.cover {
    position: absolute;
    width: 100%;
    height: 100%;
    background-color: gray;
    opacity: 0.9;
    z-index: 10;
    margin-top: 0;
    font-size: 24px;
    display: flex;
    align-items: center;
    justify-content: center;

    -webkit-user-select: none; /* Chrome all / Safari all */
    -moz-user-select: none; /* Firefox all */
    -ms-user-select: none; /* IE 10+ */
    user-select: none; /* Likely future */
    /* https://css-tricks.com/almanac/properties/u/user-select/  */
    transition: 0.5s;
}

.cover:hover {
    visibility: visible;
    opacity: 0;
    /*
    transition: opacity 0.5s linear;
    */
}

.previewP {
    color: white;
    font-size: 100px;
    letter-spacing: 10px;
    font-weight: bold;
    z-index: 11;
    position: absolute;
}