/* ============================================================
   S2 GRAMMAR CHALLENGE – STYLE v2
   Enhanced game-like UI with light/dark themes
   ============================================================ */

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --primary: #2563EB;
  --primary-dark: #1D4ED8;
  --primary-light: #DBEAFE;
  --primary-glow: rgba(37, 99, 235, 0.3);
  --accent: #7C3AED;
  --accent-light: #EDE9FE;
  --secondary: #F59E0B;
  --secondary-dark: #D97706;
  --secondary-light: #FEF3C7;
  --success: #10B981;
  --success-light: #D1FAE5;
  --danger: #EF4444;
  --danger-light: #FEE2E2;
  --bg: #F0F4FF;
  --bg2: #FFFFFF;
  --card: #FFFFFF;
  --card-hover: #F8FAFF;
  --text: #1E293B;
  --text-secondary: #475569;
  --text-muted: #94A3B8;
  --border: #E2E8F0;
  --border-active: #93C5FD;
  --shadow-sm: 0 2px 6px rgba(0,0,0,0.05);
  --shadow-md: 0 6px 20px rgba(0,0,0,0.08);
  --shadow-lg: 0 12px 40px rgba(0,0,0,0.1);
  --shadow-glow: 0 0 20px var(--primary-glow);
  --radius: 18px;
  --radius-sm: 12px;
  --radius-xs: 8px;
  --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  --font: 'Inter', -apple-system, BlinkMacSystemFont, system-ui, sans-serif;
  --mono: 'JetBrains Mono', monospace;
}

[data-theme="dark"] {
  --primary: #60A5FA;
  --primary-dark: #3B82F6;
  --primary-light: #1E3A5F;
  --primary-glow: rgba(96, 165, 250, 0.25);
  --accent: #A78BFA;
  --accent-light: #2E1065;
  --secondary: #FBBF24;
  --secondary-dark: #F59E0B;
  --secondary-light: #422006;
  --success: #34D399;
  --success-light: #064E3B;
  --danger: #F87171;
  --danger-light: #450A0A;
  --bg: #0B1120;
  --bg2: #131B2E;
  --card: #1A2340;
  --card-hover: #1F2B4A;
  --text: #F1F5F9;
  --text-secondary: #94A3B8;
  --text-muted: #64748B;
  --border: #2D3A5C;
  --border-active: #3B82F6;
  --shadow-sm: 0 2px 6px rgba(0,0,0,0.3);
  --shadow-md: 0 6px 20px rgba(0,0,0,0.4);
  --shadow-lg: 0 12px 40px rgba(0,0,0,0.5);
  --shadow-glow: 0 0 30px var(--primary-glow);
}

html, body {
  height: 100%;
  font-family: var(--font);
  font-size: 16px;
  background: var(--bg);
  color: var(--text);
  -webkit-font-smoothing: antialiased;
}

body {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  overflow-x: hidden;
}

/* === TOPBAR === */
.topbar {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 20px;
  background: var(--bg2);
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow-sm);
  flex-shrink: 0;
  backdrop-filter: blur(10px);
}

.topbar-left { display: flex; align-items: center; gap: 12px; }
.topbar-logo { height: 36px; width: auto; }
[data-theme="dark"] .topbar-logo { filter: brightness(1.3) saturate(1.2); }
.topbar-title { font-size: 1rem; font-weight: 800; color: var(--text); letter-spacing: -0.01em; }
.topbar-right { display: flex; align-items: center; gap: 10px; }

.streak-badge {
  display: flex;
  align-items: center;
  gap: 5px;
  background: linear-gradient(135deg, #FEF3C7, #FDE68A);
  padding: 5px 12px;
  border-radius: 20px;
  font-size: 0.82rem;
  font-weight: 800;
  color: #92400E;
  border: 1px solid #FCD34D;
  box-shadow: 0 2px 8px rgba(245, 158, 11, 0.2);
}

[data-theme="dark"] .streak-badge {
  background: linear-gradient(135deg, #422006, #78350F);
  color: #FBBF24;
  border-color: #92400E;
}

.streak-icon { font-size: 0.95rem; }

.theme-btn {
  width: 34px; height: 34px;
  border-radius: 50%;
  border: 1px solid var(--border);
  background: var(--card);
  display: flex; align-items: center; justify-content: center;
  cursor: pointer;
  font-size: 1rem;
  transition: transform var(--transition), background var(--transition);
}
.theme-btn:hover { transform: scale(1.1); background: var(--bg); }

/* === SCREENS === */
.screen {
  display: none;
  flex-direction: column;
  align-items: center;
  flex: 1;
  padding: 28px 20px 40px;
  max-width: 880px;
  margin: 0 auto;
  width: 100%;
  position: relative;
}
.screen.active { display: flex; animation: fadeUp 0.35s ease both; }
@keyframes fadeUp { from { opacity: 0; transform: translateY(14px); } to { opacity: 1; transform: translateY(0); } }

