<!-- La teoria del Differenziale di una Funzione -->
    body {
      font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
      background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
      margin: 0;
      padding: 20px;
      min-height: 100vh;
    }
        .container {
      max-width: 80%; /* Modificato per un contenitore più grande e responsivo */
      margin: 0 auto;
      background: white;
      border-radius: 15px;
      box-shadow: 0 10px 30px rgba(0,0,0,0.2);
      overflow: hidden;
    }
        .header {
      background: linear-gradient(135deg, #4CAF50, #45a049);
      color: white;
      padding: 30px;
      text-align: center;
    }
        .header h1 {
      margin: 0;
      font-size: 2.5em;
      text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
    }
        .content {
      padding: 30px;
    }
        .section {
      margin-bottom: 20px;
      border: 2px solid #e0e0e0;
      border-radius: 10px;
      overflow: hidden;
      transition: all 0.3s ease;
    }
        .section:hover {
      border-color: #4CAF50;
      box-shadow: 0 5px 15px rgba(76, 175, 80, 0.2);
    }
        .section-button {
      width: 100%;
      background: linear-gradient(135deg, #f8f9fa, #e9ecef);
      border: none;
      padding: 20px;
      font-size: 1.3em;
      font-weight: bold;
      color: #333;
      cursor: pointer;
      transition: all 0.3s ease;
      display: flex;
      justify-content: space-between;
      align-items: center;
    }
        .section-button:hover {
      background: linear-gradient(135deg, #4CAF50, #45a049);
      color: white;
    }
        .section-button.active {
      background: linear-gradient(135deg, #4CAF50, #45a049);
      color: white;
    }
        .arrow {
      transition: transform 0.3s ease;
      font-size: 1.2em;
    }
        .arrow.rotated {
      transform: rotate(180deg);
    }
        .section-content {
      display: none;
      padding: 25px;
      background: #fafafa;
      border-top: 1px solid #e0e0e0;
      line-height: 1.8;
    }
        .section-content.active {
      display: block;
      animation: slideDown 0.3s ease;
    }
        @keyframes slideDown {
      from {
        opacity: 0;
        transform: translateY(-10px);
      }
      to {
        opacity: 1;
        transform: translateY(0);
      }
    }
        .formula {
      background: #fff;
      padding: 15px;
      border-left: 4px solid #4CAF50;
      margin: 15px 0;
      border-radius: 5px;
      font-family: 'Courier New', monospace;
      font-size: 1.1em;
      box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    }
        .example {
      background: #e8f5e8;
      padding: 20px;
      border-radius: 8px;
      margin: 15px 0;
      border: 1px solid #c8e6c9;
    }
        .example h4 {
      color: #2e7d32;
      margin-top: 0;
    }
        .step {
      background: #fff3e0;
      padding: 15px;
      margin: 10px 0;
      border-radius: 5px;
      border-left: 3px solid #ff9800;
    }
    .step img {
        max-width: 100%; /* Rendi l'immagine responsiva */
        height: auto; /* Mantieni le proporzioni */
        display: block; /* Rimuovi spazio extra sotto l'immagine */
        margin-top: 10px; /* Spazio sopra l'immagine */
        border-radius: 5px; /* Angoli arrotondati per l'immagine */
    }
        .example img {
        max-width: 100%; /* Rendi l'immagine responsiva */
        height: auto; /* Mantieni le proporzioni */
        display: block; /* Rimuovi spazio extra sotto l'immagine */
        margin: 15px auto; /* Centra l'immagine e aggiungi spazio */
        border-radius: 5px; /* Angoli arrotondati per l'immagine */
        box-shadow: 0 4px 8px rgba(0,0,0,0.1); /* Ombra leggera */
    }
    h3 {
      color: #4CAF50;
      border-bottom: 2px solid #4CAF50;
      padding-bottom: 5px;
    }
        .highlight {
      background: #fff176;
      padding: 2px 6px;
      border-radius: 3px;
    }
     /* Stili per l'header */
    .left-image, .right-image {
      max-height: 60px;
      height: auto;
      width: auto;
      max-width: 48%;
      object-fit: contain;
    }
    .header-box {
      width: 100%;
      border: 2px dashed #28a745;
      box-sizing: border-box;
      padding: 15px;
      display: flex;
      justify-content: space-between;
      align-items: center;
      background-color: white;
      min-height: 80px;
      border-radius: 8px;
      margin-bottom: 25px;
      background: white;
      flex-wrap: wrap;
      gap: 10px;
    }