.playbutton {
    width: 40px;
    height: 40px;
    border: none;
    border-radius: 50%;
    background: #ccc url('uza.png') no-repeat center;
    background-size: 60%;
    cursor: pointer;
    transition: background-image 0.2s;
}
.playbutton.playing {
    background-image: url('pause.png');
}
audio.playbutton-audio {
    display: none;
}