/* === BACKGROUND PARTICLES === */
.bg-particles {
  position: absolute;
  inset: 0;
  pointer-events: none;
  overflow: hidden;
  z-index: 0;
}

.particle {
  position: absolute;
  border-radius: 50%;
  opacity: 0.15;
  animation: float 8s ease-in-out infinite;
}

.p1 { width: 120px; height: 120px; background: var(--primary); top: 8%; left: 2%; animation-delay: 0s; }
.p2 { width: 80px; height: 80px; background: var(--accent); top: 30%; right: 2%; animation-delay: 2s; }
.p3 { width: 60px; height: 60px; background: var(--secondary); bottom: 20%; left: 10%; animation-delay: 4s; }
.p4 { width: 100px; height: 100px; background: var(--success); bottom: 5%; right: 5%; animation-delay: 1s; }
.p5 { width: 40px; height: 40px; background: var(--primary); top: 50%; left: 50%; animation-delay: 3s; }

@keyframes float {
  0%, 100% { transform: translateY(0) scale(1); }
  50% { transform: translateY(-20px) scale(1.05); }
}

/* === HERO === */
.hero { text-align: center; margin-bottom: 24px; position: relative; z-index: 1; }

.hero-badge {
  display: inline-block;
  padding: 5px 14px;
  border-radius: 20px;
  background: var(--primary-light);
  color: var(--primary);
  font-size: 0.7rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  margin-bottom: 10px;
  border: 1px solid var(--border-active);
}

[data-theme="dark"] .hero-badge {
  background: var(--primary-light);
  border-color: var(--primary-dark);
}

.hero-title {
  font-size: clamp(2rem, 5.5vw, 2.8rem);
  font-weight: 900;
  letter-spacing: -0.03em;
  background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 60%, var(--secondary) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  text-shadow: none;
}

.hero-sub {
  margin-top: 8px;
  font-size: 1.05rem;
  color: var(--text-secondary);
  font-weight: 600;
}

/* === XP BAR (Stats) === */
.xp-bar {
  display: flex;
  justify-content: center;
  gap: 16px;
  width: 100%;
  margin-bottom: 28px;
  position: relative;
  z-index: 1;
}

.xp-item {
  display: flex;
  align-items: center;
  gap: 10px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 12px 16px;
  box-shadow: var(--shadow-sm);
  flex: 1;
  max-width: 200px;
  transition: transform var(--transition), box-shadow var(--transition);
}

.xp-item:hover { transform: translateY(-2px); box-shadow: var(--shadow-md); }

.xp-icon { font-size: 1.4rem; flex-shrink: 0; }

.xp-val {
  font-family: var(--mono);
  font-size: 1.2rem;
  font-weight: 800;
  color: var(--primary);
}

.xp-lbl {
  font-size: 0.68rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

/* === CONFIG PANEL === */
.config-panel {
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: 18px;
  margin-bottom: 28px;
  position: relative;
  z-index: 1;
}

.config-step {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 22px;
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition);
}

.config-step:hover { box-shadow: var(--shadow-md); }

.config-label {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-bottom: 14px;
}

/* Soft tinted info bar below the label */
.quest-info-bar {
  display: flex;
  align-items: center;
  gap: 8px;
  margin: 0 0 16px;
  padding: 10px 14px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text);
  background: color-mix(in srgb, var(--primary) 8%, transparent);
  border: 1px solid color-mix(in srgb, var(--primary) 18%, transparent);
  border-radius: 12px;
}
.qib-icon { font-size: 1rem; }

.step-num {
  width: 26px; height: 26px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  color: #FFFFFF;
  font-size: 0.75rem;
  font-weight: 800;
  display: flex; align-items: center; justify-content: center;
  flex-shrink: 0;
  box-shadow: 0 2px 8px var(--primary-glow);
}

/* === BUTTON GROUP === */
.btn-group { display: flex; flex-wrap: wrap; gap: 10px; }

.opt-btn {
  padding: 10px 22px;
  border: 2px solid var(--border);
  border-radius: 24px;
  background: var(--card);
  font-family: var(--font);
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition);
}

.opt-btn:hover:not(.disabled):not(.selected) {
  border-color: var(--primary);
  color: var(--primary);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px var(--primary-glow);
}

.opt-btn.selected {
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  border-color: transparent;
  color: #FFFFFF;
  box-shadow: 0 4px 16px var(--primary-glow);
  transform: translateY(-1px);
}

.opt-btn.disabled { opacity: 0.35; cursor: not-allowed; }
.opt-btn.mono { font-family: var(--mono); font-weight: 700; }

/* === TOPIC GRID === */
.topic-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 14px;
}

.topic-card {
  position: relative;
  background: var(--card);
  border: 2px solid var(--border);
  border-radius: var(--radius);
  padding: 22px 18px;
  cursor: pointer;
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  overflow: hidden;
}

.topic-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 4px;
  background: linear-gradient(90deg, var(--primary), var(--accent));
  opacity: 0;
  transition: opacity 0.3s ease;
}

