:root {
  --bg: #0f172a;
  --bg2: #1e293b;
  --bg3: #334155;
  --text: #f1f5f9;
  --text2: #94a3b8;
  --accent: #3b82f6;
  --accent2: #2563eb;
  --success: #22c55e;
  --danger: #ef4444;
  --warning: #f59e0b;
  --border: #475569;
  --radius: 8px;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.6;
}
#app { max-width: 960px; margin: 0 auto; padding: 20px; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
button, .btn {
  background: var(--accent);
  color: white;
  border: none;
  padding: 10px 24px;
  border-radius: var(--radius);
  cursor: pointer;
  font-size: 15px;
  transition: background .2s;
}
button:hover, .btn:hover { background: var(--accent2); }
button:disabled, .btn:disabled { opacity: .5; cursor: not-allowed; }
.btn-secondary { background: var(--bg3); }
.btn-secondary:hover { background: var(--border); }
.btn-success { background: var(--success); }
.btn-danger { background: var(--danger); }
.btn-danger:hover { background: #dc2626; }
input, textarea, select {
  background: var(--bg2);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 10px 14px;
  border-radius: var(--radius);
  font-size: 15px;
  width: 100%;
}
input:focus, textarea:focus { outline: none; border-color: var(--accent); }
textarea { resize: vertical; min-height: 100px; font-family: inherit; }
.card {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  margin-bottom: 16px;
}
.card h2, .card h3 { margin-bottom: 12px; }
.badge {
  display: inline-block;
  padding: 3px 10px;
  border-radius: 12px;
  font-size: 13px;
  font-weight: 600;
}
.badge-success { background: #166534; color: var(--success); }
.badge-danger { background: #7f1d1d; color: var(--danger); }
.badge-warning { background: #78350f; color: var(--warning); }
.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.grid-3 { display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 16px; }
.text-center { text-align: center; }
.text-muted { color: var(--text2); }
.mt-2 { margin-top: 8px; }
.mt-3 { margin-top: 12px; }
.mt-4 { margin-top: 16px; }
.mb-3 { margin-bottom: 12px; }
.mb-4 { margin-bottom: 16px; }
.flex { display: flex; }
.flex-between { display: flex; justify-content: space-between; align-items: center; }
.flex-center { display: flex; align-items: center; justify-content: center; }
.gap-2 { gap: 8px; }
.gap-3 { gap: 12px; }

/* Timer */
.timer {
  background: var(--bg3);
  padding: 8px 16px;
  border-radius: var(--radius);
  font-size: 18px;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}
.timer-warning { color: var(--warning); }
.timer-danger { color: var(--danger); }

/* Question styling */
.option-btn {
  display: block;
  width: 100%;
  text-align: left;
  padding: 12px 16px;
  margin-bottom: 8px;
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text);
  cursor: pointer;
  font-size: 14px;
  transition: all .15s;
}
.option-btn:hover { border-color: var(--accent); }
.option-btn.selected { border-color: var(--accent); background: rgba(59,130,246,.15); }
.option-btn.correct { border-color: var(--success); background: rgba(34,197,94,.15); }
.option-btn.wrong { border-color: var(--danger); background: rgba(239,68,68,.15); }

/* Header/nav */
.navbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 12px 0;
  margin-bottom: 24px;
  border-bottom: 1px solid var(--border);
}
.navbar h1 { font-size: 20px; }
.navbar .nav-links { display: flex; gap: 16px; align-items: center; }

/* Login page */
.login-box {
  max-width: 400px;
  margin: 80px auto;
}
.login-box h1 { text-align: center; margin-bottom: 24px; font-size: 28px; }

/* Dashboard */
.dashboard-stats { display: grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap: 16px; margin-bottom: 24px; }
.stat-card {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  text-align: center;
}
.stat-card .stat-value { font-size: 32px; font-weight: 700; color: var(--accent); }
.stat-card .stat-label { font-size: 13px; color: var(--text2); margin-top: 4px; }

/* Score bars */
.score-bar {
  height: 8px;
  background: var(--bg3);
  border-radius: 4px;
  overflow: hidden;
  margin: 8px 0;
}
.score-bar-fill {
  height: 100%;
  background: var(--accent);
  border-radius: 4px;
  transition: width .5s;
}
.score-bar-fill.good { background: var(--success); }
.score-bar-fill.warn { background: var(--warning); }
.score-bar-fill.bad { background: var(--danger); }

/* Section buttons */
.section-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 16px;
}
.section-card {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  text-align: center;
  cursor: pointer;
  transition: all .2s;
}
.section-card:hover { border-color: var(--accent); transform: translateY(-2px); }
.section-card .icon { font-size: 40px; margin-bottom: 12px; }

/* Timer bar */
.timer-bar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  background: var(--bg2);
  border-bottom: 1px solid var(--border);
  padding: 8px 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  z-index: 100;
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.4; }
}

@media (max-width: 640px) {
  #app { padding: 12px; }
  .grid-2 { grid-template-columns: 1fr; }
  .grid-3 { grid-template-columns: 1fr; }
  .dashboard-stats { grid-template-columns: 1fr 1fr; }
  .section-grid { grid-template-columns: 1fr 1fr; }
  .navbar { flex-direction: column; gap: 8px; }
  .navbar .nav-links { flex-wrap: wrap; justify-content: center; }
}

/* ── Adaptive Difficulty Badges ── */
.difficulty-badge {
  display: inline-block;
  padding: 2px 10px;
  border-radius: 12px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.5px;
  vertical-align: middle;
  margin-left: 6px;
}
.difficulty-easy { background: #1b5e20; color: #a5d6a7; }
.difficulty-medium { background: #e65100; color: #ffcc80; }
.difficulty-hard { background: #b71c1c; color: #ef9a9a; }

/* Auth Pages */
.auth-container { display:flex; align-items:center; justify-content:center; min-height:100vh; padding:20px; }
.auth-card { background:var(--bg2); border:1px solid var(--border); border-radius:12px; padding:32px; max-width:420px; width:100%; }
.auth-header { text-align:center; margin-bottom:24px; }
.auth-header h1 { font-size:24px; margin:0; }
.form-group { margin-bottom:16px; }
.form-group label { display:block; margin-bottom:6px; font-size:14px; font-weight:600; color:var(--text); }
.form-group input { width:100%; padding:10px 14px; background:var(--bg); border:1px solid var(--border); border-radius:8px; color:var(--text); font-size:15px; outline:none; transition:border-color 0.2s; }
.form-group input:focus { border-color:var(--primary, var(--accent)); }
.form-group input::placeholder { color:var(--text2); }

/* Navbar user badge */
.nav-user { display:flex; align-items:center; gap:8px; }
.nav-user-avatar { width:28px; height:28px; border-radius:50%; background:var(--accent); display:flex; align-items:center; justify-content:center; font-size:13px; font-weight:700; color:white; }