h1 {
    text-align: center;
}
input {
    margin: 0 auto;
    display: block;
    text-align: center;
}
label {
    display: block;
    font-weight: bold;
    text-align: center;
    margin-bottom: 10px;
}
.output {
    text-align: center;
    font-weight: bold;
    font-size: 1.5em;
    margin-top: 10px;
}
.addButton {
    margin-top: 10px;
    display: block;
    margin: 0 auto;
    margin-bottom: 20px;
}