.topic-card::after {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, transparent 60%, var(--primary-glow));
  opacity: 0;
  transition: opacity 0.3s ease;
  pointer-events: none;
}

.topic-card:hover {
  border-color: var(--border-active);
  transform: translateY(-4px);
  box-shadow: var(--shadow-md), 0 0 20px var(--primary-glow);
}

.topic-card:hover::before { opacity: 1; }
.topic-card:hover::after { opacity: 0.3; }

.topic-card.selected {
  border-color: var(--primary);
  background: var(--primary-light);
  box-shadow: 0 6px 24px var(--primary-glow);
}

.topic-card.selected::before { opacity: 1; }
.topic-card.selected::after { opacity: 0.5; }

.topic-card-check {
  position: absolute;
  top: 12px; right: 12px;
  width: 24px; height: 24px;
  border-radius: 50%;
  border: 2px solid var(--border);
  display: flex; align-items: center; justify-content: center;
  transition: all var(--transition);
}

.topic-card.selected .topic-card-check {
  background: linear-gradient(135deg, var(--primary), var(--accent));
  border-color: transparent;
  box-shadow: 0 2px 8px var(--primary-glow);
}

.topic-card-check svg {
  width: 13px; height: 13px;
  fill: none; stroke: #FFFFFF; stroke-width: 3;
  stroke-linecap: round; stroke-linejoin: round;
  opacity: 0; transition: opacity var(--transition);
}
.topic-card.selected .topic-card-check svg { opacity: 1; }

.topic-icon {
  width: 48px; height: 48px;
  border-radius: 13px;
  display: flex; align-items: center; justify-content: center;
  font-size: 1.4rem;
  margin-bottom: 12px;
  box-shadow: var(--shadow-sm);
}

.topic-icon.c-blue { background: var(--primary-light); }
.topic-icon.c-amber { background: var(--secondary-light); }
.topic-icon.c-green { background: var(--success-light); }
.topic-icon.c-purple { background: var(--accent-light); }
.topic-icon.c-rose { background: #ffe4ee; }

.topic-name {
  font-size: 0.93rem;
  font-weight: 700;
  color: var(--text);
  line-height: 1.3;
  margin-bottom: 4px;
}

.topic-desc {
  font-size: 0.76rem;
  color: var(--text-muted);
  font-weight: 500;
}

.topic-progress {
  margin-top: 12px;
  height: 5px;
  background: var(--border);
  border-radius: 5px;
  overflow: hidden;
}

.topic-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--success));
  border-radius: 5px;
  width: 0%;
  transition: width 0.5s ease;
}

/* === START BUTTON === */
.btn-start {
  position: relative;
  display: block;
  width: 100%;
  max-width: 480px;
  padding: 18px 36px;
  border: none;
  border-radius: var(--radius-sm);
  background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
  color: #FFFFFF;
  font-family: var(--font);
  font-size: 1.1rem;
  font-weight: 800;
  letter-spacing: 0.01em;
  cursor: pointer;
  transition: all 0.3s ease;
  box-shadow: 0 8px 24px var(--primary-glow);
  overflow: hidden;
  z-index: 1;
}

.btn-start-text { position: relative; z-index: 2; }

.btn-start-glow {
  position: absolute;
  inset: 0;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.2), transparent);
  transform: translateX(-100%);
  animation: shimmer 2.5s ease-in-out infinite;
}

@keyframes shimmer {
  0% { transform: translateX(-100%); }
  60%, 100% { transform: translateX(100%); }
}

.btn-start:hover:not(:disabled) {
  transform: translateY(-3px) scale(1.01);
  box-shadow: 0 12px 36px var(--primary-glow);
}

.btn-start:disabled {
  opacity: 0.45;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

.btn-start:disabled .btn-start-glow { animation: none; }

/* === HUD (Exercise) === */
.hud {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  padding: 10px 16px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-sm);
  margin-bottom: 10px;
}

.hud-left { display: flex; align-items: center; gap: 16px; }
.hud-right { display: flex; align-items: center; }

.hud-cell { display: flex; align-items: center; gap: 5px; }
.hud-lbl { font-size: 0.72rem; font-weight: 700; color: var(--text-muted); text-transform: uppercase; }
.hud-val { font-size: 0.9rem; font-weight: 700; color: var(--text); }
.hud-val.mono { font-family: var(--mono); }

/* SCORE BADGE — distinct from other HUD items */
.hud-score-wrap { display: flex; align-items: center; justify-content: center; }

.hud-score-badge {
  display: flex;
  align-items: center;
  gap: 6px;
  background: linear-gradient(135deg, #FEF3C7, #FDE68A);
  border: 2px solid #F59E0B;
  border-radius: 24px;
  padding: 6px 16px;
  box-shadow: 0 3px 12px rgba(245, 158, 11, 0.3);
  transition: transform 0.2s ease;
}

[data-theme="dark"] .hud-score-badge {
  background: linear-gradient(135deg, #78350F, #92400E);
  border-color: #FBBF24;
  box-shadow: 0 3px 12px rgba(251, 191, 36, 0.2);
}

