:root {
  --primary: #4facfe;
  --primary-2: #00f2fe;
  --bg: #f5f7fb;
  --text: #333;
  --muted: #666;
  --green: #2e7d32;
  --red: #c62828;
  --yellow: #f9a825;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
body { font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif; background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); min-height: 100vh; display: grid; place-items: center;}
.app { width: 92vw; max-width: 900px; background: #fff; border-radius: 20px; box-shadow: 0 20px 40px rgba(0,0,0,0.12); overflow: hidden; }
header { padding: 18px 20px; background: linear-gradient(135deg, var(--primary) 0%, var(--primary-2) 100%); color: #fff; }
header h1 { font-size: 20px; font-weight: 700; }
.progress { height: 8px; background: rgba(255,255,255,0.35); border-radius: 999px; margin-top: 12px; overflow: hidden;}
#progressFill { height:100%; width:0%; background: #fff; transition: width .25s ease; }

main { padding: 24px; }

/* Difficulty badge - SOLO TEXTO SIN FONDO */
.topbar { display: flex; align-items: center; gap: 8px; margin-bottom: 10px; }
.difficulty-badge { 
  font-size: 13px; 
  font-weight: 700; 
  padding: 0;
  border-radius: 0;
  background: transparent;
}
.diff-basic { color: #16a34a; }
.diff-intermediate { color: #f59e0b; }
.diff-advanced { color: #ef4444; }

#subtopicText { font-size: 13px; font-weight: 600; color: #667eea; padding: 6px 10px; background: #eef2ff; border-radius: 8px; display: inline-block; }

.question { font-size: 18px; font-weight: 700; color: var(--text); margin: 14px 0 18px; line-height: 1.45; }

.options { display: grid; gap: 12px; }
.option { background: #f8f9fa; border: 2px solid #e9ecef; border-radius: 12px; padding: 14px 16px; cursor: pointer; transition: .15s; }
.option:hover { border-color: var(--primary); background: #f0f8ff; }
.option.selected { border-color: var(--primary); background: #e3f2fd; }
.option.correct { border-color: #4CAF50; background: #e8f5e8; color: var(--green); }
.option.incorrect { border-color: #F44336; background: #ffebee; color: var(--red); }
.option.disabled { opacity: .7; cursor: not-allowed; }

.row { display: flex; justify-content: space-between; align-items: center; gap: 12px; margin-top: 16px; }
.btn { background: var(--primary); color:#fff; border:0; padding:12px 18px; border-radius: 10px; font-weight:700; cursor:pointer; transition:.2s;}
.btn:disabled { background:#c7c7c7; cursor:not-allowed; }
.score { display:flex; gap:12px; font-weight:700; }
.score-correct{ color: #4CAF50; } .score-incorrect{color:#F44336;}

.feedback { margin-top: 14px; padding: 12px; border-radius: 10px; border: 1px solid transparent; font-weight: 600;}
.feedback.correct { background:#e8f5e8; border-color:#4CAF50; color:#2e7d32;}
.feedback.incorrect { background:#ffebee; border-color:#F44336; color:#c62828;}

/* Screens */
.screen { display:none; }
#loadingScreen, #errorScreen { display:grid; place-items: center; color:#fff; height: 200px; }

/* Start - MÓDULOS CON ESTADÍSTICAS */
#startScreen .controls { display:flex; gap:12px; align-items:center; justify-content:center; margin: 14px 0;}
.module-option { 
  background:#f8f9fa; 
  border:2px solid #e9ecef; 
  border-radius:12px; 
  padding:14px; 
  margin:10px 0; 
  cursor:pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
}
.module-option.selected { background:#e3f2fd; border-color: var(--primary); }
.module-info { flex: 1; }
.module-title { font-weight: 700; font-size: 16px; margin-bottom: 4px; }
.module-description { font-size: 13px; color: var(--muted); }

.module-stats { 
  display: flex; 
  gap: 12px; 
  align-items: center;
}
.stat-box {
  text-align: center;
  padding: 8px 12px;
  border-radius: 8px;
  background: #fff;
  border: 1px solid #e0e0e0;
  cursor: pointer;
  transition: all 0.2s;
  min-width: 70px;
}
.stat-box:hover {
  border-color: var(--primary);
  transform: translateY(-2px);
  box-shadow: 0 4px 8px rgba(0,0,0,0.1);
}
.stat-label {
  font-size: 10px;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 4px;
}
.stat-value {
  font-size: 18px;
  font-weight: 700;
  color: var(--primary);
}
.stat-detail {
  font-size: 9px;
  color: var(--muted);
  margin-top: 2px;
}

/* Stats Detail Screen */
#statsDetailScreen { padding: 20px; }
#statsDetailScreen h2 { 
  font-size: 22px; 
  margin-bottom: 8px; 
  color: var(--text);
}
#statsDetailScreen .module-name {
  font-size: 14px;
  color: var(--muted);
  margin-bottom: 20px;
}
.stats-table {
  width: 100%;
  border-collapse: collapse;
  margin: 20px 0;
  font-size: 14px;
}
.stats-table th {
  background: #f8f9fa;
  padding: 12px;
  text-align: left;
  font-weight: 700;
  border-bottom: 2px solid #e9ecef;
}
.stats-table td {
  padding: 10px 12px;
  border-bottom: 1px solid #f0f0f0;
}
.stats-table tr:hover {
  background: #fafafa;
}
.perf-good { color: #16a34a; font-weight: 600; }
.perf-ok { color: #f59e0b; font-weight: 600; }
.perf-bad { color: #ef4444; font-weight: 600; }

/* End */
#endScreen .final-score { font-size: 42px; font-weight: 900; color: var(--primary); margin: 10px 0;}