style.css

body {
    font-family: Arial, Helvetica, sans-serif;
    background-color: #FEC919;
    color: #003082;
    padding: 12px 20px;
    margin: 8px 0;
}

p {
    margin-bottom: 0;
}

h1 {
    text-align: center;
    font-family: Verdana, Geneva, Tahoma, sans-serif;
    font-size: 20px;
    font-weight: bold;
}

input[type=text] {
    width: 100%;
    padding: 12px 20px;
    margin: 8px 0;
    background-color: #003082;
    color: #FFFEF8;
    display: inline-block;
    border: 1px solid;
    border-color: #FEC919;
    box-sizing: border-box;
    font-family: Verdana, Geneva, Tahoma, sans-serif;
    font-size: 25px;
    font-weight: bold;
}

input[type=text]:focus {
    border-color: #13313B;
}

.output {
    width: 100%;
    height: 200px;
    margin: 8px 0;
    display: inline-block;
    box-sizing: border-box;
    font-family: Verdana, Geneva, Tahoma, sans-serif;
    font-size: 25px;
    font-weight: bold;
}

.missing {
    color: #C9100A;
}