.hud-score-badge.pulse {
  animation: scorePulse 0.4s ease;
}

@keyframes scorePulse {
  0% { transform: scale(1); }
  50% { transform: scale(1.15); }
  100% { transform: scale(1); }
}

.hud-score-star { font-size: 1rem; }

.hud-score-num {
  font-family: var(--mono);
  font-size: 1.2rem;
  font-weight: 800;
  color: #92400E;
}

[data-theme="dark"] .hud-score-num { color: #FBBF24; }

.hud-quit {
  padding: 6px 14px;
  border: 1px solid var(--danger);
  border-radius: 20px;
  background: var(--danger-light);
  color: var(--danger);
  font-family: var(--font);
  font-size: 0.78rem;
  font-weight: 700;
  cursor: pointer;
  transition: all var(--transition);
}
.hud-quit:hover { background: var(--danger); color: #FFF; }

/* === PROGRESS BAR === */
.progress-track {
  width: 100%;
  height: 6px;
  background: var(--border);
  border-radius: 6px;
  margin-bottom: 24px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--accent), var(--success));
  background-size: 200% 100%;
  border-radius: 6px;
  width: 0%;
  transition: width 0.4s ease;
  animation: progressShine 2s linear infinite;
}

@keyframes progressShine {
  0% { background-position: 0% 0; }
  100% { background-position: 200% 0; }
}

/* === QUESTION CARD === */
.question-card {
  width: 100%;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 30px 26px;
  box-shadow: var(--shadow-md);
  margin-bottom: 20px;
}

.q-stem {
  font-size: 1.08rem;
  font-weight: 600;
  color: var(--text);
  line-height: 1.7;
  margin-bottom: 22px;
}

.q-stem .blank {
  display: inline-block;
  min-width: 90px;
  border-bottom: 2.5px dashed var(--primary);
  margin: 0 4px;
}

.options-list { display: flex; flex-direction: column; gap: 10px; }

.option-btn {
  display: flex;
  align-items: center;
  width: 100%;
  padding: 15px 20px;
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--card);
  font-family: var(--font);
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--text);
  text-align: left;
  cursor: pointer;
  transition: all var(--transition);
  position: relative;
  overflow: hidden;
}

.option-btn::before {
  content: '';
  position: absolute;
  left: 0; top: 0; bottom: 0;
  width: 4px;
  background: var(--primary);
  opacity: 0;
  transition: opacity var(--transition);
}

.option-btn:hover:not(.correct):not(.wrong):not(.revealed) {
  border-color: var(--primary);
  background: var(--card-hover);
  transform: translateX(4px);
}

.option-btn:hover:not(.correct):not(.wrong):not(.revealed)::before { opacity: 1; }

.option-btn.correct {
  border-color: var(--success);
  background: var(--success-light);
  color: var(--success);
  font-weight: 700;
  cursor: default;
  animation: correctPop 0.3s ease;
}

.option-btn.correct::before { opacity: 1; background: var(--success); }

@keyframes correctPop {
  0% { transform: scale(1); }
  50% { transform: scale(1.02); }
  100% { transform: scale(1); }
}

.option-btn.wrong {
  border-color: var(--danger);
  background: var(--danger-light);
  color: var(--danger);
  opacity: 0.75;
  cursor: default;
  animation: shake 0.35s ease;
}

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  25% { transform: translateX(-6px); }
  75% { transform: translateX(6px); }
}

.option-btn.revealed { cursor: default; opacity: 0.4; }

/* === NEXT BUTTON === */
.btn-next {
  margin-top: 28px;
  padding: 15px 36px;
  border: none;
  border-radius: var(--radius-sm);
  background: linear-gradient(135deg, var(--primary), var(--accent));
  color: #FFFFFF;
  font-family: var(--font);
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  transition: all var(--transition);
  box-shadow: 0 4px 16px var(--primary-glow);
}
.btn-next:hover { transform: translateY(-2px); box-shadow: 0 8px 24px var(--primary-glow); }
.btn-next.hidden { display: none; }

/* === RESULTS === */
.results-wrap {
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.results-trophy {
  font-size: 3.5rem;
  margin-bottom: 8px;
  animation: bounce 1s ease infinite;
}

@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-8px); }
}

.results-title {
  font-size: 1.8rem;
  font-weight: 900;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 20px;
}

.results-card {
  width: 100%;
  max-width: 480px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 30px 26px;
  text-align: center;
  box-shadow: var(--shadow-md);
  margin-bottom: 24px;
}

.results-score-lbl {
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.results-score {
  font-family: var(--mono);
  font-size: 2.8rem;
  font-weight: 800;
  color: var(--primary);
  margin: 8px 0;
  text-shadow: 0 2px 10px var(--primary-glow);
}

.results-remark {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 20px;
}

.results-stats {
  display: flex;
  justify-content: center;
  gap: 36px;
  margin-bottom: 20px;
}

