/* ══════════════════════════════════════════════════════
   Quiz Hub — Shared Styles
   Each course loads this + sets CSS custom properties
   for theming via :root overrides in their HTML.
   ══════════════════════════════════════════════════════ */
:root {
  --bg: #08090e; --bg-raised: #0f1118; --bg-card: #151821; --bg-card-hover: #1a1e2a;
  --bg-glass: rgba(18,21,32,0.72); --border: rgba(255,255,255,0.06); --border-accent: rgba(108,140,255,0.25);
  --text: #e8eaf0; --text-secondary: #a0a8c0; --text-dim: #5e6580;
  --accent: #6c8cff; --accent-soft: rgba(108,140,255,0.1); --accent-glow: rgba(108,140,255,0.15);
  --green: #22d3a7; --green-soft: rgba(34,211,167,0.1); --green-border: rgba(34,211,167,0.25);
  --red: #f06070; --red-soft: rgba(240,96,112,0.1); --red-border: rgba(240,96,112,0.25);
  --yellow: #f0b040; --yellow-soft: rgba(240,176,64,0.1); --yellow-border: rgba(240,176,64,0.25);
  --purple: #a78bfa; --purple-soft: rgba(167,139,250,0.1);
  --font: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --mono: 'JetBrains Mono', monospace;
  --radius: 16px; --radius-sm: 10px; --radius-xs: 6px;
  --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body { font-family: var(--font); background: var(--bg); color: var(--text); min-height: 100vh; overflow-x: hidden; }

/* ── NAV BAR ── */
.nav-bar {
  position: sticky; top: 0; z-index: 100;
  display: flex; align-items: center; gap: 0.5rem;
  padding: 0 1.5rem; height: 56px;
  background: rgba(8,9,14,0.85); backdrop-filter: blur(20px) saturate(1.6);
  border-bottom: 1px solid var(--border);
}
.nav-bar a {
  color: var(--text-secondary); text-decoration: none; font-size: 0.82rem; font-weight: 600;
  padding: 0.4rem 0.75rem; border-radius: 8px; transition: all var(--transition);
}
.nav-bar a:hover { color: var(--accent); background: var(--accent-soft); }
.nav-title {
  font-size: 1rem; font-weight: 800; color: var(--text);
  display: flex; align-items: center; gap: 0.45rem;
  background: linear-gradient(135deg, #e8eaf0 0%, var(--accent) 100%);
  -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text;
}
.nav-spacer { flex: 1; }
#langToggle {
  background: transparent; border: 1px solid var(--border-accent); color: var(--accent);
  font-size: 0.78rem; font-weight: 700; padding: 0.32rem 0.85rem; border-radius: 20px;
  cursor: pointer; font-family: var(--font); transition: all var(--transition); letter-spacing: 0.02em;
}
#langToggle:hover { background: var(--accent); color: #fff; }

/* ── CONFIG PANEL ── */
.config-panel { max-width: 1100px; margin: 0 auto; padding: 1.5rem 1.5rem 0; }
.config-toggle {
  display: flex; align-items: center; gap: 0.6rem; cursor: pointer;
  padding: 0.75rem 1rem; border-radius: var(--radius); margin-bottom: 0.75rem;
  background: var(--bg-raised); border: 1px solid var(--border);
  transition: all var(--transition); user-select: none;
}
.config-toggle:hover { border-color: var(--border-accent); }
.config-toggle .cfg-icon { font-size: 1.1rem; }
.config-toggle .cfg-label { font-size: 0.88rem; font-weight: 700; flex: 1; }
.config-toggle .cfg-summary { font-size: 0.78rem; color: var(--text-dim); font-weight: 500; }
.config-toggle .cfg-arrow { transition: transform var(--transition); color: var(--text-dim); font-size: 0.9rem; }
.config-toggle.open .cfg-arrow { transform: rotate(180deg); }
.config-body { display: none; animation: slideDown 0.3s ease-out; }
.config-body.show { display: block; }
@keyframes slideDown { from { opacity: 0; transform: translateY(-8px); } to { opacity: 1; transform: translateY(0); } }

.config-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; padding-bottom: 1.5rem; }
@media (max-width: 700px) { .config-grid { grid-template-columns: 1fr; } }

.cfg-card {
  background: var(--bg-raised); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 1.15rem; transition: border-color var(--transition);
}
.cfg-card:hover { border-color: rgba(255,255,255,0.1); }
.cfg-card h4 {
  font-size: 0.68rem; text-transform: uppercase; letter-spacing: 0.1em;
  color: var(--text-dim); margin-bottom: 0.75rem; font-weight: 700;
}

