body {
    background-color: #000;
    color: #fff;
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    text-align: center;
}

#sendBtn {
    width: 150px;
    height: 150px;
    font-size: 24px;
    display: flex;
    justify-content: center;
    align-items: center;
}

footer {
    position: absolute;
    bottom: 20px;
}