body {
    background-color: lightblue;
    text-align: center;
    font-family: Arial;
}

.calculadora {
    background-color: white;
    width: 250px;
    margin: auto;
    margin-top: 100px;
    padding: 20px;
    border-radius: 10px;
}

#pantalla {
    width: 200px;
    height: 30px;
    font-size: 20px;
}

button {
    width: 45px;
    height: 45px;
    font-size: 18px;
}