.topics-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: var(--space-8) var(--space-4);
}

.topics-header {
  text-align: center;
  margin-bottom: var(--space-12);
  position: relative;
}

.topics-header::after {
  content: '';
  position: absolute;
  bottom: -20px;
  left: 50%;
  transform: translateX(-50%);
  width: 100px;
  height: 4px;
  background-color: var(--primary-500);
  border-radius: var(--radius-full);
}

.topics-header h1 {
  font-size: 2.5rem;
  color: var(--neutral-900);
  margin-bottom: var(--space-4);
}

.topics-header p {
  font-size: 1.25rem;
  color: var(--neutral-600);
  max-width: 600px;
  margin: 0 auto;
}

.topics-list {
  margin-top: var(--space-16);
}

.topic-section {
  margin-bottom: var(--space-16);
  padding: var(--space-8);
  background-color: white;
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
  position: relative;
  overflow: hidden;
}

.topic-section::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 4px;
  height: 100%;
  background-color: var(--primary-500);
}

.topic-section h2 {
  margin-bottom: var(--space-6);
  color: var(--primary-800);
  position: relative;
  padding-left: var(--space-2);
}

.subtopics {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--space-6);
}

.subtopic-card {
  background-color: rgba(255, 255, 255, 0.8);
  backdrop-filter: blur(10px);
  border: 1px solid rgba(255, 255, 255, 0.2);
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.05);
  padding: var(--space-6);
  border-radius: var(--radius-lg);
  transition: all var(--transition);
  height: 100%;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  position: relative;
}

.subtopic-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.1) 0%, rgba(20, 184, 166, 0.1) 100%);
  opacity: 0;
  transition: opacity var(--transition);
  z-index: -1;
}

.subtopic-card:hover {
  transform: translateY(-5px) translateX(-2px);
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
  border-color: rgba(59, 130, 246, 0.2);
}

.subtopic-card:hover::before {
  opacity: 1;
}

.subtopic-card h3 {
  color: var(--primary-700);
  margin-bottom: var(--space-2);
  font-size: 1.15rem;
  font-weight: 600;
  transition: color var(--transition-fast);
}

.subtopic-card:hover h3 {
  color: var(--primary-800);
}

.subtopic-card p {
  color: var(--neutral-600);
  font-size: 0.9rem;
  margin-bottom: 0;
}

/* Responsive Styles */
@media (max-width: 768px) {
  .topics-header h1 {
    font-size: 2rem;
  }
  
  .topics-header p {
    font-size: 1rem;
  }
  
  .topic-section {
    padding: var(--space-6) var(--space-4);
  }
  
  .topic-section h2 {
    font-size: 1.5rem;
  }
  
  .subtopics {
    grid-template-columns: 1fr;
  }
}

/* Glassmorphism Effect for Cards */
.subtopic-card {
  background: rgba(255, 255, 255, 0.7);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border: 1px solid rgba(255, 255, 255, 0.3);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
}

/* Additional styling for topic sections */
#introduction::before { background-color: var(--primary-600); }
#python-libraries::before { background-color: var(--secondary-600); }
#data-cleaning::before { background-color: var(--accent-500); }
#data-transformation::before { background-color: var(--success-500); }
#descriptive-statistics::before { background-color: var(--primary-800); }
#data-visualization::before { background-color: var(--secondary-500); }
#mini-projects::before { background-color: var(--accent-600); }
#external-data::before { background-color: var(--warning-500); }
#statistics::before { background-color: var(--primary-500); }
#ml-ready::before { background-color: var(--error-500); }

/* Animation for the cards */
.subtopic-card {
  transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
}

.subtopic-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 12px 24px rgba(0, 0, 0, 0.2);
}