body {
    font-family: Arial, sans-serif;
    text-align: center;
    padding: 20px;
}

.calculator {
    display: inline-block;
    padding: 10px;
    border: 1px solid #333;
    border-radius: 5px;
}

#display {
    width: 100%;
    height: 40px;
    margin-bottom: 10px;
    text-align: right;
    padding-right: 10px;
    font-size: 24px;
}

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

.buttons button {
    padding: 20px;
    font-size: 18px;
    margin: 5px;
    cursor: pointer;
}