.calculator {
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.2);
    padding: 20px;
    width: 300px;
}

#display {
    width: 100%;
    height: 50px;
    background-color: #333;
    color: #fff;
    font-size: 24px;
    text-align: right;
    border: none;
    padding: 10px;
    margin-bottom: 20px;
    border-radius: 5px;
}

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

button {
    background-color: #333;
    color: #fff;
    font-size: 18px;
    border: none;
    padding: 15px;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.3s;
}

button:hover {
    background-color: #555;
}

button:active {
    background-color: #000;
}