#c {
    width: 560px;
    height: 340px;
    border: 1px solid black;
    background: #f5f5f5;
    display: block;
    margin: auto;
}

#controls {
    text-align: center;
    margin-top: 10px;
}

button {
    padding: 10px 20px;
    background: #000000;
    color: #ffffff;
    border: none;
    cursor: pointer;
    font-size: 1em;
    border-radius: 5px;
}

#balance {
    margin-top: 10px;
    font-weight: bold;
}