body {
    background-color: #000000;
}
#calculator {
    font-size: 0;
    white-space: nowrap;
    text-align: center;
}
.number-area {
    resize: none;
    text-align: right;
    font-size: 50px;
    background-color: rgba(0, 0, 0, 0);
    border-color: rgba(0, 0, 0, 0);
    color: #ffffff;
    width: 480px;
    height: 60px;
}
.button {
    font-size: 50px;
    margin: 10px;
    width: 100px;
    height: 100px;
    border: 0;
    border-radius: 50px;
    color: #ffffff;
    transition: background-color 0.5s ease-in-out;
}
.button.math-symbol {
    font-size: 60px;
    background-color: #f1a43c;
}
.button.symbol {
    color: #010101;
    background-color: #a5a5a5;
}
.button.number {
    background-color: #333333;
}
.button.zero:first-child {
    border-top-right-radius: 0;
    border-bottom-right-radius: 0;
    margin-right: 0;
}
.button.zero:nth-child(2) {
    border-top-left-radius: 0;
    border-bottom-left-radius: 0;
    margin-left: 0;
    width: 120px;
    color: rgba(0, 0, 0, 0)
}