:root {
  --bg: #0b1120;
  --bg2: #111827;
  --bg3: #1a2540;
  --card: #162035;
  --border: #1e3a5f;
  --accent: #00d4ff;
  --accent2: #0099cc;
  --text: #e2e8f0;
  --text2: #94a3b8;
  --success: #22c55e;
  --error: #ef4444;
  --warning: #f59e0b;
}

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

body {
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.6;
}

a { color: var(--accent); text-decoration: none; }
a:hover { color: #33ddff; text-decoration: underline; }

/* Navigation */
nav {
  background: var(--bg2);
  border-bottom: 1px solid var(--border);
  padding: 0 2rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--accent);
  text-decoration: none;
}

.nav-brand span { color: var(--text); }

.nav-links { display: flex; gap: 1.5rem; }
.nav-links a {
  color: var(--text2);
  font-size: 0.9rem;
  transition: color 0.2s;
}
.nav-links a:hover { color: var(--text); text-decoration: none; }

/* Hero */
.hero {
  background: linear-gradient(135deg, var(--bg) 0%, var(--bg3) 50%, #0d1f3a 100%);
  padding: 4rem 2rem;
  text-align: center;
  border-bottom: 1px solid var(--border);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(ellipse at center, rgba(0,212,255,0.05) 0%, transparent 60%);
  pointer-events: none;
}

.hero h1 {
  font-size: 2.5rem;
  font-weight: 800;
  margin-bottom: 0.5rem;
  background: linear-gradient(135deg, #fff 0%, var(--accent) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  color: var(--text2);
  font-size: 1.1rem;
  max-width: 600px;
  margin: 0 auto 2rem;
}

/* Main container */
.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 2rem;
}

/* Section */
.section { margin-bottom: 3rem; }

.section-title {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--accent);
  margin-bottom: 1.25rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--border);
}

/* Card grid */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 1.25rem;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
  transition: transform 0.2s, border-color 0.2s, box-shadow 0.2s;
  cursor: pointer;
}

.card:hover {
  transform: translateY(-3px);
  border-color: var(--accent);
  box-shadow: 0 8px 24px rgba(0,212,255,0.1);
}

.card-icon { font-size: 2rem; margin-bottom: 0.75rem; }
.card h3 { font-size: 1.05rem; font-weight: 700; margin-bottom: 0.4rem; }
.card p { font-size: 0.85rem; color: var(--text2); margin-bottom: 0.75rem; }
.card .badge {
  display: inline-block;
  background: rgba(0,212,255,0.1);
  border: 1px solid rgba(0,212,255,0.3);
  color: var(--accent);
  font-size: 0.75rem;
  padding: 0.2rem 0.6rem;
  border-radius: 999px;
}

/* Quiz page */
.quiz-header {
  background: var(--bg2);
  border-bottom: 1px solid var(--border);
  padding: 1.5rem 2rem;
}

.quiz-header h1 { font-size: 1.5rem; font-weight: 700; }
.quiz-header p { color: var(--text2); font-size: 0.9rem; margin-top: 0.25rem; }

.quiz-controls {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
  margin-bottom: 2rem;
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
}

.quiz-controls label { font-size: 0.9rem; color: var(--text2); }

select {
  background: var(--bg2);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 0.5rem 1rem;
  border-radius: 8px;
  font-size: 0.9rem;
  cursor: pointer;
}

select:focus { outline: none; border-color: var(--accent); }

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.6rem 1.4rem;
  border-radius: 8px;
  border: none;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
}

.btn-primary {
  background: var(--accent);
  color: #000;
}
.btn-primary:hover { background: #33ddff; }

.btn-outline {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text);
}
.btn-outline:hover { border-color: var(--accent); color: var(--accent); }

.btn-success {
  background: var(--success);
  color: #000;
}
.btn-success:hover { background: #16a34a; }

/* Progress */
.progress-bar {
  height: 4px;
  background: var(--border);
  border-radius: 2px;
  margin-bottom: 2rem;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent2), var(--accent));
  border-radius: 2px;
  transition: width 0.3s ease;
}

.progress-text {
  text-align: right;
  font-size: 0.8rem;
  color: var(--text2);
  margin-bottom: 0.5rem;
}

/* Question card */
.question-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 2rem;
  margin-bottom: 1.5rem;
}

.question-num {
  font-size: 0.8rem;
  color: var(--accent);
  font-weight: 600;
  margin-bottom: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.question-text {
  font-size: 1.05rem;
  font-weight: 500;
  margin-bottom: 1.5rem;
  line-height: 1.7;
}

