body {
    display: flex;
    flex-direction: column; /* stack elements vertically */
    align-items: center;    /* center all children by default */
    margin: 0;
    padding: 0px;
    font-family: Arial, sans-serif;
    background-color: #ffffff;
    color: #333;
  }
  
  /* Make header span the full width */
  header {
    background-color: #2d88f3;
    color: white;
    padding: 1rem 0;
    text-align: center;
    width: 100%;          /* extend full width */
    margin: 0;            /* remove extra margins if any */
  }
  
  header h1 {
    margin: 0;
    font-size: 2.5rem;
  }
  
  label, select, input, button {
    display: block;
    margin: 10px 0;
    text-align: center;
  }
  
  #result {
    margin-top: 20px;
    font-weight: bold;
  }