:root {
    --headerButtonColor: #e9125a;
    --bodyBg: #DFD8CA;
  }
  * {
    margin: 0;
    padding: 0;
  }
  
  nav {
    display: flex;
    justify-content: flex-start;
    padding: 1rem;
    background-color: var(--headerButtonColor);
  }
  
  .container {
    margin: auto;
    text-align: center;
  }
  
  body {
    background-color: var(--bodyBg);
    color: white;
  }
  
  a {
    padding: 0.5rem;
    font-size: 1.4rem;
    text-decoration: none;
    color: white;
  }
  
  .active {
    border-bottom: 3px solid white;
  }
  
  h1 {
    text-align: center;
    margin: 1rem;
    font-size: 2.5rem;
  }
  
  label {
    font-size: 1.3rem;
    display: block;
    padding: 1rem;
    text-align: center;
  }
  
  input {
    display: block;
    width: 40%;
    margin: auto;
    font-size: 1rem;
  }
  
  button {
    width: 40%;
    margin: 1rem;
    padding: 0.4rem;
    background-color: var(--headerButtonColor);
    border: none;
    color: white;
    cursor: pointer;
    font-weight: bold;
    font-size: 1.2rem;
  }
  
  #output {
    text-align: center;
    font-size: 1.3rem;
  }
  
  .formula {
    margin: auto;
    text-align: center;
    font-size: 2rem;
    border: 3px solid var(--headerButtonColor);
    padding: 1rem;
    width: 40%;
  }
  
  form {
    text-align: center;
  }
  
  p {
    font-size: 1.4rem;
  }
  
  .button-centre {
    text-align: center;
    margin: auto;
  }