/* Lecture Notes Page Styles */
@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@300;400;500;600;700&display=swap');

/* Page Header */
.lecture-notes-header {
  text-align: center;
  margin-bottom: 3rem;
  padding: 2rem 0;
}

.page-title {
  font-family: 'Poppins', sans-serif;
  font-size: 2.5rem;
  font-weight: 700;
  color: #2c3e50;
  margin: 0 0 0.5rem 0;
}

.page-subtitle {
  font-family: 'Poppins', sans-serif;
  font-size: 1.1rem;
  color: #666;
  font-weight: 400;
  margin: 0;
}

/* Categories Section */
.categories-section {
  margin-bottom: 3rem;
  text-align: center;
}

.section-heading {
  font-family: 'Poppins', sans-serif;
  font-size: 1.3rem;
  font-weight: 600;
  color: #2c3e50;
  margin-bottom: 1.5rem;
}

.category-filters {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: center;
}

.category-filter {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: white;
  color: #2c3e50;
  border: 2px solid #e0e0e0;
  border-radius: 25px;
  padding: 0.6rem 1.25rem;
  font-family: 'Poppins', sans-serif;
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.3s ease;
  outline: none;
}

.category-filter:hover {
  border-color: #2c3e50;
  background: #f8f9fa;
  transform: translateY(-2px);
}

.category-filter.active {
  background: linear-gradient(135deg, #2c3e50 0%, #34495e 100%);
  color: white;
  border-color: #2c3e50;
  box-shadow: 0 4px 12px rgba(44, 62, 80, 0.25);
}

.category-filter i {
  font-size: 0.9rem;
}

/* Notes Grid */
.lecture-notes-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 2rem;
  margin-bottom: 3rem;
}

/* Note Cards */
.lecture-note-card {
  background: white;
  border-radius: 12px;
  overflow: hidden;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
  transition: all 0.3s ease;
  border: 1px solid #f0f0f0;
  display: flex;
  flex-direction: column;
}

.lecture-note-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 25px rgba(0, 0, 0, 0.15);
}

/* Card Thumbnail */
.card-thumbnail {
  position: relative;
  width: 100%;
  height: 180px;
  overflow: hidden;
  background: linear-gradient(135deg, #f5f7fa 0%, #e8ecf1 100%);
}

.card-thumbnail img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.3s ease;
}

.lecture-note-card:hover .card-thumbnail img {
  transform: scale(1.05);
}

.thumbnail-placeholder {
  width: 100%;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #bdc3c7;
}

.thumbnail-placeholder i {
  font-size: 4rem;
}

.category-badge {
  position: absolute;
  top: 1rem;
  right: 1rem;
  background: linear-gradient(135deg, #2c3e50 0%, #34495e 100%);
  color: white;
  padding: 0.4rem 0.9rem;
  border-radius: 20px;
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  box-shadow: 0 2px 8px rgba(44, 62, 80, 0.3);
}

/* Card Content */
.card-content-area {
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  flex-grow: 1;
}

.note-title {
  font-family: 'Poppins', sans-serif;
  font-size: 1.3rem;
  font-weight: 600;
  color: #2c3e50;
  margin: 0 0 1rem 0;
  line-height: 1.4;
}

/* Meta Info */
.note-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  margin-bottom: 1rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid #f0f0f0;
}

.meta-item {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  color: #777;
  font-size: 0.85rem;
}

.meta-item i {
  color: #20b2aa;
  font-size: 0.9rem;
}

/* Summary */
.note-summary {
  color: #555;
  line-height: 1.6;
  margin-bottom: 1.5rem;
  flex-grow: 1;
  font-size: 0.95rem;
}

/* Card Footer */
.card-footer {
  margin-top: auto;
}

.read-notes-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.6rem;
  width: 100%;
  background: linear-gradient(135deg, #2c3e50 0%, #34495e 100%);
  color: white;
  border: none;
  border-radius: 8px;
  padding: 0.85rem 1.5rem;
  font-family: 'Poppins', sans-serif;
  font-weight: 500;
  font-size: 0.95rem;
  text-decoration: none;
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  box-shadow: 0 2px 8px rgba(44, 62, 80, 0.2);
  cursor: pointer;
}

.read-notes-btn:hover {
  background: linear-gradient(135deg, #34495e 0%, #2c3e50 100%);
  transform: translateY(-1px);
  box-shadow: 0 4px 16px rgba(44, 62, 80, 0.3);
  color: white;
  text-decoration: none;
}

.read-notes-btn i {
  font-size: 0.85rem;
  transition: transform 0.3s ease;
}

.read-notes-btn:hover i {
  transform: translateX(3px);
}

/* Empty State */
.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 4rem 2rem;
  color: #999;
  text-align: center;
}

.empty-state i {
  font-size: 4rem;
  margin-bottom: 1rem;
  color: #ddd;
}

.empty-state p {
  font-family: 'Poppins', sans-serif;
  font-size: 1.1rem;
  margin: 0;
}

/* Responsive Design */
@media (max-width: 768px) {
  .page-title {
    font-size: 2rem;
  }
  
  .page-subtitle {
    font-size: 1rem;
  }
  
  .lecture-notes-grid {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }

  .category-filters {
    gap: 0.75rem;
  }

  .category-filter {
    font-size: 0.85rem;
    padding: 0.5rem 1rem;
  }

  .card-thumbnail {
    height: 160px;
  }
}

@media (max-width: 480px) {
  .lecture-notes-header {
    padding: 1rem 0;
  }

  .categories-section {
    margin-bottom: 2rem;
  }

  .section-heading {
    font-size: 1.1rem;
  }
}