.res-stat { text-align: center; }
.res-icon { font-size: 1.2rem; margin-bottom: 4px; }
.res-val { font-family: var(--mono); font-size: 1.1rem; font-weight: 700; color: var(--text); }
.res-lbl { font-size: 0.7rem; font-weight: 600; color: var(--text-muted); text-transform: uppercase; margin-top: 2px; }

.divider { height: 1px; background: var(--border); margin: 16px 0; }

.review-panel { width: 100%; max-width: 600px; margin-bottom: 24px; }
.review-heading { font-size: 1rem; font-weight: 700; color: var(--text); margin-bottom: 12px; }
.review-list { display: flex; flex-direction: column; gap: 10px; }

.review-item {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 14px 16px;
  text-align: left;
}

.review-q { font-size: 0.88rem; color: var(--text); margin-bottom: 6px; line-height: 1.5; }
.review-a { font-size: 0.82rem; font-weight: 700; color: var(--success); }

.btn-again {
  padding: 15px 40px;
  border: none;
  border-radius: var(--radius-sm);
  background: linear-gradient(135deg, var(--primary), var(--accent));
  color: #FFFFFF;
  font-family: var(--font);
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  transition: all var(--transition);
  box-shadow: 0 4px 16px var(--primary-glow);
}
.btn-again:hover { transform: translateY(-2px); box-shadow: 0 8px 24px var(--primary-glow); }

/* === FOOTER === */
.site-footer {
  text-align: center;
  padding: 16px;
  font-size: 0.76rem;
  color: var(--text-muted);
  border-top: 1px solid var(--border);
  background: var(--bg2);
  margin-top: auto;
  flex-shrink: 0;
}
.app-version {
  opacity: 0.7;
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}

/* === RESPONSIVE === */
@media (max-width: 600px) {
  .topbar-title { display: none; }
  .topic-grid { grid-template-columns: 1fr; }
  .xp-bar { flex-direction: column; gap: 10px; }
  .xp-item { max-width: none; }
  .hud { flex-wrap: wrap; gap: 8px; padding: 10px 12px; }
  .hud-left { gap: 10px; }
  .question-card { padding: 22px 16px; }
  .screen { padding: 20px 16px 32px; }
  .hud-score-badge { padding: 5px 12px; }
  .hud-score-num { font-size: 1rem; }

  /* Compact builder layout on mobile (Reported Speech + Relative Clauses):
     reduce vertical padding and tighten gaps so the question and options
     fit on one screen with less scrolling. */
  .builder-card { padding: 16px 14px; }
  .builder-source { padding: 12px 14px; margin-bottom: 14px; }
  .builder-step { margin-bottom: 14px; }
  .builder-step-label { margin-bottom: 8px; }
  .builder-instr { margin: 4px 0 12px; padding: 8px 12px; }
  .pronoun-chips { gap: 7px; }
  .pronoun-chip { padding: 7px 16px; }
  .clause-build { gap: 10px; }
  .clause-assembled { min-height: 44px; padding: 8px 10px; gap: 7px; }
  .clause-tiles { gap: 7px; }
  .word-tile { padding: 6px 13px; }
  .assembled-tok { padding: 5px 11px; }
}

@media (min-width: 601px) and (max-width: 900px) {
  .topic-grid { grid-template-columns: repeat(2, 1fr); }
}

/* === UTILITY === */
.hidden { display: none !important; }


/* ============================================================
   PASSAGE EXERCISE
   ============================================================ */
.passage-instructions {
  max-width: 760px;
  margin: 0 auto 16px;
  padding: 14px 20px;
  background: var(--accent-light);
  border: 1px solid var(--border-active);
  border-left: 4px solid var(--primary);
  border-radius: 12px;
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--text-secondary);
  line-height: 1.5;
}

.passage-card {
  max-width: 760px;
  margin: 0 auto;
  padding: 28px 32px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 18px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.06);
}

.passage-title {
  font-size: 1.25rem;
  font-weight: 800;
  color: var(--text);
  margin-bottom: 18px;
  letter-spacing: -0.01em;
}

.passage-body {
  font-size: 1.05rem;
  line-height: 2.4;
  color: var(--text);
  text-align: left;
}

.blank-wrap {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  margin: 0 2px;
  vertical-align: middle;
  white-space: nowrap;
}

.blank-num {
  font-family: var(--mono);
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--text-muted);
}

.blank-select {
  font-family: var(--font, 'Inter', sans-serif);
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--primary);
  padding: 4px 8px;
  border: 2px solid var(--border-active);
  border-radius: 8px;
  background: var(--bg2);
  cursor: pointer;
  transition: all 0.15s ease;
  min-width: 56px;
  text-align: center;
  appearance: none;
  -webkit-appearance: none;
  background-image: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='10' height='6' viewBox='0 0 10 6'><path d='M1 1l4 4 4-4' stroke='%232563EB' stroke-width='2' fill='none' stroke-linecap='round'/></svg>");
  background-repeat: no-repeat;
  background-position: right 8px center;
  padding-right: 24px;
}