.options { display: flex; flex-direction: column; gap: 0.75rem; }

.option {
  display: flex;
  align-items: flex-start;
  gap: 1rem;
  padding: 0.9rem 1.2rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.15s;
  background: var(--bg2);
}

.option:hover { border-color: var(--accent); background: rgba(0,212,255,0.05); }

.option.selected {
  border-color: var(--accent2);
  background: rgba(0,153,204,0.15);
}

.option.correct {
  border-color: var(--success);
  background: rgba(34,197,94,0.1);
}

.option.wrong {
  border-color: var(--error);
  background: rgba(239,68,68,0.1);
}

.option-letter {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  border: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.8rem;
  font-weight: 700;
  flex-shrink: 0;
  color: var(--text2);
}

.option.selected .option-letter { background: var(--accent2); border-color: var(--accent2); color: #fff; }
.option.correct .option-letter { background: var(--success); border-color: var(--success); color: #fff; }
.option.wrong .option-letter { background: var(--error); border-color: var(--error); color: #fff; }

.option-text { flex: 1; line-height: 1.5; font-size: 0.95rem; }

/* Navigation buttons row */
.quiz-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 1rem;
}

/* Results */
.results-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 2rem;
  text-align: center;
  margin-bottom: 2rem;
}

.score-circle {
  width: 120px;
  height: 120px;
  border-radius: 50%;
  border: 4px solid var(--accent);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  margin: 0 auto 1.5rem;
}

.score-num {
  font-size: 2rem;
  font-weight: 800;
  color: var(--accent);
  line-height: 1;
}

.score-total { font-size: 0.8rem; color: var(--text2); }

.result-status {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.result-status.pass { color: var(--success); }
.result-status.fail { color: var(--error); }

.result-detail { color: var(--text2); font-size: 0.9rem; }

.review-list { margin-top: 2rem; }

.review-item {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1rem 1.25rem;
  margin-bottom: 0.75rem;
  display: flex;
  align-items: flex-start;
  gap: 1rem;
}

.review-icon { font-size: 1.1rem; flex-shrink: 0; padding-top: 2px; }
.review-q { font-size: 0.85rem; color: var(--text); margin-bottom: 0.3rem; }
.review-a { font-size: 0.8rem; color: var(--text2); }
.review-a .correct-a { color: var(--success); font-weight: 600; }
.review-a .wrong-a { color: var(--error); text-decoration: line-through; }

/* Info pages */
.info-content {
  max-width: 800px;
}

.info-content h2 {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--accent);
  margin: 2rem 0 1rem;
  padding-bottom: 0.4rem;
  border-bottom: 1px solid var(--border);
}

.info-content h3 { font-size: 1.1rem; font-weight: 700; margin: 1.5rem 0 0.5rem; }

.info-content p { color: var(--text2); margin-bottom: 1rem; line-height: 1.8; }
.info-content p strong { color: var(--text); }

.info-content ul, .info-content ol {
  padding-left: 1.5rem;
  margin-bottom: 1rem;
  color: var(--text2);
}

.info-content li { margin-bottom: 0.4rem; line-height: 1.7; }

.info-box {
  background: var(--card);
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent);
  border-radius: 8px;
  padding: 1rem 1.25rem;
  margin: 1rem 0;
  font-size: 0.9rem;
  color: var(--text2);
}

.tag-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 1rem;
}

.tag {
  background: rgba(0,212,255,0.1);
  border: 1px solid rgba(0,212,255,0.2);
  color: var(--accent);
  font-size: 0.8rem;
  padding: 0.3rem 0.75rem;
  border-radius: 999px;
}

/* Footer */
footer {
  background: var(--bg2);
  border-top: 1px solid var(--border);
  padding: 2rem;
  text-align: center;
  color: var(--text2);
  font-size: 0.85rem;
  margin-top: 4rem;
}

footer a { color: var(--text2); }
footer a:hover { color: var(--accent); }

/* Utilities */
.hidden { display: none !important; }
.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-4 { margin-top: 2rem; }
.text-center { text-align: center; }
.text-muted { color: var(--text2); }
.fw-bold { font-weight: 700; }

/* Responsive */
@media (max-width: 640px) {
  .hero h1 { font-size: 1.8rem; }
  .card-grid { grid-template-columns: 1fr; }
  nav { padding: 0 1rem; }
  .nav-links { display: none; }
  .container { padding: 1rem; }
  .question-card { padding: 1.25rem; }
}