/* Chapter chips */
.ch-chips { display: flex; flex-wrap: wrap; gap: 0.35rem; }
.ch-chip {
  padding: 0.35rem 0.65rem; border-radius: 8px; font-size: 0.76rem; font-weight: 600;
  border: 1px solid var(--border); background: transparent; color: var(--text-dim);
  cursor: pointer; transition: all var(--transition); font-family: var(--font); line-height: 1;
}
.ch-chip.active { background: var(--accent); color: #fff; border-color: var(--accent); box-shadow: 0 2px 12px rgba(108,140,255,0.25); }
.ch-chip:hover:not(.active) { border-color: var(--accent); color: var(--text-secondary); }
.ch-chip-action {
  padding: 0.3rem 0.55rem; border-radius: 6px; font-size: 0.68rem; font-weight: 700;
  border: 1px dashed var(--border); background: transparent; color: var(--text-dim);
  cursor: pointer; transition: all var(--transition); font-family: var(--font);
  text-transform: uppercase; letter-spacing: 0.06em;
}
.ch-chip-action:hover { border-color: var(--accent); color: var(--accent); }

/* Segmented controls */
.seg-ctrl { display: flex; gap: 3px; background: rgba(255,255,255,0.03); border-radius: var(--radius-sm); padding: 3px; }
.seg-btn {
  flex: 1; padding: 0.55rem 0.75rem; border-radius: 8px; font-size: 0.82rem; font-weight: 600;
  border: none; background: transparent; color: var(--text-dim);
  cursor: pointer; transition: all var(--transition); font-family: var(--font); text-align: center;
}
.seg-btn.active { background: var(--accent); color: #fff; box-shadow: 0 2px 12px rgba(108,140,255,0.3); }
.seg-btn:hover:not(.active) { color: var(--text-secondary); background: rgba(255,255,255,0.04); }

/* Toggle switches */
.toggle-row { display: flex; align-items: center; gap: 0.75rem; padding: 0.5rem 0; cursor: pointer; user-select: none; }
.toggle-row .toggle-label { font-size: 0.85rem; font-weight: 500; color: var(--text-secondary); flex: 1; }
.toggle-switch {
  width: 40px; height: 22px; border-radius: 11px; position: relative;
  background: rgba(255,255,255,0.08); border: 1px solid rgba(255,255,255,0.1);
  transition: all var(--transition); flex-shrink: 0;
}
.toggle-switch::after {
  content: ""; position: absolute; top: 2px; left: 2px;
  width: 16px; height: 16px; border-radius: 50%; background: var(--text-dim);
  transition: all var(--transition);
}
.toggle-row input { display: none; }
.toggle-row input:checked + .toggle-switch { background: var(--accent); border-color: var(--accent); }
.toggle-row input:checked + .toggle-switch::after { transform: translateX(18px); background: #fff; }

/* Stats row */
.stats-row { display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 0.75rem; margin-bottom: 0.75rem; }
@media (max-width: 600px) { .stats-row { grid-template-columns: 1fr 1fr 1fr; } }
.stat-card {
  background: var(--bg-raised); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 1rem 1.15rem; text-align: center; position: relative; overflow: hidden;
}
.stat-card::before { content: ""; position: absolute; top: 0; left: 0; right: 0; height: 2px; }
.stat-card.missed-stat::before { background: linear-gradient(90deg, transparent, var(--yellow), transparent); }
.stat-card.score-stat::before { background: linear-gradient(90deg, transparent, var(--accent), transparent); }
.stat-card.progress-stat::before { background: linear-gradient(90deg, transparent, var(--green), transparent); }
.stat-value { font-size: 1.8rem; font-weight: 800; font-family: var(--mono); line-height: 1.1; }
.stat-label { font-size: 0.7rem; color: var(--text-dim); margin-top: 0.3rem; text-transform: uppercase; letter-spacing: 0.06em; font-weight: 600; }

/* Action buttons */
.action-row { display: flex; gap: 0.6rem; flex-wrap: wrap; }
.btn {
  padding: 0.7rem 1.5rem; border-radius: var(--radius-sm); font-size: 0.88rem; font-weight: 700;
  border: none; cursor: pointer; font-family: var(--font); transition: all var(--transition);
  display: inline-flex; align-items: center; gap: 0.4rem;
}
.btn-primary {
  background: linear-gradient(135deg, var(--accent) 0%, #5a7ae6 100%); color: #fff;
  box-shadow: 0 4px 20px rgba(108,140,255,0.3);
}
.btn-primary:hover { box-shadow: 0 6px 28px rgba(108,140,255,0.45); transform: translateY(-1px); }
.btn-ghost { background: transparent; border: 1px solid var(--border); color: var(--text-secondary); }
.btn-ghost:hover { border-color: var(--accent); color: var(--accent); }
.btn-warn { background: var(--yellow-soft); border: 1px solid var(--yellow-border); color: var(--yellow); }
.btn-warn:hover { background: rgba(240,176,64,0.18); }
.btn-warn:disabled { opacity: 0.35; cursor: not-allowed; }
.btn-sm { padding: 0.45rem 0.9rem; font-size: 0.78rem; border-radius: 8px; }

