body {
    font-family: Arial, sans-serif;
    background-color: #f4f4f4;
    display: flex;
    height: 630px;
    justify-content: center;
    align-items: center;
    margin: 0;
}

.calculator {
    background: #817b7b;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0px 4px 15px rgba(0,0,0,0.2);
    text-align: center;
    width: 300px;
}

input[type="text"] {
    width: 90%;
    padding: 10px;
    font-size: 18px;
    margin-bottom: 10px;
    border: 1px solid #ccc;
    border-radius: 5px;
    text-align: right;
    background-color: #fafafa;
}

input[type="button"] {
    width: 50px;
    height: 50px;
    margin: 5px;
    font-size: 18px;
    border: none;
    border-radius: 5px;
    background-color: #e0e0e0;
    cursor: pointer;
    transition: background-color 0.2s;
}

input[type="button"]:hover {
    background-color: #ccc;
}