style.css

html {
    font-family: "Electrolize", serif;
    font-size: 10px;
  }

  body {
    margin: 0;
  }
  
  h1 {
    text-align: center;
    border-bottom: 2px solid black;
    font-size: 3.5rem;
    line-height: 150%;
    margin: 1rem 0;
  }

  .container {
    max-width: 650px;
    width: 60%;
    margin: 0 auto;
    margin-top: 3em;
  }

  .container > p {
    font-size: 2.5rem;
  }

  .form {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    column-gap: 2.5rem;
    row-gap: 2rem;
    padding-bottom: 2rem;
    border-bottom: 1px dotted gray;
  }

  .form label {
    font-size: 2.25rem;
  }
  
  .form input[type="number"] {
    width: 15rem;
    height: 2.5rem;
    font-size: 1.5rem;
    border-radius: 5px;
    border: 1px solid rgb(167, 167, 167)    ;
    box-shadow: 0 2px 5px rgba(0,0,0,0.25);
    padding-left: 5px;
  }

  .form input[type="number"]:focus,
  .form input[type="number"] :focus-visible {
    outline: 2px solid rgb(63, 141, 243);
  }

  .form input[type="submit"],.btn {
    padding: 0.5em 0.75em;
    font-size: 1.5rem;
    border-radius: 5px;
    border: 1px solid gray;
    background-color: rgb(226, 221, 221);
    box-shadow: 0 2px 10px -1px rgba(0,0,0,0.25);
    cursor: pointer;
    transition: all 0.15s ease;
  }

  .form input[type="submit"]:hover {
    background-color: rgb(79, 79, 79);
    color: whitesmoke;
  }

  .form input[type="submit"]:active {   
    box-shadow: none;
  }

  .resultParas p {
    font-size: 2rem;
  }

  .lastResult {
    display: inline-block;
    color: white;
    padding: 1rem;
    margin: 0.5em 0;
  }

  .btn {
    visibility: hidden;
  }

  @media (max-width: 700px) {
    html {
      font-size: 9px;
    }

    .container {
      width: 80%;
    }
  }