body {
    font-family: Arial, sans-serif;
    background-color: lightblue;
    text-align: center;
    margin: 0;
    padding: 30px 15px;
}

h1 {
    color: navy;
    margin-bottom: 25px;
}

.calculator {
    box-sizing: border-box;
    max-width: 500px;
    margin: auto;
    padding: 30px;
    background-color: white;
    border: 2px solid navy;
    border-radius: 10px;
}

.calculator > label {
    display: block;
    font-size: 18px;
    margin-bottom: 10px;
}

input[type="number"] {
    box-sizing: border-box;
    width: 100%;
    padding: 10px;
    font-size: 18px;
    margin-bottom: 20px;
    border: 1px solid gray;
    border-radius: 4px;
}

fieldset {
    padding: 15px;
    border: 1px solid gray;
}

fieldset label {
    display: inline-block;
    margin: 5px;
}

p {
    font-size: 20px;
    margin-bottom: 0;
}

output {
    color: navy;
    font-weight: bold;
}