body {
    font-family: Arial, sans-serif;
    background-color: #f0f0f0;
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh; 
    
    padding: 20px;
    box-sizing: border-box; 
}

.utility-container {
    background: #ffffff;
    border-radius: 10px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
    padding: 20px;
    
    /* FIX 3: Make width responsive. 
       Use max-width so it shrinks on phones, but stays 400px on desktop */
    width: 100%;
    max-width: 400px;
    
    text-align: center;
}
  
  h1, h2 {
    margin-bottom: 20px;
    color: #333;
  }
  
  .input-section input {
    width: calc(50% - 10px);
    padding: 10px;
    margin: 5px;
    border: 1px solid #ccc;
    border-radius: 5px;
    font-size: 1rem;
  }
  
  .buttons button {
    padding: 10px;
    margin: 5px;
    font-size: 1.2rem;
    color: #fff;
    border: none;
    border-radius: 5px;
    cursor: pointer;
  }
  
  #add { background: #4caf50; }
  #subtract { background: #ff9800; }
  #multiply { background: #2196f3; }
  #divide { background: #f44336; }
  
  /* Style for Clear Buttons (shared by all clear actions) */
  .clear-button {
    background: #d32f2f;
    color: white;
    padding: 10px;
    font-size: 1rem;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    margin: 10px 5px 0;
  }
  
  .clear-button:hover {
    background: #b71c1c;
  }
  
  .result-section {
    width: 90%;
    padding: 10px;
    margin-top: 10px;
    border: none;
    border-radius: 5px;
    background-color: #f9f9f9;
    text-align: center;
    font-size: 1.2rem;
    color: #333;
    min-height: 40px;
  }
  
  #natoResult {
    background: #e8f5e9;
    color: #333;
  }
  
  #history {
    list-style: none;
    padding: 0;
  }
  
  #history li {
    background: #f9f9f9;
    margin: 5px 0;
    padding: 10px;
    border-radius: 5px;
    font-size: 0.9rem;
    color: #333;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
  }