.mod-row .word { font-weight: 700; }
.mod-row .word.red { color: var(--red); }
.mod-row .word.green { color: var(--green); }
.mod-row .example { color: var(--muted); font-style: italic; }

/* ── Chapter subtitle ── */
.chapter-subtitle {
  font-family: var(--font-sans);
  font-size: .85rem;
  color: var(--muted);
  margin: 2px 0 20px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--hairline);
}

/* ─── MOBILE SLIDE HEIGHT ────────────────────────────────────────── */
@media (max-width: 520px) {
  .slide-card { min-height: 50vh; padding: 22px 18px; }
  .slide-header h2 { font-size: 1.4rem; }
  .overview-label { font-size: .78rem; min-width: 80px !important; }
}

/* ─── SLIDE DECK CONTAINER ───────────────────────────────────────── */
.slide-deck {
  padding: 0 0 100px;  /* bottom clearance for fixed nav bar */
}
@media (max-width: 520px) {
  .slide-deck { padding: 0 0 90px; }
  .examples-row .example-card { padding: 10px 12px; }
  .trap-row { font-size: .82rem; }
}

/* ══════════════════════════════════════════════════════════════════
   DARK MODE — DEFINITIVE OVERRIDES (Batch 21)
   Strategy: every text-bearing element under .slide-card gets explicit
   light color. Bold/strong tags get explicit color. No exceptions.
   ══════════════════════════════════════════════════════════════════ */

/* Slide card — dark background, light text by default */
body.dark .slide-card {
  background: #141414 !important;
  color: #F0F0F0 !important;
  border-color: rgba(255,255,255,.1) !important;
}
body.dark .summary-slide .slide-card { background: #0A0A0A !important; }
body.dark .slide.title-slide .slide-card { background: #050505 !important; color: #FFFFFF !important; }

/* Every direct text element inside slide-card → light */
body.dark .slide-card *:not(a) {
  color: inherit;
}

/* But these specific elements need explicit colors */
body.dark .slide-card,
body.dark .slide-card p,
body.dark .slide-card div,
body.dark .slide-card span,
body.dark .slide-card li,
body.dark .slide-card td,
body.dark .slide-card h1,
body.dark .slide-card h2,
body.dark .slide-card h3,
body.dark .slide-card h4 { color: #F0F0F0 !important; }

/* Headings */
body.dark .slide-card .slide-header h2 { color: #FFFFFF !important; }
body.dark .slide-card .slide-sub        { color: #C0C0C0 !important; }
body.dark .slide-card .slide-explanation { color: #E0E0E0 !important; }

/* Bold/strong/em tags — keep amber for emphasis or white */
body.dark .slide-card strong,
body.dark .slide-card b { color: #FFE4A0 !important; }
body.dark .slide-card em,
body.dark .slide-card i { color: #C0C0C0 !important; }

/* Overview rows */
body.dark .slide-card .overview-row,
body.dark .slide-card .summary-row {
  background: rgba(255,255,255,.06) !important;
  border-color: rgba(255,255,255,.12) !important;
  border-left-color: var(--amber) !important;
}
body.dark .slide-card .overview-label   { color: #FFFFFF !important; font-weight: 700; }
body.dark .slide-card .overview-desc    { color: #E0E0E0 !important; }
body.dark .slide-card .overview-row .title { color: #FFFFFF !important; }
body.dark .slide-card .overview-row .ex    { color: #C0C0C0 !important; }
body.dark .slide-card .overview-row .num   { color: var(--amber) !important; }

/* Summary rows */
body.dark .slide-card .summary-row .label { color: var(--amber) !important; }
body.dark .slide-card .summary-row .form  { color: #FFFFFF !important; }
body.dark .slide-card .summary-row .ex    { color: #C0C0C0 !important; }

/* Panel pairs */
body.dark .slide-card .panel {
  background: rgba(255,255,255,.05) !important;
  border-color: rgba(255,255,255,.15) !important;
}
body.dark .slide-card .panel-head        { color: #FFFFFF !important; }
body.dark .slide-card .panel-head.green  { background: #1a4a28 !important; color: #A0E8B0 !important; }
body.dark .slide-card .panel-head.red    { background: #4a1a1a !important; color: #F0A0A0 !important; }
body.dark .slide-card .panel-body .ex .sent { color: #F0F0F0 !important; font-style: italic; }
body.dark .slide-card .panel-body .ex .note { color: #A0A0A0 !important; }