/* ── MAIN QUIZ AREA ── */
.quiz-wrapper { max-width: 820px; margin: 0 auto; padding: 0 1.5rem 3rem; min-height: 60vh; }

.empty-hero { text-align: center; padding: clamp(3rem, 10vh, 6rem) 1.5rem; position: relative; }
.empty-hero::before {
  content: ""; position: absolute; top: 20%; left: 50%; transform: translateX(-50%);
  width: 400px; height: 300px;
  background: radial-gradient(ellipse, rgba(108,140,255,0.08), transparent 70%);
  pointer-events: none;
}
.empty-icon { font-size: 3.5rem; margin-bottom: 1.2rem; display: block; position: relative; }
.empty-hero h2 {
  font-size: clamp(1.5rem, 3vw, 2rem); font-weight: 800; position: relative;
  background: linear-gradient(135deg, #e8eaf0, var(--accent)); -webkit-background-clip: text; -webkit-text-fill-color: transparent;
}
.empty-hero p { color: var(--text-dim); font-size: 1.02rem; line-height: 1.7; margin-top: 0.7rem; max-width: 480px; margin-left: auto; margin-right: auto; position: relative; }

/* Practice navigation */
.practice-nav { display: flex; align-items: center; justify-content: space-between; padding: 0.65rem 0; margin-bottom: 1rem; }
.practice-nav .nav-btn {
  display: inline-flex; align-items: center; gap: 0.4rem;
  padding: 0.55rem 1.1rem; border-radius: var(--radius-sm); font-size: 0.85rem; font-weight: 600;
  border: 1px solid var(--border); background: var(--bg-raised); color: var(--text-secondary);
  cursor: pointer; font-family: var(--font); transition: all var(--transition);
}
.practice-nav .nav-btn:hover:not(:disabled) { border-color: var(--accent); color: var(--accent); background: var(--accent-soft); }
.practice-nav .nav-btn:disabled { opacity: 0.25; cursor: not-allowed; }
.practice-counter { font-size: 0.88rem; font-weight: 700; color: var(--text); display: flex; align-items: center; gap: 0.6rem; }
.q-dots { display: flex; gap: 4px; align-items: center; }
.q-dot { width: 8px; height: 8px; border-radius: 50%; background: rgba(255,255,255,0.08); transition: all var(--transition); flex-shrink: 0; }
.q-dot.current { background: var(--accent); box-shadow: 0 0 8px rgba(108,140,255,0.5); transform: scale(1.3); }
.q-dot.answered-ok { background: var(--green); }
.q-dot.answered-bad { background: var(--red); }

/* Quiz card */
.quiz-card {
  background: var(--bg-card); border: 1px solid var(--border); border-radius: 20px;
  padding: clamp(1.5rem, 3vw, 2rem); margin-bottom: 1.25rem;
  transition: all 0.4s ease; position: relative; overflow: hidden;
  box-shadow: 0 4px 32px rgba(0,0,0,0.2);
}
.quiz-card::before {
  content: ""; position: absolute; top: 0; left: 0; right: 0; height: 3px;
  background: linear-gradient(90deg, var(--accent), var(--purple)); opacity: 0.5;
  transition: opacity var(--transition);
}
.quiz-card.answered-correct { border-color: var(--green-border); }
.quiz-card.answered-correct::before { background: var(--green); opacity: 1; }
.quiz-card.answered-wrong { border-color: var(--red-border); }
.quiz-card.answered-wrong::before { background: var(--red); opacity: 1; }

.q-header { display: flex; align-items: center; gap: 0.6rem; margin-bottom: 1rem; flex-wrap: wrap; }
.q-badge { font-family: var(--mono); font-size: 0.72rem; font-weight: 700; padding: 0.3rem 0.7rem; border-radius: 8px; letter-spacing: 0.02em; }
.q-badge.num { background: var(--accent-soft); color: var(--accent); }
.q-badge.study { background: var(--green-soft); color: var(--green); }
.q-badge.math { background: var(--purple-soft); color: var(--purple); }
.q-chapter-tag { font-size: 0.72rem; color: var(--text-dim); font-weight: 500; margin-left: auto; }

.q-text { font-size: clamp(1.02rem, 1.6vw, 1.12rem); line-height: 1.65; margin-bottom: 1.25rem; font-weight: 500; color: var(--text); }