.blank-select:hover { border-color: var(--primary); }
.blank-select:focus { outline: none; box-shadow: 0 0 0 3px var(--accent-light); }
.blank-select.filled {
  background-color: var(--accent-light);
  border-color: var(--primary);
}

/* Text-input blanks (e.g. Passive Voice) */
.blank-input {
  font-family: var(--font, 'Inter', sans-serif);
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--primary);
  padding: 4px 10px;
  border: 2px solid var(--border-active);
  border-radius: 8px;
  background: var(--bg2);
  transition: all 0.15s ease;
  width: 175px;
  max-width: 100%;
  text-align: center;
}
@media (max-width: 600px) {
  .blank-input { width: 150px; }
}
.blank-input:hover { border-color: var(--primary); }
.blank-input:focus { outline: none; box-shadow: 0 0 0 3px var(--accent-light); }
.blank-input.filled {
  background-color: var(--accent-light);
  border-color: var(--primary);
}
.blank-prompt {
  font-family: var(--mono);
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--text-muted);
  font-style: italic;
}
/* Input blanks may be wide, so allow the wrap to break onto a new line */
.passage-body .blank-wrap:has(.blank-input) {
  white-space: normal;
}

/* ============================================================
   PASSAGE REVIEW (results)
   ============================================================ */
.passage-review {
  font-size: 1.02rem;
  line-height: 2.6;
  color: var(--text);
  text-align: left;
}

.rev-blank {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  margin: 0 3px;
  padding: 2px 8px;
  border-radius: 8px;
  vertical-align: middle;
  font-weight: 700;
  white-space: nowrap;
}

.rev-blank.correct {
  background: var(--success-light);
  border: 1.5px solid var(--success);
}
.rev-blank.wrong {
  background: var(--danger-light);
  border: 1.5px solid var(--danger);
}

.rev-mark {
  font-size: 0.85rem;
  font-weight: 900;
}
.rev-blank.correct .rev-mark { color: var(--success); }
.rev-blank.wrong .rev-mark { color: var(--danger); }

.rev-ans { color: var(--success); }
.rev-blank.correct .rev-ans { color: var(--success); }
.rev-wrong {
  color: var(--danger);
  text-decoration: line-through;
  text-decoration-thickness: 2px;
}
.rev-correct {
  color: var(--success);
  font-weight: 800;
  padding-left: 2px;
}
.rev-correct::before {
  content: "\2192";
  margin-right: 3px;
  color: var(--text-muted);
  font-weight: 700;
}

/* Explanation info icon + popover */
.rev-info {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 18px;
  height: 18px;
  margin-left: 4px;
  border: none;
  border-radius: 50%;
  background: var(--primary);
  color: #fff;
  font-family: Georgia, 'Times New Roman', serif;
  font-style: italic;
  font-weight: 700;
  font-size: 0.74rem;
  line-height: 1;
  cursor: pointer;
  flex: 0 0 auto;
  transition: transform 0.12s ease, background 0.12s ease;
}
.rev-info:hover { transform: scale(1.15); }
.rev-info.open { background: var(--text); }

.rev-popover {
  position: absolute;
  left: 50%;
  bottom: calc(100% + 10px);
  transform: translateX(-50%);
  width: max-content;
  max-width: 280px;
  white-space: normal;
  background: var(--text);
  color: var(--bg2);
  font-size: 0.82rem;
  font-weight: 500;
  line-height: 1.45;
  text-align: left;
  padding: 9px 12px;
  border-radius: 10px;
  box-shadow: 0 8px 24px rgba(0,0,0,0.28);
  z-index: 50;
}
.rev-popover::after {
  content: "";
  position: absolute;
  top: 100%;
  left: var(--caret-shift, 50%);
  transform: translateX(-50%);
  border: 7px solid transparent;
  border-top-color: var(--text);
}
/* The review blank must be the positioning context for the popover */
.rev-blank { position: relative; }

/* Responsive: passage on mobile */
@media (max-width: 600px) {
  .passage-card { padding: 20px 18px; }
  .passage-body { font-size: 0.98rem; line-height: 2.3; }
  .passage-review { font-size: 0.95rem; }
}

/* ============================================================
   BUILDER EXERCISE (Relative Clauses)
   ============================================================ */
.builder-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-md);
  padding: 22px;
  max-width: 760px;
  margin: 18px auto 0;
}

/* Source sentences */
.builder-source {
  display: flex;
  flex-direction: column;
  gap: 10px;
  background: var(--bg);
  border-radius: var(--radius-sm);
  padding: 16px 18px;
  margin-bottom: 22px;
}
.src-line {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  font-size: 1.06rem;
  line-height: 1.5;
  color: var(--text);
}
.src-num {
  flex: 0 0 auto;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  background: var(--primary);
  color: #fff;
  font-size: 0.8rem;
  font-weight: 800;
  display: grid;
  place-items: center;
  margin-top: 2px;
}

