#tts_main {
    display: inline-block;
    margin-bottom: 10px;
    padding: 6px 20px;
    background-color: #000;
    color: #fff;
    cursor: pointer;
    border-radius: 5px;
    text-align: center;
    font-weight: bold;
}

@media only screen and (max-width: 640px) {
    #tts_main {
        width: 100%;
    }
  }