body {
  font-family: 'Segoe UI', sans-serif;
  margin: 0;
  padding: 0;
  line-height: 1.6;
  background: #fff;
  color: #333;
}

.navbar {
  background: white;
  padding: 1rem 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid #eee;
  position: sticky;
  top: 0;
  z-index: 999;
}

.navbar .logo {
  font-weight: bold;
  font-size: 1.2rem;
}

.navbar nav a {
  margin: 0 1rem;
  text-decoration: none;
  color: #333;
}

.hero {
  text-align: center;
  padding: 3rem 1rem;
  background: #f9f9f9;
}

.hero h1 {
  font-size: 2.5rem;
  margin-bottom: 1rem;
}

.highlight {
  color: #2b6cb0;
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: 2rem;
  margin: 1rem 0;
}

.cta-btn {
  background: #2b6cb0;
  color: white;
  padding: 0.75rem 1.5rem;
  text-decoration: none;
  border-radius: 8px;
  display: inline-block;
  margin-top: 1rem;
}

.features {
  text-align: center;
  padding: 3rem 1rem;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 2rem;
  margin-top: 2rem;
}

.feature {
  padding: 1rem;
}

.topics {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(270px, 1fr));
  gap: 2rem;
  padding: 2rem;
}

.topic-card {
  background: #f1f1f1;
  padding: 1.5rem;
  border-radius: 12px;
}

.topic-card .tags span {
  display: inline-block;
  margin: 0.25rem;
  background: #ddd;
  padding: 0.3rem 0.6rem;
  border-radius: 8px;
  font-size: 0.85rem;
}

.topic-card.blue .study-btn {
  background: #2b6cb0;
}

.topic-card.green .study-btn {
  background: #38a169;
}

.topic-card.red .study-btn {
  background: #e53e3e;
}

.study-btn {
  display: block;
  color: white;
  padding: 0.5rem;
  text-align: center;
  margin-top: 1rem;
  border-radius: 8px;
  text-decoration: none;
}

.exam-btn {
  margin-top: 0.5rem;
  padding: 0.4rem;
  border-radius: 6px;
  width: 100%;
  background: white;
  border: 1px solid #ccc;
}