/* Example cards */
body.dark .slide-card .example-card {
  background: rgba(255,255,255,.06) !important;
  border-color: rgba(201,160,80,.5) !important;
}
body.dark .slide-card .example-card .ex-text { color: #FFFFFF !important; }
body.dark .slide-card .example-card .ex-note { color: #C0C0C0 !important; }

/* Formula blocks */
body.dark .slide-card .formula-block {
  background: rgba(255,255,255,.08) !important;
  color: #FFFFFF !important;
  border-color: rgba(255,255,255,.2) !important;
}
body.dark .slide-card .formula-block .arrow  { color: var(--amber) !important; }
body.dark .slide-card .formula-block .result { color: #4CAF82 !important; }

/* Trap rows */
body.dark .slide-card .trap-row { border-bottom-color: rgba(255,255,255,.08) !important; }
body.dark .slide-card .trap-wrong { background: rgba(192,57,43,.25) !important; color: #FFB0A0 !important; }
body.dark .slide-card .trap-right { background: rgba(39,174,96,.25) !important; color: #A0E8B0 !important; }
body.dark .slide-card .trap-arrow { color: var(--amber) !important; }
body.dark .slide-card .trap-note  { color: #A0A0A0 !important; }

/* Watch-out boxes */
body.dark .slide-card .watch-out {
  background: rgba(201,160,80,.18) !important;
  border-color: var(--amber) !important;
  color: #FFE4A0 !important;
}
body.dark .slide-card .watch-out strong { color: var(--amber) !important; }
body.dark .slide-card .watch-out em     { color: #FFD080 !important; }

/* Exam strategy callouts */
body.dark .slide-card .exam-note {
  background: rgba(46, 125, 82, 0.25) !important;
  border-color: #5ecf85 !important;
  color: #A0E8B0 !important;
}
body.dark .slide-card .exam-note strong { color: #5ecf85 !important; }
body.dark .slide-card .exam-note em     { color: #7FE89F !important; }

/* Compare pair */
body.dark .slide-card .compare-pair .side {
  background: rgba(255,255,255,.06) !important;
  border-color: rgba(255,255,255,.15) !important;
  color: #F0F0F0 !important;
}

/* Mod rows */
body.dark .slide-card .mod-row {
  background: rgba(255,255,255,.06) !important;
  border-color: rgba(255,255,255,.12) !important;
  color: #F0F0F0 !important;
}

/* Preserve dark text on amber CTA buttons (intentional design) */
body.dark .slide-card a[style*="background:var(--amber)"],
body.dark .slide-card a[style*="background: var(--amber)"],
body.dark a[style*="background:var(--amber)"],
body.dark a[style*="background: var(--amber)"],
body.dark button[style*="background:var(--amber)"],
body.dark .lc-cta-btn {
  color: #1A1A1A !important;
  background: var(--amber) !important;
}

/* Header / chapter meta in dark */
body.dark .chapter-num      { color: var(--amber) !important; }
body.dark .chapter-subtitle { color: #C0C0C0 !important; }
body.dark .breadcrumb       { color: #A0A0A0 !important; }
body.dark .breadcrumb a     { color: var(--amber) !important; }
body.dark .breadcrumb strong { color: #FFFFFF !important; }

/* Deck nav bar + buttons in dark mode */
body.dark .deck-nav {
  background: #141414 !important;
  border-top-color: rgba(255,255,255,.1) !important;
}
body.dark .deck-btn {
  background: transparent !important;
  color: #E0E0E0 !important;
  border-color: rgba(255,255,255,.2) !important;
}
body.dark .deck-btn:hover:not(:disabled) { border-color: var(--amber) !important; color: var(--amber) !important; }
body.dark .deck-btn:disabled { opacity: 0.35; }
body.dark .deck-btn.primary { background: var(--amber) !important; color: #1A1A1A !important; border-color: var(--amber) !important; }
body.dark .counter, body.dark .deck-counter { color: #A0A0A0 !important; }

/* Lesson complete banner — keep amber bg, dark text */
body.dark .lc-banner {
  background: var(--amber) !important;
  color: #1A1A1A !important;
}
body.dark .lc-banner * { color: #1A1A1A !important; }

.chapter-nav { display: none !important; }