.playbgmusic,
.stopbgmusic{
    animation: pulse 2.1s ease-in-out infinite;
    transform-origin: center;
}

@keyframes pulse{
    0%{
        transform: scale(1);
    }
    50%{
        transform: scale(1.18);
    }
    100%{
        transform: scale(1);
    }
}