.calculator {
    width: 80%;
    background: #f3f3f3;
    padding: 20px;
    border-radius: 10px;
    border: 3px solid #000;
    margin: 0 auto;
}

#display {
    width: 100%;
    height: 50px;
    font-size: 24px;
    text-align: right;
    margin-bottom: 10px;
    padding: 10px;
    box-sizing: border-box;
    border: 3px solid #ccc;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

button {
    padding: 20px;
    font-size: 18px;
    cursor: pointer;
    border: none;
    background: #333;
    border-radius: 50px;
    color: #fff;
}

.operator {
    background: #f39c12;
    color: #fff;
}

#equal {
    grid-row: span 2;
    background: #24ae60;
}