.overlay {
    position: absolute;
    background: #000;
    opacity: 0;
    left: 0;
    top: 0;
    width: 100%;
}

.overlay-fade-in {
    opacity: 0.5;
    transition: opacity 0.1s linear;
}

.overlay-fade-out {
    opacity: 0;
    transition: opacity 0.1s linear;
}