#calculator-buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
}

#calculator-buttons button {
    margin: 0 8px 8px 0;
    font-weight: bold;
}

#non-unique-identifier {
    text-align: right;
    font-size: 1.5em;
    font-weight: bold;
    padding: 10px;
}