* {
    box-sizing: border-box;
  }
  body {
    font-family: 'Inter', sans-serif;
    background: linear-gradient(to right, #e0f7fa, #fff);
    margin: 0;
    padding: 40px;
    color: #333;
  }
  h1 {
    text-align: center;
    font-size: 36px;
    color: #00695c;
    margin-bottom: 40px;
  }
  .container {
    max-width: 1200px;
    margin: auto;
  }
  .section {
    background: #ffffff;
    border-radius: 16px;
    padding: 24px 32px;
    margin-bottom: 24px;
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.05);
    transition: all 0.3s ease;
    cursor: pointer;
  }
  .section:hover {
    transform: translateY(-2px);
    box-shadow: 0 12px 24px rgba(0, 0, 0, 0.08);
  }
  .section-title {
    font-size: 20px;
    font-weight: 600;
    margin-bottom: 12px;
    color: #004d40;
  }
  .lessons {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.4s ease;
    padding-left: 15px;
  }
  .lessons.open {
    max-height: 12500px;
  }
  .lessons a {
    display: block;
    padding: 8px 0;
    color: #00796b;
    text-decoration: none;
    font-size: 16px;
  }
  .lessons a:hover {
    text-decoration: underline;
  }
  footer {
    text-align: center;
    margin-top: 60px;
    font-size: 14px;
    color: #777;
  }