body {
    font-family: Arial, sans-serif;
    background-color: #f7f9fc;
    margin: 0;
    padding: 0;
  }
  
  /* HEADER */
  header {
    background-color: #1f2937;
    color: white;
    padding: 40px 20px;
    text-align: center;
  }
  
  /* SECTIONS */
  section {
    background: white;
    margin: 20px auto;
    padding: 24px;
    max-width: 800px;
    border-radius: 10px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.05);
  }
  
  /* HEADINGS */
  h1 {
    margin-bottom: 10px;
  }
  
  h2 {
    margin-top: 0;
    margin-bottom: 10px;
  }
  
  h3 {
    margin-top: 20px;
  }
  
  /* BUTTONS */
  button {
    background-color: #2563eb;
    color: white;
    border: none;
    padding: 10px 16px;
    margin-top: 10px;
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.2s ease;
  }
  
  button:hover {
    background-color: #1d4ed8;
  }
  
  /* INPUTS */
  input[type="file"],
  input[type="number"] {
    margin-top: 8px;
    padding: 10px;
    width: 100%;
    max-width: 320px;
    border-radius: 6px;
    border: 1px solid #d1d5db;
  }
  
  /* HELPER TEXT */
  .helper-text {
    font-size: 13px;
    color: #6b7280;
    margin-top: 6px;
    line-height: 1.4;
  }
  
  /* OUTPUT BOX */
  #output {
    background: #f1f5f9;
    padding: 16px;
    border-radius: 6px;
    font-family: monospace;
    white-space: pre-wrap;
  }
  
  /* LEARN MORE */
  .learn-more-container {
    margin-top: 10px;
  }
  
  .learn-more-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    font-weight: bold;
    padding: 12px;
    border-radius: 6px;
    background-color: #f1f5f9;
    transition: background 0.2s ease;
  }
  
  .learn-more-header:hover {
    background-color: #e2e8f0;
  }
  
  .learn-more-content {
    overflow: hidden;
    max-height: 0;
    transition: max-height 0.3s ease;
  }
  
  /* 🔥 THIS WAS MISSING — REQUIRED FOR TOGGLE */
  .learn-more-content.open {
    max-height: 1000px; /* big enough to fit content */
  }
  
  /* FOOTER */
  footer {
    text-align: center;
    padding: 20px;
  }