/* Steps */
.builder-step { margin-bottom: 22px; }
.builder-step:last-child { margin-bottom: 4px; }
.builder-step-label {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 800;
  font-size: 0.95rem;
  color: var(--text);
  margin-bottom: 12px;
}
.bstep-num {
  flex: 0 0 auto;
  width: 26px;
  height: 26px;
  border-radius: 50%;
  background: var(--accent);
  color: #fff;
  font-size: 0.85rem;
  font-weight: 800;
  display: grid;
  place-items: center;
}

/* Step 1: pronoun chips */
.pronoun-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}
.pronoun-chip {
  font-family: inherit;
  font-size: 1rem;
  font-weight: 700;
  padding: 10px 20px;
  border-radius: 999px;
  border: 2px solid var(--border);
  background: var(--card);
  color: var(--text);
  cursor: pointer;
  transition: all 0.15s ease;
}
.pronoun-chip:hover {
  border-color: var(--border-active);
  transform: translateY(-1px);
}
.pronoun-chip.selected {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
  box-shadow: var(--shadow-glow);
}

/* Step 2: clause builder */
.clause-build { display: flex; flex-direction: column; gap: 14px; }
.clause-assembled {
  min-height: 52px;
  border: 2px dashed var(--border-active);
  border-radius: var(--radius-sm);
  background: var(--bg);
  padding: 12px 14px;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
}
.clause-placeholder {
  color: var(--text-muted);
  font-style: italic;
}

.full-answer {
  margin-top: 1rem;
  padding: 1rem;
  background: var(--bg);
  border-radius: 0.5rem;
  border-left: 4px solid var(--primary);
  font-size: 1.1rem;
  line-height: 1.5;
  color: var(--text);
}
.full-answer-lbl {
  font-weight: 700;
  color: var(--text-secondary);
  margin-right: 0.5rem;
  font-size: 0.9rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}
.assembled-tok {
  display: inline-block;
  background: var(--primary);
  color: #fff;
  font-weight: 700;
  font-family: inherit;
  font-size: 1rem;
  padding: 6px 12px;
  border: none;
  border-radius: var(--radius-xs);
  box-shadow: var(--shadow-sm);
  cursor: pointer;
  position: relative;
  transition: all 0.15s ease;
}
.assembled-tok:hover {
  background: var(--danger, #ef4444);
  transform: translateY(-2px);
}
.assembled-tok:hover::after {
  content: '\00d7';
  margin-left: 6px;
  font-weight: 800;
}
.clause-tiles {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}
.word-tile {
  font-family: inherit;
  font-size: 1rem;
  font-weight: 600;
  padding: 9px 16px;
  border-radius: var(--radius-xs);
  border: 2px solid var(--border);
  background: var(--card);
  color: var(--text);
  cursor: pointer;
  transition: all 0.15s ease;
}
.word-tile:not(.used):hover {
  border-color: var(--accent);
  transform: translateY(-2px);
  box-shadow: var(--shadow-sm);
}
.word-tile.used {
  opacity: 0.35;
  background: var(--bg);
  border-style: dashed;
  cursor: default;
  pointer-events: none;
}
.word-tile.used:hover {
  border-color: var(--border);
  transform: none;
  box-shadow: none;
}
.clause-clear {
  align-self: flex-start;
  font-family: inherit;
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--text-secondary);
  background: transparent;
  border: none;
  cursor: pointer;
  padding: 4px 2px;
}
.clause-clear:hover { color: var(--danger); }

/* Step 3: placement */
.place-line {
  display: block;
  font-size: 1.06rem;
  line-height: 1.9;
  color: var(--text);
}
.place-seg { padding: 2px 0; }
/* Keeps the last word of a segment + its gap button together on one line
   (no orphan gaps), while leading words wrap freely word-by-word. */
.place-unit {
  display: inline-flex;
  align-items: center;
  gap: 0;
  white-space: nowrap;
  vertical-align: middle;
}
.place-gap {
  font-family: inherit;
  border: none;
  background: transparent;
  cursor: pointer;
  padding: 0;
  margin: 0 0.3em; /* symmetric space on both sides of the + dot */
  vertical-align: middle;
}
.gap-dot {
  display: inline-grid;
  place-items: center;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  background: var(--primary-light);
  color: var(--primary);
  font-weight: 800;
  font-size: 0.85rem;
  border: 2px dashed var(--border-active);
  transition: all 0.15s ease;
}
.place-gap:hover .gap-dot {
  background: var(--primary);
  color: #fff;
  transform: scale(1.1);
}
.place-gap.selected .gap-dot {
  background: var(--accent);
  color: #fff;
  border-style: solid;
  border-color: var(--accent);
}

