.bg {
    position: fixed;
    top: 0;
    left: 0;
    height: 100vh;
    width: 100vw;
    background-color: #000;
    background-position: center center;
    background-repeat: no-repeat;
    background-size: cover;
    z-index: 30;
    opacity: 0;
    transition: opacity 1s;
}

.bg--active {
    opacity: 1;
}

.bg-filter {
    position: fixed;
    top: 0;
    left: 0;
    height: 100vh;
    width: 100vw;
    background: rgba(0, 0, 0, .35);
    z-index: 40;
}