body {
    margin: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #121212;
    color: #e0e0e0;
    line-height: 1.6;
  }

  .main-heading {
    text-align: center;
    font-size: 2.5rem;
    color: #ffffff;
    margin-top: 30px;
    margin-bottom: 20px;
    letter-spacing: 1px;
    font-weight: 600;
    text-shadow: 0 0 10px rgba(255, 255, 255, 0.1);
  }
  
  .notes-organizer-grid {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 40px 20px;
    gap: 30px;
  }

  .year-card {
    background-color: #1e1e1e;
    border-radius: 12px;
    box-shadow: 0 4px 14px rgba(0, 0, 0, 0.4);
    width: 90%;
    max-width: 600px;
    padding: 20px;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
  }
  
  .year-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.5);
  }
  
  .year-card h3 {
    margin-top: 0;
    font-size: 1.5rem;
    color: #ffffff;
    border-bottom: 1px solid #333;
    padding-bottom: 8px;
  }
  
  details {
    margin-top: 15px;
    background: #2c2c2c;
    border: 1px solid #3c3c3c;
    border-radius: 8px;
    overflow: hidden;
  }
  
  summary {
    padding: 12px;
    font-weight: bold;
    cursor: pointer;
    color: #90caf9;
    background-color: #2c2c2c;
    transition: background-color 0.2s ease;
  }
  
  summary:hover {
    background-color: #383838;
  }
  
  /* List styling */
  ul {
    list-style: none;
    padding: 10px 20px;
    margin: 0;
  }
  
  li {
    margin-bottom: 8px;
  }
  
  a {
    text-decoration: none;
    color: #bbdefb;
    background-color: transparent;
    padding: 6px 8px;
    border-radius: 6px;
    display: inline-block;
    transition: background-color 0.3s ease, color 0.3s ease;
  }
  
  a:hover {
    background-color: #1a237e;
    color: #ffffff;
  }
  
  details[open] summary {
    background-color: #343434;
  }
  
  @media (max-width: 600px) {
    .year-card {
      width: 95%;
    }
  }