body {
    text-align: center;
}

#addButton {
    background-color: rgb(240, 103, 103);
    display: inline-block;
    width: 129px;
    height: 50px;
    font-size: 40px;
    border-width: 3px;
}
#subtractButton {
    background-color: rgb(238, 238, 103);
    display: inline-block;
    width: 129px;
    height: 50px;
    font-size: 40px;
    border-width: 3px;
}
#multiplyButton {
    background-color: rgb(143, 210, 143);
    display: inline-block;
    width: 129px;
    height: 50px;
    font-size: 40px;
    border-width: 3px;
}
#divideButton {
    background-color: rgb(155, 155, 235);
    display: inline-block;
    width: 129px;
    height: 50px;
    font-size: 40px;
    border-width: 3px;
}
#input1 {
    display: block;
    margin-top: 10px;
    width: 520px;
    height: 50px;
    font-size: 30px;
    border-width: 2px;
    text-align: center;
    margin-left: auto;
    margin-right: auto;
}
#input2 {
    display: block;
    width: 520px;
    height: 50px;
    font-size: 30px;
    border-width: 2px;
    text-align: center;
    margin-left: auto;
    margin-right: auto;
}
#output {
    display: block;
    width: 520px;
    height: 50px;
    font-size: 30px;
    border-width: 2px;
    background-color: rgb(226, 225, 225);
    text-align: center;
    margin-left: auto;
    margin-right: auto;
}