.q-options { display: flex; flex-direction: column; gap: 0.55rem; }
.q-opt {
  display: flex; align-items: flex-start; gap: 0.85rem;
  padding: 0.85rem 1.1rem; border: 1px solid var(--border); border-radius: var(--radius);
  cursor: pointer; font-size: 0.95rem; line-height: 1.55; transition: all var(--transition);
  background: transparent; color: var(--text); font-family: var(--font); text-align: left; width: 100%;
}
.q-opt .opt-letter {
  width: 28px; height: 28px; border-radius: 8px; flex-shrink: 0;
  display: flex; align-items: center; justify-content: center;
  font-family: var(--mono); font-size: 0.75rem; font-weight: 700;
  background: rgba(255,255,255,0.04); color: var(--text-dim); border: 1px solid var(--border);
  transition: all var(--transition);
}
.q-opt:hover:not(.locked) { border-color: var(--accent); background: var(--accent-soft); }
.q-opt:hover:not(.locked) .opt-letter { background: var(--accent); color: #fff; border-color: var(--accent); }
.q-opt.locked { cursor: default; }
.q-opt.correct { border-color: var(--green-border); background: var(--green-soft); }
.q-opt.correct .opt-letter { background: var(--green); color: #fff; border-color: var(--green); }
.q-opt.wrong { border-color: var(--red-border); background: var(--red-soft); opacity: 0.7; }
.q-opt.wrong .opt-letter { background: var(--red); color: #fff; border-color: var(--red); }
.q-opt.missed { border-color: var(--green-border); border-style: dashed; }

.q-feedback {
  margin-top: 1rem; padding: 1rem 1.15rem; border-radius: var(--radius-sm);
  font-size: 0.92rem; line-height: 1.6; display: none; animation: fadeIn 0.35s ease-out;
}
.q-feedback.show { display: block; }
@keyframes fadeIn { from { opacity: 0; transform: translateY(4px); } to { opacity: 1; transform: translateY(0); } }
.q-feedback.correct-fb { background: var(--green-soft); color: var(--green); border: 1px solid var(--green-border); }
.q-feedback.wrong-fb { background: var(--red-soft); color: var(--red); border: 1px solid var(--red-border); }
.q-feedback strong { font-weight: 700; }

/* Results */
.results-summary {
  background: var(--bg-card); border: 1px solid var(--border); border-radius: 24px;
  padding: clamp(2rem, 4vw, 3rem); text-align: center; margin-top: 1.5rem;
  position: relative; overflow: hidden;
}
.results-summary::before { content: ""; position: absolute; top: 0; left: 0; right: 0; height: 3px; }
.results-summary.good::before { background: linear-gradient(90deg, transparent, var(--green), transparent); }
.results-summary.ok::before { background: linear-gradient(90deg, transparent, var(--yellow), transparent); }
.results-summary.bad::before { background: linear-gradient(90deg, transparent, var(--red), transparent); }
.results-summary h2 { font-size: 0.82rem; text-transform: uppercase; letter-spacing: 0.1em; color: var(--text-dim); font-weight: 700; margin-bottom: 1rem; }
.big-score { font-size: clamp(3rem, 8vw, 4.5rem); font-weight: 900; font-family: var(--mono); line-height: 1; }
.big-score.good { color: var(--green); } .big-score.ok { color: var(--yellow); } .big-score.bad { color: var(--red); }
.results-sub { color: var(--text-dim); font-size: 1rem; margin-top: 0.5rem; font-weight: 500; }

.chapter-breakdown { display: grid; grid-template-columns: repeat(auto-fill, minmax(90px, 1fr)); gap: 0.5rem; margin-top: 2rem; }
.ch-score { background: rgba(255,255,255,0.02); border: 1px solid var(--border); padding: 0.65rem 0.5rem; border-radius: var(--radius-sm); text-align: center; }
.ch-score .ch-label { font-size: 0.65rem; color: var(--text-dim); font-weight: 600; text-transform: uppercase; letter-spacing: 0.06em; }
.ch-score .ch-val { font-size: 1rem; font-weight: 800; font-family: var(--mono); margin-top: 0.15rem; }

.kbd-hints { display: flex; gap: 1rem; justify-content: center; margin-top: 1rem; flex-wrap: wrap; }
.kbd { font-family: var(--mono); font-size: 0.68rem; color: var(--text-dim); display: flex; align-items: center; gap: 0.3rem; }
.kbd kbd { display: inline-block; padding: 0.15rem 0.45rem; border-radius: 4px; background: rgba(255,255,255,0.06); border: 1px solid var(--border); font-family: var(--mono); font-size: 0.68rem; }

@media (max-width: 768px) {
  .nav-bar { padding: 0 1rem; }
  .config-panel, .quiz-wrapper { padding-left: 1rem; padding-right: 1rem; }
  .stat-value { font-size: 1.4rem; }
  .quiz-card { padding: 1.25rem; border-radius: 16px; }
  .kbd-hints { display: none; }
}