/* ---- Builder review (answer key) ---- */
.builder-review { text-align: left; }
.br-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 8px;
}
.br-num {
  width: 26px; height: 26px;
  border-radius: 50%;
  background: var(--primary);
  color: #fff; font-weight: 800; font-size: 0.8rem;
  display: grid; place-items: center;
}
.br-marks {
  font-weight: 800;
  font-size: 0.9rem;
  color: var(--text-secondary);
  background: var(--bg);
  padding: 3px 10px;
  border-radius: 999px;
}
.br-source {
  display: flex;
  flex-direction: column;
  gap: 2px;
  color: var(--text-secondary);
  font-size: 0.92rem;
  margin-bottom: 10px;
}
.br-badges { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 10px; }
.bm {
  font-size: 0.8rem;
  font-weight: 700;
  padding: 3px 10px;
  border-radius: 999px;
}
.bm-ok { background: var(--success-light); color: var(--success); }
.bm-no { background: var(--danger-light); color: var(--danger); }
.br-yours, .br-correct {
  font-size: 0.96rem;
  line-height: 1.5;
  margin-top: 4px;
}
.br-yours { color: var(--text-secondary); }
.br-correct { color: var(--text); }
.br-lbl { font-weight: 800; margin-right: 4px; }
.br-hl {
  background: var(--success-light);
  color: var(--success);
  font-weight: 700;
  padding: 1px 5px;
  border-radius: 5px;
}

/* ============================================================ */
/* BUILDER v3 ADDITIONS: instructions, score badge, check btn,  */
/* and immediate per-step feedback states                       */
/* ============================================================ */

/* Per-question instructions */
.builder-instr {
  margin: 4px 0 18px;
  padding: 10px 14px;
  background: var(--primary-light);
  border-left: 4px solid var(--primary);
  border-radius: var(--radius-xs);
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-secondary);
  line-height: 1.5;
}

/* Cumulative score badge in the builder HUD (gold, like MC) */
.score-badge {
  display: flex;
  align-items: center;
  gap: 6px;
  background: linear-gradient(135deg, #FEF3C7, #FDE68A);
  border: 2px solid #F59E0B;
  border-radius: 24px;
  padding: 6px 16px;
  margin-right: 10px;
  box-shadow: 0 3px 12px rgba(245, 158, 11, 0.3);
  transition: transform 0.2s ease;
}
[data-theme="dark"] .score-badge {
  background: linear-gradient(135deg, #78350F, #92400E);
  border-color: #FBBF24;
  box-shadow: 0 3px 12px rgba(251, 191, 36, 0.2);
}
.score-badge.pulse { animation: scorePulse 0.4s ease; }
.sb-star { font-size: 1rem; }
.score-badge #builder-score {
  font-family: var(--mono);
  font-size: 1.2rem;
  font-weight: 800;
  color: #92400E;
}
[data-theme="dark"] .score-badge #builder-score { color: #FBBF24; }

/* Check Answer button */
.btn-check {
  display: block;
  margin: 22px auto 0;
  padding: 14px 40px;
  border: none;
  border-radius: 999px;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  color: #fff;
  font-family: inherit;
  font-size: 1.05rem;
  font-weight: 800;
  cursor: pointer;
  box-shadow: var(--shadow-glow);
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}
.btn-check:hover { transform: translateY(-2px); box-shadow: 0 8px 24px rgba(59,130,246,0.4); }
.btn-check.hidden, .btn-next.hidden { display: none; }
.clause-clear.hidden { display: none; }

/* ---- Step 1 feedback: pronoun chips ---- */
.pronoun-chip.locked { cursor: default; pointer-events: none; }
.pronoun-chip.correct {
  background: var(--success);
  border-color: var(--success);
  color: #fff;
  box-shadow: 0 0 0 3px var(--success-light);
}
.pronoun-chip.wrong {
  background: var(--danger);
  border-color: var(--danger);
  color: #fff;
  text-decoration: line-through;
}
.pronoun-chip.locked:not(.correct):not(.wrong) { opacity: 0.5; }
.chip-tick {
  display: inline-block;
  margin-left: 4px;
  font-weight: 900;
}
.clause-tick {
  display: inline-block;
  margin-left: 6px;
  color: var(--success);
  font-weight: 900;
  font-size: 1.1em;
}

/* ---- Step 2 feedback: assembled clause ---- */
.clause-assembled.fb-ok {
  border-style: solid;
  border-color: var(--success);
  background: var(--success-light);
}
.clause-assembled.fb-no {
  border-style: solid;
  border-color: var(--danger);
  background: var(--danger-light);
}
.fb-correct {
  display: inline-block;
  font-weight: 800;
  color: var(--success);
  margin-left: 4px;
}
.word-tile.locked { cursor: default; pointer-events: none; }

/* ---- Step 3 feedback: placement gaps ---- */
.place-gap.locked { cursor: default; pointer-events: none; }
.place-gap.gap-correct .gap-dot {
  background: var(--success);
  color: #fff;
  border-style: solid;
  border-color: var(--success);
  box-shadow: 0 0 0 3px var(--success-light);
}
.place-gap.gap-wrong .gap-dot {
  background: var(--danger);
  color: #fff;
  border-style: solid;
  border-color: var(--danger);
}