.btn_b::before{
    content: "\f068" !important;
}
.btn_a::before{
    content: "\f067" !important;
}

@media only screen and (max-width: 767px){
    .scroll-prevent {
        position: fixed;
        z-index: -1;
        width: 100%;
        height: 100%;
        overflow-y: scroll;
    }
}